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SCIENCE 
 
 X 
 
 FOR THE 
 
 SCHOOL AND FAMILY. 
 
 PART III. 
 
 MINERALOGY AND GEOLOGY. 
 
 BY 
 
 WORTHINGTON HOOKER, M,D,, 
 
 PEOFE8SOB OF THE THEORY AND PRACTICE OF MEDICINE IN YALE COLLEGE, 
 
 AUTHOR OF "HITMAN PHYSIOLOGY," "CHILD'S BOOK OF NATURE," 
 
 "NATURAL HISTORY," &C. 
 
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 NEW YORK: 
 HARPER & BROTHERS, PUBLISHERS, 
 
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 1 865. 
 
x 
 
 LIBRARY 
 
 By Dr. Worthington Hooker. 
 
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/ 
 
 PREFACE. 
 
 THIS book is intended to meet the wants of beginners in the study 
 of Geology, and especially young beginners. There are many ele- 
 mentary books, so called, on this science, but they all, so far as I 
 have seen them, contain much matter which is suited only to those 
 who have already become acquainted with the subject. They cover 
 too much ground for a beginner. And, besides this, they are not 
 sufficiently simple in their explanations and illustrations. These 
 
 defects I have endeavoreehto avoid -in the construction of this book. 
 
 _ . 
 My object has been to produce a text-book fitted to prepare those 
 
 who are wholly unacquainted with the subject for the farther study 
 of it in the books of professed geologists. I would gladly have left 
 this task to some of them, but, as no one has met the existing want, 
 I have undertaken to do it, though with some hesitation, from my 
 lack of familiarity with the full minutiae of the subject. But per- 
 haps the fact that I have been obliged to be, to some extent, a learn- 
 er, in order to accomplish my task, has the better fitted me for it, as 
 I have thus become sensible of the wants of the learners for whom 
 I write. 
 
 As in my Chemistry (Part II.), so in this book, I have made it a 
 point to convey to the pupil simply that knowledge of the study 
 which every well-informed person ought to possess, leaving out those 
 minutiae which are of value only to one who intends to be a thorough 
 geologist. I have also brought out very prominently those common 
 geological phenomena which are within the scope of ordinary ob- 
 servation, so that the pupil may be prompted, by what he learns in 
 
IV PBEFACE. 
 
 this book, to prosecute his observations and investigations in his 
 daily walks, and in his travels to different localities, far or near. 
 
 I do not go largely into Mineralogy, but present enough of it sim- 
 ply to prepare the pupil for the study of Geology. Observe in this 
 connection the natural succession of subjects in the three parts of 
 this portion of my series. The Natural Philosophy properly pre- 
 cedes the Chemistry, and this latter the Mineralogy and Geology, 
 each study preparing the pupil to understand what comes after. It 
 should be remarked here that these studies, together with that of 
 Zoology, should precede the study of Physical Geography, for ac- 
 quaintance with them is absolutely essential to any thing like a full 
 knowledge of that science ; and yet it is very common to see class- 
 es wearily plodding through some book on Physical Geography, 
 who, from lack of this preparation, find most of it a terra incognita, 
 and know but little of what they have passed through when they ar- 
 rive at their journey's end. Let me not be understood to say that 
 this science should not be studied at all till after the pupil has gone 
 through with the "Studies that I have mentioned. It is only the full 
 consideration of it that should be delayed till that period. It should 
 be introduced, more or less, throughout the whole previous course, 
 mingled with the teaching of Geography as it is now ordinarily pur- 
 sued. But this can not be done properly and effectually unless the 
 study of the natural sciences be made a part of education from the 
 outset, as is contemplated in my series of books, beginning with the 
 "Child's Book of Common Things," and ending with the present 
 work. That this view of the matter is correct is readily seen if you 
 observe how tributary are the natural sciences to the interest and 
 value of the study of Geography, for without their contributions to 
 it this branch is nothing more than mere dry topography and sta- 
 tistics. 
 
 The materials for this book I have drawn from various sources. 
 Foremost stand the works of Professor Dana, and especially that 
 
PREFACE. V 
 
 grand American book, his Manual of Geology. Then there are the 
 books of Lyell, Hitchcock, Hugh Miller, Phillips, Gray and Adams, 
 Kichardson, etc. I mention with special pleasure some smaller 
 works from the English press. "The Past and Present Life of the 
 Globe," by Page, is a most able and interesting commentary on the 
 life-record of the earth's formation. " Geology in the Garden," by 
 Rev. Henry Eley, shows in a very ingenious manner what may be 
 learned about English Geology by following out the suggestions de- 
 rived from the examination of the soil of a garden. One of the 
 best books for a beginner that I have met with is the " School Man- 
 ual of Geology, "by Mr. Jukes, local director of th*e geological sur- 
 vey of Ireland. It would be well for the teacher to have some of 
 the books which I have mentioned for the purpose of reference, so 
 that he may, if he wishes, bring up additional matter in his teach- 
 ing, or answer any inquiries of his pupils on points that may not be 
 fully treated in this book. This would be in consonance with the 
 principles I laid down in the preface to my Natural History in regard 
 to the relative use of text-books and books for reference. 
 
 I may say of this book as I said of Part II., that in the present 
 state of education it is adapted to high schools and academies ; and 
 yet it would be within the grasp of the older pupils of our common 
 schools if they had studied in their proper time all the other books 
 of the series, for this is no greater height than is reached in some 
 other branches, where all the steps of the gradation are taken from 
 the beginning, as, for example, in Mathematics. 
 
 That such studies as are provided for in the series, of which this 
 is the concluding book, should be pursued, to some extent, before 
 arriving at the high school or the academy, is very clear, if you con- 
 sider the fact that the majority of pupils end their education when 
 they pass from the higher classes of the common school. Most of 
 these engage in various arts and trades, and so have to do constantly 
 in the business of their life with the principles that are learned in 
 
V PREFACE. 
 
 these studies. Why, then, should not these principles be taught to 
 them, it is pertinent to ask, if it be the great object of education to 
 prepare one to act well his part in life ? And in the case of those 
 who are not to pursue any art in which the principles of natural 
 science are brought into play, a knowledge of the phenomena that 
 abound around us in air, water, and earth is not only valuable as 
 information, and as a source of enjoyment, but also as a means of 
 mental culture. 
 
 The questions in this and the previous parts I have put at the end 
 of the book, believing that when they are nearer to the text both 
 pupil and teacher are apt to depend on them too much. For this 
 reason also I have the numbers refer to the pages, while in the Index 
 I have the more definite reference to the paragraphs. In the Glos- 
 sary there are no definitions, but references to paragraphs where the 
 explanation of the terms can be found. W. HOOKER. 
 
 January, 1865. 
 
CONTENTS. 
 
 CHAPTER PAGE 
 
 I. MINERAL SUBSTANCES 9 
 
 II. CONSTRUCTION OF MINERALS.. 14 
 
 III. CARBON AND ITS COMPOUNDS 23 
 
 IV. SULPHUR AND ITS COMPOUNDS 33 
 
 V. METALS AND THEIR ORES 39 
 
 VI. OXY-SALTS AND HALOID SALTS 49 
 
 VII. EARTHY MINERALS 56 
 
 VIII. ROCKS 67 
 
 IX. THE EARTH AS IT IS 79 
 
 X. PRESENT CHANGES IN THE EARTH 90 
 
 XI. CONSTRUCTION OF THE EARTH 123 
 
 XII. RECORD OF LIFE IN THE ROCKS 160 
 
 XIII. AZOIC AGE 181 
 
 XIV. AGE OF MOLLUSKS 187 
 
 XV. AGE OF FISHES 201 
 
 XVI. AGE OF COAL 213 
 
 XVII. AGE OF REPTILES 236 
 
 XVIII. AGE OF MAMMALS 261 
 
 XIX. AGE OF MAN 305 
 
 XX. CONCLUDING OBSERVATIONS 314 
 
SITZ 
 
 MINERALOGY AND GEOLOGY, 
 
 CHAPTER I. 
 
 MINERAL SUBSTANCES. 
 
 1. Different Forms of Minerals. As solid substances 
 alone are kept in mineral cabinets, minerals are thought 
 of by most people as being only in the solid form. But 
 there are mineral liquids and gases. Mercury is a liquid 
 mineral. Water is a liquid composed of two mineral 
 gases, oxygen and hydrogen. The atmosphere is a mix- 
 ture of three mineral gases oxygen, nitrogen, and car- 
 bonic acid, and holds always in solution some of a min- 
 eral liquid water. All minerals are, in one sense, solid, 
 for the atoms of which liquids and gases are composed 
 are solid. All matter is undoubtedly, as Newton sup- 
 posed, formed of " solid, massy, hard, impenetrable par- 
 ticles" (Part I., 14). 
 
 2. Relation of Heat to the Forms of Matter. The form 
 which many mineral substances assume is dependent 
 upon the degree of temperature to which they are ex- 
 posed. Thus water appears in the three forms solid, 
 liquid, and gaseous, according to the degree of heat. 
 We ordinarily speak of it as a liquid substance, because 
 under all ordinary circumstances it has this form ; but 
 there are localities, as the tops of some mountains and 
 the extreme polar regions, where its ordinary condition 
 is that of a solid. For the same reason, we speak of 
 metals, with the exception of mercury, as solids ; but 
 there was a time, in ages long gone by, as you will see 
 in the geological part of this book, when these metals 
 
 A 2 
 
10 MINERALOGY. 
 
 were in a liquid state, and, with such a degree of heat as 
 prevailed then, the water must have been in the vapor- 
 ous form. Some of the gases have been reduced to a 
 liquid and even a solid state by the combined influence 
 of cold and pressure, and some have been made liquid 
 by cold alone. 
 
 3. Substances which are Not Mineral. Those sub- 
 stances are not considered mineral which have been pro- 
 duced by living agencies. They are of three kinds: 1. 
 Organized substances, or those which are found in the 
 structures of animals and vegetables. These are called 
 organized because they have organs in them, as sap-ves- 
 sels, blood-vessels, etc. Their mode of growth or in- 
 crease is different from that of minerals, for minerals in- 
 crease by additions wholly upon the outside, while or- 
 ganized substances grow at every point, internally as well 
 as externally, by the circulation in their organs. 2. Sub- 
 stances contained in living organs, being formed by them, 
 as starch, sugar, fats, etc. 3. Substances which come 
 from certain changes in those of the first and second 
 classes, as, for example, alcohol produced from sugar. 
 For a more full exposition of this subject I refer you to 
 Chapter XIX. of Part II. 
 
 4. All Matter Once Mineral. There was a time when 
 there was no life on this earth of ours, and, therefore, all 
 the matter was mineral. This is indicated in the Mosaic 
 account of the creation, for vegetable and animal life 
 were introduced after certain preparations had been 
 made for them ; and what is thus indicated has been de- 
 monstrated to be true by the examination of the rocks 
 by geologists, as you will see hereafter. This lifeless 
 period occupied a long series of ages. All this time no 
 organic substances were formed, for life always presides 
 over their formation, using, indeed, such agencies as heat, 
 light, and chemical action, but directing and controlling 
 them. (Part II., 509.) 
 
 5. Life Introduced by the Creator. When the earth 
 
MINEEAL SUBSTANCES. 11 
 
 was brought to a proper state for the agencies of life, 
 then, and not till then, was life introduced by the Crea- 
 tor upon the stage of action. Then the mineral matter 
 in earth, water, and air began to be acted upon by the 
 new agencies, and there were evolved living forms, veg- 
 etable and animal. And these forms were capable of 
 producing substances which no mere chemical action of 
 the mineral atoms was able to produce during all the 
 long lifeless ages of the world, or during the long ages 
 since. The elements of which starch, sugar, fat, etc., are 
 composed, have been in existence ever since the matter 
 of our world was first created, and they exist now abun- 
 dantly in the air and water ; and yet, though they have 
 always been acting upon each other, never have they 
 been able so to combine as to produce these substances, 
 unless life come in to direct their action. Life is contin- 
 ually evolving new forms and substances from dead min- 
 eral matter, which in the change it endows with proper- 
 ties that it did not before possess. 
 
 6. Decay. In what is termed the decay of animal and 
 vegetable substances, we have the opposite of the proc- 
 esses alluded to in 5. Here we have a return of living 
 substances to the state of dead mineral matter. There 
 is no actual decay that is, no real loss of matter, but 
 merely change in the relations of the atoms which com- 
 pose the substances. Life has let go its control, and the 
 atoms obey the common laws of chemistry. For exam- 
 ple : an egg has life in it, and that life, with the aid of 
 a proper degree of heat, evolves within that prison of 
 chalk a complicated living form a bird ; but let that 
 life in some way be destroyed, and chemical action at 
 once begins its work, returning the matter to the min- 
 eral world by combinations of its atoms in new forms. 
 One of these combinations, for example, is a gas, which 
 is the cause of the peculiarly disagreeable odor of a de- 
 caying egg sulphureted hydrogen, resulting from the 
 union of sulphur with hydrogen gas. 
 
1 2 MINERALOGY. 
 
 7. Mineral Matter in Vegetables and Animals. Or- 
 ganic substances are not wholly destitute of mineral 
 matters, and some have large quantities of such matter 
 in them. There is silica or flint in plants, especially in 
 the grasses ; but this is one of the most extensively dif- 
 fused of minerals, making up most of the sand of the 
 earth, entering largely into the composition of granite 
 and other rocks, and being more or less mingled up with 
 the common earth every where. Then there is carbon- 
 ate of lime, the mineral which constitutes the lime- 
 stones, the chalks, and the marbles, making up the shells 
 of the shell-fish and the skeletons of the coral animals ; 
 and phosphate of lime is the chief constituent of bone. 
 But, in these and all other similar cases, there is mere 
 deposition of mineral matter in interstices in the living 
 organs, and no real change of it into living matter. 
 
 8. Rocks Formed from the Mineral Substances in Ani- 
 mals. Quite a large portion of the rocks in the earth 
 have been formed from the mineral remains of animals. 
 It is supposed by some geologists that this is true of all 
 which are composed of carbonate of lime. It is at least 
 extensively true of them, as we know by the remains of 
 shells and corals found in. them. Much, if not all, the 
 marble in the world was once a conglomerate of such 
 remains, and was crystallized into its beautiful granular 
 condition chiefly by the agency of heat. So, also, some 
 flinty rocks are formed from the silica of the shields or 
 skeletons of animals and vegetables, for the most part 
 exceedingly minute in size. It is thus that these liv- 
 ing forms gather from the water in which they live ma- 
 terial for their structure, which, when they die, is laid 
 down to be consolidated into rock. This interesting 
 subject, barely touched here, will be fully treated of here- 
 after. 
 
 9. Minerals Simple and Compound. Some minerals 
 are found in nature in their simple elementary state 
 alone, while others are found only in combination with 
 
MINERAL SUBSTANCES. 13 
 
 other elements, and others still are found in both condi- 
 tions. I will give some examples of each. Some of the 
 noble metals (so called), as gold and platinum, are never 
 found combined with any other element. On the other 
 hand, the metals potassium, sodium, calcium, magnesium, 
 aluminum, and ammonium are never found uncombined. 
 Silver, copper, and mercury are among the examples of 
 metals that are found in their simple state, or, as it is 
 commonly expressed, found native, and also combined 
 with other elements, as sulphur, oxygen, etc., in the form 
 of ores. While oxygen is, in its simple state, in the mix- 
 ture which we call air, it also appears in combination 
 with almost all the elements, and forms from one third 
 to one half of the crust of the earth. Hydrogen, which 
 is so abundant as one of the elements of water, is never 
 found uncombined. The same may be said of chlorine, 
 one of the elements of common salt. Sulphur and car- 
 bon are both found native as well as combined, but phos- 
 phorus is always in combination. 
 
 10. Minerals that Contain Many Elements. There is 
 very great difference in degree in the compound char- 
 acter of the minerals found in mineralogical cabinets. 
 While there are many of those compounds which were 
 brought to your notice in Part II. oxyds, sulphurets, 
 salts, etc. there are also many which are much more 
 compound than these. The only approach made to such 
 complex compounds by the processes of chemistry is in 
 the double salts, such as alum, and the tartrate of anti- 
 mony and potash. As examples, I mention mica, called 
 isinglass by the common people, which is composed of 
 silica, alumina, oxyd of iron, fluoric acid, and water ; and 
 that splendid mineral, so much used for making costly 
 vases and other ornamental articles, lapis-lazuli, which is 
 composed of silica, alumina, soda, lime, iron, sulphuric 
 acid, sulphur, chlorine, and water. 
 
 11. Mixtures of Compounds in the Rocks. In many 
 of the rocks there are mixtures of the mineral compounds. 
 
14 MINERALOGY. 
 
 Granite is in contrast with marble in this respect. While 
 the latter is composed of one compound mineral, the 
 carbonate of lime, the former has mingled together in a 
 confused manner three compounds mica, feldspar, and 
 quartz. The eye can generally distinguish readily the 
 three kinds of crystals imperfectly formed. A full con- 
 sideration of the composition of the rocks will claim our 
 attention in another chapter. 
 
 12. Mineralogy, Geology, and Chemistry. While Min- 
 eralogy has an intimate relation with Chemistry, it dif- 
 fers from it. It gets from Chemistry the composition of 
 the various minerals of which it treats, but it has noth- 
 ing to do, as Chemistry has, with what can be made out 
 of these substances, or what can be extracted from them. 
 It treats of substances simply as they are found in na- 
 ture, without regard to any action that might be induced 
 by mingling them together. Mineralogy is preparatory 
 to Geology, because it gives us a knowledge of the min- 
 eral substances which make up the rocks. The three 
 sciences are thus, as you see, linked together, and the 
 proper order for their study is that which I have adopted. 
 
 CHAPTER II. 
 
 CONSTRUCTION OF MINERALS. 
 
 13. Crystallization. When a mineral substance takes 
 on a solid form, the atoms or particles are disposed to an 
 arrangement which is termed crystallization. It is a 
 very definite and exact arrangement, with straight lines, 
 perfect angles, and plane, smooth faces. Crystals of 
 quartz, commonly called rock crystal, are familiar exam- 
 ples. Mica is another of quite a different kind, the crys- 
 tals being foliated that is, in leaves. When the proc- 
 ess of forming the crystal is not interfered with by any 
 circumstance, as, for example, agitation, all parts of it 
 
CONSTRUCTION OF MINERALS. 
 
 15 
 
 are perfect. The crystal of alum, for in- 
 stance, is a perfect double pyramid, the 
 shape being given in Fig. 1, which is an 
 octahedron that is, a body with eight 
 equilateral angles, the lines all being ex- 
 actly equal, and the spaces also. The name 
 Fig. i. j s f rom two Greek words, octo, eight, and 
 hedra, base. In Fig. 2 you have the crystals of alum as 
 
 Fig. 2. 
 
 they appear when their formation is interfered with by 
 some disturbing cause. In the glistening white marble 
 the crystals are so crowded together as they form that 
 none of them are perfect. The same is true of the crys- 
 tals of quartz, mica, and feldspar in granite. 
 
 14. Crystals of Different Sizes. As crystals increase 
 by additions upon the outside, the crystals of any sub- 
 stance may vary greatly in size. Quartz crystals are 
 sometimes very large. There is one at Milan which is 
 3^ feet long, 5-J in circumference, and weighs 870 pounds. 
 Of course, the larger crystals of any substance will have 
 precisely the same shape with the smaller. 
 
16 MINERALOGY. 
 
 15. Crystallization and Vital Growth Contrasted. 
 While crystallization adds to the outside alone, in living- 
 growth there is addition made to every part of the sub- 
 stance. The additions in the case of the crystal are in- 
 variably the same, and all parts of it are alike ; but a 
 living growth, whether vegetable or animal, commonly 
 differs much in its different parts. A finger and a quartz 
 crystal, for example, differ widely in this respect. Far- 
 ther: while crystallization tends to straight lines and 
 exact angles, the growth of animal and vegetable sub- 
 stances tends to curved lines, and its angles, when it 
 makes any, are not sharply defined. The branches of 
 trees are more or less rounded, and, while they have a 
 general angulai 1 arrangement with the trunk of the tree, 
 the angles are not definite. 
 
 16. Exceptions. While what I have said of crystalli- 
 zation is generally true, there are some exceptions. The 
 
 faces of diamonds are commonly con- 
 vex instead of plane, and the edges 
 are therefore curved. In Fig. 3 you 
 have the usual form of spathic iron 
 (carbonate of iron) and* pearl spar 
 (magnesian carbonate of lime). There 
 is sometimes seen in limestone, in 
 clay-stones, and in some other rocks, 
 a disposition to gather in spherical forms, and the proc- 
 ess is at least akin to crystallization. The arrangements 
 of crystals are very often in beautiful and varied imita- 
 tion of branches, leaves, and flowers. This is very fa- 
 miliar to us in the frostings on our windows. This is 
 seen in other minerals, as in alabaster in the Mammoth 
 Cave of Kentucky, where leaves, vines, and flowers are 
 imitated, some of the " rosettes" being, as stated by Pro- 
 fessor Dana, a foot in diameter. In all such cases the 
 curvings are in the arrangements of the crystals, each in- 
 dividual crystal probably being in its usual form. 
 
 17. Mineral Matter in Living Substances. This sub- 
 
.3ITT 
 
 CONSTRUCTION 
 
 ject has been already spoken of in 7. 1 introduce it 
 again here to notice the fact that the mineral matter is 
 never deposited in living substances in any thing like a 
 crystalline form. Though there is much silica (quartz) 
 in the rushes, there are no quartz crystals ; and the phos- 
 phate of lime in bones, though its particles are deposited 
 after a certain definite plan (as seen in Fig. 84 in my 
 "Human Physiology"), exhibits no resemblance to the 
 crystals of this mineral. 
 
 18. Crystallization not Confined to Minerals. Though 
 organized substances, vegetable or animal, never take on 
 a crystalline form, yet some of the products contained 
 within them may do so. JThis is the case with the sugar 
 of the sugar-cane and other plants. The " candying" 
 
 of raisins is an example of the crystalli- 
 zation of sugar. The crystals which 
 sugar is disposed to form are of the 
 shape seen in I?ig. 4, a six-sided prism, 
 as you may observe in what is called 
 rig. 4. rock-candy. In the form of loaf sugar 
 
 the crystals are huddled together, and are therefore im- 
 perfect, just as in the case of marble. Many of the veg- 
 etable alkaloids, morphine, caffein, etc. ( 590, Part II.), 
 are obtained in the crystalline form. In all these cases 
 the crystals are never formed so long as the substance 
 remains under the influence of the living agency. Sug- 
 ar, for example, never crystallizes in the living plant, but 
 only after it is taken from it. 
 
 19. Modes of Crystallization. There are various modes 
 in which crystallization occurs. 1. One of the most com- 
 mon modes is by deposit from a solution. Thus alum, 
 salt, sugar, etc., may form crystals from a solution, the 
 water passing off by evaporation. When the substance 
 can be dissolved in larger amount by hot water than by 
 cold, as is the casje with alum, but not with salt, consid- 
 erable crystallization can be obtained before evaporation 
 begins by introducing into hot water as much of the 
 
18 MINERALOGY. 
 
 substance as it can take up, and then allowing the solu- 
 tion to cool. The formation of frost is really crystalliza- 
 tion by deposition from a solution, for the water depos- 
 ited in solid form was dissolved in the air ( 96, Part 
 II.). Warm air will hold more water in solution than 
 cold, and, therefore, when warm air becomes cooled, it 
 deposits some of its water in the shape of dew when the 
 cold is moderate, and in the solid form when it is severe. 
 2. A liquid or a gas may be converted into a solid with 
 a crystalline arrangement. Various examples of this 
 are familiar to you, as the formation of ice from water, 
 the freezing of mercury, and the solidification of melted 
 metals on cooling. The mosfc common example which 
 we have of the conversion of a gas or vapor into a crys- 
 talline solid is in the formation of frost from the vapor 
 of water in the air. 3. A mineral substance which is 
 not crystallized may become so by heat, and perhaps 
 some other agencies acting in connection with this. 
 Many rocks, as you will see illustrated in another part 
 of this book, owe their crystalline character to this cause. 
 It is in this way that marble has been made out of com- 
 mon chalk or limestone, it differing from them not in 
 chemical composition, but merely in being crystalline. 
 
 20. Water of Crystallization. The crystals of many 
 minerals have water incorporated with them, and, as its 
 presence is essential to their crystalline condition, it is 
 termed their water of crystallization. For a more full 
 statement in regard to this, I refer you to 164, Part II. 
 
 21. Amorphous and Dimorphous Minerals. A mineral 
 is said to be amorphous when it is destitute of all trace 
 of crystalline form. The term comes from two Greek 
 words, a, without, and morphe, form. When a mineral 
 appears in crystals of two forms, sometimes the one and 
 sometimes the other, it is said to be dimorphous, the first 
 part of the term coming from the Greek word dis, twice. 
 
 22. Arrangements of Crystals. Crystals forming in 
 groups are arranged variously by the influence of cir- 
 
CONSTRUCTION OF MINERALS. 
 
 19 
 
 cumstances. This is exemplified in the huddling togeth- 
 er of imperfectly formed crystals in 
 marble, loaf sugar, etc., and in the 
 extremely varied forms of frost-work 
 and other similar crystallizations ( 
 16). Some crystals are arranged in 
 the form of a cross, as seen in Fig. 5. 
 Sometimes two similar crystals are 
 united together, and then we are said 
 to have a twin crystal. The crys- 
 
 Fig. 5. 
 
 
 tals of common salt are apt to as- 
 
 sume the hopper arrangement rep- 
 
 resented in Fig. 6. This is because 
 
 that, as the evaporation takes place, 
 
 the gravity of the salt makes the 
 
 mass sink constantly a little below 
 
 the surface, and each set of crystals 
 
 is deposited on the upper and outer edge of the preced- 
 
 ing set. 
 
 23. Regularity of Form in Rocks. We have some- 
 thing akin to crystallization in a rude way in the gen- 
 eral lines and faces of rocks. We have the laminated 
 arrangement in the slate rocks, and the magnificent co- 
 lumnar arrangement in the trap rocks, as exemplified in 
 the Giant's Causeway. Then there are joints, so called, 
 running across strata or layers of rock, and dividing 
 them sometimes as evenly as if it were done with a 
 knife. All this will be fully illustrated in the geological 
 portion of this book. 
 
 24. Cleavage. Some minerals can have layers chip- 
 ped or cleaved off, leaving as smooth surfaces as before. 
 Mica is a very familiar example of cleavage from planes. 
 
 Sometimes the cleavage can 
 be made from angles, as 
 seen in Fig. V, and some- 
 times from edges, as seen in 
 Fig. 8. The planes made 
 Fig. i. Fig.s. by cleaving a crystal are 
 
20 
 
 MINERALOGY. 
 
 called its cleavage planes. Minerals sometimes cleave 
 in only one direction, as common mica and foliated gyp- 
 sum, and sometimes in two, three, or four directions. 
 In many minerals it is difficult to effect cleavage ; in 
 some, as quartz, it is impossible, though even in this case 
 it has been done by heating the crystal, and then plung- 
 ing it into cold water. 
 
 25. Primary Forms. While there is vast variety in 
 the forms of crystals as found in nature, mineralogists 
 have discovered by cleavage that the primary or funda- 
 mental forms are few in number. There are only thir- 
 teen of these forms, which are the solids that have been 
 obtained from the various minerals by cleavage. These 
 are divided into six classes, each class containing those 
 which can be produced by cleavage from each other. 
 The first contains the three solids represented in Figs. 9, 
 
 Fig. 9. Fig. 10. Fig. 11. 
 
 10, and 11, the cube having four equal square sides, the 
 octahedron having for sides eight equilateral triangles, 
 and the rhombic dodecahedron, whose twelve sides are 
 equal rhombic planes.* I will show by figures how the 
 
 * The name dodecahedron is from the Greek words dodeka, twelve, 
 and hedra, base. A rhombic plane, or rhomb, is a plane with four 
 equal sides, those which are opposite being parallel, and the angles 
 being unequal, two of them being acute and two obtuse. It differs 
 from a square in being oblique-angled instead of right-angled. You 
 
 see the difference in the two fig- 
 ures. The angles of the square 
 are all equal, but in the rhomb a 
 and its opposite angle are equal, 
 being obtuse, and b and its oppo- 
 site angle are equal, being acute. 
 
CONSTRUCTION OF MINERALS. 
 
 21 
 
 cube and the octahedron can be converted into each oth- 
 er by cleavage. If the cube have its angles cleaved as 
 indicated by the dotted lines in Fig. 12, you have as a 
 
 Fig. 1-2. 
 
 Fig. 13. 
 
 Fig. 14. 
 
 result the body represented by Fig. 13. If you continue 
 the process, you will at length obtain the solid represent- 
 ed in the middle of Fig. 14 that is, the octahedron. If, 
 on the other hand, you take an octahe- 
 dron, and cleave it as represented in Fig. 
 1 5, you will at length obtain the cube as 
 indicated. These processes, and other 
 similar ones in regard to other forms, 
 may be gone through with very satisfac- 
 torily with raw potatoes and a common 
 knife. 
 
 26. Secondary Forms. If with a knife you make such 
 cleavages as are represented in Fig. 8, you produce a 
 secondary form. Now, in nature, this result is not pro- 
 duced by cleavage, but by an omission to fill out the 
 whole figure, the omission falling short in various de- 
 grees in different cases. The omission may occur on the 
 angles instead of the edges, as seen in Fig. 7. 
 
 Instead of omission there may be addi- 
 tion, as represented in Fig. 16. Here, by 
 an addition in the shape of a low pyramid 
 to each side of a cube, the dodecahedron is 
 produced. The addition on one of the faces 
 of the cube is shaded to make it obvious. 
 The increase is by layer upon layer of particles, each 
 layer having a less number of particles than the pre- 
 ceding one. This is indicated, in a coarse way, by 
 
 Fig. 16. 
 
22 MINERALOGY. 
 
 Fig. 1 7, the particles or molecules being 
 in reality so minute that no inequality 
 is perceptible to the eye on the surface 
 of the crystal. 
 
 27. Constancy in the Forms of Crys- 
 tals. Notwithstanding the immense 
 Fig. 17. variety in the secondary forms of crys- 
 
 tals, there is, in the case of each mineral, a strict adher- 
 ence to its own form or forms in all essential character- 
 istics. The size and number of faces may differ in dif- 
 ferent specimens so much as to give them an entirely 
 different appearance, but the mineralogist will discover 
 their relation to each other by observing that the corre- 
 sponding angles are exactly the same, and by cleavage 
 he will find the same fundamental form. " Crystals are, 
 therefore," says Professor Dana, "the perfect individuals 
 of the mineral kingdom. The mineral quartz has a spe- 
 cific form and structure, as much as a dog or an elm, 
 and is as distinct and unvarying as regards essential char- 
 acters, although, owing to counteracting causes during 
 formation, these forms are not always assumed. In 
 whatever part of the world crystals of quartz may be 
 obtained, they are fundamentally identical." 
 
 28. Symmetry. In all the modifications of crystals 
 seen in the production of secondary forms there is a 
 wonderful symmetry. If one part is modified, all the 
 corresponding parts are modified, and in the same way, 
 either over the whole crystal or over just one half of it. 
 Thus, if we find a plane in place of an edge, we shall find 
 the other edges also replaced by planes of precisely the 
 same width, as seen in Fig. 8 ; and so of the angles 
 also, as represented in Fig. 7. So, if there be two planes 
 in place of any edge or angle, there will be found the 
 same planes replacing the other edges or angles ; and 
 the same is true if there be many replacing planes, as 
 there often are. You see how this secures a regularity 
 pleasing to the eye in the midst of extreme variety, thus 
 
CAEBON AND ITS COMPOUNDS. 23 
 
 adding largely to the beauty of the mineral world. Ob- 
 serve that there is here some analogy to the symmetry 
 that appears in living forms. The two halves of a face, 
 for example, are generally exactly alike, just as are the 
 corresponding parts of a crystal. What the agency is 
 that produces the result is in both cases a wonderful 
 mystery. All that we know is that in the one case the 
 deposition of matter is guided unerringly by a living 
 agency, and in the other by one that is not living. 
 
 CHAPTER III. 
 
 CAEBON AND ITS COMPOUNDS. 
 
 I PEOCEED now to treat of different kinds of minerals, 
 grouping them according to their natural affinities. 
 
 29. Diffusion of Carbon. As carbon is one of the four 
 grand elements in the composition of vegetable and ani- 
 mal substances, there is a constant interchange in regard 
 to it between the vegetable, animal, and mineral worlds, 
 and therefore it is widely diffused, and appears in vari- 
 ous combinations. Combined with oxygen, it exists ev- 
 ery where in the atmosphere in the form of carbonic 
 acid, which is one of the gases that are more or less min- 
 gled or dissolved in the water of the earth. The car- 
 bonates are important salts, the most important being 
 the carbonate of lime, which appears in the various forms 
 of chalk, limestone, and marble, and in the animal world 
 makes the hard covering of shell-fishes and the skeletons 
 of the coral animals. The immense stores of coal laid 
 up in the bowels of the earth is almost wholly carbon. 
 
 30. The Diamond. In strong contrast with the im- 
 mense provision of carbon in the form of coal, this ele- 
 ment is laid up here and there in very small quantities, 
 equally for the use of man, in the most costly and splen- 
 did of gems. That the diamond is pure carbon is proved 
 
24 MINERALOGY. 
 
 by burning it in oxygen gas, the product being carbonic 
 acid gas, a compound of carbon and oxygen, just as in 
 the burning of charcoal. As in pure charcoal and an- 
 thracite we have carbon alone, the diamond differs from 
 them merely in the arrangement of the atoms. It is this 
 alone that causes the immense difference in characteris- 
 tics. When the diamond is colored, as it sometimes is, 
 there is coloring matter intimately mingled with the car- 
 bon, as glass is colored with something added to it. But 
 the quantity of coloring matter is so exceedingly minute 
 that it could not be detected unless a considerable amount 
 of diamond were burned, an experiment so expensive that 
 I presume that it never has been tried. 
 
 31. Qualities of the Diamond. It is the hardest of all 
 substances. Its lustre is peculiar ; and other gems that 
 are similar to it in this respect are said to have an ada- 
 mantine lustre. Its reflection of light is exceedingly 
 brilliant. It is commonly colorless, but sometimes red, 
 yellowish, orange, green, or black. The rose diamond is 
 highly valued for the beauty of its color, and so also is 
 the green diamond. The black diamond is very rare, 
 and therefore commands a high price, although it has no 
 beauty. 
 
 32. Size of Diamonds. In speaking of the size of dia- 
 monds the term carat is used. This is the name of a 
 bean, which was used in its dried state by the natives of 
 Africa in weighing gold, and in India in weighing dia- 
 monds. Though the bean is not used for this purpose 
 now, the name is retained, and the carat is nearly four 
 grains Troy. The largest diamond known is in the pos- 
 session of the Great Mogul. It weighed originally 900 
 carats, or 2769 grains, but it was reduced by cutting to 
 861 grains. It is of the size of half a hen's egg, and is in 
 that form. The Pitt or Regent diamond weighs 419 
 grains. The famous Koh-i-noor weighed originally 186 
 carats, but was reduced by recutting one third. 
 
 33. Cost of Diamonds. The cost of diamonds depends 
 
CARBON AND ITS COMPOUNDS. 25 
 
 upon the weight, the purity, and the color. A diamond 
 which, after being cut, weighs one carat, is worth com- 
 monly 8. The price increases largely with the size, for 
 one weighing four carats would be worth 128, and one 
 often carats would be 800. When we get Tip to twenty 
 carats the prices rise much more rapidly. The Regent 
 diamond is estimated at 125,000. 
 
 34. Cutting of Diamonds. The art of cutting and pol- 
 ishing diamonds was unknown till 1456, when it was dis- 
 covered by Louis Berquen, of Bruges. The process is 
 thus described by Professor Dana. " The diamond is cut 
 by taking advantage of its cleavage, and also by abrasion 
 with its own powder, and by friction with another dia- 
 mond. The flaws are first removed by cleaving it, or 
 else by sawing it with an iron wire, which is covered 
 with diamond powder a tedious process, as the wire is 
 generally cut through after drawing it across five or six 
 times. After the portion containing flaws has thus been 
 cut off, the crystal is fixed to the end of a stick, in a 
 strong cement, leaving the part projecting which is to be 
 cut; and another being prepared in the same manner, 
 the two are rubbed together till a facet is produced. By 
 changing the position, other facets are added in succes- 
 sion till the required form is obtained. A circular plate 
 of soft iron is then charged with the powder produced 
 by the abrasion, and this, by its revolution, finally polish- 
 es the stone. To complete a single facet often requires 
 several hours." The expense of cutting the Regent dia- 
 mond was estimated at 5000 sterling, and the mere fil- 
 ings at 7000 sterling. 
 
 35. Uses of the Diamond. The most familiar use of 
 the diamond is cutting glass. It is also used for lenses 
 in microscopes. Diamonds that can not be worked are 
 sold under the name of bort^ for various uses. Splinters 
 of bort are made into fine drills for drilling artificial 
 teeth and gems of various kinds. 
 
 36. Localities of Diamonds. Diamonds are found in 
 
 B 
 
26 MINERALOGY. 
 
 various parts of India and of Brazil, in Africa, in the isl- 
 and of Borneo, and in the Urals of Russia. The original 
 rock of the diamond appears to be a quartz rock; but the 
 diamonds are almost always obtained from amid the 
 sands and $e*bbles which have come from the rocks, and 
 are scattered in the rivers and brooks. In Brazil, collec- 
 tions are made of these sands and pebbles, and by wash- 
 ing them in a series of boxes the diamonds are discovered 
 and gathered. If a negro be so fortunate as to find a 
 diamond weighing 1 7 \ carats, he gains a boon which is 
 above the price of gems the boon of liberty. 
 
 37. Graphite. Graphite, or Plumbago, commonly call- 
 ed black lead, although there is not a particle of lead in 
 it, is composed of carbon, with a small proportion of iron, 
 commonly to the amount of from 4 to 10 per cent. Some 
 have supposed it to be a carburet of iron ; but it is not a 
 chemical compound. It is only a mixture of the carbon 
 and iron, and that the iron is not essential is shown by 
 the fact that in some cases there is scarcely a trace of it. 
 Graphite is soft, and has a shining lustre. It is some- 
 times compact, and sometimes crystalline, usually in the 
 foliated form, but occasionally in six-sided prisms. It is 
 used in making lead-pencils, in lessening the friction of 
 machinery, in giving a gloss to stoves, etc. Commonly, 
 in preparing graphite for pencils, the solid mineral is cut 
 up into pieces of the requisite size ; but a method has of 
 late been adopted by which the mineral is finely pow- 
 dered, and then, by great pressure, made into solid sheets, 
 from which the pieces are obtained. 
 
 38. Coal. The varieties of coal are divided into two 
 classes, the bituminous and the non-bituminous. The 
 former have, in addition to the carbon, hydrogen, which 
 in the combination produces carbureted hydrogen, or 
 common illuminating gas, and it is the burning of this, 
 that is, its union with the oxygen gas of the air, that 
 causes the flame. In the non-bituminous, the anthracite, 
 on the other hand, we have only the blue flame in the 
 
CARBON AND ITS COMPOUNDS. 27 
 
 beginning of its combustion, which comes from the car- 
 bonic oxyd gas as it unites with the oxygen of the air to 
 form carbonic acid. The formation of this gas in the an- 
 thracite fire is fully explained in 67, Part II. It is from 
 the bituminous coal that the illuminating gSfcs produced, 
 there being no hydrogen in the anthracite for its forma- 
 tion. The explanation of the process is this: By the ap- 
 plication of heat the hydrogen is driven off, and it takes 
 with it enough of the carbon to make it carbureted hy- 
 drogen ; but most of the carbon is left behind in a light, 
 porous condition, to which is given the name of coke. 
 
 39. Anthracite. This is the common name given to 
 coal which is either mostly or wholly free from bitumen. 
 It is supposed that it was subjected to more heat than 
 the bituminous was after its formation, by which the bi- 
 tuminous elements were driven off. The coke, which is 
 left after the making of illuminating gas, is very much 
 the same thing as anthracite, except that, as it has not 
 been subjected to great pressure, it has not the same 
 closeness of structure. Anthracite is hard, and so is often 
 called very appropriately stone coal. From 80 to 90 per 
 cent, of it is carbon. Then there is from 4 to 7 per cent, 
 of water, and there are some impurities, as silica, alumi- 
 na, lime, magnesia, etc. The redness of the ash of some 
 kinds of coal comes from the presence of oxyd of iron. 
 The slag^ or glassy substance which you find in the refuse 
 of the combustion, is composed of silicates. These do 
 not form with the ordinary burning of coal in grates, be- 
 cause the heat is not intense enough. The clinker which 
 collects on the inside of stoves is slag. The reason that 
 oyster-shells put into the fire clear off the clinker is that 
 the lime makes the silicates more fusible, and so dislodges 
 the clinker, mingling it with the burning coal. Anthra- 
 cite has a fine lustre, and often an iridescent play of col- 
 ors. It is capable of a high polish, and has sometimes 
 been made into inkstands and other articles. 
 
 40. Bituminous Coal. This is softer than anthracite, 
 
28 
 
 MINERALOGY. 
 
 and has less lustre. Its chief varieties are the pitching 
 or caking coal, which in burning is apt to cake or unite 
 into solid masses, and the cannel coal, which burns with 
 so clear a flame that it has sometimes been used as can- 
 dles. Inkstslros, boxes, etc., are made from it. The min- 
 eral called jet, so much used in jewelry, is allied to can- 
 nel coal, but has a much deeper color, and is capable of 
 a brilliant polish. Brown coal, or lignite, is not so per- 
 fectly formed coal as the other varieties, and the struc- 
 ture of the original wood is often apparent in it. 
 
 41. Coal of Vegetable Origin. That coal is made from 
 plants might be properly inferred from the remains and 
 impressions of the plants found in the layers of rocks be- 
 tween which the coal is packed, and sometimes found 
 even in the coal itself. But the proof is more positive 
 than this. Vegetable structure is found in the coal by 
 microscopical examination. A piece of anthracite coal 
 which has been partially burnt is used, because the vege- 
 table cells, being somewhat silicious, remain unaltered 
 
 in the burning out 
 O f a p 0r tion of the 
 carbon. In Fig. 1 8, 
 , we have repre- 
 sented a small bit 
 of such a piece of 
 anthracite as seen 
 through the micro- 
 scope. The ducts 
 lie side by side, as 
 they did ages ago 
 in the woody fibre 
 of the plant. In b 
 two of the ducts are 
 very highly magnified, the white spaces showing us the 
 silica, and the black lines the carbon which was not 
 burned out. The evidence from such an examination is 
 not as clear in soft bituminous coal, because the original 
 texture is not so well preserved. 
 
 Fig. 18. 
 
CARBON AND ITS COMPOUNDS. 29 
 
 42. Why Coal is called a Mineral. Coal being thus of 
 vegetable origin, and retaining the evidences of this in 
 its very texture, it might at first thought appear that it 
 could hardly be called a mineral. The reason that it is 
 proper to call it so I will point out. Thenoarbon, which 
 is the chief component of all kinds of coal almost the 
 only component of one kind, the anthracite does not ex- 
 ist in the vegetable as carbon, but, chemically united with 
 oxygen and hydrogen, it forms woody fibre. It is just 
 as sulphur does not exist as sulphur in sulphate of lime 
 (gypsum), but as a part of a compound united chemical- 
 ly in it with oxygen and lime, as carbon in wood is united 
 chemically with oxygen and hydrogen. Now when wood 
 is made to produce coal a chemical change occurs, a real 
 decomposition is effected, so that carbon now appears in 
 its uncombined state. The form, indeed, of woody fibre 
 may remain, but it is no longer wood the compound of 
 carbon, oxygen, and hydrogen. These elements are sep- 
 arated from each other; and if they are combined, as may 
 be the case in bituminous coal, it is a recombination after 
 separation. A farther chemical change or decomposition 
 is produced when the coal is burned, all the carbon then 
 passing off by forming carbonic acid gas with the oxy- 
 gen of the air. The first process is as strictly and fully a 
 chemical change as the last, and it is by chemical changes 
 that minerals are produced. We have here a clear case 
 of the passage of an organized substance under the con- 
 trol of living agencies over into the mineral kingdom, 
 where chemical laws bear sway. 
 
 43. Peat. In peat we have an example of imperfect 
 formation of coal, the approach to the completion of the 
 process being different in different cases. It accumulates 
 in sivampy places, mostly from the growth of mosses of 
 one genus, Sphagnum. The roots continually die below 
 as the plant grows upward ; and as these roots, by the 
 partial decomposition under water, change into peat, a 
 bed of great thickness may after a time be formed. 
 
30 MINERALOGY. 
 
 There is sometimes a depth of forty feet in a peat-bed. 
 The beds in some countries are very extensive. They 
 cover one tenth of Ireland, and one of them is fifty miles 
 long and two or three in breadth. It is estimated that 
 the amount -of peat in Massachusetts is 120 millions of 
 cords. 
 
 44. Diffusion of Coal in the Earth. The stores of coal 
 in the earth are immense. The provision which has been 
 made by the Creator in this respect for the wants of man, 
 and the means which have been adopted for bringing the 
 coal within his reach, are among the highest evidences 
 of far-reaching design and system in the construction of 
 the earth. This point, barely alluded to here, will be 
 fully developed in another part of this book. 
 
 45. Amber. This is a resin from some tree which has 
 been chemically changed, or mineralized, as it is express- 
 ed. It is found in lumps of various sizes, from small bits 
 up to even the size of a man's head. It is commonly of 
 a yellowish color, has considerable lustre, and is suscep- 
 tible of a polish. It is appropriated to ornamental pur- 
 poses, but it is not highly prized in this respect, as it is 
 soft, yielding readily to the knife, and, besides, can be 
 easily counterfeited. It is used in making a superior 
 transparent varnish. There are sometimes seen in speci- 
 mens of amber insects and parts of insects, which became 
 enveloped in the resin in its semi-liquid state. Such spec- 
 imens are highly prized, because it is supposed these in- 
 sects lived ages before the creation of man. Imitations, 
 therefore, have sometimes been made, and have been 
 palmed off upon those who are not able to distinguish 
 insects of those early ages from the insects of the pres- 
 ent day,* Amber becomes electric when it is rubbed, 
 
 
 
 * In the geological part of this book you will learn that both the 
 animals and plants of the early ages of the earth differed, in some re- 
 spects, from those which exist at the present time. The imposture 
 referred to reminds me of one which was once detected in the court- 
 room when a will case was on trial. The will, on being held up to 
 
5IT7J 
 
 CARBON AND ITS 
 
 and therefore its Greek name electron gave rise to the 
 term electricity. 
 
 46. Bitumen. There are various kinds of bitumen, 
 some solid and some fluid. They are supposed to be 
 produced from vegetable matters buried in the earth ; 
 and as they are commonly found in the neighborhood of 
 active or extinct volcanoes, it is inferred that they have 
 been driven to the surface by the internal heat of the 
 earth. I w^ll notice some of the varieties. Asphaltum, 
 or mineral pitch, is solid. It was the chief ingredient 
 in the cement used in building the walls of Babylon and 
 of the Temple in Jerusalem. It has lately been success- 
 fully employed in forming a composition for paving 
 streets, and a cement for covering roofs. It is very 
 abundant on the shores of the Dead Sea, which is called 
 Asphaltites for this reason. The most remarkable local- 
 ity of it is the Pitch Lake in the island of Trinidad. It 
 is about a mile and a half in circumference, and while 
 the asphaltum is near the shores sufficiently hard at most 
 seasons to sustain men and quadrupeds, it grows soft and 
 warm as you go toward the centre, and there it is in a 
 boiling state. Petroleum is a dark fluid, which becomes 
 solid on exposure to the air. This is so abundant in the 
 Burmese Empire that it is used as lamp-oil, and as fuel, 
 by being mixed with ashes or earth. The most power- 
 ful springs of it there are on the Irawady. In one local- 
 ity there are 520 wells, yielding annually 400,000 hogs- 
 heads. There are many localities of petroleum in this 
 country. It was formerly collected and sold by the In- 
 dians ; and, as the Senecas were prominent in the trade, 
 
 the light, was found to have been written on paper which, by its wa- 
 ter-mark, was shown to have been manufactured subsequent to the 
 date of the document. So, in these imitations of amber, the date 
 fixed by the recent character of the insects shows, to the practiced eye 
 of one who understands the distinctions between insects of the present 
 age and those of ages previous to the creation of man, that the speci- 
 mens are not real amber. 
 
32 MINERALOGY. 
 
 it acquired the name of Seneca oil, which it still retains. 
 Naphtha is a light, limpid fluid of a yellowish color, and 
 is a purer article than petroleum, from which it can be 
 obtained by distillation. It is a hydrocarbon ; that is, 
 it is composed of hydrogen and carbon. As there is no 
 oxygen in its composition, it is used, as you learned in 
 Part II., by the chemist to preserve potassium and so- 
 dium in their metallic state. 
 
 47. Carbonic Acid. The qualities of thjs gas you 
 learned in Part II., Chap. III. It is constantly furnished 
 to the air from the respiration of animals, from fires, and 
 from the decomposition of vegetable and animal matters. 
 As it is constantly absorbed by the leaves of plants, its 
 undue accumulation in the atmosphere is prevented. 
 There are localities where this gas is produced in the 
 earth in large quantities. In some mineral springs, as at 
 Saratoga, it gives briskness and a slight pungent taste to 
 the waters. This large production of it appears in the 
 neighborhood of some volcanoes. A cavern near Na- 
 ples, the Grotto del Cane, has a world-wide reputation on 
 account of the abundance of this gas in it, which fills the 
 cavern up to the level of the lower margin of its en- 
 trance. This gas has a great agency in relation to one 
 of the most important and extensive of the rocks of the 
 earth, the limestone, which is a combination of this gas 
 with lime. The carbonate of lime of the rocks is contin- 
 ually being dissolved in the water that comes in contact 
 with them ; and then the shell-fish and the coral animals 
 appropriate this to make their shells and skeletons, which 
 eventually become, as you have seen ( 8), limestone 
 rock, thus returning the carbonate of lime to the source 
 from which it came. Now it is the carbonic acid in the 
 water which enables it to dissolve sufficient of the lime- 
 stone to supply the shell-fish and the corals with this ma- 
 terial. For a full elucidation of this interesting point I 
 refer you to Part II., 306. 
 
 48. Carbureted Hydrogen. This, which is the common 
 
SULPHUR AND ITS COMPOUNDS. 
 
 33 
 
 illuminating gas, produced from bituminous coal artifi- 
 cially, is produced naturally in many localities, and prob- 
 ably comes from the action of heat upon bituminous 
 coal, or some other substance of a kindred character. In 
 the village of Fredonia, New York, near Lake Erie, this 
 gas issues so abundantly from a slate rock that it is col- 
 lected, and is used by the inhabitants for lighting the 
 place. 
 
 CHAPTER IV. 
 
 SULPHUR AND ITS COMPOUNDS. 
 
 49. Native Sulphur. This substance is of a 
 pale yellow color. It is found both crystallized 
 and uncrystallized. Its crystallized 
 form is an octahedron, as seen in Fig. -- N 
 1 9. When sulphur is melted, and then 
 left to crystallize, the crystal takes the 
 form seen in Fig. 20, which is very dif- 
 Fi g . w. f eren t from the forms which are as- 
 sumed in nature. Sulphur is often found in fis- 
 sures and cavities in lava. The most important 
 locality of sulphur is Sicily. Sixteen or seven- 
 teen thousand tons are imported annually into 
 England from Sicily, to say nothing of the sup- 
 ply to other countries. Much of the sulphur 
 of commerce is obtained from the sulphurets of iron and 
 copper. The sulphur is driven off from these ores by 
 heat, and is collected in brick chambers. It is one of the 
 ingredients of gunpowder, and is used in bleaching and 
 in the manufacture of sulphuric acid, as described in 
 249, Part II. 
 
 50. Sulphurets of Iron. The bisulphuret of iron is one 
 of the most common ores in the earth, and has been known 
 from ancient times, when it received the name of pyrites, 
 from the Greek word pur, fire, because, as Pliny says, 
 
 B2 
 
 Fig. 20. 
 
34 MINEEALOGY. 
 
 / 
 
 " there is much fire in it," referring to its readily strik- 
 ing fire with steel. It occurs, when crystallized, in the 
 primary forms of cube, octahedron, and dodecahedron 
 (Figs. 9, 10, and 11), and in a variety of secondary forms. 
 Its color is a bronze-yellow, and the lustre is often bril- 
 liant. As the lustre is metallic, it has been often supposed 
 by common people to be gold, and specimens which have 
 been found are every now and then taken to some person 
 of known scientific character in the community for in- 
 quiry on this point. It has therefore received the name 
 of " fool's gold." The distinction between it and gold 
 is, however, easily made, for the pyrites is very hard, is 
 not malleable like gold, and on the application of strong 
 heat it gives off sulphurous fumes. It is not much prized 
 as an ore for obtaining iron, because of the difficulty of 
 ridding it entirely of the sulphur ; but it is much used 
 for obtaining sulphate of iron (green vitriol or copperas), 
 sulphuric acid (oil of vitriol), and sulphur. There is a 
 magnetic iron pyrites, which is softer and liable to tar- 
 nish. There is also an arsenical iron pyrites, nearly half 
 of which is arsenic. Its color is silver- white, with a shin- 
 ing lustre, and on being struck with steel it gives a spark 
 with a garlic odor. 
 
 51. Copper Pyrites. This is not a sulphuret of copper, 
 but of copper and iron, nearly one third of it being iron. 
 It has a deeper color than iron pyrites, is softer, yielding 
 readily to the knife, and does not strike fire with steel. 
 Its color is such that it looks like gold, but it is at once 
 distinguished from it by its crumbling under the knife. 
 Much of the metal copper is obtained from this ore, and 
 sulphate of copper (blue vitriol) is largely manufactured 
 from it. There is a copper ore called copper glance, a 
 sulphuret in which the proportion of iron is very small. 
 It is of a lead-gray color. There is also a sulphuret of a 
 dark steel-gray color^ of a very compound character, there 
 being in its composition six ingredients sulphur, copper, 
 antimony, arsenic, iron, zinc, and silver. Sometimes the 
 
SULPHUR AND ITS COMPOUNDS. 35 
 
 silver in it amounts to 30 per cent., and then it is called 
 argentiferous gray copper ore. 
 
 52. Sulphuret of Lead. The common name of this min- 
 eral is galena. Its crystals are in the form of the cube 
 and its secondaries. Its color is lead-gray, and its lustre 
 is shining. There is often sulphuret of silver incorpo- 
 rated with it, and it is then called argentiferous galena. 
 It is the ore from which the metal lead is obtained, na- 
 tive lead being exceedingly rare. I have told you how 
 the galena is freed from the sulphur in Part II., 193, 
 and in 210 how the silver is obtained from the galena 
 when it is argentiferous. There are vast quantities of 
 galena in various parts of the United States, especially in 
 Missouri, Illinois, Iowa, and Wisconsin. It is so abund- 
 ant in the last-named state that the miners seldom take 
 the trouble to get out the ore deeper than twenty-five or 
 thirty feet. Three millions of pounds have been obtained 
 from one spot which is not over fifty yards square. 
 
 53. Sulphuret of Silver. This mineral, commonly called 
 silver glance, occurs in the form of the dodecahedron and 
 its secondaries. Its color is lead-gray, and it has a me- 
 tallic lustre. There is also a sulphuret of silver and an- 
 timony, which is of a black color, and therefore is some- 
 times called black silver. There is also a sulphuret of 
 silver and iron, and one of silver and copper. 
 
 54. Sulphuret of Antimony. This sulphuret appear sin 
 prisms, and has a gray color and metallic lustre very much 
 like those of galena. It is the ore from which is obtained 
 nearly all the antimony of commerce. There are also 
 some sulphurets of lead and antimony combined together. 
 
 55. Sulphurets of Arsenic. There are two sulphurets 
 of arsenic. One is of a red color, is translucent, some- 
 times transparent, and its crystals are usually in the pris- 
 matic form. It is called realgar. The other, called or- 
 piment, is of a lemon-yellow color. Both are used as 
 pigments, and also as coloring substances in pyrotechnic 
 mixtures. They are obtained chiefly in Koordistan and 
 China. 
 
36 MINERALOGY. 
 
 56. Sulphuret of Mercury. This is more abundant than 
 any of the other ores of mercury, and most of this metal 
 is obtained from it. It is called both cinnabar and ver- 
 milion. The latter is its name as sold in the shops. It 
 is used as a pigment, and is the coloring matter in red 
 sealing-wax. The principal mines of this ore are in Aus- 
 tria, Spain, Peru, and Upper California. 
 
 57. Sulphuret of Zinc. This mineral, commonly called 
 blende, the Black Jack of miners, appears in octahe- 
 drons, dodecahedrons, and forms that are secondary to 
 these. It has a waxy lustre, and when a cleavage face 
 is made the lustre is brilliant. It is very apt to be found 
 in company with lead ores, and it abounds in the lead 
 mines of Missouri and Wisconsin. 
 
 58. The Three Vitriols. The green vitriol (sulphate 
 of iron), the blue (sulphate of copper), and the white 
 (sulphate of zinc), are all familiar to you. They exist in 
 nature in company with the sulphurets of the same met- 
 als, from which they are really produced. A sulphate 
 differs from a sulphuret in having oxygen in it, as you 
 learned in Part II. Now if a sulphuret, of iron for ex- 
 ample, be exposed to the air in a moist state, it is decom- 
 posed, and the sulphur and the iron, absorbing oxygen 
 from the air, become, the one sulphuric acid and the oth- 
 er oxyd of iron, and these two uniting form sulphate of 
 iron. So also sulphate of copper is formed from sulphu- 
 ret of copper, and sulphate of zinc from sulphuret of zinc. 
 
 Green vitriol, or copperas, is largely used in dyeing 
 and tanning, because, in connection with an ingredient in 
 nut-galls and many kinds of bark, it gives a black color. 
 Common ink is essentially a combination of copperas 
 with this ingredient. 
 
 59. Sulphate of Lead. This is usually in company with 
 galena, and is the result of its decomposition, after the 
 manner indicated in speaking of the vitriols. Its color is 
 white, or light gray, or green. Its crystals are some- 
 times splendid. 
 
SULPHUR AND ITS COMPOUNDS. 3V 
 
 60. Gypsum. This is sulphate of lime. When crys- 
 tallized and free from all impurities it has a pearly lus- 
 tre, and the clearness of glass. About a fifth part of it 
 is water. This water is driven off in preparing it for 
 making casts, ornamental work for walls, etc. The man- 
 ner of using it for these purposes is described in 320, 
 Part II. Gypsum is a white and soft mineral, and ap- 
 pears in many forms, some of which are very beautiful. 
 One of these is the satin spar^ so called from the splen- 
 did lustre of its delicate fibrous arrangement. Another, 
 called alabaster, which is generally snowy white, being 
 compact, with a fine grain, is cut into vases and orna- 
 ments of various kinds. Sometimes gypsum is composed 
 of exceedingly thin leaves, laid together so evenly that a 
 multitude of them make a crystal clearer than the clear- 
 est glass. The name selenite, which has been given to 
 this and some other varieties of gypsum, comes from se- 
 lene, the Greek word for moon. There is an anhydrous 
 sulphate of lime, that is, one which has no water incor- 
 porated with it, the term coming from two Greek words, 
 aw, without, and udor, water. Gypsum occurs abundant- 
 ly in many parts of this country. Fine specimens are 
 found near Lockport, New York. As before noticed ( 
 1 6), in the Mammoth Cave of Kentucky alabaster appears 
 with its crystals arranged in various forms of flowers, 
 branches of shrubbery, vines, etc. 
 
 Common limestone has sometimes been mistaken for 
 gypsum by persons who are ignorant of chemistry and 
 mineralogy. Professor Hitchcock relates a case of this 
 kind. A farmer supposed that he had found gypsum on 
 his farm, and his neighbors, believing it, bought large 
 quantities of the material for agricultural purposes. Aft- 
 er grinding up a considerable amount of it, some one ac- 
 cidentally discovered that it was limestone. The error 
 might have been avoided by simply testing the sub- 
 stance with acid. A drop would have occasioned an ef- 
 fervescence, showing that it was carbonate, and not sul- 
 
38 MINERALOGY. 
 
 phate of lime, the acid taking the lime to itself, .and set- 
 ting free the carbonic acid gas. See 60, Part II. 
 
 61. Sulphates of Magnesia and Soda. The slender, 
 spicula-like crystals of Epsom salts (sulphate of magne- 
 sia), which are probably familiar to you, are prisms. Mi- 
 nute crystals of this mineral are often present in the 
 earth on the floors of the limestone caves in the western 
 part of this country. In the Mammoth Cave of Ken- 
 tucky feathery masses of the crystals adhere to the roof, 
 looking like snow-balls. The common name of this min- 
 eral came from the fact that at Epsom, in England, the 
 waters of the springs hold it in solution. The crystals 
 of Glauber's salt are also prisms, but they are coarse 
 compared with those of Epsom salts. Both of these 
 salts are present in sea-water. 
 
 62. Sulphate of Baryta. This is so heavy a mineral 
 that it is called heavy spar. The crystals, which are 
 translucent, sometimes transparent, are often very beau- 
 tiful. It is found abundantly in some localities in this 
 country, as Cheshire, Conn. ; Pillar Point, N. Y. ; near 
 Fredericksburg, Va. It is extensively ground up for use 
 in paints, being mixed with white lead. The mixture 
 has various names, according to the proportions of the 
 various ingredients : Venice White, when there are equal 
 parts of the two ; Hamburg White, when the lead is half 
 the weight of the sulphate of baryta ; and Dutch White, 
 when it is one third. 
 
 .63. Sulphuric and Sulphurous Acids. That intense 
 acid, sulphuric acid, or oil of vitriol, as it is commonly 
 called, is occasionally found near volcanoes and sulphur 
 springs. Sulphurous acid, the pungent and suffocating 
 gas which is produced whenever sulphur is burned, is 
 often very abundant about volcanoes when they are in 
 action. 
 
 64. Sulphureted Hydrogen. This very offensive gas is 
 common at sulphur springs, and it is by its agency that 
 articles of silver are so readily blackened in such locali- 
 
METALS AND THEIR ORES. 39 
 
 ties, the sulphur of the gas uniting with the silver to form 
 a sulphuret of that metal. This gas is also sometimes 
 generated about volcanoes. 
 
 CHAPTER V. 
 
 METALS AND THEIR ORES. 
 
 65. Native Metals. A metal is said to occur native 
 when it is found either pure or mingled with some other 
 metal in the form of an alloy ; in other words, when it is 
 not united chemically with any other substance. 
 
 66. Ores. When a metal is united chemically with 
 any substance, the compound is called an ore. The metal 
 is in this case said to be mineralized. The most common 
 of these compounds are sulphurets, oxyds, and carbon- 
 ates. The word ore is sometimes used in a less strict, 
 sense for alloys, and even native metals are often termed 
 ores. On the other hand, it is proper to state that to 
 the compounds of some of the metals the term is not ap- 
 plied at all. I refer to the earths and alkalies, which are 
 combinations of certain metals with oxygen, to their 
 salts, and to the combinations of these same metals with 
 chlorine, iodine, etc. These metals, potassium, sodium, 
 etc., have been discovered comparatively at a recent date, 
 are never found native, and, when obtained by chemical 
 processes, are, most of them, preserved in their metallic 
 state with difficulty. You see, then, the propriety of not 
 calling their compounds ores. It is to the compounds 
 of the well-known metals only that the term is applied. 
 
 67. Positions and Associations of Ores. The ores of 
 metals are sometimes scattered here and there in rocks, 
 in collections small and large ; but commonly they are 
 in veins, or lodes, as they are called, or in layers between 
 layers of rock. They are associated with quartz, carbon- 
 ate of lime, and various other minerals. Often two or 
 more different ores are mingled together. 
 
40 MINERALOGY. 
 
 68. Obtaining Metals from their Ores. Sometimes this 
 is a very simple process. For example, in the case of 
 bismuth, all that is necessary is to heat the pounded ore, 
 and the melted metal runs out. So, if you have a sul- 
 phuret of lead, or mercury, or antimony, heat will fully 
 decompose the compound, driving off the sulphur. But 
 sometimes the use of some other substance is required 
 for the decomposition of the ore. Thus, if we have an 
 oxyd of iron, we heat it with charcoal. Here the oxygen 
 quits the iron to unite with the carbon, forming carbonic 
 acid, which flies off, leaving the metallic iron. 
 
 69. Gangues and 'Impurities. The rock in which an 
 ore is found is called the gangue. Much of this is separ- 
 ated from the ore in collecting it, and much more of it, 
 perhaps, by the process called washing, in which the ma- 
 terial, coarsely powdered, is subjected to a current of 
 water, that washes away the lighter pieces, leaving those 
 which are rendered heavy by the presence of the metal. 
 The impurities which are often mingled with ores are 
 got rid of in various ways. Sometimes^/tees, so called, 
 are used for this purpose. This is done with most iron 
 ores. There is commonly mixed with these ores quartz 
 or clay ; and as quartz is pure silica, and silica consti- 
 tutes 75 per cent, of clay, the ore is reduced by strongly 
 heating it together with a substance which will form a 
 silicate, that is, a glass, w^th the silica ( 342, Part II.). 
 Such a substance is common limestone. 
 
 Other processes will be noticed hereafter in the case 
 ^of particular ores. 
 
 70. Iron. The most common of the ores of this metal 
 are oxyds and sulphurets. Of the latter I have already 
 spoken in 50. Its ores are more abundant in the earth 
 than those of any other metal, because it is the most ex- 
 tensively and variously useful of all the metals. They 
 are the common coloring ingredients of rocks, and there- 
 fore of soils. Red and yellow are the most frequent col- 
 ors, but they color also a dull green, brown, and black. 
 
METALS AND THEIR ORES. 41 
 
 Iron is present in a small amount in many vegetable and 
 animal substances, and in our blood it is an essential, 
 though a minute ingredient ( 663, Part IL). 
 
 71. Meteoric Iron. Native iron has not been ascer- 
 tained to occur except in meteorites, and there it is al- 
 loyed with nickel, and with a small amount of other met- 
 als tin, cobalt, copper, and manganese. The mass in 
 the cabinet of Yale College, from Texas, weighing 1635 
 pounds, contains from 90 to 92 per cent, of iron, and from 
 8 to 10 per cent, of nickel, the mixture of the two metals 
 not being uniform throughout the mass. There is one 
 mass of meteoric iron in South America which is sup- 
 posed to weigh 30,000 pounds. 
 
 72. Magnetic Iron Ore. This ore has this name from 
 its magnetic properties. It is an oxyd of iron, of an iron- 
 black color, generally in granular masses, but sometimes 
 in distinct crystals, which are octahedrons or dodecahe- 
 drons, or their secondary forms. This very superior ore 
 of iron is as widely disseminated as any ore of this met- 
 al. Nearly all the Swedish iron ore is of this kind. In 
 Sweden and Lapland there are mountains of it. When 
 a mass of this ore is in a state of magnetic polarity it is 
 a lodestone or natural magnet. The lodestone was first 
 found in the province of Magnesia, and was called mag- 
 nes by Pliny, and hence the terms magnet and magnetism. 
 
 73. Hematite. This, like thp magnetic iron ore, is an 
 oxyd, but is distinguished from it by its powder being 
 red. It is this which has given it its name, from the 
 Greek word haima, blood. This mineral appears in va- 
 rious forms, generally in granular mass, in Iamina3, or 
 earthy, and easily powdered. What is called red chalk is 
 one of the varieties. This ore is abundant in this coun- 
 try. The two iron mountains in Missouri consist for the 
 most part of this ore piled up "in masses of all sizes, from 
 a pigeon's egg to a middle-sized church." 
 
 74. Limonite, or Brown Iron Ore. This is not merely 
 an oxyd of iron, but a hydrated oxyd, containing water 
 
42 MINERALOGY. 
 
 to about 14 per cent. One of its forms is yellow ochre, 
 which is used as a common material in paint. The pow- 
 der of this ore is also used for polishing metallic surfaces. 
 75. Chromic Iron. This mineral is composed chiefly 
 of the oxyds of two metals, iron and chromium. The 
 oxyd of the latter acts as an acid, as mentioned in 301, 
 Part II., and the mineral is therefore said to be a chro- 
 mate of iron. There are, however, two other compo- 
 nents, alumina and magnesia, which vary in quantity in 
 different specimens. This mineral is quite abundant at 
 Barehills, near Baltimore, in Lancaster county, Pennsyl- 
 vania, and several other places in this country. Its crys- 
 tals are octahedrons. It is valuable in the manufacture 
 of the chrome pigments, of which the chrome yellow is 
 the principal. 
 
 76. Carbonate of Iron. This miner- 
 al varies in color from light gray to 
 dark brown or nearly black on ex- 
 posure. Its crystals sometimes have 
 curved faces, as represented in Fig. 
 21. Metallic iron is extensively ob- 
 tained from this ore. 
 77. Native Copper. This occurs in company with ores 
 of the metal, commonly in the neighborhood of igneous 
 rocks that is, rocks which have been made and thrust 
 upward in the crust of tl^ earth by the agency of heat. 
 There is often silver with the copper, either intimately 
 mixed with it, making an alloy, or collected by itself in 
 small masses or in strings. Copper is next to iron in 
 abundance. There are famous mines in Cornwall, En- 
 gland, in Brazil, and in Siberia. Perhaps the most ex- 
 traordinary copper region in the world is in the vicinity 
 of Lake Superior. It is found there in veins filling up 
 fissures in the rocks, and it is cut out in monstrous blocks 
 with chisels and drills. One mass, weighing nearly 4000 
 pounds, was carried to Washington, and a large mass has 
 been since got out which was estimated to weigh 200 
 
METALS AND THEIR ORES. 43 
 
 tons. As you will see in another part of this book, the 
 geologist has found clear proof that the native copper of 
 this region was produced in Nature's great furnaces from 
 ores of the metal ages upon ages before the creation of 
 man. 
 
 The sulphurets of copper and the sulphate were no- 
 ticed in the preceding chapter. I go on now to notice 
 the principal of the other ores of this metal. 
 
 78. Oxyds of Copper. There are two oxyds, a red and 
 a black one. The metal can be obtained from them by 
 heating with charcoal, the oxygen uniting with the car- 
 bon to form carbonic acid gas, which flies off. 
 
 79. Carbonates of Copper. There are two carbonates. 
 One of them, called malachite, is of a light green color, 
 and, as it is capable of a high polish, it is used in various 
 ways for ornamental articles. Its value, when manufac- 
 tured as veneering or inlaid work, is about three guineas 
 per pound, and there are at least two pounds and a half 
 in a square foot of finished work. In Russia, where large 
 pieces of it can TDC obtained, slabs for tables, mantle- 
 pieces, vases, etc., are made from it. The blue carbonate 
 sometimes presents splendid crystals. 
 
 80. Silicate of Copper. This mineral, a compound of 
 silica or silicic acid with oxyd of copper, has a bluish- 
 green color. Sometimes the green carbonate and this 
 silicate are united in one mineral. 
 
 81. Lead. Native lead is exceedingly rare. Its most 
 common ore, galena, and the sulphate I noticed in the 
 preceding chapter. The oxyd of lead, minium, is what 
 is commonly called red lead. The carbonate is the white 
 lead of commerce. The chromate of lead is the chrome 
 yellow used by painters. 
 
 82. Tin. The native metal is exceedingly rare. The 
 chief ore is an oxyd, the sulphuret being seldom found. 
 This is an ingredient in pewter and bronze, and in the 
 amalgam put on the backs of mirrors, and some of its 
 salts are employed in dyeing. The tin used in making 
 
44 MINERALOGY. 
 
 tin- ware is iron in the form of sheets covered with tin, 
 which does not oxydize as readily as tin does. The chief 
 tin mines are 'at Cornwall, in England, in the island of 
 Banca, in Malacca, and in Austria. It is supposed, from 
 some allusion in ancient history, that the Cornwall mines 
 were worked some centuries before the Christian era. 
 
 83. Zinc. This metal never occurs native. I have al- 
 ready noticed its chief ore, the sulphuret, in 57, and the 
 sulphate in 58. The other ores which are at all promi- 
 nent are the red oxyd and the carbonate. For the uses 
 of this metal I refer you to 198, Part II. 
 
 84. Antimony. This metal is occasionally found na- 
 tive. Its usual combinations are with sulphur, or with 
 sulphur and lead together. It is sometimes also com- 
 bined with oxygen, arsenic, lime, nickel, silver, and cop- 
 per. The chief use of the metal is in the composition of 
 type-metal. In medicine there is used a double salt, in 
 which antimony is one of the bases, the tartrate of anti- 
 mony and potash. 
 
 85. Cobalt. There are two arsenical ores of this met- 
 al that is, ores in which it is combined with arsenic. 
 Zaffre is a beautiful coloring material prepared from the 
 ores of cobalt. Smalt is glass colored with zaffre and 
 reduced to a fine powder. This is used to give a deli- 
 cate blue tinge to writing paper and to linen. 
 
 86. Nickel. Native nickel is never of terrestrial or- 
 igin, but it is one of the ingredients in the alloy which 
 we have in meteorites, as stated in 71. It has two ar- 
 senical ores, a carbonate, various compound sulphurets, 
 etc. German silver, so called, is an alloy of copper, 
 nickel, and zinc. 
 
 87. Bismuth. This is found native, and also combined 
 with oxygen, carbonic acid, silica, and the metal tellu- 
 rium. It is an ingredient in the most superior kind of 
 type-metal, in the " mosaic gold," and in an alloy used 
 in soldering pewter. Most of it comes from one locality, 
 Schneeberg, in Saxony, It is obtained from the rocks 
 
METALS AND THEIR OSS^gOSff^^ 45 
 
 in which it is present by powdering coarsely, and then 
 exposing to strong heat in a kiln. The bismuth is melt- 
 ed only, and runs into a trough at the bottom. 
 
 88. Manganese. The ores of this metal are some of 
 them composed of but two ingredients, as the oxyds and 
 sulphurets; and others are very compound, containing 
 silica, iron, lime, magnesia, etc. The peroxyd is used by 
 the chemist for obtaining oxygen gas, and is employed 
 largely in bleaching. Some of the salts of this metal are 
 used in calico printing. Manganese gives a violet color 
 to glass. 
 
 89. Mercury. This is the only metal that is liquid in 
 all ordinary temperatures. It becomes solid at 39 be- 
 low zero, and therefore can not be used in thermometers 
 in the arctic regions. It crystallizes in cubes. It is 
 sometimes found native, commonly in globules scattered 
 here and there, but sometimes in such quantities that it 
 can be dipped up in pails. It is related that the mines 
 of mercury in Mexico were discovered by a hunter, who, 
 as he clambered up a mountain, caught hold of a shrub, 
 which, giving way at the root, let out a stream of what 
 he supposed was liquid silver. The rapidity with which 
 this metal runs, occasioned by its great weight, gave to 
 it the name of quicksilver. The purity of the mercury 
 is judged of by the workmen by watching it as it is 
 dropped upon glass. If in running, instead of preserv- 
 ing fully its characteristic globular shape, it forms a 
 queue, or drags a tail, as it is expressed, there is lead or 
 some other impurity present. Mercury is used in a va- 
 riety of ways. It is the liquid used in barometers, and 
 generally in thermometers. It is used for silvering mir- 
 rors, an amalgam being formed with tin for this purpose. 
 Its disposition to amalgamate with other metals is made 
 use of extensively in extracting gold and silver from the 
 impurities with which they are mixed, as described in 
 213, Part II. Then there are various preparations and 
 combinations of this metal employed in medicine. The 
 
46 MINEEALOGY. 
 
 most common ore of mercury, the sulphuret, was noticed 
 in 56. 
 
 90. Silver. This metal is found pure, in alloy, and in 
 chemical combination with sulphur, arsenic, chlorine, va- 
 rious acids, etc. When it is found native it is not usu- 
 ally alone, but is alloyed with copper, and sometimes 
 with gold. The copper in the alloy sometimes amounts 
 to 10 per cent. The chief ores of silver, the sulphur ets, 
 were noticed in 53. 
 
 91. Gold. This metal has no disposition to unite with 
 oxygen or with other elements, and therefore is found 
 in nature either pure, or alloyed with some other metals, 
 chiefly silver and copper. The only chemical compound 
 formed by gold in nature is with tellurium, termed a tel- 
 lurid of gold, and this is quite rare. As you have al- 
 ready learned, iron and copper pyrites have often been 
 supposed to be gold by those who are ignorant in regard 
 to minerals. But the distinction is easily made, for gold 
 flattens out on being hammered, and is readily cut, while 
 the pyrites break in pieces on being hammered, and nei- 
 ther of them can be cut in slices, no impression even be- 
 ing made by the knife on the iron pyrites. Besides, the 
 pyrites, on being exposed to a strong heat, emit a sul- 
 phureous odor, while the melting gold is odorless. Gold 
 is commonly found in grains or rounded masses of vari- 
 ous sizes, but sometimes it is crystallized in the form of 
 the cube or octahedron. Sometimes large lumps have 
 been found. The largest lump that has yet been ob- 
 tained was from California. It furnished 109 pounds 
 and 4 ounces of pure gold. Gold is diffused in most 
 countries in small quantities ; but there are some locali- 
 ties where it abounds, as the Urals, Hungary, Spain, va- 
 rious parts of South America and Africa, but especially 
 Australia and California. In these two last localities it 
 was discovered but recently in California in 1848, and 
 in Australia in 1851. A locality along the coast of Afri- 
 ca, opposite Madagascar, has been supposed to be the 
 
METALS AND THEIR ORES. 47 
 
 Ophir of Solomon's time. The Russian mines, that is, 
 those of the Urals and Siberia, were, till of late, the lar- 
 gest sources of gold, but the mines of California and Aus- 
 tralia far surpass them ; and it is stated by Professor 
 Dana that " the whole product of Europe, Asia, Africa, 
 and South America is far less at the present time than 
 is derived from Australia or the United States." 
 
 92. Modes of Obtaining Gold. If the gold be in rock, 
 this is pounded up and sifted, and the sand thus obtained 
 washed in a pan. The gold being seven times heavier 
 than the same bulk of sand or gravel, those portions of 
 the sand which have gold attached to them subside to 
 the bottom of th pan, while the other portions, being 
 lighter, run off with the water. The portions which 
 subside are subjected to the amalgamation process, in 
 which mercury unites with the gold, forming an amal- 
 gam, and thus separates the metal from the sand. The 
 gold is then obtained from the amalgam by means which 
 are detailed in 213, Part II., where the whole process 
 is fully described. This sorting of gold by washing is 
 carried on extensively in nature in the alluvial washings, 
 as they are called. The grains and scales found in the 
 gravel and sand in the beds of streams and on their bor- 
 ders were once in rocks, which were worn away by 
 means that will be made clear to you in another part of 
 this book. The gold, on account of its weight, is always 
 lagging behind the materials that accompany it at the 
 start ; and the larger are the pieces of the metal, the less 
 distance are they carried, for small pieces have a larger 
 surface in proportion to their weight for the water to 
 act upon ( 193, Parti.). For the same reason, a round 
 piece is not carried as far as a scale. When there is a 
 rock in the path of a stream, the pieces of gold collect 
 there, the lighter gravel and sand being carried along 
 by the water. The formation of this "pocket" of gold 
 is very much like the gathering of the golden grains in 
 the bottom of the pan in artificial washing. Sometimes, 
 
48 MINERALOGY. 
 
 on the borders of a stream, the material which has been 
 drifted down previously .may have much gold in it. To 
 bring it to light, the stream is turned across it, to per- 
 form on a large scale the same operation of washing that 
 is done in a small way with the pan. The processes 
 necessary for separating the gold when it is alloyed with 
 silver or copper I will not stop to describe. 
 
 93. Uses of Gold. The usefulness of this metal results 
 from its malleability, its ductility, its rich color, its sus- 
 ceptibility of a high polish, and its indisposition to tarnish 
 on exposure. A gold-beater can hammer a grain of gold 
 into a leaf covering a space of 50 square inches, and its 
 thickness is only the 282,000th of an inch. Its ductility 
 equals its malleability, as is shown in the wire of gold 
 lace. It is from these two qualities that gilding is so 
 cheap, and therefore so common, thereby making this 
 costly metal a great convenience to the people at large. 
 For ordinary uses, gold is alloyed with silver and copper 
 to give it the requisite hardness. The standard gold of 
 the United States contains nine parts of pure gold to 
 one of alloy. The word carat, used so often in speaking 
 of the purity of gold in the market, means one twenty- 
 fourth ; so that if any specimen is said, for example, to 
 be twenty carats fine, it is meant that the pure gold is to 
 the alloy as 20 to 4, and so of other proportions. 
 
 94. Platinum and its Associate Metals. Platinum is 
 seldom found alone, but is commonly mingled with more 
 or less of certain rare metals iridium, rhodium, palla- 
 lium, and osmium and such common metals as iron 
 and copper. It occurs usually in small grains, but some- 
 times is found in pieces of considerable size. The lar- 
 gest mass that has yet been found weighed 21 pounds 
 Troy. Platinum is often spoken of as being the heavi- 
 est substance known, but there is one metal, iridium, 
 that is a very little heavier. Its color is between that 
 of tin and steel, though in the alloys in which it is usu- 
 ally found it is darker than this. It is very malleable, 
 
OXY-SALTS AND HALOID SALTS. 49 
 
 especially when heated. Its ductility is so great that 
 Dr. Wollaston succeeded in making a wire of it the two 
 thousandths (-^oVo) of an inch in diameter. In fusibility 
 this metal and mercary^ stand at opposite ends of the 
 scale. While mercury may be said to melt at 39 be- 
 low zero, platinum can not be melted in the hottest 
 furnace, as is shown in the crucibles of the chemist that 
 are made of it. The metals iridium, rhodium, and os- 
 mium, which are found in company with platinum, are 
 very hard, and are used for points to gold pens. There 
 is a mineral called iridosmine, because composed of irid- 
 ium and osmium, which is the hardest alloy known. 
 This mineral, which is found in scales, is also used for 
 pointing gold pens. 
 
 CHAPTER VI. 
 
 OXY-SALTS AND HALOID SALTS. 
 
 95. The two Classes of Salts. Those salts which are 
 formed by the union of acids with oxyds are called oxy- 
 salts, because they have oxygen in their composition. 
 There is, besides, a class of salts which contain no oxy- 
 gen, but are composed of a metal and some other element. 
 Common salt is an example. This is composed of chlo- 
 rine and sodium, and is a chlorid of sodium. This is the 
 principal salt of this class, and hence the name given to 
 the whole class, haloid, from two Greek words, hols, sea- 
 salt, and eidos, like. Some of the oxy-salts have been al- 
 ready treated of in other connections, as the sulphates in 
 the chapter on sulphur and its compounds, from their 
 natural association with the sulphurets. 'There are also 
 some which will be reserved for another chapter, as the 
 silicates, on the same principle of natural grouping. 
 
 96. Nitrate of Potash. This salt, commonly called ni- 
 tre or saltpetre, is produced in India and South America 
 from the decomposition of animal substances in the soil 
 
 C 
 
50 MINERALOGY. 
 
 in hot and dry weather succeeding a rain. It is also pro- 
 duced in the same way in Egypt, and appears in light 
 tufts, which are gathered up by a sort of broom, and 
 the nitre is separated from its impurities by lixiviation, 
 and is crystallized by evaporation. It is found diffused 
 in the earth on the floor of some of our Western caverns, 
 and is apt to appear in crusts or needle-like crystals on 
 their walls. This salt is that one of the ingredients of 
 gunpowder that furnishes the oxygen required for the 
 combustion. 
 
 97. Nitrate of Soda. This is very much like nitre; like 
 that, it deflagrates when thrown upon the fire, and it has 
 the same supply of oxygen in it that nitre has ; and it 
 would answer the purpose equally well in gunpowder if 
 it did not readily deliquesce that is, gather moisture 
 from the atmosphere. Both this salt and the nitre are 
 used for obtaining nitric acid. 
 
 98. Common Salt. This is composed of chlorine and 
 sodium, two elements which never appear in nature un- 
 combined. Its crystals are the cube and its secondaries. 
 A peculiarity in the arrangement of its crystals when 
 they are formed in a solution was shown in 22. This 
 mineral is very thoroughly diffused in the earth, mostly, 
 however, in solution, nearly one thirtieth of all the water 
 in the sea being common salt. Lakes that have no outlet 
 to the sea are very salt. This is the case with the Great 
 Salt Lake of this country, the Dead Sea, and the Caspian 
 Sea. Over one fifth of the water of the Great Salt Lake 
 is salt, and the proportion is even greater in the case of 
 the Dead Sea. There are famous salt mines where the 
 solid mineral is obtained in Poland, Hungary, Spain, Sici- 
 ly, and Switzerland. In the extensive mines near Cracow 
 chapels, halls, etc., are excavated far below the surface, 
 their roofs being supported by immense pillars of salt, 
 which, on being lighted up, present a magnificent ap- 
 pearance. In Northern Africa there are hills of salt. In 
 this country vast quantities of salt are obtained by evap- 
 
OXY-SALTS AND HALOID SALTS. 51 
 
 oration from the water of salt springs. The springs in 
 Onondago county, New York, are the most productive, 
 one seventh part of the water being salt. In hot climates 
 much salt is obtained from sea water by evaporation. 
 The manner in which this is done is described in 358, 
 Part II. 
 
 99. Borate of Soda. Nearly half (47 per cent.) of this 
 salt, commonly called borax, is water. It abounds in a 
 lake in Thibet, where it is literally dug out from the bor- 
 ders and shallow places. As the borax is deposited from 
 the water, the holes made in gathering it are soon filled 
 up. This lake is at so high an elevation that it is frozen 
 over the greater part of the year. The acid which en- 
 ters into the composition of borax, boracic acid, is some- 
 times found in the vicinity of volcanoes, exhaling from 
 springs in the earth. It is present in the hot vapors of 
 the lagoons in Tuscany, from which it is obtained by let- 
 ting the vapor pass into cold water to condense it, and 
 then allowing the solution to evaporate. This leaves the 
 boracic acid in large crystalline flakes. 
 
 100. Carbonate of Lime. This mineral, in the forms of 
 common limestone, chalk, and marble, constitutes about 
 one seventh part of the crust of the globe, and therefore 
 will be brought quite largely to your notice in the geo- 
 logical part of this book. There are mountains made of 
 it, and there are extensive deposits of it in layers of rock. 
 It appears also in smaller quantities in many other forms, 
 some of them exceedingly beautiful. It is readily distin- 
 guished from other minerals by dropping some acid, as 
 the sulphuric, upon it, this occasioning an effervescence 
 by uniting with the lime and setting free the carbonic 
 acid, as already stated in 60. Exposed to a red heat 
 the carbonic acid is driven off, and we have the lime left 
 alone. This is what is done in the lime-kiln, and it is in 
 this way that the lime used for making mortar and other 
 purposes is obtained. Hydraulic lime, which has this 
 name because it will "set" under water, is made from 
 
52 MINERALOGY. 
 
 limestone in which there are some silica and clay, and 
 sometimes magnesia. Marl, which is of so great use in 
 agriculture, is a mixture of carbonate of lime with clay. 
 When carbonate of lime is deposited from the waters of 
 a mineral spring it is called calcareous tufa. Crystalli- 
 zation is prevented in this case from the constant mo- 
 tion of the water. Chalk, though abundant in England, 
 France, and many other countries, is not found at all in 
 this country, though the other common forms of carbon- 
 ate of lime are present in large quantities. 
 
 101. Calcareous Spar. This name is usually given to 
 the crystallized varieties of carbonate of lime. The crys- 
 tals vary exceedingly from the variety of their secondary 
 forms. Some fanciful names are given to some of them 
 from their peculiar shapes, as dog-tooth spar and nail- 
 head spar. They are various in color, commonly white 
 or light gray, or reddish or yellowish, and sometimes 
 wine-yellow, red, rose, or violet. The crystals of Ice- 
 land spar, so called because they were first brought from 
 Iceland, are transparent, and they exhibit double refrac- 
 tion that is, objects seen through the crystal appeal- 
 double. Satin spar has its name from the satin lus- 
 tre which its beautifully fibrous arrangement presents. 
 There is a form of carbonate of lime, called aragonite, 
 that crystallizes after a diiferent plan from that of calca- 
 reous spar, and it is much harder. 
 
 102. Marble. This is a granular limestone, the grains 
 being imperfect crystals from their encroaching on each 
 other during their formation. The finest varieties are 
 called statuary marble, the best coming from Carrara, in 
 Italy, the island of Paros, and some other localities in the 
 same quarter. The coarse kinds are the common mar- 
 bles, which are either white or clouded with various col- 
 oring substances. In some marbles there are shells or 
 corals, these being composed of the same mineral with 
 the marble itself. Indeed, it is supposed by some that 
 all marble and other forms of carbonate of lime are made 
 
OXY-SALTS AND HALOID SALTS. 53 
 
 of the shells and skeletons of animals, and that it is by 
 the agency of fire chiefly that their forms have been to 
 so great an extent destroyed, the particles that composed 
 them having taken on a crystalline arrangement in the 
 marble. There is one mode of arrangement, differing 
 from the ordinary one, which I will notice in passing. 
 We see it in both marble and common limestone. It 
 gives to marble a grayish color, and an appearance re- 
 sembling the roe of a fish, from the rounded dots with 
 which it is speckled. It is called oolitic marble, and the 
 limestone which is composed of these round grains is 
 called oolite. This term comes from the Greek word 
 don, egg. 
 
 103. Stalactites and Stalagmites. In many limestone 
 caves the carbonate of lime accumulates overhead in 
 shapes like icicles, and these are called stalactites. Ac- 
 cumulations also occur on the floor of the cave similar in 
 form to those which we sometimes see on the ground 
 under dripping icicles, and these are called stalagmites. 
 The resemblance in form in the two cases is very strik- 
 ing. For the chemical explanation of these formations 
 I refer you to 307, Part II. Sometimes the stalactites 
 and stalagmites meet, forming pillars, and these may, in 
 the course of time, become very large, so that, where the 
 roof is high, the appearance by torch-light is magnificent. 
 In Weyer's Cave, which is a mile and a half in extent, 
 and in some parts forty feet high, many of the stalactites 
 being of a delicate white color, in contrast with the blue 
 limestone of the walls, the scene is exceedingly grand 
 and beautiful. 
 
 104. Magnesian Carbonate of Lime. This mineral, 
 called dolomite, is composed of carbonate of lime and 
 carbonate of magnesia. Its crystals, which are rhombo- 
 hedrons, are often curved, as seen in Fig. 3. Much of 
 the coarser kind of white marble in use for building is 
 dolomite in the granular or imperfectly crystallized 
 form. 
 
54 MINERALOGY. 
 
 105. Fluor Spar, This is a fluorid of calcium, com- 
 posed of fluorine (one of the chlorine family) and calci- 
 um, which is the metallic base of lime. Neither of these 
 elements is ever found in nature. The crystals of fluor 
 spar are the cube and the octahedron, and their seconda- 
 ries. Their colors, which are bright, are white, light 
 green, purple, and yellow ; sometimes rose-red and sky- 
 blue. Fluor spar phosphoresces brightly when put upon 
 hot iron, giving out various colors. It is an abundant 
 mineral in Derbyshire, England, and it is therefore often 
 called Derbyshire spar. In the massive* or granulated 
 form it is susceptible of a high polish, and vases, candle- 
 sticks, and various articles of ornament are made from 
 it. This mineral is present in very small quantities in 
 the teeth and bones of animals ; and as there must be a 
 supply of it for these structures from some source, it is 
 found in some plants, which, of course, have imbibed it, 
 as is the case with silex, from the earth. 
 
 106. Apatite. Most of this mineral, whose beautiful 
 crystals present much variety of form, is a compound of 
 phosphoric acid and lime that is, a phosphate of lime. 
 But there is intimately incorporated with this fluor spar, 
 and a very small quantity of the chlorid of calcium. 
 
 107. Salts of Magnesia. The sulphate of magnesia 
 was noticed in 61. The carbonate appears like some 
 of the varieties of carbonate of lime and dolomite. Sul- 
 phate of magnesia (Epsom salt) is often made from it. 
 This is done by means of sulphuric acid, the acid seizing 
 the magnesia and uniting with it, the carbonic acid gas, 
 of course, flying off as it is released. The hydrate of 
 magnesia is a compound of magnesia and water, the lat- 
 ter being nearly one third of the whole. Borate of mag- 
 
 * The term massive is applied to minerals that are imperfectly 
 crystallized that is, having parts of crystals huddled together in a 
 confused mass. The crystals thus massed together may be granular, 
 or fibrous, or laminated. We have a familiar example of the gran- 
 ular in marble, and of the laminated in slate rocks. 
 
OXY-SALTS AND HALOID SALTS. 55 
 
 nesia, called boracite, is a compound of boracic acid and 
 magnesia. 
 
 108. Chlorid of Ammonium. This was formerly sup- 
 posed to be composed of muriatic acid and ammonia, 
 but modern chemistry has discovered that it is a com- 
 pound of chlorine and ammonium, a metal which has 
 never yet been seen, but whose existence has been satis- 
 factorily proved, as shown in 230, Part II. The com- 
 mon name of this mineral is sal ammoniac. It occurs 
 in the vicinity of volcanoes, and is the result of volcanic 
 action. 
 
 109. Alum. Common alum is a double salt, a combi- 
 nation of sulphate of alumina and sulphate of potash. 
 But there are other alums a soda alum, in which there 
 is sulphate of soda in place of the sulphate of potash ; a 
 magnesia alum, in which there is sulphate of magnesia ; 
 an iron alum, in which there is sulphate of iron ; an am- 
 monia alum, in which there is sulphate of ammonia; and 
 a manganese alum, in which there is sulphate of manga- 
 nese. Then there is what is called feather alum, which 
 is not a double salt, but a simple hydrous sulphate of 
 alumina, and therefore can not, strictly speaking, be call- 
 ed an alum. This is more abundant in nature than any 
 of the true alums. This salt, the potash alum and the 
 iron alum, often impregnate the rocks called clay slates, 
 and when thus charged they are termed aluminous slates 
 or shales. Alum is often obtained from these rocks by 
 lixiviation. 
 
 110. Phosphates of Alumina. Wavellite, a mineral 
 which is found adhering to rocks in small hemispheres, 
 is a phosphate of alumina, having combined with it a 
 small amount of fluorid of aluminum. Turquois, an 
 opaque greenish-blue mineral, much used for ornament, 
 is a phosphate of alumina, having combined with it 
 phosphates of copper and iron in small quantities. This 
 gem is often imitated, and the counterfeits are some- 
 times so good that they can be detected only by chemi- 
 cal tests. 
 
56 MINERALOGY. 
 
 CHAPTER VII. 
 
 EAETHY MINERALS. 
 
 111. Composition. A large proportion of the earthy 
 minerals are silicates of the earths alumina, lime, mag- 
 nesia, etc. These earths, as you learned in Part II., are 
 oxyds of metals, and, united with siHca (that is, silicic 
 acid), they form salts called silicates. The different 
 kinds of glass are artificial silicates, many of them very 
 beautiful, but surpassed greatly in beauty by many of 
 the natural silicates found in the rocks. Many of these 
 silicates are very compound, the silica being united with 
 several bases at the same time. Some examples of 
 double salts (salts in which one acid is united with two 
 bases) were brought to your notice in the alums, and 
 some other salts, in the preceding chapter. But many 
 of the earthy minerals are much more compound than 
 this. Some have not only several bases, but more than 
 one acid. Thus, in that beautiful azure-blue mineral, la- 
 pis lazuli, we have both silicic acid and sulphuric acid. 
 Some of the earthy minerals, on the other hand, have a 
 very simple composition. Thus the splendid sapphire 
 and common emery are both the pure earth alumina, 
 that is, oxyd of aluminum ; and then we have, as you 
 will see, many varieties of quartz, which is pure silica, or 
 silicic acid. 
 
 112. Silica. This substance constitutes about 45 per 
 cent, of the crust of the earth, some rocks being entirely 
 composed of it, but more of them having it in combina- 
 tion or in mixture. In the granite we have it in both 
 these states, for the quartz is pure silica; and while this 
 is mixed with two other minerals, mica and feldspar, in 
 these minerals, as you will see in another part of this 
 
EAETHY MINERALS. 57 
 
 chapter, the silica is in chemical combination with other 
 substances, forming silicates. Silica is a very hard sub- 
 stance, scratching glass readily, but inferior in hardness 
 to the diamond. It is insoluble, and can not be melted, 
 even in the strongest heat that can be obtained by the 
 blow-pipe. It appears in greater variety of form and 
 color than any other mineral, but its qualities are so 
 marked that it is easily recognized. As it is so abun- 
 dant in the rocks, and yet hard and insoluble, its frag- 
 ments abound, most of the pebbles in gravel and in the 
 common soil, most of the sand, and much of the hard 
 grains even in what we call fertile earth, being silica. 
 Of course, in every case where there is a decided color 
 there is something besides the silica that is, there is 
 some coloring substance. But where the mineral, when 
 colored, is clear and transparent, there is so little of a 
 foreign substance, and it is so intimately mixed or com- 
 bined with the silica, that it can hardly be regarded as 
 an impurity. But sometimes, especially w r hen the min- 
 eral is opaque, the impurity is palpable oxyd of iron, 
 clay, etc. Flint is one of those opaque forms. This, 
 which was formerly in such wide use in muskets and in 
 the common tinder-boxes, but is now superseded by per- 
 cussion caps and lucifer matches, is quite an abundant 
 mineral, and is extensively used in pottery. 
 
 113. Quartz. There are said to be three varieties of 
 quartz the vitreous, the only one which appears in crys- 
 talline forms, its name coming from the fact that its frac- 
 ture is glassy ; the chalcedonic, generally translucent, 
 with a waxy lustre, often exhibiting several colors, gen- 
 erally fantastically arranged ; and the jaspery, of a dull 
 red, sometimes yellow color. But in common language, 
 even among mineralogists, it is only specimens of the 
 first variety that are usually spoken of as quartz ; and, 
 on the other hand, the two terms silica and quartz are 
 often used as being synonymous. The crystals of quartz 
 are usually six-sided prisms, terminated with six-sided 
 
 C2 
 
58 
 
 MINERALOGY. 
 
 pyramids, but modified so as to present much variety. 
 Some of the forms are represented in Fig. 22. Some of 
 the crystals have the pyramidal terminations at both 
 ends. 
 
 Fig. 22. 
 
 Nothing can be more pure and transparent than clear, 
 uncolored, limpid quartz. The common name for it is 
 rock crystal. It is said that it was to this mineral that 
 the ancients first gave the appellation of crystal, from its 
 resemblance to perfectly clear ice, the Greek word for 
 ice being krustallos. It is often used in jewelry, and also 
 to make lenses for optical instruments. The amethyst, 
 so called, is a variety having a purple or red color from 
 the presence of some oxyd or oxyds. The rich purple 
 specimens, so much prized for jewelry, derive their color 
 from the oxyd of manganese. Sometimes the crystals 
 of quartz have a light yellow color, and then are called 
 false topaz. Smoky quartz appears with various degrees 
 of color. Crystals with the lighter shades are often very 
 beautiful, and are sometimes used in jewelry. Sometimes 
 quartz is filled with golden-yellow spangles of mica; but 
 the artificial imitations of this mineral, contrary to the 
 general fact that nature excels art, transcend in beauty 
 the original. The colors of what is called ferruginous 
 quartz, yellow, brownish-yellow, and red, are produced 
 from oxyd of iron, and hence its name,/emm being the 
 Latin word for iron. 
 
 114. Chalcedony. This kind of quartz, as already 
 stated, does not appear in crystalline form, but in spher- 
 
EARTHY MINERALS. 59 
 
 ical arid nodular masses. In its various forms it is used 
 for making various articles cameos, snuff-boxes, but- 
 tons, marbles, etc. The carnelian, which is so familiar to 
 you, is of a bright red color, sometimes yellow. There 
 is one variety of an apple-green hue, the color being given 
 to it by nickel, the metal found alloyed with iron in me- 
 teorites (71). In agate the colors are arranged either 
 irregularly in spots or clouds, or in regular layers around 
 a centre. Sometimes the lines are zigzag, like the lines 
 of a fortification, and then it is called fortification agate. 
 Sometimes the oxyd of iron is arranged in this mineral 
 in moss-like branches, giving it the name of moss agate. 
 In the onyx the differently colored material is in horizon- 
 tal layers, the colors being commonly a light brown and. 
 a white. This is the mineral which is used for cameos, 
 the figures being cut in one layer, the other layer furnish- 
 ing the background. The variety of chalcedony called 
 cat's eye, of a greenish-gray color, has internal reflections 
 of light which resemble those of the eye of a cat. 
 
 115. Opal. This mineral belongs to neither of the va- 
 rieties of quartz, differing from them in composition by 
 containing water, the water varying in different speci- 
 mens from 5 to 12 per cent. The colors of opal vary 
 much from the presence of coloring matters, which, espe- 
 cially in the dark and thoroughly opaque specimens, may 
 be regarded as impurities. The color of the noble opa\ 
 so highly prized as a gem, is commonly milky, and has a 
 play of brilliant but delicate internal reflections. In the 
 fire opal these reflections are afire-red iu color. Opal 
 has not as muoh hardness as quartz. 
 
 116. Silica in Solution. I have stated that silica is in- 
 soluble. It" is ordinarily so. But sometimes it is dis- 
 solved in water by means of the potash in it, as explained 
 in gr 265, Part II. Thus, in the waters of the geysers 
 and some other hot springs, there is silica in considerable 
 quantity. Here, undoubtedly, heat aids the solution, but 
 it is not its principal cause, for silica is dissolved in water 
 
60 MINERALOGY. 
 
 at ordinary temperatures to some extent in all parts of 
 the globe, as is shown by its deposition in grasses and 
 other plants, and in the textures of animals also, especial- 
 ly some of those minute animals called infusoria, as you 
 will see in another part of this book. These deposits 
 are of course made from solution, the solvent being the 
 sap in vegetables and the blood in animals. 
 
 117. Silica in two States. There are two states, then, 
 in which silica exists, the soluble and the insoluble. Most 
 of it in the world is in the insoluble state, in the rocks 
 and pebbles, and sand and grains in the soil ; but some 
 of it is changing continually from this state into the solu- 
 ble, and as continually passing back again by deposition. 
 Thus, by the agency which I have mentioned, some of 
 the silica in the soil (which came originally from the 
 rocks) is dissolved in the water, and finds its way into 
 the plant by the sap, where it is deposited in the texture, 
 and when deposited it is insoluble again. If the plant 
 decay or is burned the silica is returned again to the 
 earth. The same succession of changes we have also in 
 relation to some animals. And it is supposed that the 
 insoluble silica which we have in chalcedony, jasper, etc., 
 is a deposit from the soluble state. 
 
 118. Petrifactions with Silica. When wood decays in 
 water which contains considerable silica in solution, pet- 
 rifaction occurs ; that is, as the particles of wood are re- 
 moved in the process of decay, particles of silica are de- 
 posited in their place. Of course the silica is deposited 
 from a solution of it that penetrates the wood. The ar- 
 rangement of the wood is preserved, so that it appears 
 as if the wood had been turned into stone. , Some speci- 
 mens are exceedingly beautiful when sawn across what 
 was the grain of the wood and polished. 
 
 119. Silicates of Lime. These are of so little import- 
 ance that I need not describe them. The same is true 
 of the boro-silicates that is, compounds of silicic and bo- 
 racic acids with lime combined together in one mineral. 
 
EARTHY MINERALS. 61 
 
 120. Silicates of Magnesia. These are of t^vo classes, 
 the hydrous and the anhydrous. In them all, which are 
 numerous, there is not merely a silicate of magnesia, but 
 there are also other oxyds, some in one and some in an- 
 other, as oxyd of iron, alumina (oxyd of aluminum), lime 
 (oxyd of calcium), the oxyd of manganese, etc. These 
 additional oxyds are generally small in amount, but in 
 some cases they make quite a considerable portion of the 
 mineral. I will notice only the most important of these 
 silicates. 
 
 121. Talc. This is one of the softest of minerals, being 
 easily cut with a knife. It is commonly of a light green 
 color, and has an unctuous feel. One of its varieties, 
 scaly talc, is the French chalk so familiar to us. Anoth- 
 er, the soapstone (steatite), is found in extensive beds, 
 and is used for many purposes fireplaces, linings for 
 stoves, etc. It is, you know, rather soft, but heat hard- 
 ens it. Powdered soapstone is used for lessening the 
 friction of machinery. 
 
 122. Serpentine. This, when so pure as* to be called 
 precious serpentine, is almost a pure hydrous silicate of 
 magnesia, the only additional oxyd in it being that of 
 iron in the small quantity of 0.2 per cent. that is, -^Jijth 
 of the wjiole. When polished it is a very rich-looking 
 stone, the color being green. Other varieties contain 
 more of the oxyd of iron. There are some rocks com- 
 posed wholly of serpentine, and others that*have ser- 
 pentine mingled with other minerals. The verd-antique 
 marble is granular limestone with serpentine scattered 
 through it. Serpentine was so named from its resem- 
 blance to the skin of a serpent, being streaked or spotted. 
 
 123. Chlorite. This is a dark green hydrous silicate 
 of magnesia, alumina, and iron, there being in it 17 per 
 cent, of alumina and 34 of magnesia. In some parts of 
 the earth there are extensive deposits of this mineral, 
 and also of a slaty rock, which is called chlorite slate, 
 because chlorite is its chief constituent. 
 
(32 MINERALOGY. 
 
 124. Pyroxene. This is a very common mineral, and 
 has many varieties. The colors also are various, being 
 shades of green from the lightest to the darkest. One 
 variety is even white. One of the additional oxyds is 
 lime, which differs in quantity very much in the different 
 varieties. Pyroxene occurs in various rocks granite, 
 limestone, the lavas, etc. 
 
 125. Hornblende. This constitutes a large part of 
 some rocks, as trap and some kinds of slates, giving to 
 them great toughness. Like pyroxene, it contains lime, 
 and some of its varieties it is difficult to distinguish from 
 that mineral. Some of its varieties are beautiful. The 
 famous asbestos is a very remarkable one, being arranged 
 in such slender silky fibres that it may be woven like 
 cotton or linen into cloth. This cloth is incombustible, 
 and, when soiled, can be effectually cleaned at once by 
 putting it into the fire. The Greenlanders use asbestos 
 for lamp-wicks, and in ancient times it was used for this 
 purpose in the temples, its incombustibility being thought 
 to give it a sacred character. Amianthus is a variety of 
 asbestos which has a satin lustre. In Siberia and Spain, 
 gloves, ribbons, and purses are made of it. The differ- 
 ence between the tough hornblende that we find in rocks 
 and this very delicate variety of it is no greater than 
 that between common wood and the delicate varieties 
 of wood which we see in the forms of cotton and linen, 
 and in the textures of leaves, flowers, etc., as noticed in 
 511, Part II. 
 
 126. Alumina. This is an oxyd of aluminum, a metal 
 which is never found in nature, but is obtained artificial- 
 ly from its compounds. Though this metal has been lit- 
 tle known till lately, it is coming into considerable use, 
 especially among the French, on account of qualities 
 which are noticed in 238, Part II. The oxyd alumina 
 is familiar to us in the form of emery. This is granular. 
 But it also appears in various crystalline forms, and, 
 when clear, is exceeded in costliness only by the dia- 
 
EARTHY MINERALS. 63 
 
 mond. It is the sapphire^ and is of various colors. It 
 is only the blue crystals that commonly receive this 
 name, while a red crystal of it is called the Oriental ruby, 
 and a yellow one the Oriental topaz. This mineral is in 
 hardness inferior only to the diamond, scratching quartz 
 quite easily. Alumina is the essential ingredient of all 
 clay, and is therefore very abundant, entering into the 
 composition of many rocks, and forming a constituent 
 more or less of the soil. It is calculated that aluminum, 
 its base, is one twentieth part of the crust of the earth. 
 
 127. Spinel. This mineral is composed essentially of 
 alumina and magnesia intimately combined, there being 
 small quantities in it of other substances, as oxyd -of 
 iron, silica, and chromic acid. The finely-colored crys- 
 tals are prized as gems in jewelry, and the red is the 
 common ruby, in distinction from the Oriental, which is 
 a sapphire. There are some varieties of spinel in which 
 the oxyd of zinc is a prominent ingredient. 
 
 128. Silicates of Alumina. There are a few silicates 
 of alumina that have no other substance in combination, 
 one of which is named Sillimanite, in honor of Professor 
 Silliman, sen., of Yale College. But most of the silicates 
 of this earth are quite compound, having various oxyds 
 and other substances combined with them, as lime, 
 magnesia, potash, soda, oxyd of iron, lithia, oxyd of man- 
 ganese, etc. I will notice a few of those which are most 
 prominent in interest. 
 
 129. Feldspar. This mineral, which is a silicate of 
 alumina and potash, is one of the three crystalline con- 
 stituents of granite, and its partially formed crystals are 
 easily distinguished in the coarser specimens of that 
 rock. It is not as hard as quartz, and is more brittle. 
 Its crystals are commonly four or six-sided prisms, and 
 have a pearly lustre. Two of its usual crystals are rep- 
 resented in Fig. 23 (p. 64). The colors of this mineral 
 are commonly white, milk-white, gray, and flesh-colored, 
 but sometimes the crystals are violet and green. Some- 
 
64 
 
 MINERALOGY. 
 
 times feldspar is opalescent 
 that is, resembling opal in lus- 
 tre, and some specimens of 
 this variety are used in jew- 
 elry. Sometimes it is irides- 
 cent, from the glistening of 
 minute crystals of specular 
 .iron contained in it. Feld- 
 spar is used largely in the 
 manufacture of porcelain, the 
 clay which comes from the 
 decomposition of the feldspar 
 being called 'kaolin. Albite, so called from the fact that 
 white is its most common color, differs from feldspar 
 chiefly in containing soda instead of potash. It takes 
 the place of feldspar sometimes in the rocks. It does 
 so in granite, and albite granite differs from feldspar 
 granite in having a lighter color, owing to the whiteness 
 of the albite. Ldbradoriteis another mineral sometimes 
 found in granite. It differs from feldspar and albite in 
 having a large percentage of lime. 
 
 130. Mica. This is another of the three constituents 
 of granite. It has chiefly the same substances in its 
 composition as feldspar, but there are added small 
 amounts of oxyd of iron, fluoric acid, and water. It has 
 many varieties, but that which is so familiar to us under 
 the common but inappropriate name of isinglass con- 
 sists of extremely thin plates, transparent, with a bright 
 lustre, the colors being white, yellow, gray, brown, and 
 blackish green. It is very elastic, being unlike talc in 
 this respect, though resembling it in some others. It is 
 used for doors in lanterns and windows in ships, where 
 glass, from its brittleness, is liable to be broken. As it 
 bears heat well it is used much in stoves. In Siberia, 
 where it is obtained in large quantities, it is used in place 
 of glass. Plates of it three feet square have been brought 
 from that country, and they have been obtained of the 
 
EARTHY MINERALS. 65 
 
 same size in our own country in several localities in 
 New Hampshire. 
 
 131. Garnet. In this mineral there are combined the 
 silicates of alumina, lime, iron, and manganese, and the 
 various colors of the different specimens generally come 
 from the difference in proportions of these ingredients. 
 The most common color is deep red. In an emerald- 
 green variety the color is caused by oxyd of the metal 
 chromium. Clear garnets of a deep red color are highly 
 prized in jewelry. 
 
 132. Tourmaline. The usual form of the crystals of 
 this mineral is a prism terminating in a low pyramid. 
 They are commonly long, and the sides are apt to be fur- 
 rowed. The most common colors are black, blue-black, 
 and dark brown ; but, besides these, there are wide vari- 
 eties, as bright and pale red, grass-green, yellow, etc., 
 even to white. Though alumina is the chief base in all 
 the varieties, the differences in the composition of some 
 of the varieties are considerable. For example, in a black 
 variety there was found to be 24 per cent, of oxyd of iron, 
 while in a red variety there was no iron at all, but 5 per 
 cent, of the peroxyd of manganese, a frequent cause of 
 this color in minerals. Some red and yellow tourmalins 
 are of great value as gems. A Siberian tourmaline of 
 the red variety, now in the British Museum, is considered 
 to be worth 500. 
 
 133. Topaz. This is said to be a silicate combined 
 with a fluorid. If so, it must be a combination of sili- 
 cate of alumina with fluorid of the metal aluminum, for 
 there can be no such thing as a fluorid of alumina any 
 more than there can be a chlorid of soda. In explana- 
 tion of this I refer you to 352, Part II. The clear crys- 
 tals of topaz are used in jewelry, and it is a curious fact 
 that the color can be altered for this purpose by exposure 
 to heat. The Brazilian topaz can be thus made so to re- 
 semble the real rose-red ruby that it can not be distin- 
 guished from it except by an electrical test. When the 
 
66 MINERALOGY. 
 
 most clear, pellucid pebbles of topaz are cut with facets 
 and set, they appear by daylight precisely like diamonds. 
 
 134. Lapis Lazuli. In this beautiful azure-blue miner- 
 al we have a compound of silica, alumina, soda, lime, iron, 
 sulphuric acid, sulphur, chlorine, and water. It is plain 
 that the silicic acid and the sulphuric acid must form with 
 some of these oxyds a silicate and a sulphate, which are 
 intimately combined together, but how some of these 
 substances are combined we know not. The color is at- 
 tributed to sulphuret of sodium. There are some speci- 
 mens of this mineral whose composition differs somewhat 
 from that given above. 
 
 135. Beryls and Emeralds. A beryl is a silicate of 
 alumina and glucina, while an emerald is the same, col- 
 ored with oxyd of chromium to the amount ofless than 
 one per cent. The color is mostly green pale in the 
 beryl, but decided and rich in the emerald. The best 
 emeralds are brought from Granada, where they are 
 found in dolomite ( 104). One, weighing six ounces, 
 cost the owner, Mr. Hope, of London, 500. Emeralds 
 of larger size, but of less beauty, are obtained in Siberia. 
 One in the royal collection of Russia measures four and a 
 half inches by twelve. The finest beryls come from Si- 
 beria, Hindostan, and Brazil. Some beryls of very great 
 size have been obtained in this country, but they are 
 seldom transparent. A hexagonal prism was found in 
 Grafton, New Hampshire, of such enormous size that it 
 weighed 2900 pounds. It is four feet in length. The 
 chrysoberyl is a combination of alumina and glucina, 
 sometimes with a little iron. The color is indicated by 
 the name, which comes from two Greek words, chrysos, 
 yellow, and beryllos, beryl. 
 
 136. Zircon. This mineral, which is a silicate of the 
 earth zirconia, has various colors. The clear crystals are 
 in common use in jewelry. "When they are red they are 
 called hyacinths. This variety has some resemblance to 
 the red spinel. Zircon is used in jeweling watches. 
 
ROCKS. 67 
 
 CHAPTER VIII. 
 
 ROCKS. 
 
 137. Connection of Mineralogy with Geology. In this 
 chapter we shall pass over ground that connects miner- 
 alogy with geology. We have looked at minerals in de- 
 tail and in their separate condition, merely alluding to 
 them occasionally as being masses, but now we are defi- 
 nitely to consider these masses preparatory to a view of 
 them as a whole, making up the crust of the earth. It 
 is such a view that constitutes Geology, the term being 
 derived from two Greek words, ge^ earth, and logos^ dis- 
 course. 
 
 138. Definition of Rock. The word rock, in common 
 language, is applied only to such mineral aggregates of 
 considerable size as are solid ; but the geologist gives it 
 a wider meaning. He speaks of all such aggregates as 
 rocks, whether they are solid or made up of loose mate- 
 rial. Thus the clay slate, and the strata of clay mud, 
 which, by long-continued pressure, or this and heat to- 
 gether, might ultimately become clay slate, are both 
 equally regarded as rock. The same may be said of 
 sandstones and deposits of sand. The geologist, how- 
 ever, often uses the word rock in its ordinary sense, the 
 context showing in which sense he does use it. 
 
 139. Elementary Substances in the Rocks. There are 
 between sixty and seventy elements, but only nine of 
 them enter to any great extent into the composition of 
 the rocks, viz., oxygen, silicon, aluminum, calcium, mag- 
 nesium, potassium, sodium, iron, and carbon. Of these 
 only one, oxygen, is a gas, but that is so abundant that 
 it is supposed to constitute nearly or quite one half of 
 all the ponderable matter in the globe. These elements, 
 
68 GEOLOGY. 
 
 it is stated by Dana, make up ^^ths of the rocks as a 
 whole. But there are some other elements which enter 
 into the composition of some rocks. Sulphur exists in 
 sulphate of lime or gypsum, which in some parts of the 
 earth occurs as a rock in beds of considerable extent. 
 This is the only compound containing sulphur of which 
 any rocks are made. Sulphurets, as you saw in Chapter 
 IV., are abundant, but they are only ores in rocks, and 
 do not enter into their composition. Hydrogen is an- 
 other element that is present in some rocks. It is pres- 
 ent in the water, which is, as you have seen, a component 
 of hydrous minerals, and some of these, as gypsum and 
 serpentine, form rocks. The amount of water in gypsum 
 is 21 per cent. 
 
 140. Compounds in the Rocks. The elements of which 
 I have spoken do not form rocks as elements, but as com- 
 pounds. Thus oxygen forms with silicon a compound, 
 silica or silicic acid ; and this silica constitutes rock of 
 itself (quartz rock) ; or makes a part of a mixture of rock, 
 as in the quartz of granite ; or, uniting with some oxyds, 
 makes silicates, as in the feldspar and mica of granite, in 
 serpentine, in chlorite, etc. The most important of the 
 compounds which compose the rocks of the globe are 
 silica, carbonate of lime, and various silicates, viz., feld- 
 spar, mica, hornblende, and pyroxene. Besides these, the 
 only minerals that have any large share in making up 
 the earth's crust are chlorite, serpentine, talc, gypsum, 
 and coal. All these minerals have been sufficiently de- 
 scribed in previous chapters. 
 
 141. Crystalline and Uncrystalline Rocks. It is plain 
 that marble is crystalline, although none of the individ- 
 ual crystals, as they were crowded together in their for- 
 mation, was completed. The glistening is occasioned 
 by the small portions of the faces of the crystals which 
 reflect the light. The same incomplete crystalline struc- 
 ture is seen in the three minerals that compose granite, 
 as we look at a fractured face of that rock. But sand- 
 
ROCKS. 69 
 
 stones were evidently formed by a different process. 
 Here we have grains mechanically mixed, as in a layer 
 of sand on a sea-shore, and then in some way becoming 
 solid rock. The grains themselves may have been form- 
 ed at the outset when they were a part of some other 
 rock by a crystallizing process ; but after the original 
 rock became broken and worn in one way and another 
 into these grains, they became arranged by the agency 
 of water in layers, and changed into solid rock by means 
 which we shall hereafter consider. 
 
 142. Rocks Composed of a Single Mineral. Rocks 
 sometimes are composed of one mineral alone. Pure 
 limestone, in its three varieties of common limestone, 
 chalk, and marble, is of this character, being simple car- 
 bonate of lime. Sometimes, though a rock may be a 
 single mineral throughout, that mineral may not be sim- 
 ple in its composition. Thus the rock called dolomite 
 is a magnesian carbonate of lime, or, in other words, 
 carbonate of lime and carbonate of magnesia intimately 
 combined, so as to make one mineral. Other examples 
 of rocks composed of a single mineral are quartz rock, 
 gypsum (sulphate of lime), serpentine, etc. 
 
 143. Rocks Composed of more than one Mineral. 
 Most rocks are constituted by a mixture of different 
 minerals. Granite is a familiar example, being a mix- 
 ture of quartz, feldspar, and mica. Sometimes the ingre- 
 dients are so finely mingled that, different from granite, 
 the composite minerals can not be at all distinguished. 
 Pudding-stones are aggregates or conglomerates of peb- 
 bles, united by some cementing mineral, most commonly 
 silica, or oxyd of iron, or carbonate of lime. The peb- 
 bles may be of one kind or of different kinds, and they 
 vary much in size. When the conglomerate contains 
 angular pieces instead of rounded pebbles, it is called 
 breccia. Usually the pebbles or pieces are granite, or 
 quartz, or carbonate of lime, and the conglomerate is ac- 
 cordingly said to be respectively granitic, quartzose, or 
 
70 GEOLOGY. 
 
 calcareous, this latter term being commonly applied to 
 all compositions in which there is limestone. 
 
 144. Stratified and Unstratified Rocks. It is manifest 
 to the most superficial observer that some rocks are in 
 layers or strata, while others have a very different ar- 
 rangement. A full consideration of the modes of con- 
 struction of the different forms of rock belongs to an- 
 other part of this book. Suffice it to say now that the 
 materials of the stratified rocks were assorted and laid 
 down by water, and then by some means became solidi- 
 fied, while the unstratified were made under the influ- 
 ence of strong heat. 
 
 145. Silicious, Argillaceous, and Calcareous Rocks. 
 Stratified rocks are divided into three classes, according 
 to their composition. The first class is the silicious or- 
 arenaceous. This is the sandy division, called arenaceous 
 from arena, the Latin word for sand, and silicious, be- 
 cause the grains of which the rock is composed are 
 silica, or silex, as it is commonly called. The second 
 class, the argillaceous, are made of clay, which is a mix- 
 ture of silex and alumina, commonly in the proportion 
 of about three of the former to one of the latter. The 
 name comes from argil, a term applied technically to 
 alumina, and probably to clay. It is a characteristic of 
 rocks of this class that they give out a peculiar earthy 
 odor when breathed upon, which is not owing to the 
 presence of alumina simply, but to a combination of this 
 with some oxyd of iron. Calcareous rocks are those 
 which are composed of lime and carbonic acid. These 
 three classes of rocks are seldom found pure, but they 
 run into each other. For example, there are sandstones 
 which are not wholly silicious, the silicious grains being 
 united together by carbonate of lime. Whether any si- 
 licious or argillaceous rock has the carbonate of lime in 
 it can at once be ascertained by the application of sul- 
 phuric acid ( 60.) 
 
 I pass now to consider some of the individual rocks. 
 
BOCKS. 
 
 71 
 
 146. Granite. Ordinary granite is a mixture of quartz 
 or silex, mica, and feldspar. There is great variety in 
 this rock, according to the varying proportions of these 
 minerals, and each variety is termed feldspathic, mica- 
 ceous, or quartzose, as one or the other mineral predom- 
 inates. There are other variations also. Sometimes 
 hornblende is present in place of mica, and then the rock 
 is called syenite. This is even more durable than com- 
 mon granite. Its name comes from Syene, in Upper 
 Egypt, the locality from which most of the stones of the 
 ancient Egyptian monuments were obtained. These are 
 not, however, true syenite, but a red granite, containing 
 considerable dark-colored mica. The rock of Mount Si- 
 nai is real syenite. When albite is in the place of feld- 
 spar, the rock is called albite granite ( 129). When 
 talc replaces it, it is called protogine. When the feldspar 
 appears in the granite in large crystals, it is called por- 
 phyritic granite. There is a peculiarity in the crystal- 
 line arrangement of one kind of granite which produces 
 figures over its surface like small Oriental characters, 
 and hence this variety is styled graphic granite. In Fig. 
 25 is given the surface of a slab of this granite, and in 
 Fig. 24 its end. The colors of granite vary much, but it 
 
 Fig. 25. 
 
 is usually grayish, white, or flesh-colored. 
 Rocks of the granite family are widely disseminated in 
 the earth, often forming extensive mountain ranges. In 
 some parts of the Andes granite rises to the height of 
 12,000 feet. In the Alps, the Aiguille de Dree is a solid 
 spire of granite 4000 feet high. There is much granite 
 
72 GEOLOGY. 
 
 , 
 
 of different kinds in New England, Massachusetts being 
 truly the granite state of the Union, though New Hamp- 
 shire is generally called so. 
 
 147. Uses of Granite. Granite, on account of its dura- 
 bility, is one of the most valuable materials for buildings 
 and monuments. It was much used by the ancients, and 
 there are obelisks of granite in Egypt that have been ex- 
 posed to the weather for three thousand years, and yet 
 are in good condition. Commonly, the finer is the tex- 
 ture of granite, the more durable is it. Syenite, which is 
 so durable, is of a fine texture, but it owes its durability 
 partly to the toughness which hornblende imparts ( 
 125). If there be pyrites or any other ore of iron dis- 
 seminated through the rock, it impairs its value essen- 
 tially, because by decomposition rust is produced, defac- 
 ing and often crumbling the stone. Some granites, which 
 present a good appearance on being taken out of the 
 quarry, very soon crumble on continued exposure to the 
 air without any obvious cause. This shows the neces- 
 sity of proper examination in selecting granite for build- 
 ing. As feldspar contains a large proportion of alumina, 
 feldspathic granite is much used in obtaining the kaolin 
 for making porcelain. 
 
 148. Gneiss. This is a rock which has precisely the 
 same mixture of minerals in it that granite has, but the 
 arrangement is different. It is a stratified rock. It is 
 foliated ; that is, it is in leaves, and is split easily in dif- 
 ferent thicknesses, varying from a few inches to a foot 
 or more. This cleavage occurs where the mica is most 
 abundant. When it cleaves in thin slabs it is used for 
 flagging, but when it can be got out in thick blocks it 
 is used for building. Some of the buildings of Amherst 
 College are constructed of this material, and present a 
 fine appearance. There are many quarries of it in Mas- 
 sachusetts, and some in Connecticut. 
 
 149. Slates, Shales, and Schists. These terms are oft- 
 en used as being synonymous ; but when they are used 
 
as having different meanings, the disuuUlilOlJS are these: 
 Slate is the term used when the rock splits into thin 
 laminae, and when the word is used alone it means clay 
 slate. But there are mica slates, hornblende slates, etc. 
 The word shale is used when the rock, though slaty, is 
 more brittle than slate, and so crumbles readily. Schist 
 includes rocks so coarse that it would not be proper to 
 call them slates or shales. It comes from the Greek word 
 schistoS) divided or split. 
 
 Mica slate, or schist (for it is called by both names), has 
 the same ingredients with gneiss, but has less of feldspar 
 and more of mica in it. The scales of mica give a glis- 
 tening appearance to the surface of the slabs, which are 
 used for flag-stones, hearth-stones, and door-steps. Fur- 
 naces are sometimes lined with them. Scythe-stones are 
 made out of varieties that have a fine grain. 
 
 Hornblende slate, or schist, is more durable than mica 
 slate, from the toughness which the hornblende gives it 
 ( 125), and is therefore very valuable for flagging. 
 
 Talcose slate, or schist, is brittle, but is used for fire- 
 stones. 
 
 . Clay slate has about the same composition with mica 
 slate, but the ingredients are so finely mixed that they 
 can not be distinguished from each other. The colors 
 are commonly bluish, greenish, gray, or reddish. Slate 
 is used for roofing, and for making drawing-slates, pen- 
 cils, etc. 
 
 150. Quartz Rock. This is composed of quartz, either 
 in the granular or arenaceous (sandy) form. There are 
 varieties which result from the admixture of other sub- 
 stances, as mica, feldspar, etc. In these varieties there is 
 regular stratification, especially in the micaceous, which 
 often cleaves into slabs, like gneiss and mica slate ; but 
 when the rock is unmixed granular quartz there is no ob- 
 vious stratification. Quartz rock is used for flag-stones, 
 hearth-stones, and fire-stones, and in the form of cobble- 
 stones for paving. The fine sand into which this rock 
 
 D 
 
4 GEOLOGY. 
 
 sometimes crumbles is employed in making glass, and in 
 sawing and polishing marble. The sand of our sand- 
 paper comes from this source. The buhrstone^ which is 
 made into mill-stones, is quartz rock that is full of little 
 spaces or cells, these making the surface rough with sharp 
 minute edges crossing each other in every direction. 
 
 151. Sandstones. These usually consist mostly of sili- 
 cious sand, some of the varieties of quartz rock approach- 
 ing very nearly to them in character. Sometimes there 
 is much clay in their composition, and then the rock is 
 called an argillaceous sandstone. Sometimes there are 
 silicious pebbles imbedded in the rock, making it in part 
 a pudding-stone, and in that case, if the rock be very 
 hard, it is called a grit rock or mill-stone grit. Some 
 sandstones that readily split into comparatively thin lay- 
 ers are much used for flagging-stones. Sandstones have 
 dull colors of various kinds, from white, through grades 
 of yellow, red, and brown, even to black, these being 
 caused, of course, by various substances combined with 
 the silex or quartz. When sandstone has a fine, even 
 grain, it is a very beautiful building material. More cau- 
 tion is necessary in selecting sandstone for building than 
 granite, because varying circumstances of exposure to* 
 air, moisture, and heat have so much influence upon it. 
 The sandstone obtained chiefly from New Jersey and va- 
 rious localities in the valley of the Connecticut, now so 
 much used in almost all parts of the country to which it 
 can be carried by water, is generally an excellent mate- 
 rial. That used in building the Capitol at Washington, 
 which came from the Potomac, is, unfortunately, an infe- 
 rior article. 
 
 152. Trappean Rocks. This appellation is given to 
 certain rocks which have such resemblance to each other 
 as makes it proper to group them together. The term 
 trap comes from a Swedish word meaning stair, the rocks 
 of this class often presenting to the eye an appearance 
 like steps. The term greenstone is applied to the com- 
 
ROCKS. Y5 
 
 pact rocks of this class in which hornblende is largely 
 present, and imparts a green color. Basalt is much like 
 greenstone, but is black or grayish-black. It contains 
 small grains of a silicate of magnesia and iron, called ol- 
 ivine, from its olive-green color. Trachyte is a grayish- 
 white rock composed of feldspar, hornblende, and mica. 
 Clinkstone is a grayish-blue feldspathic rock, which bears 
 this name because it rings like iron when struck with a 
 hammer. The term porp hyry is used in reference to the 
 structure of rocks rather than their composition. It is 
 applied to any feldspathic rock that has crystals dissem- 
 inated through it. It is called greenstone porphyry, ba- 
 saltic porphyry, etc., according to the material which 
 makes up the body of the rock, or, as it is commonly ex- 
 pressed, the base of the rock. What the ancients called 
 porphyry is a rock having a base of compact feldspar, 
 with imbedded crystals of feldspar of various sizes, from 
 a very small size up to a length of three fourths of an 
 inch. The name amygdaloid refers also to structure. 
 It comes from two Greek words, amygdale, almond, and 
 eidos, like, and is applied to any rock of the trap family 
 that has in it rounded cavities filled with some mineral 
 different from the base of the rock. The appearance is 
 as if the rock was once in a pasty state, and, when so, 
 these rounded bodies were mixed up with it like almonds 
 in cake. 
 
 153. Tendency of Trappean Rocks to the Columnar 
 Form. In some cases the tendency of rocks of the trap 
 family to take on a columnar arrangement is shown in 
 the most decided manner. One of the most noted ex- 
 amples is in FingaPs Cave, on the island of Staffa, rep- 
 resented in Fig. 26 (p. 76). Another is the Giant's Cause- 
 way, in Ireland. The columns vary from 20 to 200 feet in 
 height, and are jointed, presenting, therefore, an appear- 
 ance as if they had been built up by putting one pentag- 
 onal or five-sided stone upon another. Where the sea 
 has dashed against them they are more or less worn 
 
76 
 
 GEOLOGY. 
 
 Fig. 26. 
 
 away above, and below extend to unknown depths be- 
 low the water. Looking like ruins of some ancient 
 work too great for man, it is not strange that popular 
 tradition has connected with them the agency of giants. 
 In most cases the tendency is only partially exhibited, 
 as, for instance, in East and West Rock, at New Haven. 
 The columns are prisms, having from three to eight 
 sides, commonly five or six, and 
 they are generally divided into 
 blocks by joints, as seen in 
 Fig. 27. Each block is usually 
 concave on its upper part, hav- 
 ing the lower convex end of 
 the block above fitting into it. 
 ___ Commonly the columns stand 
 
 Fig. 27. 
 
 upright, but sometimes 
 they are horizontal, as in 
 Fig. 28, representing a ba- 
 saltic dike in North Caro- 
 lina. The appearance in this case is that of a wall built 
 as a fortification. Sometimes the columns are in the po- 
 sition represented in Fig. 29. Sometimes the columnar 
 and massive forms are conjoined, as seen in this figure. 
 A remarkable example both of this position of columns 
 
 Fig. 28. 
 
EOCKS. 77 
 
 and their union with the massive rock is 
 to be seen on Mount Holyoke, in Massa- 
 chusetts, in Titan's Piazza, so called be- 
 cause there is a group of columns of 
 greenstone pointing downward from the 
 overhanging rock above. 
 
 The manner in which rocks of this 
 family are formed will be considered in 
 another part of this book. 
 
 154. Trappean Rocks in this Country. 
 Beginning at the north, there is a belt of trap extending 
 130 miles along the Bay of Fundy, where the violence 
 of the waves has exposed to view magnificent groups of 
 columns three and four hundred feet in height. In the 
 neighborhood of Boston, at Nahant, Lynn, etc., there are 
 ridges, some of them rising to the height of 500 feet. 
 A range beginning at East and West Rock, New Ha- 
 ven, extends up the valley of the Connecticut almost to 
 Vermont, including Mounts Tom and Holyoke, which 
 rise to a height of over a thousand feet. The noted 
 Palisades, on the Hudson, are greenstone. Three ridges 
 of trap extend through the State of New-Jersey, and 
 trap rocks are found in beds and elevations as far south 
 as North Carolina. But it is west of the Rocky Mount- 
 ains that trap most abounds and reaches the highest ele- 
 vations. Columbia River has on each side of it mount- 
 ains of trap, in some cases even a thousand feet in height. 
 The appearance of the columns is seen in Fig. 30, p. 78. 
 
 155. Lavas. The materials thrown out from volca- 
 noes become, as they solidify, what are called lava?^ The 
 various kinds differ in structure and composition, and, 
 of course, in color. There are two classes of lavas the 
 light colored, in which feldspar is the chief constituent, 
 and the dark colored, or basaltic, which are grayish- 
 blue, even to black. The structure of lavas depends 
 upon circumstances. That which cools under pressure, 
 and while shut in from the atmosphere, is compact ; but 
 
78 
 
 GEOLOGY. 
 
 Fig. 30. 
 
 that which is at the surface, owing to rapidity of cool- 
 ing and the action of the air, is porous, and has the name 
 of scoria. What is called pumice, it is supposed, was 
 cooled by being thrown into water. Though its mineral 
 constitution is the same with the hard, compact lava, it 
 will float on water from its great porousness. It is used 
 for polishing various substances, as wood, ivory, mar- 
 ble, glass, parchment, etc. Obsidian and pitchstone are 
 vitreous or glassy lavas, the former resembling glass 
 more than the latter, which receives its name from its 
 pitCivJ lustre. The lavas are very much like the rocks 
 of the trap family, a fact which is of much significance 
 in relation to the formation of the latter, as you will sec 
 in a future stage of our investigation. 
 
 There are other rocks limestone, serpentine, etc.; 
 but these I have spoken of sufficiently before. 
 
THE EARTH AS IT IS. 7 9 
 
 CHAPTER IX. 
 
 THE EARTH AS IT IS. 
 
 156. The Earth as a Whole. The earth is a ball near- 
 ly round, composed of solid, liquid, and gaseous substan- 
 ces, the gaseous occupying the interstices of both solids 
 and liquids, there being also a gaseous envelope around 
 the earth of about fifty miles in thickness. The most 
 abundant liquid is water, which fills up all the cavities 
 on the earth's surface. If the solid part of the earth 
 were uniform instead of having its present diversified 
 condition, it would every where be covered with water, 
 the atmosphere remaining, as now, outside of the liquid 
 envelope. The earth, as a whole, has been found, by vari- 
 ous observations and calculations, to be between five and 
 six times the weight of water, and about two and a half 
 times as heavy as the average of common rocks. This 
 great weight of the earth is owing to the pressure to 
 which its internal parts are subjected from the influence 
 of gravitation. Every thing is attracted toward the 
 centre, and therefore any internal portion of the globe is 
 pressed toward this centre by the weight of all which is 
 outside of it. It is just as the lower portions of the air 
 that is, those which are close to the earth are con- 
 densed by the pressure of those portions outside of them 
 through gravitation, as illustrated in 152, Part I. It 
 has been calculated that at the depth of 34 miles in the 
 earth air would be so condensed that it would be as 
 heavy as water, and at the depth of 362 miles water 
 would be so condensed that it would be as heavy as 
 mercury, although here upon the surface of the earth 
 water is so little compressed by the strongest pressure 
 man can bring to bear upon it that it is regarded practi- 
 
.80 
 
 GEOLOGY. 
 
 cally as incompressible. It is also calculated that steel 
 at the centre of the globe would be compressed into a 
 fourth of its bulk, and most rocks into an eighth of their 
 bulk. 
 
 157. Form of the Earth. I have said that the earth is 
 nearly round. Its deviation from a perfectly spherical 
 shape is very slight that is, compared with its whole 
 bulk. Though it bulges out at the equator 13^ niiles, 
 this, in a ball eight thousand miles in diameter, is but a 
 small matter. This can be shown by the diagram, Fig. 
 31. Let the curved line PEPE represent the circum- 
 
 
 Fig. 31. 
 
 ference of the earth as it is with the line running through 
 the poles, PP. But this is not a true circle, for the di- 
 ameter EE is longer than the diameter PP. The true 
 circle described by the diameter PP revolving on the 
 
THE EAKTH AS IT IS. 81 
 
 centre c would be PePe. The truth in regard to the 
 shape of the earth is represented here, but much exag- 
 gerated how much you shall see. The line PP is on 
 the scale of 2600 miles to the inch, to represent the 8000 
 miles of the earth's diameter. Of course -^th of an inch 
 would be 260 miles, and to make the amount of exagger- 
 ation alluded to above apparent to the eye, an inner cir- 
 cle at this distance from the outer one is drawn. You 
 see, then, that a tenth of the distance between the outer 
 and inner circle ( 3 ff) would be 26 miles, and the bulging 
 of the earth at the equator is but half of this amount. 
 To get at the real, unexaggerated fact, then, you must 
 take only the -^ih part of the distance from e to the in- 
 ner circle to represent the bulging of the earth, and this 
 would be adequately represented by merely doubling the 
 line of the figure at e, and letting it gradually diminish to 
 the single line as you go to the poles PP. But small, 
 comparatively, as this equatorial bulging is, it is supposed 
 to be of very great importance in tending to keep the 
 earth always revolving uniformly on one axis the polar 
 axis. With the very rapid revolution of the earth (1000 
 miles every hour), and its more rapid motion in its orbit 
 (68,000 miles every hour), even a slight deviation from 
 regularity in the revolution would be attended with dis- 
 astrous results. There are inferences to be drawn from 
 the shape of the earth in reference to its formation, but 
 these will be spoken of in another chapter. 
 
 158. Crust of the Earth. In the crust of the earth, so 
 often spoken of by geologists, is included all that portion 
 of the globe of which we have any knowledge through 
 their investigations. Of course we know nothing defi- 
 nitely and certainly of the contents of the interior of the 
 earth ; but great depths have been reached in mining, 
 and besides, as you will see in future portions of this 
 book, there have been upheavals of the crust which have 
 opened to view vastly greater depths than the miner has 
 ever reached. The foundation of this crust is every 
 D2 
 
82 GEOLOGY. 
 
 where rock. However deep may be the cavities which 
 hold the water, there is a rocky bottom, and, dig wher- 
 ever you will, rock is found beneath the earth and sand. 
 It is said by Bakewell that " the crust of the globe with 
 which we are acquainted does not exceed, in comparative 
 thickness, that of a wafer to an artificial globe three feet 
 in diameter." 
 
 159. Land and "Water. The surface of the globe is 
 reckoned as containing about 211,000,000 square miles, 
 of which about 150,000,000 are covered with water, and 
 61,000,000 appear as land. The proportion of water-sur- 
 face to land-surface is nearly 8 to 3. 
 
 160. Elevations and Depressions in the Earth's Sur- 
 face. The elevations in the forms of hills, table-lands, 
 and mountains vary exceedingly, the highest being 
 Mount Everest, in the Himalaya range, which is 29,000 
 feet, or five and a half miles high. The ocean varies 
 much in depth, sometimes probably reaching to 50,000 
 feet, though no satisfactory soundings have ever ascer- 
 tained such a depth. The average depth is somewhere 
 from 15,000 to 20,000 feet. Often about the continents 
 there is a fringe, as we may term it, of shallows. On the 
 coast of the United States, off the State of New Jersey, 
 there is such a fringe 80 miles in width, the depth at its 
 edge (where the ocean really begins) being only 600 feet, 
 while the depth across the ocean, in a line from New- 
 foundland to Ireland, has been found to be from 10,000 
 to 15,000 feet. Some extensive waters, also, between dif- 
 ferent bodies of land, can not be regarded as parts of the 
 ocean. In the waters separating Great Britain from Eu- 
 rope the depth is less than 600 feet, and in a large part 
 of the German Ocean it is only 93 feet. Similar facts 
 have been discovered in regard to the waters between 
 Asia and the islands appended to it. These should really 
 be considered as a part of the continent of Asia, and Great 
 Britain as a part of the continent of Europe. 
 
 Although the projection of the earth at the equator is 
 
THE EARTH AS IT IS. 83 
 
 so small compared with the whole earth, as was shown 
 by Fig. 31, yet it is much greater than the mountainous 
 projections on its surface, for the amount of this projec- 
 tion is 1 3^ miles, while the height of the highest of the 
 mountains is 5^ miles. It is to be observed, also, that the 
 depressions are much greater than the elevations, with 
 the exception of the grand equatorial one, for in some 
 cases they probably reach, as already stated, a depth of 
 50,000 feet ; and, if the ocean were laid bare, we should 
 see irregularities like those on the land, but on a much 
 larger scale. Between the so-called Banks of Newfound- 
 land and Newfoundland itself there is one of those deep 
 submarine valleys, while at the Banks there is a plateau 
 of rock that comes within about 250 feet of the surface. 
 The water on this plateau abounds in fish, which choose 
 such shallow places rather than the deep ocean valleys. 
 South of the Banks the Atlantic Ocean reaches the im- 
 mense depth of 30,000 feet. 
 
 161. Arrangement of the Land. There are some pecul- 
 iarities in the arrangement of the land of the earth that 
 are worthy of notice. The great bulk of it is in the 
 northern hemisphere, up about the arctic region, there 
 being nearly three times as much land north of the equa- 
 tor as there is south of it. As it extends from the north 
 down into the southern hemisphere it narrows very 
 much, as seen in the shape of North America and Africa, 
 which is triangular. The same disposition of the land 
 is essentially carried out in Hindostan and other exten- 
 sions southward of the continent of Asia. Notice, be- 
 sides this, that the land is really divided into two great 
 parcels, the Eastern and Western Continents, for Europe, 
 Asia, and Africa may be regarded as one ; and that there 
 are two great oceans between them, one of them being 
 much larger than the other. It may be remarked here 
 that, in the present state of the world, it is a very great 
 advantage and convenience to have the narrower ocean, 
 the Atlantic, lying between those portions of the world 
 
84 GEOLOGY. 
 
 which, from their common civilization, have so much in- 
 tercourse with each other. It would be a great bar to 
 this intercourse to have so wide an ocean as the Pacific 
 lying between America and Europe. I have spoken of 
 the two grand masses of land as extending from the arc- 
 tic region down into the southern hemisphere; but ob- 
 serve that it is not an unbroken extension of land. By 
 an arrangement of the waters, as noticed by Professor 
 Guyot, there is a band of water from east to west cut- 
 ting the land in two almost completely so nearly that 
 it requires only two short canals to be made by man to 
 finish the communication. This belt is composed of the 
 two oceans, the Mexican Ocean in the western hemi- 
 sphere, and the Mediterranean Sea, the Red Sea, and the 
 seas of the East Indies in the eastern. You can readily 
 see how this arrangement promotes largely the inter- 
 course by water throughout the earth, and how import- 
 ant it is that those parts of the plan which the Creator 
 has purposely left to the ingenuity and enterprise of man 
 should be carried into execution. 
 
 162. Arrangement of Mountains Mountains are not 
 scattered about here and there in a confused manner, 
 but there is an obvious general plan in their arrange- 
 ment. They are to a great extent placed in chains or 
 ranges, as you see in the Rocky Mountains, the Andes, 
 the Appalachians, the Pyrenees, the Urals, the Himala- 
 yas, etc. Perhaps the most remarkable fact about these 
 mountain chains is that they are so arranged as to in- 
 close large basins of land on the continents. Thus in 
 North America the immense basin watered by the Mis- 
 sissippi and other rivers lies between the great ranges 
 of mountains on the east and the west. It is this basin 
 arrangement, with great mountain walls, that is the 
 grand characteristic of a continent in distinction from 
 an island. Notice another great fact in the arrange- 
 ment. The highest mountains are placed on that side 
 of the continent which is toward the broadest ocean. 
 
THE EARTH AS IT IS. 85 
 
 Thus the Rocky Mountains are higher than the range of 
 mountains which run down from Maine to Georgia, 
 called by the general name of the Appalachian range. 
 So also, as the Pacific Ocean is broader opposite to 
 South America than opposite North America, the Andes 
 are much higher than the Rocky Mountains. The same 
 plan, essentially, is carried out in Africa, Australia, and 
 also in Europe and Asia, though not in so clear and sim- 
 ple a manner. 
 
 There is much variation in the arrangement of differ- 
 ent ranges of mountains. They are more commonly 
 curved than straight, and the manner in which the indi- 
 vidual mountains stand toward each other is very differ- 
 ent in different cases. 
 
 There are certain prevalent directions of the chains of 
 mountains, and the same is true of groups of islands, 
 which are often really the summits of submerged mount- 
 ain ranges. In the Pacific Ocean they have usually a 
 northwesterly direction, or trend, as it is termed. 
 
 163. Volcanoes. Some mountains throw out occasion- 
 ally from their summits large quantities of liquid lava 
 and matter in gaseous form ; often also solid rocks, ash- 
 es, mud, etc. The exhibitions made in these eruptions 
 are among the most magnificent in nature. About two 
 thirds of the volcanoes are on islands, and the greater 
 part of the other third are near the ocean on the conti- 
 nents. This nearness to water is supposed to show that 
 steam must have much to do with the eruptions, which 
 also seems to be proved by the fact that in these erup- 
 tions great quantities of steam escape. In Fig. 32 (p. 86), 
 in which the shaded parts indicate the localities of vol- 
 canoes, not only is their vicinity to the ocean shown, but 
 the fact that, like ordinary mountains, they are very often 
 arranged in ranges. 
 
 164. Plateaus and Lowlands. Any extended region, 
 whether it be flat or diversified, if it be much elevated 
 above the level of the sea, is called a plateau, while the 
 
86 
 
 GEOLOGY. 
 
 Fig. 32. 
 
 term lowland is applied to regions that are less than a 
 thousand feet above that level. The great valley of the 
 Mississippi, the plains of the Amazon, and the pampas 
 of La Plata, are examples of the latter. Plateaus some- 
 times extend between ranges. Both plateaus and low- 
 lands may have single mountains or mountain ridges. 
 The term table-land is often applied to plateaus, especial- 
 ly when their surface is little diversified. One of the 
 most elevated plateaus in the world is that of Thibet, ly- 
 ing between the Himalayas and the Kuen-Luen Mount- 
 ains, the height varying from 11,000 to 15,000 feet. The 
 State of New York is a plateau, varying in height from 
 1500 to 2500 feet. The Great Salt Lake lies in a corner 
 of a plateau by the Rocky Mountain range, which has an 
 altitude of from 4000 to 5000 feet. There are some lofty 
 plateaus in South America. The city of Quito is situa- 
 ted on a plateau at an elevation of nearly 10,000 feet, and 
 the city of Potosi on one at an elevation of 13,330 feet, 
 the Lake Titicaca being on the same plateau at the height 
 of 12,830 feet. We often see the same arrangement in 
 a small way among hills of ordinary size. An elevated 
 plain skirts a hill, or lies between hills, making a plateau 
 of small extent. There may be a pond also in such a 
 plain, like the lakes that are sometimes found in the im- 
 mense plateaus. 
 
THE EARTH AS IT IS. 87 
 
 165. Rivers. Rivers come from mountains and pla- 
 teaus, and, having gathered the waters from these, run 
 through the lowlands into the sea. There is system 
 here as well as in the arrangement of mountains. For 
 example, the great basin included between the Rocky 
 Mountains and the Apalachian range has a grand river 
 system, the Mississippi being its principal river. Then 
 there are two other great systems in North America, in 
 which the St. Lawrence and the Mackenzie are the chief 
 rivers ; but these are not as extensive as that of the 
 grand basin of the continent. In South America there 
 are also three principal systems, that of the La Plata, 
 corresponding with that of the Mississippi in North 
 America, that of the Amazon in the east, and that of the 
 Orinoco in the north. The systematic arrangement, 
 which is so obvious in the case of the large rivers of the 
 globe, exists as really with the smaller rivers, though, 
 from the influence of local circumstances, it is not always 
 as manifest. 
 
 166. Lakes. Lakes are formed by rivers and streams 
 of various sizes, which pour their waters into depressions 
 on the land from which they can not escape readily, in 
 some cases not at all. These depressions are of various 
 shapes and sizes. Those from which the water has no 
 outlet are salt lakes, as, for example, the Dead Sea in 
 Asia, and the Great Salt Lake of this country. 
 
 167. Relation of Mountains to Fertility. The position 
 of mountains has a great influence upon the fertility of a 
 country by detaining the winds and condensing their 
 moisture. Observe how the winds are produced. There 
 are two principal causes of them, heat and the rotation 
 of the earth, and consequently the winds that blow from 
 the tropics, or trades, as they are called, are eastern 
 winds, while the winds coming from the colder regions 
 are western. The winds from the east, being warm, are 
 therefore loaded with moisture, while the cold western 
 winds have comparatively little moisture, and continual- 
 
GEOLOGY. 
 
 ly gather or take tip more as they bend toward the equa- 
 tor, and are therefore drying winds. For this reason, 
 more rain falls on the eastern side of a continent than on 
 the western. "The annual amount of rain in Europe is 
 32 inches, while in the temperate zone in the United 
 States, east of the Mississippi, it is 44 inches, the differ- 
 ence being still greater if we compare the eastern part 
 of South America with the opposite side of the Atlantic 
 Ocean. You can see now what influence the mountains 
 have on fertility in the case of the American continent. 
 Its highest mountains are on the western side, and there- 
 fore the warm eastern winds sweep with their moisture 
 over almost the whole breadth of the continent, parting 
 with it here and there from condensing influences. Fer- 
 tility is the result of this diffusion over the continent of 
 this moisture, and hence America is appropriately called 
 by Professor Guyot the Forest Continent. Where the 
 moisture deposited from the passing wind is not enough 
 to produce forests, we have the prairies and the pampas. 
 Now if the low Appalachians were on the west and the 
 high Rocky Mountains were on the east of North Amer- 
 ica, most of the moisture of the trades would be con- 
 densed at once, and be poured back into the Atlantic 
 Ocean, and in that case the great river system of the 
 continent's basin would not exist, but in place thereof a 
 desert. You can readily apply for yourself the above ex- 
 planation to the desert of Sahara, in Africa, and other 
 great deserts, and therefore I need not dwell farther on 
 this interesting subject. 
 
 168. Circulation ofWater. Water is every where in 
 motion on the earth. Rising continually from every 
 point of the surface by being dissolved in the air, it is 
 brought down again to the earth by being condensed 
 from its vaporous state. There is, therefore, a constant 
 circulation of the water back and forth between the 
 earth and its envelope of air. In the earth itself it is 
 never at rest, but insinuates itself among all loose parti- 
 
THE EARTH AS IT IS. 89 
 
 cles and masses, runs down all declivities in streams 
 small and large toward the ocean, and is agitated by the 
 winds and the tides. Not only is its motion kept up in 
 these ways, but there are great systematic currents in the 
 ocean, which maintain a free circulation between differ- 
 ent quarters of the globe, and exert a marked influence 
 upon the climates of many countries. The great Gulf 
 Stream is one of these currents. By all of these means 
 of motion there is secured a circulation of water in the 
 earth which in its system and thoroughness bears an 
 analogy to the circulation of the blood in the body. 
 What extensive and varied effects it produces in this 
 circulation upon the solid materials of the earth's surface 
 you will learn in succeeding chapters. 
 
 169. How the Earth's Surface is Diversified. I have 
 already spoken of some of the grand features of the 
 earth's surface. But there are subordinate features 
 which diversify it greatly bluffs, hills of various con- 
 tours, valleys with and without streams, collections of 
 rock differing in arrangement, shape, and color, some be- 
 ing stratified and others not; rocks jutting out from the 
 ground, boulders of various sizes, etc. A material addi- 
 tion is made to this diversity by water every where en- 
 livening the scene by its motion in obedience to every 
 impulse. And then we have life, with its endless varie- 
 ty of shape, and color, and motion. 
 
 170. Treasures in the Crust of the Earth. As you have 
 already seen, there are precious treasures of every varie- 
 ty scattered among the rocks, and earth, and sand of the 
 globe for the use of man. There are immense stores of 
 coal ; metals of every kind, and in quantities suited to the 
 amount of uses to which they can be appropriated ; pre- 
 cious gems of every quality and hue ; granite, sandstone, 
 marble, etc., for building ; clay for pottery and bricks, 
 etc. 
 
90 GEOLOGY. 
 
 CHAPTER X. 
 
 PKESENT CHANGES IN THE EARTH. 
 
 171. Ages of the Earth. The earth is older than 6000 
 years, as has been absolutely demonstrated by the re- 
 searches of geologists. Here is an apparent discrepancy 
 between what is revealed by the works of God and his 
 written revelation; but it is only apparent. I shall 
 speak of this point particularly in another place, and let 
 it now suffice to say that it is the belief of most geolo- 
 gists that the days of Moses represent long ages, and 
 that the time which has elapsed since the earth was 
 finally fitted for man is a very small period compared 
 with the length of time expended by the Creator in its 
 construction and preparation. It is my intention, in this 
 chapter, to treat of those changes which are matter of 
 observation and history. The word present, in the title 
 of the chapter, refers to the whole time in which man 
 has inhabited the earth, in distinction from the long pe- 
 riods consumed in its preparation for his use. It is not 
 always easy to make this distinction, and some changes 
 will be noticed in this chapter which began far back of 
 the age of man. This is necessary, because the same 
 agents which prepared the world for its present purpose 
 have produced all the changes since man was introduced 
 upon the scene. 
 
 172. Agents of Change. The agents by which changes 
 are constantly produced in the earth are heat, water, air, 
 chemical processes, attraction, electricity, and life, both 
 vegetable and animal. The manner in which they act 
 will be developed as we proceed, and therefore I will 
 not dwell on this subject here, but will only notice in a 
 few words the principal of these agents. Water and air 
 are every where kept in motion by the influence of heat 
 
PRESENT CHANGES IN THE EARTH. 91 
 
 and attraction, as was fully explained in Part I. But 
 water has a larger agency in producing the changes in 
 the earth than air. Through the influence of heat it is 
 carried up constantly into the atmosphere in evapora- 
 tion, and then falls in rain, snow, etc., and in seeking its 
 level in obedience to attraction, effects a large portion of 
 these changes. The influence of heat is seen in the erup- 
 tions of volcanoes and other phenomena, and these indi- 
 cate to some extent the agency which heat had in build- 
 ing up the earth, as do the present effects of moving wa- 
 ter what agency that had in the work. It is these aque- 
 ous and igneous agencies, as they are termed, which, oft- 
 en acting in opposition and sometimes in unison, have 
 for the most part arranged and consolidated the mate- 
 rials of the earth, so as to put it into its present condi- 
 tion ; and therefore it is necessary to view their present 
 operations, that we may understand those which were 
 carried on in the ages that preceded the advent of man, 
 when the earth was being prepared by successive steps 
 to be his habitation. This will be, then, the line of our 
 investigation in the present chapter. 
 
 173. Water Changing the Locality of Materials. What 
 we see in the washings of every shower on slopes and 
 hill-sides exemplifies some of the vast changes which wa- 
 ter is producing on a large scale in the earth. Different 
 kinds of materials are moved according to the different 
 degrees of rapidity with which the water flows. If you 
 look at a mountain torrent you see nothing in its course 
 but large stones, because not only mud and sand, but 
 pebbles of considerable size, are carried along by the 
 force of the water. If you go farther on, where the 
 stream is less rapid, you will find the pebbles, and if the 
 rapidity lessens as you follow the stream, there will be 
 sand on its bottom ; and when the water moves on slow- 
 ly through a plain, you will find the sediment deposited 
 to be mud. The explanation of this sorting out of ma- 
 terial by moving water has been given in 1 93, Part I., 
 
92 GEOLOGY. 
 
 and it is not necessary to repeat it here. The pebbles, 
 and sand, and mud moved by water were all once in solid 
 rock, and how the rocks are thus broken up will be seen 
 hereafter. The deposit of these materials is regulated 
 by other varying circumstances as well as those which I 
 have mentioned, as I will now proceed to illustrate. 
 
 174. Deposits in Rivers and on their Borders. A riv- 
 er descending some slope of considerable pitch always 
 brings along with it much solid matter, and if it after- 
 ward move sluggishly through a plain, this matter will 
 be deposited quite evenly over its bottom. If the river be 
 narrowed much at any point the water will move so rap- 
 idly there that it will carry the material suspended in it' 
 on beyond, and then, if it spread out suddenly over a 
 large surface, there will be much matter deposited, ex- 
 cept in the direct line which the main body of the water 
 takes. On either side of this channel that is, on the 
 flats will the most of the deposit be made. In some 
 cases the plain on either side of a river is so high that 
 the water flows over it only when it is temporarily raised 
 by a freshet. This is termed the flood-plain. In this 
 case there is some addition to the plain every time that 
 a freshet occurs, until at length the land is raised so high 
 that the flood does not overflow it. This process, year 
 after year, tends to make that part of the plain immedi- 
 ately bordering on the river higher than the rest of the 
 plain, because, the farther the water is from the river, the 
 less has it suspended in it from the settling of the sedi- 
 ment which is continually going on. And as some of 
 the matter is deposited on the bottom of the river itself, 
 the river is gradually raised, and may be, after a while, 
 on a level which is above the adjoining land, except that 
 which forms the banks. These results are shown by 
 
 Figs. 33 and 34. Let 
 
 _ valley, and b a stream 
 
 Fig. 33. of water which runs 
 
PRESENT CHANGES IN THE EARTH. 
 
 93 
 
 Fig. 
 
 through it, occasionally overflowing its banks. In the 
 overflows mud will be deposited over the valley-flat, and 
 
 after a while the result 
 m indicated in Fig. 34 
 will be realized. Just 
 this process has been 
 gone through with along the Mississippi, so that there 
 is a natural levee, as it is termed, on each side of the 
 river. The inhabitants are obliged to raise this in cer- 
 tain places to prevent inundations from freshets. Some- 
 times a break (crevasse) occurs in the levee, and much 
 damage is done in the country adjoining. The same 
 process goes on, and the same results occur at length in 
 those cases where the land along a river is inundated at 
 all seasons. 
 
 175. Improvement of Rivers. A very pretty illustra- 
 tion of the manner in which the solid material in rivers 
 is deposited is furnished us by a mode of improving river 
 navigation sometimes practiced. We will take a particu- 
 lar case. The river issues from a gorge, and then spreads 
 out over a large flat surface, there being, of course, a chan- 
 nel through the flat for the main body of the water to 
 flow in. The object of the plan of improvement is to 
 prevent accumulation of sediment in the channel, and. 
 even, if possible, to carry out sediment already deposit- 
 ed. This is done by building piers of stone across the 
 flats out toward the channel, as indicated in Fig. 35. 
 
 Fig. 35. 
 
 Let a be the gorge, c c the flats across which the piers 
 stretch, as represented, and b the channel. The piers, d, 
 d, d, it is obvious, will somewhat detain the water on the 
 flats, and so allow the sediment to fall from it in larger 
 
94 GEOLOGY. 
 
 amount than it otherwise would ; and this detention at 
 the sides of the channel will cause more water to flow 
 through it, and to flow more rapidly. Then, as the flats 
 fill up with sediment, this effect upon the flow in the 
 channel will continually increase. 
 
 176. Deposits in Lakes. In every lake there is more 
 or less deposit of sediment from the river or rivers that 
 flow into it, and also from all smaller streams that do so, 
 even to the little rill temporarily made by a shower. 
 The tendency, then, is to fill up the lake, and in time the 
 result would be the conversion of the lake into a river. 
 If a lake have a river entering at one end and issuing 
 at the other, the deposit is made in that part of it where 
 the river enters, and the extent to which it reaches de- 
 pends on circumstances. The more rapid the entering 
 river, and the more shallow the lake, the greater- will be 
 the space over which the deposit will be made. The wa- 
 ter of the entering river is of course turbid, while that 
 of the issuing river is clear, the sediment being all depos- 
 ited long before the water reaches that end of the lake. 
 In the Lake of Geneva, which is thirty-seven miles long, 
 and varies in breadth from two to eight miles, we have 
 all this exemplified. The Rhone enters it muddy, but it 
 issues beautifully clear at the city of Geneva. The ra- 
 pidity with which the filling up goes on may be judged 
 of by the fact that the town of Port Vellais, which, eight 
 centuries ago, was on the edge of the lake, is now more 
 than a mile and a half distant from it. The great lakes 
 of this country are continually growing smaller. There 
 are facts which show that their shores, in many places, 
 were once far away outside of where they now are. 
 There is, for example, south of Lake Erie, and distant 
 from it from four to eight miles at different points, a 
 ridge made up of sand, gravel, and rounded pebbles, just 
 as the shore of the lake is now. Moreover, when wells 
 are dug, or any excavations made in this ridge, there are 
 found deeply buried in the soil pieces of decayed wood, 
 
PRESENT CHANGES IN THE EARTH. 
 
 95 
 
 small and large, and such shells as are now met with in 
 the lake. 
 
 177. Deltas. The name delta is commonly given to 
 the accumulation from a river at its mouth as it empties 
 into a sea or the ocean, when it has gone so far as to form 
 flats, through which the river runs usually with a net- 
 work of channels. The name is given from the common 
 resemblance in the form of this accumulation to the Greek 
 letter A, which is called Delta. The shape which the de- 
 posit tends to take is fairly represented by Fig. 36. From 
 
 Fig. 36. 
 
 the point where the river enters the sea the sedimentary 
 matter spreads out or radiates, and at the same time it is 
 tossed about and beaten back by tides and the waves. It 
 is this action of the sea, in opposition to the prolongation 
 of the river current into it, that produces the bars so often 
 found in such cases. These bars are indicated in the fig- 
 ure at the sea-extremity of the delta. The numerous sand- 
 bars formed at the mouth of the Mississippi render the en- 
 trance to it difficult and hazardous. Sometimes even isl- 
 ands are formed. Thus, about fifty years ago, an island 
 was formed opposite the mouth of the Hoogly River, 
 which in 1818 was two miles long and half a mile wide, 
 was covered with vegetation, and was inhabited ; but 
 afterward this was gradually swept away, and dwindled 
 to a mere small sand-bank. It is common there, and in 
 other cases also, for islands to form, and then be de- 
 stroyed by the change of currents from the formation 
 
96 GEOLOGY. 
 
 of new islands. There is no delta formed at the mouth 
 of the Amazon, because there is an ocean current that 
 sweeps by, and this carries the sediment discharged by 
 that river up by the coast of Guiana, where it is deposit- 
 ed, forming immense muddy shoals and swampy tracts. 
 
 178. Amounts of Deposits from Rivers. The amount 
 of sediment deposited by large rivers is enormous. The 
 Ganges pours such a quantity of mud and sand into the 
 Bay of Bengal that the water is seen to be colored by 
 it sixty miles from the shore. It is calculated that in 
 the rainy season each year this river discharges into the 
 sea an amount of solid matter equal in weight to fifty-six 
 pyramids, estimating a pyramid to contain 6,000,000 of 
 tons of granite. Mr. Lyell states that " if a fleet of more 
 than eighty Indiamen, each freighted with one thousand 
 four hundred tons weight of mud, were to sail down the 
 river every hour of every day and night for four months 
 continually, they would only transmit from the higher 
 country to the sea a mass of solid matter equal to that 
 borne down by the Ganges in the flood season, as the 
 exertions of a fleet of about two thousand such vessels 
 going down daily with the same burden, and discharg- 
 ing it into the gulf, would be no more than equivalent to 
 the operations of the great river. Yet, in addition to 
 this, it is probable that the Burrampooter conveys an- 
 nually as much solid matter to the sea as the Ganges." 
 The amount of land made by such enormous quantities 
 of sediment is very great. Most of the lower part of 
 Louisiana was formed by sediment brought down by the 
 Mississippi, and the land has encroached upon the water 
 several leagues since New Orleans was built. The solid 
 matter annually discharged by the Mississippi is two 
 thousand million (2,000,000,000) tons. This is sufficient 
 to cover a township six miles square with earth thirty 
 feet deep. 
 
 179. Extent of Deltas. The deltas of very large riv- 
 ers are of great extent. That of the Nile is about as 
 
PRESENT CHANGES IN THE EARTH. 97 
 
 large as the State of Vermont. That of the Ganges is 
 much larger, being 220 miles long, and having a base on 
 the sea of 200 miles. It is bounded on either side by an 
 arm of the Ganges, and near the sea it is intersected by 
 a net-work of rivers and creeks, and is a resort for croc- 
 odiles and tigers. The material constantly brought down 
 the river is encroaching upon the sea, and it now forms 
 a slope extending out about a hundred miles. This real- 
 ly ought to be taken into the account in estimating the 
 extent of the formation. 
 
 180. Consolidation of Deposits. In some cases the 
 consolidation into rock of the deposits of sediment by 
 water is going on at the present time, especially where 
 there is mingled with the sand and mud some agglutina- 
 ting material like carbonate of lime. From this cause 
 there is rock continually forming in the sediment dis- 
 charged by the River Rhone. In the Museum at Mont- 
 pellier there is a cannon which was taken from the sea 
 near the Rhone's mouth incased in a crystalline calcare- . 
 ous matter, and having scattered through it broken 
 shells. But the whole subject of the consolidation of 
 mud and sand into rock will be treated of hereafter, and 
 I will not dwell upon it farther here. 
 
 181. Water Encroaching upon Land. Thus far I have 
 spoken only of the encroachment of land upon water by 
 the deposit of material brought to lakes and the sea by 
 rivers. But there is sometimes the opposite effect the 
 wearing away of land by the action of water. Much of 
 the eastern coast of England is wearing away, and many 
 localities of towns have disappeared in the German 
 Ocean. Some of the coast of Long Island is encroached 
 upon rapidly by the sea ; and at Cape May, in Delaware, 
 land is destroyed at the average annual rate of nine feet. 
 Sullivan's Island, South Carolina, was worn away in three 
 years to the extent of a quarter of a mile. Some of the 
 Shetland Isles have been destroyed by the sea, and the 
 granite rocks of some of them that are now wasting 
 
 E 
 
98 
 
 GEOLOGY. 
 
 away, standing up in the midst of the water, look in the 
 distance like fleets of vessels. On the coast of France, 
 especially in Brittany, where the tides rise to a great 
 height, the sea is constantly encroaching upon the land, 
 and occasionally does so to a large extent. In the ninth 
 century many villages were carried away. Great changes 
 have occurred in Holland from time to time, the land 
 sometimes gaining upon the sea, and sometimes the re- 
 verse. At one time the tide, breaking through a dam, 
 overflowed seventy-two villages, and irretrievably de- 
 stroyed thirty-five of them. Other examples in abund- 
 ance might be cited, but these will suffice. 
 
 182. Erosive Power of Water. Water, acting by it- 
 self mechanically, exhibits in the course of time great 
 erosive results. The hardest rocks can not resist it, much 
 less the softer ones. The Pulpit Rock, so called, at N"a- 
 hant, Mass., seen in Fig. 37, is an example of the erosive 
 
 Fig. 37. 
 
 action of the waves continually dashing against it year 
 after year. But little of the rock is worn away each 
 
PJBESENT CHANGES IN THE EARTH. 99 
 
 day, but this little daily work sums up largely when con- 
 tinued through centuries. Water does much erosive 
 work by rubbing one solid surface against another. This 
 we see on the sea-shore, as the waves, lashing the shore, 
 jostle the pebbles, great and small, against each other. 
 The same thing is done with the grains of sand and mud 
 wherever there is water moving them. Every pebble 
 and grain that is carried down by a river toward the 
 sea grows continually smaller by being rubbed on its 
 passage by the accompanying grains and pebbles, as well 
 as by the friction of the water itself. We see this mode 
 of erosion exemplified in the pot-holes seen in rocks 
 where there is shallow water running over them. The 
 stones contained in them are rounded by the constant 
 friction, and at the same time wear the hole in the rock 
 continually larger. In the Franconia Notch of the White 
 Mountains there is a pot-hole in granite, called the " Ba- 
 sin," which is fifteen feet deep and about twenty in di- 
 ameter. 
 
 183. Niagara Falls. One of the most striking exam- 
 ples of the erosive power of water we have in the Falls 
 of Niagara. The river runs over hard limestone, but 
 under this are soft shales. The result is that the water 
 at the Falls continually wears away the shales, and the 
 limestone falls from want of support below, the water 
 above pressing it downward. The edge of the fall is 
 therefore constantly receding at a rate calculated vari- 
 ously by different persons, from one foot to three feet 
 annually. This is a slow recession, but in the course of 
 centuries the change is a great one. There is the most 
 decided proof that the Falls were once seven miles far- 
 ther down the river than they are now, so that they 
 have receded all that distance, the process having begun 
 long ages before the creation of man. As the layers of 
 rock, instead of being perfectly horizontal, dip a little in 
 running back toward Lake Erie, the height of the fall is 
 constantly lessening as it recedes. It can therefore nev- 
 
100 GEOLOGY. 
 
 er recede entirely to the lake, because, before it reaches 
 there, the fall will cease to be sufficient for the wearing 
 away of the shales underlying the limestone. 
 
 184. Canons of Colorado. The case just cited of ero- 
 sion by water, though so striking, is by no means so 
 strong a one as some others ; for, while the rocks eroded 
 by the water of the fall are soft, there are instances of 
 vast and rapid erosion in solid tough rock. The stron- 
 gest example is in the canons of Colorado, which are riv- 
 ers running between perpendicular walls of rock, as rep- 
 resented in Fig. 38, in some cases standing even 6000 
 feet in height. These passages through the rocks were 
 actually worn by the water, incredible as it may at first 
 thought appear. We have some comparatively recent 
 erosions, which show that such monstrous erosions are 
 possible, if there be a sufficient length of time allowed 
 for them. For example, the River Simeto, having been 
 dammed up by an eruption from Mount Etna in 1603, 
 cut a passage through hard blue basaltic rock in a little 
 over two centuries, which w 7 as from fifty to several hun- 
 dred feet in width, and in some places fifty feet deep. 
 It is rather difficult to realize that water can accomplish 
 such an amount of erosion, but a little reflection on some 
 common results with which we are familiar will help us 
 to do this. We see the stone steps of public buildings 
 very soon worn by the friction of the many feet that pass 
 over them. But this friction is not constant ; it is so in- 
 termittent that it occupies but a small portion of the time 
 that passes from day to day. If it were constant, the 
 stone would soon be so much worn as to require being 
 replaced by another. Now the friction of water erodes 
 stone like the friction of footfalls; and if it be constant 
 through century after century perhaps age after age 
 the erosion, we can see, will be great in amount. 
 
 185. Rocks Disintegrated by Frost. As there are crev- 
 ices and interstices in rocks, the water enters into these, 
 and in cold weather becomes frozen there. In freezing, 
 
PRESENT CHANGES IN THE EARTH. 
 
 101 
 
 Fig. 38. 
 
 as you learned in 329, Part I., it increases in bulk. The 
 result of this expansion of the water is that it tears the 
 rocks in pieces, the fragments being of all sizes, from 
 
10'2 GEOLOGY. 
 
 grains up to even large masses. The softer rocks, as the 
 shales, are broken into small fragments as the water gets 
 into their numerous small interstices ; but in the case of 
 the harder rocks, the water enters cracks and crevices 
 that it finds here and there, and the fragments separated 
 by the frost are of considerable size. It is chiefly from 
 this action of frost on rocks that, at the foot of such rocky 
 fronts as are presented by East and West Rock at New 
 Haven, and by the Palisades of the Hudson River, there 
 are accumulations of fragments of rock of various sizes. 
 Such an accumulation is called a talus. In Fig. 39 one 
 
 of these is represented. 
 You see a difference in 
 size of the stones in dif- 
 ferent parts of this talus. 
 
 ^ sa== ^_ Br ^ ^ This results from the fact 
 
 Fig. 39. that every agitation from 
 
 the falling of the fragments, and the action of water and 
 wind, tends, by friction, to make the fragments smaller, 
 and to remove the smallest of them away from the foot 
 of the rock. Some of them are, in process of time, con- 
 verted into sand, and even fine powder, and these the 
 rains may remove, or the tides, if the foot of the rock be 
 so situated as to be exposed to them. 
 
 186. Chemical Action of Water. Water ordinarily 
 contains dissolved in it both solids and gases, which en- 
 able it to act chemically upon the rocks. For example, 
 the limestone or calcareous rocks are acted upon by wa- 
 ter containing carbonic acid gas in it ; and as rain, falling 
 through the air, becomes charged with this gas, which it 
 finds there, water is continually carrying off calcareous 
 matter from such rocks, supplying thus the sea with ma- 
 terial for the shells of the animals that live in it in such 
 abundance with these coverings upon them. Water thus 
 charged also acts with facility upon the oxyds and sul- 
 phurets of iron which are so often present in rocks, and 
 also upon the alkalies that enter into the composition of 
 
n 
 
 PEESENT CHANGES IN THE EARTH^ . 103 
 
 the feldspathic rocks, so that even the harder i\pcks are 
 not full proof against the chemical action of waiter. It 
 is from this action on these rocks that the silex is pro- 
 vided for the grains, and grasses, and other plants, in a 
 condition to be dissolved and carried up the plant in the 
 sap. Even the granite, of which man constructs his most 
 enduring monuments, is every where being slowly worn 
 away by this action, and thus ever furnishes its quota of 
 fertility to the soil in the alkali and clay that come from 
 its decomposing feldspar. 
 
 187. Weathering. This is a term which includes, to 
 some extent, the mechanical action of water with its 
 chemical. The idea is that rocks, on exposure to the 
 weather that is, to rain and air, are more or less disin- 
 tegrated, and sometimes even changed in chemical con- 
 stitution, either at the same time or after the disintegra- 
 tion. This weathering is sometimes exhibited in a very 
 striking manner by ancient monuments. This is the case 
 with the Druidical monuments in the north of England, 
 which are constructed of a very hard rock called mill- 
 stone grit. Three monstrous pillars, called the Devil's 
 Arrows, having had the rain beating upon them for two 
 thousand years, are furrowed deeply all down their sides, 
 the furrows being deepest at their summits, and becom- 
 ing wider and less distinct toward the bottom. Crags 
 of rock too hard to crumble under the weathering often 
 present the same furrows. Where rocks are porous, and, 
 as we may say, loosely constructed, as are many sand- 
 stones, the disintegration of weathering goes on largely 
 and rapidly, and we have in such localities impercepti- 
 ble gradations from earth to solid rock. This may be 
 seen often where the rocks jut out from the soil, but 
 more especially in digging down through the success- 
 ive gradations of soil and crumbling rock to the hard 
 rock itself. The same weathering which disintegrates 
 the rocks does the same work among the fragments of 
 rock, small and great, in the soil, for both water and air 
 
104 GEOLOGY. 
 
 are present there. Sometimes stones scale off from this 
 weathering process. In many cases this occurs in a very 
 regular manner. A beautiful example of this I found in 
 a boulder of greenstone nearly two feet in diameter. It 
 had a covering, in the form of a shell, of about a third of 
 an inch in thickness, of the same composition with the 
 boulder itself. Parts of this shell had been broken off. 
 but it was evident that it had been whole quite recently, 
 The first thought of any one that had no knowledge of 
 such results of weathering would be, that the boulder 
 had in some way received a coating of stone ; but this 
 could not in any way occur, and we are shut up to the 
 conclusion that this rind, as we may call it, of the boul- 
 der was separated from the body of the stone by the 
 weathering process. 
 
 It is supposed that the famous Loggan, or rocking 
 stones, referred to in 100, Part I., have been shaped so 
 as to rock by this weathering. If a rock having a small 
 base rest upon another, the weathering will be apt to go 
 on quite rapidly on the under side, from the dampness 
 and the continued shade, and the base may after a while 
 become so narrow that the rock, though a large one, may 
 be easily moved back and forth upon it. 
 
 188. Glaciers. Having spoken of the effects of water 
 in its liquid state, I pass now to consider those which 
 are produced by it in its solid condition. You will find 
 in another chapter that, great as these effects are at the 
 present time, they were vastly greater in ages of the 
 world long gone by. Both glaciers and icebergs had a 
 large agency in preparing some portions of the earth for 
 the use of man. 
 
 A glacier is simply a river of ice. It flows down a 
 valley from the regions of eternal snow and frost above. 
 It does not merely slide, for the ice is somewhat plastic, 
 and so bends to accommodate itself to the different 
 widths of the valley and to uneven surfaces. The flow, 
 it is true, is very slow, but it is constant ; else the snow 
 
PRESENT CHANGES IN THE EARTH. 105 
 
 that feeds it above would increase from year to year. 
 The rate of flow varies from varying circumstances. 
 Professor Hughes built a house on a glacier, and he 
 found it to move during fifteen years at the average rate 
 of eight inches daily, or over three quarters of a mile 
 during the whole time. A glacier is made out of snow 
 which becomes consolidated into ice, partly by pressure 
 and partly by the infiltration of water, which, by freez- 
 ing, unites all the grains of snow together. In Fig. 40 
 (p. 106) is represented one of the grand glaciers of the 
 Swiss Alps, the glacier of the Viesch. A glacier carries 
 along whatever of loose material it finds in its course, 
 and therefore there is always a row of loose stones, of 
 various size, lying along upon the ice on each side of the 
 glacier. These are called the lateral moraines. In the 
 glacier of the Yiesch there is, as you see, a row of stones 
 along the middle. This, which is called a medial mo- 
 raine, arises from the union of two glaciers in one, as 
 two rivers of water unite. In this case the two lateral 
 moraines of the glaciers which are adjacent to each other 
 unite at the confluence. 
 
 189. Termination of a Glacier. The colder is the cli- 
 mate the farther down does the glacier extend. The 
 termination is higher up in the summer than in the win- 
 ter, and it varies in different seasons, according to the 
 temperature of the season. The locality of the end varies 
 sometimes even miles in the course of a series of years. 
 The glacier is sometimes spoken of as retreating, but this 
 language is, of course, not strictly correct, for there can 
 be no movement backward. The apparent retreat is 
 owing to the melting of the lower part of the glacier to 
 a higher point than before. Toward the termination of 
 a glacier the moraines become less and less distinct from 
 the melting of the ice, and at the very end there issues a 
 stream of water, carrying along with it, to a greater or 
 less distance, much of the loose material which the gla- 
 cier has brought down from the rocks. The stream 
 E 2 
 
106 
 
 GEOLOGY 
 
 Fig. 40. 
 
PRESENT CHANGES IN THE 
 
 which comes from the glacier of the Viesch is seen in 
 Fig. 41. 
 
 Fig. 41. 
 
 190. Effects of Glaciers. Fragments of rock of vari- 
 ous sizes, from large stones to pebbles, and even sand, 
 become imbedded in the bottom and on the sides of the 
 glacier. These, held firmly in the ice, rub on the bottom 
 and sides of the valley, and when these are laid bare by 
 the melting of the glacier toward its termination, the 
 rocks exhibit varous marks, as grooves, stria3, scratches, 
 roundings, smoothings, etc., according to the shape and 
 character of the fragments that have been brought in 
 contact with them under the immense pressure of the 
 glacier. Stones that are loose are crushed and ground 
 to sand, some even to mud. Fig. 42 (p. 108) shows the 
 side of a glacier valley after the melting of the glacier. 
 The rocks are striated, smoothed, and rounded wherever 
 the ice has been, while the portions which were above 
 its reach present the usual rough and ragged appearance 
 of hard rocks. 
 
 All the crushed and ground matter is at length 
 
108 
 
 GEOLOGY. 
 
 
 Fig. 42. 
 
 brought to the termination of the glacier, together with 
 the stones imbedded in the ice and those accumulated 
 on the surface. Much of the finer matter is carried 
 away by the stream of the glacier, to be deposited here 
 and there, while the more bulky parts are heaped up at 
 the end of the glacier in what is called the terminal mo- 
 raine. As the limit of the glacier varies, as already 
 stated, very much from year to year, these terminal de- 
 posits are scattered in heaps over quite a large space, 
 and are much changed from time to time by the moving 
 ice and water. 
 
 191. Icebergs. In very cold regions the glaciers ex- 
 tend down to the very borders of the sea, and the end 
 of a glacier breaking off into the water, forms an ice- 
 berg. Icebergs are of various sizes, many of them reach- 
 ing a height of 200, some even 300 feet above the sur- 
 face of the water. As, from the specific gravity of ice, 
 only one twelfth of it is above the surface, we see only a 
 small part of an iceberg. For the 300 feet that we see 
 there are 3300 feet (considerably over half a mile) be- 
 neath the surface of the water. A representation of an 
 iceberg seen by CaDtain Ross is given in Fig. 43. Ice- 
 
PRESENT CHANGES IN THE EARTH. 109 
 
 Fig. 43. 
 
 bergs are sometimes very extensive. A French expe- 
 dition measured several which were a mile in breadth, 
 and one which was 13 miles long and 100 feet high. 
 Icebergs appear often in great numbers. Scoresby 
 counted 500 of them starting from the frozen regions at 
 one time for the south. Dr. Kane saw 280 in Baffin's 
 Bay at one time. Like glaciers, icebergs are more or 
 less loaded with fragments of rock, great and small, and 
 this load is dropped in the sea as the iceberg melts. It 
 is supposed that the Banks of Newfoundland were in 
 great part made by deposition from icebergs, and the 
 accumulation is constantly going on. These bergs not 
 only drop material, but they grind much of it up into 
 sand, and even mud, by dragging, as they often do, on 
 the floor of the sea. Sometimes they are stranded, and 
 then, moved by the waves, they roll back and forth, stir- 
 ring up the muddy bottom, and crushing any fragment 
 
110 GEOLOGY. 
 
 of rock that icebergs may have dropped there. Captain 
 Couthoy saw one stranded on the Grand Bank, and the 
 water was charged with mud at the distance of a quar- 
 ter of a mile. 
 
 192. Water a great Leveler. By the various ways 
 which I have mentioned, water is continually making 
 additions to the comminuted solids of the earth, the 
 sands, and the soils. This is going on in a large way by 
 the deposit of sediment by large rivers, by the streams 
 at the terminations of glaciers, and by the grindings of 
 icebergs. But much more of this is effected in the ag- 
 gregate by what water is doing in a small way in every 
 part of the earth's surface. The weathering that is done 
 all around you every day is the representative of vast 
 operations that are gradually changing matter in form, 
 locality, and properties over the whole globe. The tend- 
 ency of all this, on the whole, is to bring the heights of 
 the earth down, so that water may be called the great 
 leveler. If there were no operations going on, or to be 
 instituted, in opposition to this tendency, in time the sol- 
 id matter of the earth would be one level, the oceans 
 being filled up with the ruins of the rocks, the water 
 therefore covering up the land, and making a universal 
 ocean. It would require long ages, it is true, to produce 
 this result, but it would finally come. What operations 
 tend to prevent this will be seen farther on. 
 
 193. Agency of Heat. As water generally exerts a 
 leveling influence, heat elevates, and thus tends to pre- 
 serve the equilibrium in the earth's crust. While water 
 wears down rocks, volcanoes are throwing up melted 
 rock to be consolidated as it cools ; and earthquakes, 
 which are connected with volcanic action, lift up, as you 
 will soon see, vast tracts of country to a higher level, 
 while the same elevating process is going on in other 
 tracts in a gradual manner. The opposition of the aque- 
 ous and igneous agencies will be more obvious when we 
 come to consider their operation in the construction of 
 the earth in the ages long gone by. 
 
PKESENT CHANGES IN THE EARTH. Ill 
 
 194. Volcanoes. The most striking present manifest- 
 ations of the agency of heat we have in volcanoes. 
 These are the grand chimneys of the earth; and, as vents 
 for the great furnace of fire in its interior, undoubtedly 
 save the earth's crust from most disastrous consequences. 
 The manner in which the volcanic mountains were con- 
 structed will be shown in the chapter on the formation 
 of the earth. Volcanoes are extinct or active^ the ex- 
 tinct being those mountains which, from their shape 
 and composition, are known to have been once in oper- 
 ation, though not since the advent of man, and the active 
 being those which have been eruptive since his advent. 
 While some active volcanoes are continually active, most 
 of them have seasons of eruption, with intervals of rest 
 of various lengths. The shape of a volcano is more or 
 less conical, the cone being truncated, that is, without a 
 top. When it is inactive, the cavity of the crater or 
 opening is shut up with a crust of solid lava. It is sup- 
 posed that the occasion of an eruption is the introduction 
 of water in some way into the interior, generating steam. 
 The expansions of the steam produce the earthquakes 
 which so commonly precede an eruption. The steam at 
 length accumulates to such an extent that it bursts the 
 solid cover of the crater, scattering its fragments and 
 dust aloft, with sheets of flame, followed by the overflow 
 of the lava. The steam which escapes forms above the 
 volcano a bright cloud, and with it there are continual 
 discharges of lightning, with thunder, the explanation of 
 which has been found in the fact that steam escaping 
 from a boiler has decidedly electrical properties. The 
 dust and the condensed steam produce, of course, show- 
 ers of rain and mud in the neighborhood. The matters 
 thrown out from a volcano are various in their charac- 
 ter. When the eruption is about to terminate showers 
 of cinders fall, and the last of the eruption is a mixture 
 of smoke and vapor. 
 
 195. Vesuvius. There is no record of the action of 
 
112 GEOLOGY. 
 
 this volcano previous to the Christian era, although it 
 had the structure of a volcanic mountain. It had been 
 so long inactive that vines grew all over the interior of 
 the crater. In A.D. 79, after a series of shocks during a 
 dozen years previous, an eruption occurred which buried 
 up the cities of Herculaneum and Pompeii. There was 
 not much lava thrown out in this eruption, but chiefly 
 loose material, such as sand, ashes, cinders, and stones. 
 The steam which rose at the same time from the volca- 
 no, being condensed in the air, fell in showers, and, be- 
 ing mingled with the ashes and sand, currents of mud 
 ran into the streets, houses, and cellars, filling them up. 
 " Hence it is," says Hitchcock, " that when these cities 
 were first excavated, more than a hundred years ago, ev- 
 ery thing enveloped was in a most perfect state of pres- 
 ervation the pavements of lava, with deep ruts worn by 
 the carriage wheels ; the names of their owners over the 
 doors of the houses ; the frescoed paintings as bright as 
 though put on but yesterday ; fabrics in the shops still 
 showing their texture ; vessels of fruit so well preserved 
 as to be easily recognized ; bread retaining the stamp of 
 the baker, and medicine yet remaining on the apotheca- 
 ry's counter. The whole constitute perfect examples of 
 fossil cities." Some skeletons have been found incased 
 in tuff or tufa (porous volcanic rock), finely preserved. 
 Around the neck of one was a chain of gold, and on the 
 bones of the fingers were jeweled rings. Resina was built 
 over the buried Herculaneum, but this was destroyed by 
 a river of lava in 1631. In Fig. 44 you have represented 
 the appearance of the crater of Vesuvius in 1829. The 
 top of the volcano was blown off in 1822 to the extent 
 of more than 800 feet* 
 
 196. Etna. This volcano, on the island of Sicily, is 
 about 90 miles in circumference, and is nearly two miles 
 high. In its eruption in 1669 its lava destroyed fourteen 
 towns and villages before arriving at Catania, and thero, 
 although the wall was 60 feet high, it accumulated to 
 
PRESENT CHANGES IN THE EARTH. 113 
 
 Fig. 44. 
 
 such an extent as to pour over it, and, after destroying 
 a part of it, ran on a distance of 15 miles, and then emp- 
 tied into the sea. Mantell says of one of Etna's erup- 
 tions, " If any person could accurately fancy the effect of 
 500,000 sky-rockets darting up at once to a height of 
 three or four thousand feet, and then falling back in the 
 shape of red hot-balls, shells, and large rocks of fire, he 
 might have an idea of a single explosion of this burning 
 mountain ; but it is doubtful whether any imagination 
 can conceive the eifect of one hundred of such explosions 
 in the space of five minutes, or of twelve hundred or more 
 in the course of an hour, as we saw them." 
 
 197. Crater of Kilauea. This volcano, which is always 
 active, is on the island of Hawaii. It is the most remark- 
 able and singular volcano in the world. It is not a trun- 
 cated cone, but a crater situated on high land near the 
 
114 GEOLOGY. 
 
 base of Mount Loa. It is a chasm eight miles in circum- 
 ference, and situated in the midst of another chasm still 
 greater in extent, that is surrounded by a precipice vary- 
 ing from 200 to 400 feet in height. In the midst of the 
 inner chasm stand up fifty or sixty conical craters, many 
 of which are continually in action. Rivers of melted lava 
 run about among the craters, and red-hot stones, with cin- 
 ders and ashes, are sent up with flame from those which 
 are active, in some cases to an immense height. 
 
 198. Tomboro, This is a volcanic mountain in the isl- 
 and ofSumbawa. Lyell thus speaks of an eruption of it 
 in 1815: "It began on the 5th of April, and was most 
 violent on the llth and 12th, and did not entirely cease 
 till July. The sound of the explosions was heard in Su- 
 matra, at the distance of 970 geographical miles in a di- 
 rect line, and at Ternate, in an opposite direction, at the 
 distance of 720 miles. Out of a population of 12,000, only 
 twenty-six individuals survived on the island. Violent 
 whirlwinds carried up men, horses, cattle, and whatever 
 else came within their influence, into the air; tore up the 
 largest trees by their roots, and covered the whole sea 
 with floating timber. Great tracts of land were covered 
 with lava, several streams of which, issuing from the cra- 
 ter of the Tomboro Mountains, reached the sea. So heavy 
 was the fall of ashes that they broke into the president's 
 house at Birna, forty miles east of the volcano, and ren- 
 dered it, as well as many other dwellings in town, unin- 
 habitable. On the side of Java the ashes were carried to 
 a distance of 300 miles, and 217 toward Celebes, in suffi- 
 cient quantity to darken the air. The floating cinders to 
 the windward of Sumatra formed, on the 12th of April, a 
 mass two feet thick and several miles in extent, through 
 which ships with difficulty forced their way. The dark- 
 ness occasioned in the daytime by the ashes in Java was 
 so profound that nothing equal to it was ever witnessed 
 in the darkest night." 
 
 199. Graham's Island. This island rose up out of the 
 
PRESENT CHANGES IN THE EARTH. 
 
 115 
 
 sea off the island of Sicily in the year 1831. Fig. 44, a, 
 represents it as it appeared on the 18th of July. On the 
 
 Fig. 44, a. 
 
 4th of August it appeared as seen in Fig. 44, b (p. 116). 
 It was 180 feet high, and over a mile in circumference. 
 It was composed mostly of loose material, and therefore 
 was so far washed away by the water in the course of 
 two or three years that there was nothing left but a rocky 
 shoal. Many other islands have been seen to rise out of 
 the sea, and there are also many which are composed of 
 lava, showing that they were produced, we know not 
 
116 GEOLOGY. 
 
 Fig. 44, 6. 
 
 when, by volcanic action. There is a group of such isl- 
 ands in the Grecian Archipelago, the advent of some of 
 which is indeed known. A new island was thrown up 
 near Iceland in 1783, consisting of high cliffs, and from 
 various parts of it there were emitted fire, smoke, and 
 pumice. This island was taken formal possession of by 
 his Danish majesty, but before a year had passed there 
 was nothing left to show where it was but a reef of 
 rocks. 
 
 200. Earthquakes. As earthquakes very generally 
 precede an eruption of a volcano, and cease when the 
 lava pours forth, the conclusion is legitimately arrived at 
 that all earthquakes are caused principally by the move- 
 ments of pent-up volcanic matter. When they occur at 
 a considerable distance from volcanoes, they are owing 
 to heavings of that vast body of melted matter which is 
 contained in the interior of the earth ; and it has been 
 observed in such cases that, when there has been a suc- 
 cession of earthquakes, they have ceased when some vol- 
 cano has, by its eruption, relieved the pressure, or when 
 some earthquake of great violence has had the same 
 effect. Thus, in 1811, there were many earthquakes in 
 South Carolina, which ceased altogether when Caraccas 
 
PRESENT CHANGES IN THE EARTH. 117 
 
 and Laguyra, in South America, were destroyed. Anoth- 
 er cause of earthquakes has been supposed to be a bend- 
 ing in the earth's crust, arising from changes of tempera- 
 ture. On this point Professor Dana gives the following 
 familiar illustrations : " All are familiar with the cracking 
 sounds occurring at intervals in a board floor of a house, 
 and arising from change of temperature, especially in a 
 room in winter that is heated during the day ; and with 
 the more common sounds of similar character from the 
 jointed metallic pipe of a stove or furnace, given out aft- 
 er a fire is just made, or during its decline. In each case 
 there is a strain or tension accumulating for a while from 
 contraction or expansion, which relieves itself finally by 
 a movement or slip at some point, though too slight a 
 one to be perceived ; and the action and effects are quite 
 analogous to those connected with the lighter kind of 
 earthquakes." Besides the vibration or wave movement 
 produced in the earth in an earthquake, there is also a 
 vastly more rapid vibration, which causes the sensation 
 of sound. The latter vibration commonly extends much 
 farther than the former. 
 
 201. Effects of Earthquakes. Earthquakes produce va- 
 rious effects according to their violence, extent, and ac- 
 companying circumstances. They are chiefly fractures 
 of the earth's crust, sometimes very extensive; displace- 
 ments, either elevations or depressions for the most part ; 
 the draining of lakes, and the production of new lakes ; 
 the production of waves in the sea, sometimes to a great 
 distance ; and the destruction of life in fishes from the 
 mere shock that is given to them. The displacements 
 and fractures often involve a great destruction of human 
 life. In the famous earthquake at Lisbon in 1755, the 
 greater part of the city was thrown down, and 60,000 
 persons were killed. Some most remarkable elevations 
 and depressions have attended earthquakes. The coast 
 of Chili was in 1822 raised three feet over a space of 
 100,000 square miles, an area equal to half of France. In 
 
118 GEOLOGY. 
 
 the year 1772, while PapandayaDg, one of the loftiest vol- 
 canoes in the island of Java, was in eruption, the mount- 
 ain, to the extent of 15 miles in length and 6 in width, 
 fell in with all its inhabitants, and wholly disappeared. 
 
 202. Solfataras. There are localities in the neighbor- 
 hood of volcanoes, or where volcanoes formerly existed, 
 from which sulphur vapors arise, and result in incrusta- 
 tions of sulphur. Carbonic acid gas also often escapes 
 from the action of some acid, as the sulphuric, upon car- 
 bonate of lime or limestone. 
 
 203. Geysers. Hot springs are very apt to occur in 
 volcanic neighborhoods, and when they are found where 
 there are no volcanoes, as in Virginia, there is evidence 
 in the character of the rocks that volcanic action has 
 been present at some time in the past. The famous hot 
 springs of Iceland are called geysers. In the Great Gey- 
 ser (Fig. 45) we have, in a mound of silicious rock, a ba- 
 sin-shaped cavity about fifty feet in diameter. From this 
 cavity there goes down perpendicularly into the earth a 
 pipe some eight or ten feet in diameter to the depth of 
 seventy-eight feet ; and in the eruptions of the geyser 
 there issues from this a huge column of water to the 
 height of 150, sometimes 200 feet. As the water mounts 
 up it is divided into numberless jets, and descends in 
 the form of spray, making an immense and splendid 
 fountain. The basin is sometimes empty, but is usually 
 filled with beautifully transparent water, boiling brisk- 
 ly. When the boiling is violent, and especially when 
 the issuing stream throws up the water, subterranean 
 noises are heard like the booming of distant cannon, and 
 the earth is slightly shaken. Each eruption is termina- 
 ted by a column of steam, which shoots upward with a 
 thundering noise. The hot water, from causes alluded 
 to in 116, dissolves some of the silica in the rocks 
 within, and as it falls deposits this, and thus forms the 
 mound. Much of the silicious matter is also deposited 
 in the region round about, the moisture being diffused 
 
PRESENT CHANGES IN THE EARTH. 
 
 119 
 
 Fig. 45. 
 
 by the winds blowing upon the descending spray. Wood 
 is often found in the neighborhood petrified from this 
 cause. 
 
 204. Explanation. The action of the geyser is inter- 
 mittent, and its explanation has been thus given by Ly- 
 ell : " Suppose water percolating from the surface of the 
 earth to penetrate into the subterranean cavity A D 
 (Fig. 46, p. 120) by the fissures F F, while at the same 
 time steam at an extremely high temperature, such as is 
 commonly given out from the vents of lava currents 
 during their solidification, emanates from the fissures C 
 
120 
 
 GEOLOGY. 
 
 Fig. 46. 
 
 C. A portion of the steam 
 is at first condensed into 
 water, while the tempera- 
 ture of the water is eleva- 
 ted by the latent heat thus 
 evolved, till at last the low- 
 er part of the cavity is filled 
 with boiling water, and the 
 upper part with steam un- 
 der high pressure. The ex- 
 pansive force of the steam 
 becomes at length so great 
 that the water is forced up the fissure or pipe E B, and. 
 runs over the rim of the basin. When the pressure is 
 thus diminished, the steam in the upper part of the cav- 
 ity A expands until all the water, D, is driven into the 
 pipe; and when this happens, the steam, being the light- 
 er of the two fluids, rushes up through the water with 
 great velocity. If the pipe be choked up, even for a 
 few minutes, a great increase of heat must take place ; 
 for it is prevented from escaping in a latent form in 
 steam, 'so that the water is made to boil more violently, 
 and this brings on an eruption." 
 
 205. Sand Moved by Wind. In some parts of the 
 world great changes are effected by clouds of sand. 
 The sand-hills produced in this way are called dunes or 
 downs. Very commonly they come from sand that has 
 been washed up upon the shore by the sea, which, on 
 being dried, is carried inland by the winds. There are 
 many dunes of this kind in Cornwall, England, and on 
 the coast of France a great number of villages have been 
 entirely destroyed by them. They are quite common on 
 some parts of the coast of the United States, and espe- 
 cially on Cape Cod. Sometimes dunes occur in the inte- 
 rior of a country. In Egypt the westerly winds have 
 blown the sand over almost the whole of the country 
 west of the Nile, making it a desert, and the remains of 
 
PRESENT CHANGES IN THE EARTH. 
 
 121 
 
 ancient cities, with their temples and palaces, are found 
 covered in the sand. 
 
 206. Alteration of Levels. Besides the depressions 
 and elevations which, as you have seen, have been pro- 
 duced violently and suddenly by earthquakes, there are 
 other changes of a similar character which have been 
 very gradual. There is ample proof that in Sweden 
 there have been extensive alternate elevations and de- 
 pressions, which have gone on so slowly that no disturb- 
 ances have resulted. One of the most interesting evi- 
 dences of change of level is found in the pillars of what 
 has been supposed to be the Temple of Jupiter Serapis, 
 near Naples. They are represented in Fig. 47. You 
 
 i ig. 47. 
 
 see some way up the pillars a roughness of the surface. 
 This results from a collection of just such perforations 
 as are known to be made by certain sea mollusks called 
 
 F 
 
122 GEOLOGY. 
 
 lithodomes, the name coining from two Greek words, 
 lithos, stone, and domos, house, as these animals dwell 
 in the holes which they make in the stone. This shows 
 that the pillars were once, for a considerable time, im- 
 mersed in the sea as far as the upper limit of the rough- 
 ness, which is 23 feet. Here, then, was a depression of 
 the land, after the temple was built, to a depth of over 
 23 feet, and it was effected so gradually that the pillars 
 were left quietly standing. The subsequent elevation 
 must have occurred with the same slowness also. The 
 fact that Scotland has been raised up from 15 to 30 feet 
 since man came upon the scene is very beautifully dem- 
 onstrated by Hugh Miller in his Lectures on Geology. 
 The old coast-lines have been traced by him lying above 
 the present coast-lines, the identity between them, he re- 
 marks, being as decided as that " between two contigu- 
 ous steps of a stair, covered, the one by a patch of 
 brown and the other by a patch of green, in the pattern 
 of the stair-carpet." One of the most extensive and re- 
 markable of the gradual changes of level that have taken 
 place has been observed in Sweden and Norway. The 
 evidences of it having been long noticed in a rude way 
 by fishermen and pilots, men of science at length under- 
 took the investigation of it systematically, by marking 
 the rocks in different places, and observing them from 
 time to time. In this way it has been ascertained that 
 there is a rising of the land in the northern part of this 
 region, and a sinking of it in the southern part, and the 
 rate is such at some places that the movement would 
 amount to several feet in a century. And that this 
 movement has been going on for many centuries is 
 shown by the fact that such shells as are now common 
 in the Baltic Sea are found inland, beginning at the shore 
 all along up to even 400 feet above the level of the sea. 
 Other similar changes have been noticed in South Amer- 
 ica, in Greenland, and in other countries. 
 
 207. Organic Agencies. Rocks are continually form- 
 
CONSTRUCTION OF THE EARTH. 123 
 
 ing to a large extent from material provided by organic 
 agencies that is, by the agency of animals and vegeta- 
 bles, especially the former. For example, the carbonate 
 of lime that is dissolved in water is taken up by animals 
 coral animals, shell-fish, etc., and, forming their frame- 
 work their skeleton, as we may term it is afterward 
 deposited as mineral matter, becoming again, as it wa,s 
 originally, a part of the solid substance of the crust of 
 the earth. 
 
 208. Alterations made by Man. Wherever man fixes 
 his habitation he effects more or less of change in the 
 earth's surface. These changes are especially manifest 
 in cities where large bodies of men are congregated. 
 Here levels are often considerably altered, as may be 
 learned from the recollections of the oldest inhabitants. 
 But all the changes produced by man are almost as 
 nothing compared with those which come from the op- 
 erations of the natural causes that I have noticed in this 
 chapter. 
 
 CHAPTER XI. 
 
 CONSTRUCTION OF THE EARTH. 
 
 209. Stages in the Construction of the Earth. You will 
 see, in the developments which I shall make in this and 
 the succeeding chapters, that there has been a succession 
 of changes, each one occupying a long period of time, 
 the earth being brought gradually into a proper condi- 
 tion as a habitation for man. You will see that the con- 
 tinents were once mere germs of continents, and that 
 they grew to be what they are after a manifest plan, the 
 steps of which the geologist has been able to some ex- 
 tent to discover by his researches among the rocks. You 
 will see that during all this time there was much of tear- 
 ing down and rebuilding as a part of the plan, the sedi- 
 
124 GEOLOGY. 
 
 mentary ruins of rocks being the materials out of which 
 a large portion of the rocks we now find were construct- 
 ed. You will see that, although at the first there were 
 ages in which there was no life, vegetable or animal, there 
 was a long series of ages before man appeared in which 
 the earth swarmed with life, the relics being found now 
 imbedded in the rocks, differing from each other, howev- 
 er, in a marked manner, as geologists have found, in the 
 different stages of the earth's construction. It is from 
 these differences in the forms of life that geologists have 
 been able to mark out the periods or ages of the world's 
 formation. In the present chapter* it is my intention to 
 point out some of the processes by which the earth has 
 been gradually built up into its present condition, as pre- 
 paratory to the consideration of what took place in each 
 of its several ages. What you have already learned of 
 the present changes going on in the earth, you will find, 
 will throw much light upon this subject, because, as I 
 have before stated, the same agents which are at work 
 now in these changes did the work in the changes of the 
 far past. 
 
 210. Nature of Geological Evidence. The geologist 
 takes the results of processes which are now going on in 
 the earth, and, comparing them with the results which he 
 finds buried up in the rocks, adopts his conclusions in re- 
 gard to the latter, and does so without danger of error 
 if he be properly cautious. I will give a few illustrations 
 of his modes of reasoning. 
 
 The geologist finds a rock which, on examination, is 
 discovered to be of the same composition with clay, and, 
 more than this, has similar layers. He infers that the 
 rock was once clay, and in some way became solidified 
 or changed into rock. By the same reasoning he infers 
 that certain rocks were once mud, and certain others 
 were once sand. The inference in these cases is con- 
 firmed by the fact that the solidification has sometimes 
 been known to take place within a short period of time, 
 
CONSTRUCTION OF THE EARTH. 125 
 
 as you have already seen in 180, and will see more fully 
 hereafter. 
 
 The geologist finds a rock which contains imbedded in 
 it certain shells. These shells were, like the shells we 
 now pick up on the sea-shore, once inhabited by animals. 
 But how did they get into the rock? This question is 
 easily solved by the geologist. He finds shells at the 
 present time imbedded in mud or sand, the mineral char- 
 acter of which is precisely the same with that of the solid 
 rock containing the other shells. He then justly infers 
 that the latter were once in similar mud or sand, which 
 is now solidified. 
 
 He makes a farther inference in regard to this rock by 
 comparison with some other. Some of its shells may be 
 of the same species with some that are found at the pres- 
 ent day, while those found in the rock with which it is 
 compared may all be different from any of the present 
 species. His inference is that the latter rock belongs to 
 an earlier age than the former. It may have been made 
 or solidified into rock hundreds, or even thousands of 
 centuries before the other, though the two may now lie 
 in juxtaposition. The kind of observation here indicated, 
 you will find as we proceed, is largely made use of in de- 
 termining the relative ages of rocks ; for as, during al- 
 most all the ages of the earth, there have been living be- 
 ings, but differing in character from age to age, the re- 
 mains of life found in the rocks differ according to the 
 ages in which the rocks were formed. 
 
 Take another case. You often see in a block of sand- 
 stone a step perhaps at some door pebbles imbedded 
 in the material of which most of the rock was made. 
 These pebbles are such as you have seen on a shore, and 
 you know that they once were rough pieces of rock, and 
 that they were smoothed by being rubbed together along 
 time, as those you see on the shore have been, by water 
 rushing over them, and that after this was done they be- 
 came mingled with sand, and the whole became a solid 
 
126 GEOLOGY. 
 
 rock. This pudding-stone, as it is called, we can make 
 such inferences about just as clearly as we can infer the 
 mode of making a plum-pudding from its appearance. 
 
 The geologist goes much farther than this. He dis- 
 covers often in the layers of rock tracks, and even the 
 marks of rain-drops and ripples, made perhaps ages upon 
 ages ago. I will give a single example. Professor Dana 
 says of some slabs examined in Pottsville, Pennsylvania, 
 "We thus learn that there existed in the region about 
 Pottsville at that time (a period just before the coal of 
 that region was deposited) a mud flat on the border of a 
 body of water ; that the flat had been swept by wavelets, 
 leaving ripple marks ; that the ripples were still fresh 
 when a large amphibian walked across the place ; that a 
 brief shower of rain followed, dotting with its drops the 
 half-dried mud; that the waters again flowed over the 
 flat, making new deposits of detritus,* and so buried the 
 records." 
 
 211. Classes of Rocks. First, rocks are divided into 
 two grand classes, the stratified and the unstratified. 
 The stratified appear in strata or layers, and the surfaces 
 of these strata are nearly or quite parallel. They are 
 either earthy aggregates, as sandstones, or simple chemi- 
 cal precipitates from solutions, as the limestones some- 
 times are. Those which are mere aggregates were de- 
 posited as sediment, and therefore are called sedimentary 
 rocks. They are also called aqueous rocks, as are also 
 those which were precipitated, because water was the 
 agent by which the matter composing them was brought 
 to the locality and deposited. You have an example of 
 stratified rock in Fig. 48. Stratified rocks very general- 
 ly contain fossils that is, remains of plants and animals 
 which were in existence at the time that the material of 
 which they are composed was deposited, and are therc- 
 
 * This term is applied to what has been removed from the surfaces 
 of rocks by the erosion of water and other causes. When the material 
 thus removed is coarse, it is called debris. 
 
CONSTRUCTION OF THE EARTH. 
 
 327 
 
 Fig. 48. 
 
 fore called fossiliferous rocks. Metamorphic rocks are 
 stratified rocks which have been changed by the action of 
 heat, and perhaps some other auxiliary agencies. In this 
 alteration, any fossils that the rocks originally contained 
 are obliterated, the material which composed them hav- 
 ing been altered with the rest of the rock in the arrange- 
 ment of its particles. Thus limestone containing shells 
 and corals has been often converted into granular lime- 
 stone or marble, a crystalline texture being thus given to 
 the whole. The term metamorphism means transforma- 
 tion, and comes from two Greek words, meta, which is 
 the same as trans in the Latin, and morplie, form. A 
 very decisive proof that heat is the principal cause of 
 metamorphism we have in the fact that great artificial 
 heat, if long continued, changes the structure of stones. 
 Sandstone used in furnaces has sometimes been known 
 to become crystalline that is, has been metamorphosed. 
 The unstratified rocks are not divided into parallel lay- 
 ers, but they are commonly a shapeless mass, as seen in 
 Fig. 49 (p. 128). They were not deposited from sedi- 
 ment, but were formed under the influence of heat, and 
 were thrust up from within the crust of the earth. They, 
 of course, never have any fossils in them. They general- 
 
128 GEOLOGY. 
 
 Fig. 40. 
 
 ly appear in mountains, forming often their central part, 
 while the stratified abound in plains, or flank the sides 
 of the mountains. When a mass of unstratified rock, as 
 granite, stands up as the axis or central part of a mount- 
 ain, stratified rocks commonly slope off from the granite, 
 this having thrust them to the one side and the other as 
 it rose up out of the bowels of the earth. 
 
 There is one class of unstratified rocks, the trappean, 
 noticed in 152, which have a tendency to regularity of 
 shape, and in some cases the tendency is fully carried 
 out. In this they are distinguished from the shapeless 
 masses of granite and other unstratified rocks. 
 
 212. Stratification, Lamination, Joints, and Cleavage. 
 The word layer is often used as meaning the same thing 
 as stratum, but in the strict use of the latter term it in- 
 cludes all the layers of the same kind which are next to 
 each other. A stratification means a succession of lay- 
 ers, either of the same kind or of different kinds. Lay- 
 ers differ very much in thickness, according to the man- 
 ner in which they were laid down. When they are very 
 thin they are called laminae. In shales and micaceous 
 sandstones the Iamina3 are so thin that we may properly 
 speak of them as films, and it is plain that in such cases 
 the stratum or bed was formed by the very gradual ac- 
 cumulation of films of clay or of micaceous spangles, 
 which settled down at the bottom of comparatively still 
 
CONSTRUCTION OF THE EARTH. 129 
 
 water. Each film or lamina was the result, of course, of 
 a separate deposition that is, after each lamina was 
 completed, there was a pause for a time in the deposi- 
 tion from the water. In those cases in which there are 
 fifty, or even a hundred laminae in the thickness of an 
 inch, the process, including the intervals, must have been 
 very slow. Some years must have been required to lay 
 down a foot of such a bed. Where the lamination is not 
 so fine, the accumulation of the sediment of which the 
 rock was made was more rapid. The term formation is 
 applied to a series of strata that have a relation to each 
 other in similarity of fossils, and which are therefore in- 
 cluded in the same age or period. This is the general 
 idea, but the word is used rather loosely, being made to 
 refer to a larger range of strata at one time than at an 
 other. In looking at a stratified rock, you observe be- 
 side the horizontal lines which indicate the divisions be- 
 tween the layers certain lines which cross these. The 
 two sets of lines are seen in Fig. 50. The lines which 
 
 Fig. 50. 
 
 run up and down across the layers indicate planes of di- 
 vision, which are called joints. Some of thesej you see, 
 extend farther than others, and these are called master- 
 joints. There are commonly two sets of joints at right 
 angles to each other, as is represented in the figure. It 
 
 F2 
 
130 GEOLOGY. 
 
 is this arrangement that enables the workman to get out 
 readily square, or, rather, squarish blocks of stone. The 
 regularity of these divisions varies much in different 
 cases. Sometimes it is so great that the upper surface 
 of a stratum has very much the appearance of a regular 
 pavement made with nicely-fitted slabs. Where, from 
 any cause, the rocks are occasionally thrown down, ex- 
 posing new surfaces of the strata with their joints, there 
 is a resemblance to the ruins of fortifications. In Fig. 
 51 we have a view of some of the clifis of Cayuga Lake, 
 
 Fig. 51. 
 
 K. Y., which weathering and the undermining action of 
 the water are continually wearing away, so that fresh 
 surfaces show in very definite manner the planes and 
 lines of division. Cleavage^ or the slaty structure, is an- 
 other kind of division in rocks. This is sometimes par- 
 allel with the layers, and sometimes runs across them. 
 Both the larger divisions by joints, and the smaller ones 
 by cleavage, each often extend over vast regions of 
 country at the same angle, showing that some causes 
 operating extensively produce them. 
 
 213. Order of Succession of Rocks. There is a regu- 
 lar order in the stratified rocks which is never trans- 
 
CONSTRUCTION OF THE EARTH. 
 
 131 
 
 gressed, so that the geologist can apply conclusions 
 made in regard to rocks in one quarter of the world to 
 those which exist in any other quarter. There may be 
 omissions, but there is never any change in the order. 
 "As a bookbinder," says Phillips, "sometimes neglects 
 to bind in a particular leaf, so Nature sometimes omits a 
 particular rock ; but she never misplaces the rocks, as 
 the careless workman sometimes misplaces the pages." 
 There is a very signal example of such an omission in 
 the rocks of this country. We have here the cretaceous 
 or chalk formation that is, the series of rocks so called; 
 but the chalk, which forms so prominent a part of this 
 series in England, France, and many other countries, is 
 wholly absent ; that leaf in the American geological vol- 
 ume is left out. 
 
 214. Flexures of Strata. Though strata are deposited 
 generally either horizontally or nearly so, they are often 
 very much bent, as is represented in Fig. 52. There are 
 
 Fig. 52. 
 
 some magnificent exhibitions of these flexures in some 
 of the mountainous regions. Among the Alps there are 
 mountains thousands of feet high, looking, as Professor 
 Hitchcock says, " as if crumpled together by some migh- 
 ty hand." It would seem as if it were not possible 
 thus to bend rocky strata without breaking them. But 
 probably the rocks were both moistened and heated 
 when this was done. Besides, the bending force un- 
 doubtedly was made to act very gradually. Some light 
 is thrown on this point by some observations in regard to 
 the bending of ice. Though ice is a very brittle solid, 
 
132 
 
 GEOLOGY. 
 
 large blocks of it have been known gradually to bend 
 very considerably. Kane saw this in a flat block of ice 
 eight feet thick, and twenty or more wide, supported 
 only at its two ends. In the course of two months it 
 became so much bent that the middle of it was depressed 
 five feet. 
 
 215. How the Flexures are Produced. It is supposed 
 that the flexures of the strata were produced by lateral 
 pressure. This has been illustrated by a simple experi- 
 ment by Sir James Hall. He took 
 pieces of cloth, some linen and some 
 woolen, and, placing them in layers on 
 a table (Fig. 53), compressed them by 
 the weight a. He then applied press- 
 ure to the sides b b, 
 
 as shown in Fig. 54, 
 
 and found that while 
 
 the weight a was 
 raised, the layers of cloth were bent 
 in folds like those which are seen in 
 layers of rock in nature. Sir C. Lyell 
 observed a result near Boston which 
 well illustrates the action of this later- 
 al pressure. For the purpose of con- 
 verting part of an estuary, overflowed at high tide, into 
 dry land, a vast quantity of stones and sand was thrown 
 into it. The eflect of this was to push up the bottom 
 of the estuary alongside of this load of stones and sand, 
 so that it, in the course of a few months, was raised 
 six feet above high-water mark, and some five or six 
 folds were produced in it, just like the folds, small and 
 great, which the geologist finds in rocky strata. 
 
 216. Upheavals of Strata, with Fracture. Fig. 55 is a 
 
 Fig. 53. 
 
 Fig. 54. 
 
 Fig. 55. 
 
CONSTRUCTION OF THE EARTH. 
 
 133 
 
 representation of such an upheaval. Fissures of various 
 dimensions, sometimes of immense size, are made in this 
 way, and this is the origin of many of the valleys which 
 we see with steep, bold sides. Chasms and caverns are 
 produced by such upheavals ; water, by its erosive agen- 
 cy, acting, however, at the same time, and afterward in 
 many cases, especially where there are caverns of consid- 
 erable extent. Natural bridges are the result of up- 
 heavals, an example of which is given in Fig. 56, repre- 
 senting that of Icononzo, in South America. 
 
 Fig. 56. 
 
 217. Strata at different Angles. One consequence of 
 upheavals with fracture is that we have strata lying at 
 different angles, as is often shown when their projecting 
 ends or sides are laid bare. The order of the rocks is 
 thus brought to view sometimes to a great extent, as in 
 the case of Snake Mountain, in Vermont, represented in 
 Fig. 57 (p. 134). The place of fracture is at c, and there 
 is brown clay at e, extending from here west six miles to 
 Lake Champlain, and lying upon n, limestone rock. I 
 will trace the layers of rock up the mountain. At b we 
 
134 
 
 GEOLOGY. 
 
 Fig. 57. 
 
 have sand rock, at d one kind of limestone, at a another 
 kind, and the same as that on which the brown clay, 6, 
 lies ; at g is slate rock, at h are shales, and at I red sand 
 rock ; at k is debris from the sand rock, Z, and at i is a 
 cranberry meadow lying on peat. Sometimes the strata 
 in the upheaval become vertical, as seen in Fig 58, which 
 is a representation of vertical 
 strata on which a castle has 
 been built. These strata were 
 laid down horizontally far back 
 in the past, ages upon ages be- 
 fore man was introduced, and 
 then by some mighty upheaval 
 were raised to their present po- 
 sition. Sometimes strata appear to be horizontal when 
 they are very far from it. Take such a case as that pre- 
 
 i'ig. 58. 
 
 Fig. 59. 
 
 sen ted in Fig. 59. If the spectator were in the vessel, so 
 as to look at the rocks as they appear on the side p, the 
 
CONSTRUCTION OF THE EARTH. 
 
 135 
 
 strata would appear to be horizontal, when in reality they 
 lie at an angle of about 45, and gradually become verti- 
 cal as you go toward a. 
 
 218. Dip and Strike. These are terms which are much 
 used in geology, and therefore require explanation. The 
 line of variation of strata from a horizontal line is called 
 their dip. For example, in the case shown in Fig. 60, if 
 
 the angle made 
 by the lines of 
 the strata, b #, 
 with the hori- 
 
 - 60. zontal line, a, be 
 
 45 degrees, these strata are said to dip 45 degrees. The 
 strike, on the other hand, is the line of direction in which 
 the edges of the strata run. The meaning of these terms 
 can be made clear by a simple illustra- 
 tion. If you place a book on the ta- 
 ble, as seen in Fig. 61, with the edges 
 of the leaves downward, and move 
 one side of the cover away from the 
 body of the book, a line from the back 
 of the book straight down the cover, 
 #, will be the line of dip, while a line 
 along the back of the book, a a, will 
 
 Fig. 61. 
 
 be the line of strike. 
 
 219. Anticlinal and Synclinal Lines. An anticlinal 
 line is a line along which the strata dip in opposite di- 
 rections. This may be exemplified by placing the book 
 in the position seen in Fig. 62. The 
 line along the back of the book repre- 
 sents the anticlinal line. The syncli- 
 nal line is the reverse of this. To rep- 
 resent it, let the book be placed in the 
 position seen in Fig. 63 (p. 136). The 
 line at the angle of the two parts of 
 the book is the synclinal line. These 
 lines do not, however, run along sharp 
 
 Fig. C2. 
 
136 GEOLOGY. 
 
 angles, as these illustrations would in- 
 dicate, but curves, and therefore anti- 
 clinal and synclinal curves are spoken 
 of in the anticlinal the sides inclin- 
 ing upward toward each other like the 
 roof of a house, but in a curved line, 
 while the sides of a synclinal curve in- 
 cline downward toward each other, 
 like the sides of a trough. 
 
 220. Measuring Strata. Where strata outcrop we can 
 very readily take the measurement of their thickness. 
 The manner in which this is done is so well pointed out 
 by Mr. Jukes, Director of the Geological Survey of Ire- 
 land, that I will give you his description of it entire : 
 " Having procured a good map of the district we are go- 
 ing to examine, a pocket compass, and a small instrument 
 called a clinometer, by which we can determine the an- 
 gle at which a bed inclines from the horizontal plane, we 
 begin to look for exposures of rock. The district may 
 perhaps at first appear to be entirely covered by soil and 
 vegetation, but, when thoroughly examined, it may show 
 here and there some crags of bare rock, some bare cliffs 
 on the side of a river, some cutting on a road-side, or 
 some quarries. Let Fig. 64 be a piece of our map trav- 
 ersed by a brook and a road, and suppose that we find 
 some quarries of limestone in the northeast corner of the 
 district, all the beds of which dip to the southwest at an 
 angle of 20. Let us represent these limestones by the 
 cross-barred lines in the northeast corner of the figure, 
 drawing them in a northwest and southeast direction to 
 represent their strike, and indicating their dip by an ar- 
 row with 20 annexed to it. In examining the banks of 
 the brook, suppose we find, in two places lying in the 
 same line of strike, some shales, represented by plain 
 close lines ; a bed of coal, represented by a thick dark 
 line; and some sandstones, represented by dots; and, 
 for simplicity's sake, let us suppose them all to dip south- 
 
CONSTRUCTION OF THE EARTH. 
 
 137 
 
 Fig. 64. 
 
 west at 20. Then suppose that we find one or two oth- 
 er detached exposures of sandstone and shale to the 
 southwest of the above, with similar strikes and dips. 
 And, lastly, suppose that in the southwest corner of the 
 district we find some more limestone of quite a different 
 kind from that in the northeast corner, but still dipping 
 to the southwest at 20. It will be obvious that these 
 limestones in the southwest corner of the map lie above 
 all the other rocks, while the limestones in the northeast 
 corner rise out from beneath all the rest." 
 
 221. Calculating the Thickness of Strata. In the case 
 just detailed, we have data for arriving at the thickness 
 of this whole set of strata. The manner in which this 
 is done can be explained on Fig. 65 (p. 138), which rep- 
 resents a section of the district at right angles to the 
 strike of the rocks. "Suppose," says Mr. Jukes, "that 
 we wish to sink a pit at the part marked shaft in the 
 map, in search of the coal, and that, before commencing, 
 we wish to know how deep the coal is there, and how 
 far it is to the limestone below it. We take the map, 
 
GEOLOGY. 
 
 Fig. 65. 
 
 and draw the line A B from southwest to northeast 
 through the spot we select for our shaft, and then, with 
 some leveling instrument, ascertain the undulations of 
 the ground along that line, taking the level of the sea as 
 our ' datum line.' Having thus got the true outline of 
 the ground, which we may suppose to be given in Fig. 
 65, we draw lines inclined at an angle of 20 toward the 
 southwest at the several spots where the section line is 
 cut by the outcrops of the beds, or by straight lines join- 
 ing them, and this section will then show us the depth 
 at which the shaft will reach any of the beds. Similar- 
 ly, if we wish to know the thickness of the whole suc- 
 cession of beds, from the highest to the lowest, of those 
 exposed in the district, the length of the line marked 
 thickness will give it to us, when measured on the scale 
 we adopt for our map and section." 
 
 In these simple operations is indicated the mode of 
 ascertaining some great geological facts, for it is by such 
 observations and measurements that we gain a far more 
 extensive knowledge of the crust of the earth than we 
 can by the deepest mining excavations; The great up- 
 heavals have turned up to us the leaves of geological 
 history for our reading, many of which we could not 
 otherwise have read, for they would have been so deep 
 that no exploration of man could have reached them. 
 
 222. Conformable and Unconformable Strata. Strata 
 are said to be conformable when their surfaces or planes 
 
CONSTRUCTION OF THE 
 
 139 
 
 are parallel to each other. They are unconformable when 
 their planes are not parallel. Thus, in Fig. 66, all the 
 
 Fig. 6G. 
 
 horizontal strata a are conformable to each other, and so 
 are also the inclined strata b; but the strata b have the 
 strata a lying unconformably upon them. All the strata 
 b were deposited in a horizontal position, and there was 
 no upheaval till the last of them was completed. Then 
 the state of quiescence was broken, and the strata were 
 lifted up as you see ; and when the upheaving force 
 ceased to act, the upper horizontal strata began to be 
 deposited. Periods of immense length were required 
 for all these successive processes, for the upheaval was 
 probably very slow, as the depositions certainly were. 
 
 223. Faults. Whenever in a fracture of strata there 
 occurs a dislocation of them, leaving those on one side 
 of the fissure higher up than those on the other, it is 
 called a fault, a name which was first given to such a 
 
 state of things by miners. 
 In Fig. 67 you have a rep- 
 resentation of a fault. The 
 strata marked with corre- 
 sponding letters on each 
 side of the fissure were 
 continuous till they were 
 all deposited, and then, by 
 some force, either the stra- 
 ta on the right hand were depressed, or those on the left 
 were elevated. Faults vary much in the degree of dis- 
 location, from a few feet up to many thousands. Some 
 of the grand changes in the earth's crust have been pro- 
 duced by faults. 
 
 224. Denudation. This term is applied to the wear- 
 
 
140 GEOLOGY. 
 
 ing away of rocks by flowing water. This erosive pow- 
 er of water, spoken of in 186, has produced some of 
 the most immense changes that have taken place in the 
 earth. You have seen what vast quantities of material 
 it supplies to be carried down by the rivers into lakes 
 and seas. The hills and mountains, though made by 
 foldings of strata and upheavals, generally received their 
 final shaping from denudation. Though erosion by wa- 
 ter is comparatively a slow process, yet, acting through 
 long periods, it produces great effects. It is supposed 
 that the Appalachian Mountains have lost from this 
 cause as much material as is now contained in them, or 
 even more, and the same can be said of some other 
 ranges of mountains. Indeed, in the changes of the 
 long ages occupied by the earth's foundation, the great 
 majority of the rocks have been built up from materials 
 furnished by denudation from pre-existing rocks, and 
 often denudation and reconstruction have succeeded 
 each other many times over in the case of the same ma- 
 terial. This same succession is seen to a considerable 
 extent even now. 
 
 225. Faults with Denudation. Denudation has often 
 united with faults in producing great changes. This 
 may be illustrated by Fig. 68, representing a section of 
 
 a coal-field in England of several miles in extent. There 
 are four divisions, A, B, C, and D, made by faults which 
 have put the strata in them at different relative depths. 
 Thus, in A, the bed of coal, X, is 900 feet from the snr- 
 
CONSTRUCTION OF THE EARTH. 141 
 
 face, and has over it various strata of sandstone and 
 shale, 1, 2, 3, 4, and 5. In the divisions B and D there 
 is only the stratum 5 above the coal, which is only 200 
 feet from the surface, while in the division C the coal 
 lies 700 feet deep. Now, notwithstanding this displace- 
 ment of the strata, there is no appearance of the up- 
 heavals on the surface of the coal-field, but that is level. 
 If the material all remained on the spot, we should have 
 an uneven surface, and at O O there would be an eleva- 
 tion of 700 feet, for that is the amount of uplift in the 
 strata at that part of the field. The inference is that all 
 this great mass of material, indicated by the dotted line, 
 was removed by denudation. Near Chambersburg, Pa., 
 there is a fault 20 miles in length, and the depth of the 
 dislocation is 20,000 feet, and yet a man can stand with 
 one foot on one side of this fracture and the other foot 
 on the other side. What has become, then, of this im- 
 mense mass of material 20,000 feet in height ? " It must 
 have been swept," says Mr. Lesley, who gives the ac- 
 count, "into the Atlantic by the denuding flood." If 
 this had not been done there would have stood there a 
 bold precipice nearly four miles in height and twenty 
 miles in length. Long ages must have been required 
 for water to effect such a denudation. The proximity 
 in which such a fault places rocks of epochs far distant 
 from each other bring to the mind grand and over- 
 whelming conceptions of the vast periods of time which 
 have elapsed in the building up of the world. On the 
 one side of that crevice you step on limestone that was 
 made long ages before the slaty rock that you step on 
 upon the other, and by accident there are lodged in that 
 crevice fragments of a rock of still another epoch be- 
 tween the epochs of those on either side. 
 
 226. How Mountains were Made. You are now pre- 
 pared to see how mountains were built up. They were 
 not all constructed and shaped in the same way, but 
 there is much variety. I Avill indicate some of the prin- 
 
142 
 
 GEOLOGY. 
 
 cipal modes. I have already mentioned the agency of 
 flexure or plication, as illustrated by Fig. 52. Denuda- 
 tion has much to do with the formation of such mount- 
 ains, as seen in Fig. 69. Here you see on each side 
 
 Fig. 69. 
 
 strata which, if continued on over the mountain, would 
 very much increase its height ; but they were removed 
 probably by the water sweeping over the mountain all 
 the time that it was slowly rising. This is a good rep- 
 resentation of the manner in which most of the mount- 
 ain chains are made and shaped. 
 
 Take another ex- 
 ample, represented 
 in Fig. 70. Here it 
 is obvious that the 
 strata a were first 
 deposited horizon- 
 
 rig. TO. 
 
 tally ; then the middle part or axis of the mountain was 
 thrust up, tilting the strata a, and after the tilting was 
 completed the strata b were deposited. In Fig. 71 we 
 
 Fig. 71. 
 
 see a somewhat different state of things. The strata a 
 and b were both deposited before the axis of the mount- 
 ain rose, and therefore were tilted up together. After- 
 ward the strata c were formed. Now if the strata a 
 and b are the same in character in the two cases, the 
 mountain represented by Fig. 71 is of much later date in 
 the world's growth than that represented in Fig. 70. 
 
CONSTRUCTION OF THE EARTH. 143 
 
 227. Valleys- Intimately connected with the subject 
 of the formation of mountains is that of the formation 
 of valleys. These are chiefly of three kinds: 1. Valleys 
 of undulation. These occur between the hills and 
 mountains that are raised by flexures of the earth's stra- 
 ta, as represented in Fig. 52. 2. Valleys of dislocation. 
 These are caused by fissures in strata, as represented by 
 Fig. 55. Where the strata are very thick, such valleys 
 are colossal in size and bold in their features. 3. Val- 
 leys of denudation. These vary much, according as the 
 rocks acted upon by the water are soft or firm. In Fig. 
 72 is represented an example of valleys formed by de- 
 
 rig. 72. 
 
 nudation. The strata here are not all continuous, but 
 portions of some of them have been worn away by wa- 
 ter, leaving the hills with valleys between them. 
 
 228. Volcanoes. These are constructed in a different 
 way from common mountains. They are made out of 
 the matters which are ejected from them, so that, as long 
 as a volcano is active, the work of construction is to some 
 extent going on. The solid matters ejected are chiefly 
 lava, cinders, and cinders moistened and forming in their 
 solidification what is called tufa. The tendency in the 
 construction is to the form of a cone, which is sometimes 
 very perfectly carried out, as seen in the grand volcano 
 of Japan, Fusiyama, the summit of which is represented 
 in Fig. 73 (p. 144). It stands 14,000 feet high. It has 
 in its top an oval opening, one diameter of which is 3300 
 feet, and another 1800 feet, and the depth is 1000 feet. 
 This volcano has long been inactive, the latest eruption 
 recorded having occurred in 1707. But two months in 
 the year, July and August, is the summit sufficiently free 
 from snow to permit the ascent, and then the natives are 
 
- . -^-^rr=^JL. ^-^"~ "~-^ 
 
 Fig. 73. 
 
CONSTRUCTION OF THE EARTH. 
 
 145 
 
 very busy in making their pilgrimages to the mountain, 
 which they consider very sacred, and call " matchless." 
 The steepness of the sides of volcanoes depends on the 
 material of which they are formed, being steepest when 
 the material is cinders, and least so when it is lava. Most 
 frequently volcanic cones are of a mixed character, hav- 
 ing layers of lava and of consolidated cinders mingled to- 
 gether. This is represented in Fig. 74, which is intended 
 
 Fig. 74. 
 
 to be a section through some volcanic cones. The parts 
 made of short vertical lines represent the layers of lava, 
 and the long lines represent the layers of ashes and cin- 
 ders. Irregularities occur in the forms of volcanic cones 
 from various circumstances. For example, a wind pre- 
 vailing in one direction may make ejected cinders accu- 
 mulate on one side of a crater more than on another. 
 The edge of a crater may be thrown over, as in the case 
 of Vesuvius ( 195). Lava may burst out through a fis- 
 sure, and, solidifying, cause accumulation on one side of 
 the cone. 
 
 229. Trap Rocks. Though these rocks have a decided 
 resemblance to volcanic rocks in their composition, the 
 eminences formed by them, some of which are lofty 
 enough to be called mountains, were constructed in a 
 very different manner. They are igneous, and yet not 
 volcanic. They were thrust up from below, a molten 
 mass pushing up the superincumbent strata before them, 
 and gradually became solid by cooling. They came up 
 through fissures in rocks, forming dikes, so called, in 
 these fissures. If the trap was not so hard as the rocks 
 
 G 
 
146 
 
 GEOLOGY. 
 
 Fig. 75. 
 
 in which the fissure was made, then the denudation 
 
 which followed left what 
 is called a sunk dike, as 
 seen in Fig. 75. But if, 
 as is usually the case, the 
 fissured rocks were soft- 
 er than the trap, it left a 
 raised dike, as represented in Fig. 76. Hugh Miller, in 
 
 commenting upon the 
 trap eminences or dikes 
 in and about Edinburg, 
 on one of which stands 
 the Castle of Edinburg, 
 
 compares the work of the denuding agencies to the work 
 of the sculptor, because, as he brings out his figures in 
 alto relievo by chipping away around them, so have these 
 agencies brought out in bold relief the grand trap prom- 
 inences by scooping away the soft shales and sandstones 
 which flanked them. The same can be said of the twin 
 prominences, East and West Rock, that add so much to 
 the scenery about New Haven. Sandstone was all about 
 them, perhaps even covered them, until the sculptor, wa- 
 ter, with its tides, and waves, and currents, removed it. 
 " Trap scenery," remarks Hugh Miller, " may be de- 
 scribed generally as eminently picturesque. From tho 
 circumstance that its eruptive masses rise often from 
 amid level fields, and that its hard, abrupt beds, dikes, 
 and columns alternate often with rich, soft strata, that 
 decompose into fertile soils, it abounds in striking con- 
 trasts. The soft plain ascends often at one stride into a 
 hill fantastically rugged and abrupt, and bare and frac- 
 tured precipices overtop terraced slopes or level plat- 
 forms rich in verdure." 
 
 230. How the Trap Rocks were Formed. These rocks 
 were not formed below and then lifted into their places, 
 but, as I have before stated, the material in a molten 
 state was thrust up, and there cooled off and solidified 
 
CONSTRUCTION OF THE EARTH. 
 
 147 
 
 under the pressure of rocky strata, which it had lifted 
 up, and which was covered with water probably of con- 
 siderable depth. This could not happen without crea- 
 ting great commotion, especially if there were fractures in 
 the superincumbent strata, letting down the water upon 
 the surface of the red molten mass. Hugh Miller, in his 
 magnificent description of what may be imagined to have 
 occurred in the emergence of the trap rocks, speaks of 
 steam and flame issuing from the fissures up through the 
 boiling waters. This may all be correct ; but when he 
 speaks also of the heavens being dark with ashes, as if a 
 real volcano were in action, the facts which the rocks now 
 reveal to us hardly warrant such imaginings. Though fire 
 is the agent in both cases, the formation of trap rocks dif- 
 fers very decidedly from the building up of a volcanic cone. 
 The open throat or chimney, through which materials of 
 various kinds are thrown up from the volcano, is wanting 
 when the trap rocks are elevated into their position. 
 
 It is in the cooling and solidification of the molten 
 mass that the prismatic, pillar-like form is sometimes so 
 perfectly assumed, as exhibited in the Giant's Causeway, 
 Fingal's Cave, etc. The igneous origin of these prisms 
 fairly entitle them to the name of " furnaced pillars," 
 which the Ettrick Shepherd has given them. 
 
 231. Veins. There are found in the rocks what are 
 called veins that is, fissures filled with rocky material, 
 
 or with metallic ores, or with 
 both. When they are filled 
 with rocky material, this is 
 sometimes the same with the 
 rock itself in which the veins 
 are, and sometimes it is of a 
 different composition. Some- 
 times one vein traverses an- 
 other, as is shown in Fig. 
 77. This is often the case 
 Fig. 77. with veins of granite. Such 
 
GEOLOGY. 
 
 veins have often penetrated through the overlying depos- 
 its, and flowed over the rocks which they have displaced, 
 as shown in Fig. 78. Sometimes one vein is displaced 
 or faulted by another, as repre- 
 sented in Fig. 79. Here is an 
 
 Fig. 78. 
 
 outline of the section of a boulder found by Prof. Hitch- 
 cock in West Hampton, Mass. It is a fragment of a 
 granite rock which was traversed by three granitic veins. 
 These, as seen in the boulder, are bed, ef, and gh. The 
 vein bed was made first. The other two were made 
 afterward, displacing or faulting the first, as you see in 
 the figure. As the three veins were made at three dif- 
 ferent times, they are three different varieties of granite. 
 Here, then, is a record of four different formations of 
 granite, the rock itself and the three veins, and how long 
 the intervals were between them we know not they 
 may have been ages. 
 
 Veins differ from dikes in various respects. They are 
 apt to be irregular in shape, larger at one point than at 
 another, while dikes are regular and uniform. Veins 
 are often compound, containing a variety of materials, 
 sometimes a considerable variety, while dikes are sim- 
 ple, containing only one kind of material, as some volcan- 
 ic mineral or trap. And when a vein has only one kind 
 of material, this never has the arrangement that a dike 
 often presents viz., a columnar, arrangement, as if one 
 block were placed above another from the bottom to the 
 top of the dike. Those veins which are compound have 
 a very different arrangement from the columnar one of 
 
THE EARTH. 149 
 
 the dikes. It is a banded arrangement that is, the ma- 
 terials are in bands parallel with the walls of the vein. 
 The bands may be few in number or numerous. If there 
 be metallic ore in a banded vein the rocky material is 
 called the vein-stone or gangue. 
 
 Dikes are due to the injection upward of melted ma- 
 terial into openings or fissures in the rocks ; but the man- 
 ner in which veins have been produced is by no means as 
 yet fully understood, and there have been much discus- 
 sion and speculation about it. 
 
 The distinctions between dikes and veins are generally 
 recognized among geologists as I have pointed them out, 
 but sometimes there is a little confusion in the use of 
 these terms. The term lode is often given to veins, but 
 seldom to any except those which are metallic. 
 
 232. Drift This term is applied to fragments of rocks 
 which have been scattered over some portions of the 
 earth's surface by other means than the flowing of water. 
 The fragments vary in size from grains up to those which 
 are many tons in weight. When they are of any consid- 
 erable size they are called boulders. They are supposed 
 to have been scattered by means of icebergs or glaciers, 
 or both. Drift is not found at all in tropical climates. 
 In North America it appears in Canada, New England, 
 the State of New York, and in all the states west of that 
 region in the same latitude. In Europe also it is con- 
 fined to the northern part. From comparison of the 
 drift with the stationary rocks, and from other observa- 
 tions, it is manifest that all the drift came from the north. 
 In the southern hemisphere, however, it came from the 
 opposite direction. In both cases its movement was from 
 the pole toward the equator. The distance to which 
 boulders have been carried is sometimes very great, even 
 hundreds of miles. We know where they came from by 
 their composition and other circumstances. Sometimes 
 long trains of boulders are traced, as if an iceberg slowly 
 sailed along, dropping continually as it went its rocky 
 
150 GEOLOGY. 
 
 freights. In such cases it is very easy to find the source 
 of the boulders. Drift, in its passage, left in many places 
 its marks, as scratches, and furrows, and smoothings. 
 Sides of mountains exhibit often these marks, and so 
 high up in this country that we know that there is only 
 one mountain in New England, Mount Washington, that 
 lifted its head above this drift action. I will not dwell 
 longer on this interesting subject here, as it will be 
 brought before you more particularly in another part of 
 this book. 
 
 233. Subsidences and Elevations of the Earth's Crust. 
 You will find, as I proceed to notice the different ages 
 of the earth's formation, that different portions of its 
 crust were alternately submerged under the waters and 
 elevated above them. This was not done by any sud- 
 den convulsive movements, but slowly, perhaps as slowly 
 as the change of level now occurring in Sweden and 
 some other countries, as noticed in 206. These altern- 
 ate subsidences and elevations, which were generally 
 several, sometimes many in number, were necessary, as 
 you will see, for the formation and arrangement of the 
 various strata that make up the earth's crust. Some- 
 times subsidences have been prolonged through even 
 many ages. Lyell speaks of one over a large area in 
 England and Wales which continued so long that strata 
 over six miles (32,000 feet) in thickness were deposited 
 during the time. In all this period, covering not an age 
 merely, but successive ages, there was an ocean's bed in 
 that region, and this bed sank gradually and quietly as 
 the deposits of solid matter were made upon it from the 
 water lying above it. In no one of the ages of the 
 earth's formation was there so remarkable an alterna- 
 tion of subsidences and elevations as in that one in which 
 the coal was made and laid down. Each bed of coal, as 
 you will learn more fully in another chapter, was made 
 from vegetation grown upon the surface, and this being 
 submerged by a subsidence, rock was formed over it. 
 
CONSTEUCTION OF THE EARTH. 151 
 
 Then, to make another bed of coal, there was an eleva- 
 tion for another growth, which was in its turn sub- 
 merged, to be covered by a rocky deposit. Where there 
 are many beds of coal there must have been many of 
 these alternate movements. 
 
 234. Pebbles, Sand, and Earth. In several different 
 connections I have remarked upon the ways in which 
 the rocks are worked up into pebbles, sand, and earth. 
 You have seen that, while other agencies are at work, 
 water, either directly or indirectly, is the grand agent 
 directly by its own erosive power, and indirectly by 
 grinding fragments of rock, from the large to the mi- 
 nute, against each other. By these means chiefly has 
 the soil all been prepared ; and it is nothing but commi- 
 nuted rock, with soluble matter from some of the rocks 
 dissolved in the water diffused through it. It is true 
 that when seeds are put into the soil thus prepared ad- 
 ditions are made to it from the decay of vegetable mat- 
 ter, but this is a mere return of such matter to the min- 
 eral condition. All was originally mineral earth, wa- 
 ter, and air ; and in plants and animals we have life act- 
 ing only upon mineral matter, giving it, for the time be- 
 ing, new properties. It is a very important item in the 
 construction of the earth for man that the soil should be 
 thus prepared, by what may, in one sense, be considered 
 a destructive process, but in another the putting the 
 material of w T hich the rocks are composed into a special 
 form for a special purpose. If this were not done, vege- 
 tation and animal life could have flourished, at best, to 
 but a scanty extent. 
 
 235. Earth-worms and Ants. These animals, apparent- 
 ly so insignificant, are real geological workers, accom- 
 plishing in the aggregate great results in preparing the 
 soil to produce food for man and beast. The earth- 
 worm burrows in the earth, loosening it, and leaving his 
 casts here and there. He is not confined to loose soils, 
 but is ever encroaching upon hard spots, especially if 
 
152 GEOLOGY. 
 
 they be wet, as any gardener may see occasionally in 
 the trodden walks. He does more than loosen the soil. 
 He brings it up in a comminuted state, as the casts will 
 show, leaving his burrows below to cave in by the 
 weight of the earth above them. Some observations 
 have been made which show that these operations are 
 of great extent and importance. Mr. C. Darwin, who 
 made many such observations, says that "although the 
 notion may appear at first startling, it will be difficult to 
 deny the probability that every particle of earth form- 
 ing the bed from which the turf in old pasture-land 
 springs has passed through the intestines of worms." 
 If you look among the spires of grass you will find the 
 casts of these worms scattered about, for they are al- 
 ways at work swallowing earth and disgorging it, either 
 upon the surface or into their burrows. The tendency 
 of water is to wash from the surface the finer portions 
 of the soil, carrying it away or down into the ground, 
 thus leaving the coarser parts on the surface ; but the 
 earth-worms can remedy this difficulty by bringing up 
 the comminuted matter. Furnishing bait, then, for fish- 
 ing is but a small part of the earth-worm's vocation. 
 
 The ants are also at work somewhat in the same way, 
 choosing drier spots than the earth-worms do. You 
 see them in multitudes on the dry garden walk, where 
 they make their galleries underneath, from which they 
 bring the materials for their little piles on the surface. 
 They, by loosening the soil, help to produce the vegeta- 
 tion which you are continually at work to destroy ; but, 
 though operating against you in the walk, they are every 
 where else doing a good work for you in your garden. 
 They are especially useful in tropical climates, where 
 they rapidly take to pieces, as we may say, the accumu- 
 lations of dead vegetable substance, and mingle it with 
 the soil. Dr. Livingstone, the great traveler, says of the 
 labors of the ants in the forests of Africa, "These insects 
 are the chief agents employed in forming a fertile soil. 
 
CONSTRUCTION OF THE EARTH. 153 
 
 But for their labors, the tropical forests, bad as they 
 are now with fallen trees, would be a thousand times 
 worse."* 
 
 236. Corals. Coral animals, which are of the class 
 called Polypes, are the most important organic or living 
 agencies that have contributed to the construction of 
 the earth. These animals are very small, most of them 
 exceedingly so, being less than the size of a pin's head. 
 They live in companies together, sometimes each a sep- 
 arate animal, and sometimes united together by a fleshy 
 mass, making what is called a polypidom, or household 
 of polypes. When separate, each sits like a cap on the 
 summit of a column of carbonate of lime, and there takes 
 in its food as it can catch it from the passing water. To 
 this mineral column he is continually adding, and the 
 process is a singular one. The animal is ever dying be- 
 low and growing above ; and as the column may be con- 
 sidered his skeleton, he may be said to be continually 
 leaving dead skeleton below him as he grows. The 
 process is essentially the same, though modified, in the 
 case of the polypidom. In this work each animal does 
 but little, but in the aggregate vast results are accom- 
 plished. In the ages that are past these little animals 
 have made immense additions to the limestone in the 
 earth's crust, and they are continuing their work now. 
 The rocks which result from their work are not really 
 built up by these animals. They furnish the material, 
 which is broken up and changed into limestone, though 
 there are imbedded in many of these rocks the coral 
 forms. And the material is not furnished by these ani- 
 mals alone, for shell-fish and other animals abound wher- 
 ever there are corals, and their remains add to the mate- 
 
 * I have noticed the earth-worms and ants in this chapter, rather 
 than in the chapter on present changes, partly because they have un- 
 doubtedly been great geological workers in past ages, and partly be- 
 cause it is appropriate to consider their work in connection with the 
 general view of the preparation of the soil for the use of man, 
 
 G2 
 
154 GEOLOGY. 
 
 rial of the rocks. Especially is this the case with the 
 shells. 
 
 237. Coral Reefs. Along many shores there are ridges 
 or reefs made by coral animals. The mode of their con- 
 struction I will describe. These animals do not begin 
 their work on the edge of the land, for they like clear 
 water, which can not be had close to the shore. But 
 there is a limit away from the land beyond which they 
 will not work, and this limit depends on the depth of 
 water. They can not live beyond a depth of about 100 
 feet, and most often they choose a depth of 20 or 30 feet 
 to begin their operations. Where the water deepens rap- 
 idly from the shore, they are not as far away from it as 
 where it deepens gradually. Coral animals are confined 
 to certain climates. Almost 'all the shelving shores in 
 tropical seas are lined by the reefs which they make. 
 There is a remarkable exception in the case of the west- 
 ern coast of South America. Here there are no corals, 
 while they abound on the eastern coast in the same lati- 
 tudes. The reason is that the western coast has sweep- 
 ing along it a cold current from the antarctic regions. 
 Many of the coral reefs are not yet raised up to the sur- 
 face, and these hidden reefs are very dangerous to nav- 
 igation. Some reefs are of very great extent. Along 
 the coast of New Holland there is one over 1000 miles 
 in length, and for 350 miles in one part of it there is no 
 passage through it. Reefs are spoken of as being of two 
 kinds, fringing and barrier ; the former being near the 
 shore, and the latter at some distance from it, with a deep 
 channel between. The fringing reefs are very apt, after 
 a time, to become a part of the main land. The reason 
 is that there is a continual washing of material into the 
 space between the land and the reef, both from the land 
 and the sea, chiefly the former. Indeed, Florida was all 
 made in this way, reefs having continually formed age 
 after age, and then joined to the main land. Many isl- 
 ands have been formed by coral animals. A large part 
 
CONSTRUCTION OF THE EARTH. 
 
 155 
 
 of the islands of the Polynesian Archipelago, as well as 
 many of those of the Indian Ocean, came from this source. 
 238. Atolls. This name is given to certain coral isl- 
 ands having a peculiar arrangement, one of which, Whit- 
 sunday Isle, is represented in Fig. 80. There is, as you 
 
 rig. so. 
 
 see, a strip of land inclosing a lake called a lagoon. In 
 some atolls this strip of land is unbroken, while others 
 have one or more openings, so that the lagoon forms a 
 harbor. These atolls are of various shape, sometimes 
 almost circular, sometimes long and narrow, having va- 
 rious bends and indentations in the margin of land. 
 Their size varies from half a mile up to sixty miles 
 across. The manner in which they are constructed can 
 be explained by Figs. 81 and 82. We will suppose an 
 
 Fig. 81. 
 
 island around which the coral animals build reefs ; a a, 
 Fig. 81, being the reefs, and b b the water between then 
 and the island. But in the figure a mere point in the 
 middle of the island is seen standing out of the water, 
 although the bottom of the reefs is far below the lowest 
 
156 GEOLOGY. 
 
 depth which coral animals reach. What is the explana- 
 tion? It is supposed to be this. When these animals 
 just began to make the reefs, the island stood far up out 
 of the water ; but as fast as the reefs were built up the 
 island subsided, keeping the surface of the reefs all the 
 time of the subsidence under the water. The rate of 
 subsidence must have been very slow to correspond with 
 the slow growth upward of the corals, which has been 
 calculated to be only the one eighth of an inch in a year. 
 In a completed atoll, the island having wholly disap- 
 peared, we have a state of things indicated in Fig. 82, 
 
 _ a a a representing a 
 
 It^ section of the mar- 
 
 Fig- 82 - gin of land, and b b 
 
 the lagoon. An atoll, then, may be looked upon as u the 
 tomb and monument of an island altogether buried be- 
 neath the waves." 
 
 There are groups of these singular islands, in some 
 cases extending over large spaces. In the Pacific Ocean 
 there is a band of such groups 4500 miles long, and va- 
 rying from 200 to 600 miles in breadth. 
 
 Many atolls rise up from a depth of 2000 feet, and 
 therefore are mountains of coral rock standing in the 
 water over a third of a mile in height. At the rate of 
 an eighth of an inch a year, it took the coral animals 
 192,000 years to build such mountains. 
 
 239. Calcareous Shells. I have said that in the for- 
 mation of the coral rocks there were contributions of 
 shells. In fact, they every where contribute material 
 for the limestones ; but in this case, as well as in others, 
 the great work of furnishing material is done by very 
 small, even minute animals. The shells of such animals 
 have formed extensive strata in various parts of the 
 earth's crust. In Fig. 83 you see represented the shells 
 of some of the foraminifera, a class of these minute ani- 
 mals, so named because their chambers communicate by 
 numerous foramens or pores. The microscopic animals 
 
CONSTRUCTION OF THE EARTH. 157 
 
 that inhabit these 
 many - chambered 
 shells are com- 
 posed of a gelat- 
 inous fleshy sub- 
 stance, and have 
 minute prolonga- 
 tions which they 
 Fig - 83> can throw out and 
 
 retract, and which they use for swimming, crawling, and 
 gathering their food. There is great variety in the 
 shells of the different species, and the regularity, beauty, 
 and delicacy of structure of these shells are very won- 
 derful. In view of the vast amount of rocky material 
 which such minute animals have added in past ages, and 
 are now adding, to the earth's crust, it may well be said 
 that the additions made by the remains of the larger an- 
 imals, such as elephants, lions, crocodiles, whales, etc., 
 are utterly insignificant in the comparison. There is one 
 division of the foraminifera that ..are not microscopic, 
 viz., the nummulites, one of which you see at b. They 
 are of various sizes, from very minute up to the size of 
 an inch and a half in diameter. The name comes from 
 the Latin word nummus, money, because the shell re- 
 sembles a coin in shape. Sometimes limestone is com- 
 posed entirely, or nearly so, of nummulites, and then is 
 called nummulitic limestone. The Sphinx and the Pyr- 
 amids are made of this rock. It constitutes the princi- 
 pal part of several mountain ranges in the south of Eu- 
 rope, as the Alps and Pyrenees. 
 
 In soundings in different parts of the Atlantic Ocean, 
 between Ireland and Newfoundland, as far south as the 
 Azores, there has been brought up a soft, sticky mud, 
 which has been called oaze. This, on being dried and 
 examined with the microscope, was found to consist of 
 the minute shells of foraminifera. As these shells are 
 composed of carbonate of lime, when an acid, as the sul- 
 
158 GEOLOGY. 
 
 phuric, is added to oaze, brisk effervescence occurs, be- 
 cause the acid, taking the lime, sets the carbonic acid 
 gas free. Here there is an immense chalk deposit going 
 on over a large area ; and in such lengths of time as were 
 occupied by deposits and solidifications in ages gone by, 
 this deposit may become hundreds of feet thick, and be 
 solidified into rock. In limestone strata quarried near 
 Paris the rock is composed to a large extent of shells 
 no larger than millet-seeds. Ehrenberg has discovered 
 in that form of limestone which we call chalk, animals 
 much smaller than this so small that, where they nearly 
 constitute the whole mass, as they do in the chalk of 
 southern Europe, there are over a million of them in ev- 
 ery cubic inch. Soldani collected from less than an 
 ounce and a half of rock from the hills of Casciana, in 
 Tuscany, 10,454 shells of foraminifera of various species. 
 Some of the species are so minute that it would require 
 over a thousand of the shells to weigh a grain. 
 
 240. Silicious Shells. You have already learned in 
 116 that silica, or flint, is dissolved by certain means in 
 water, and then is gathered up by plants and animals, 
 becoming again solid in soluble silica. There are very 
 extensively scattered in the earth innumerable minute 
 animals and vegetables which thus gather this material 
 from the water in which they live, and then, as they 
 die, their silicious shields or shells are deposited, and 
 much of the deposit becomes in time solid rock. These 
 shields present great variety of figure, and are very beau- 
 tiful as seen under the microscope. In Fig. 84 you see 
 
 represented three 
 of the forms of 
 shells of this kind, 
 of which a stratum 
 
 Actinocyclus. Coscinodiscus o f wn ite clay about 
 
 patina. > 
 
 Fig. 84. Richmond, Va., is 
 
 chiefly composed. The stratum is from twelve to thir- 
 ty feet thick, and is of great extent. The tripoli, or rot- 
 
CONSTRUCTION OF THE EAKTH. 159 
 
 ten-stone of Germany, forming beds sometimes fourteen 
 feet thick, is made up mostly of silicious shells so mi- 
 nute that a cubic inch contains forty-one thousand million 
 (.41,000,000,000), the weight of a single shell being cal- 
 culated to weigh the y^ millionth part of a grain. Si- 
 licious deposits from vegetables and animals are often 
 mingled with calcareous deposits, and hence came' for the 
 most part the flint-stones, which, as you will see here- 
 after, are so often found in chalk. One tenth of the oaze 
 ( 239) is silicious. So much agency are the minute 
 silicious animalcules and plants known to have had in 
 furnishing material for silicious rocks, that some have 
 supposed that most rocks of this kind have received their 
 material from this source. 
 
 I remark in passing that, although the diatoms of 
 which some forms are given in Fig. 84 have heretofore 
 always been considered as animalculse, Professor Dana 
 states that they are now regarded as vegetable. 
 
 241. Seas, Lakes, and Rivers. I have thus shown you 
 what means have been employed in the building up of 
 that- part of the earth which is included under the gen- 
 eral term land. The great cavities of the sea, " the 
 store-houses" in which God "layeth up the depth," we 
 know less about, and our researches are confined mostly 
 to the comparatively shallow portions of the ocean which 
 skirt the land. The manner in which the rivers that 
 run into the sea are made I need not stop to point out 
 to you. The streamlets made by every shower illus- 
 trate that subject, so that, with what has already been 
 said in regard to rivers, your own observation can give 
 you a proper insight into it. The same can be said, for 
 the most part, of the lakes. 
 
 242. Plan in the Construction of the Earth. Enough 
 has been developed in what I have said of the construc- 
 tion of the earth to show you that, although there have 
 been commotion and much apparent confusion, there has 
 been a well-ordered plan throughout all the changes, 
 
160 GEOLOGY. 
 
 aiming at the eventual fitness of the earth for man as his 
 habitation. This will be much more obvious to you as 
 we proceed to notice the different ages of. the earth's 
 preparation, and show how the continents have grown 
 to be what they are by successive additions. In the 
 case of each continent, the form of the land first lifted 
 above the surface of the waters had a manifest reference 
 to that form which was to be given to it when it was to 
 be completed and made fit for the use of man. There 
 was in the beginning a germ, and the gradual unfolding 
 of it has been beautifully traced out by the labors of the 
 geologist. 
 
 CHAPTER XII. 
 
 RECORD OF LIFE IN THE ROCKS. 
 
 243. Life in the Different Ages of the Earth. There 
 was a period, and that a very long one, as you will see 
 in the next chapter, in which there was no life upon the 
 earth. But after that period was passed, life, vegetable 
 and animal, was introduced, and became, as you have al- 
 ready seen, a great agency in the construction of the 
 earth's crust. What the forms of life were in the succes- 
 sion of ages previous to the age of man have been made 
 out by the geologist, by observing the remains of vege- 
 tables and animals found in the strata of the rocks. The 
 life of the world, then, may be said to have written its 
 own history on tables of stone, and we are able to read 
 on these tables the various changes which the forms and 
 modes of life have taken on during the ages of the past. 
 The lengths of these successive ages we can not make 
 out with any accuracy ; we can not measure time in the 
 far past of our earth by years and centuries as we can 
 in the present ag& ; but we can, by the life-record, learn 
 the order of succession, which has marked both the con- 
 struction of different parts of the earth and the furnish- 
 
RECORD OF LIFE IN THE ROCKS. 161 
 
 ing of it with the forms of life. In the successive ages 
 there have been variations in the vegetables and ani- 
 mals, especially the latter, which designate these ages, 
 as we learn by reading the record of the rocks. The 
 farther we go back in this record the less is the resem- 
 blance of the forms of life in the past to those of the 
 present, and the gradual increase of this resemblance, as 
 we come down from the first dawning of life on the earth 
 to the present age, is very obvious. This great fact will 
 be developed to you in various ways as we proceed. 
 
 244. Nature of the Evidence. You have already had 
 some glimpses of the record, and see what is the nature 
 of the evidence that it affords. You have seen that the 
 strata were formed one upon another in a certain order, 
 and that, as the material of which they are composed was 
 deposited, various remains of vegetables and animals be- 
 came mingled with it, and in the solidification made a 
 part of the rock. You see, then, how, in the midst of 
 the various disturbances of the strata, the geologist can 
 determine the relative ages of rocks by examining the 
 remains of organic substances contained in them. The 
 strata may be vertical, or may even be so far bent over 
 that the older rock may lie upon the more recent, but 
 the life-record reveals the truth ; and, farther than this, 
 the record is essentially the same in different regions of 
 the earth, so that the conclusions of geologists in one re- 
 gion may be applied in another. For example, coal is 
 found in different countries in connection with strata 
 that contain certain organic remains ; for, in the construc- 
 tion of the earth, there were certain periods for the for- 
 mation of coal, and one especial period for this purpose. 
 In whatever country, then, such strata are found, it may 
 be rationally expected that coal may be found in connec- 
 tion with them. Other examples might be given of a 
 similar character, but this will suffice. 
 
 245. Fossils. Any remains of any kind, of vegetables 
 or animals, found in rocks or in loose earth, are called 
 
162 GEOLOGY. 
 
 fossils. The term comes from the Latin word which 
 means to dig. The remains are generally more or less 
 defective, the softer parts being removed, and only por- 
 tions of those which are hard being preserved, although 
 in some cases there has been entire preservation, as 'in 
 the case of ancient mammoths found imbedded in frozen 
 earth in Siberia. Sometimes a fossil is a mere trace, as 
 of a leaf, or simply a track of an animal. Sometimes in 
 the fossil there is not a particle of the original organized 
 substance, as when perfect petrifaction takes place (118). 
 The mineral substance in these petrified fossils diifers in 
 different cases. The most common substances are silica, 
 carbonate of lime, and clay. Analogous to petrifaction 
 is the substitution of some mineral substance for the 
 whole of an organic body, as a shell, the new substance 
 making merely a cast of it. This differs from a petrifac- 
 tion in that there is no trace of the texture of the shell 
 in the cast. Coal, strictly speaking, is a fossil, for it is 
 the remains of the vegetable substances from which it 
 came, their texture being retained in it more or less, as 
 shown in 41. 
 
 There is much difference between different organized 
 substances in regard to their preservation as fossils. 
 Bones are very durable, but the bones of birds are sel- 
 dom found, because they were borne up by their feath- 
 ers as they decayed, and the bones, being hollow, were 
 easily broken. Their tracks, however, have been exten- 
 sively observed in the layers of rock, as you will see far- 
 ther on, and the investigation of these, especially in this 
 country, by Hitchcock and others, has furnished one of 
 the most interesting chapters in geology. Insects, too, 
 are seldom found, because they are so light, and decay 
 so rapidly from the presence of air in the air tubes that 
 pervade their bodies. Such hard substances as shells 
 are more largely preserved than any other substances. 
 
 246. Abundance of Fossils. Although many organ- 
 ized substances, from the softness of their structure, 
 
RECORD OF LIFE IX THE ROCKS. 163 
 
 could not be preserved at all, arid the hard structures were 
 liable to be broken up or even destroyed, yet the rocks 
 abound in fossils. It is stated by Agassiz and Gould 
 that in most formations the number of species of animals 
 and plants found in any locality is not below that of the 
 species now living, in an area of equal extent and of a 
 similar character. For example, a coarse limestone in 
 the neighborhood of Paris contains not less than 1200 
 species of shells, more than twice the living species now 
 found in the Mediterranean. So, too, in a certain kind 
 of limestone in New York, called the Trenton limestone, 
 there have been found 170 species of shells, nearly as 
 many as are now found on the coast of Massachusetts. 
 The same is true of the individual plants and animals as 
 of their species. Extensive strata, as you have already 
 seen, are formed of the remains of animals, as corals and 
 shells, and the immense stores of coal are made up of the 
 remains of plants. Then there are the immense quanti- 
 ties of silicious fossils, for so they may be called, fur- 
 nished chiefly by those minute plants called diatoms, no- 
 ticed in 240. Of these the microscope shows us that 
 there is a great variety of species. 
 
 247. Mode of Investigating Fossils. It is on the prin- 
 ciples of the science of comparative anatomy that the 
 fossils are investigated. This science may be said al- 
 most to have be,en founded by Cuvier, who acquired a 
 marvelous skill in prosecuting its researches. From a 
 few bones, sometimes even one small bone, of an un- 
 known animal, he could make out the construction of 
 the whole frame, and the character and habits of the an- 
 imal. The principles upon which this is done are very 
 simple. As in a machine each part has a relation to ev- 
 ery other part, so it is in the machinery of an animal ; 
 the relations in this case, however, being more perfect, 
 because the builder of the machine has perfect wisdom. 
 For example, teeth of a certain kind not only require a 
 certain kind of jaw, but a certain kind of feet also. An 
 
164 GEOLOGY. 
 
 animal having the sharp, tearing teeth of a beast of prey 
 would starve if he had such feet as grass-eating animals 
 have. These principles almost every one applies, to a 
 certain extent, with great ease. The sight of a tooth, or 
 claw, or beak will suggest at once to our minds the hab- 
 its and the shape of the animal to which it belongs. And 
 by careful observation one can acquire great skill in ap- 
 plying these principles to the minute parts of animal 
 frame-work, so that a familiar acquaintance can be formed 
 with the relations of each individual bone. The same 
 thing is true, to a certain extent, of vegetables. Now 
 as in fossils there are often only parts of a vegetable or 
 animal, this skill of which I have spoken is brought into 
 requisition, and by it the living beings of the past are 
 marshaled into classes, genera, and species, just as the 
 beings of the present are. Palaeontology is the name 
 which is given to this science of the fossils. It is a word 
 derived from three Greek words palaios, ancient; ontos, 
 the genitive of the word for being ; and logos, discourse. 
 It is really the application of two sciences, botany and 
 zoology, to the remains of life left by the past. Some, 
 however, use the term in a more restricted sense, consid- 
 ering it as meaning the science of fossil animals, while 
 the term Fossil Botany is applied to the science of fossil 
 plants. 
 
 248. Living Structures of Former Ages like those of 
 the Present. Vegetables and animals were constructed 
 on the same fundamental plans in the far past that they 
 are now. The same general divisions existed. And the 
 differences result from variations which were made to 
 meet different circumstances, and not from any essential 
 alterations in general plans. This being the case, it is 
 appropriate, before we go farther, to look at the outlines 
 of the Creator's plans in the construction of the forms 
 of vegetable and animal life. A knowledge of them will 
 aid you materially in following out the developments 
 which I shall make to you in the succeeding chapters, in 
 
RECORD OF LIFE IN THE HOCKS. 
 
 165 
 
 regard to the different ages of the earth's progress or 
 growth. 
 
 249. Amphigens. The vegetable world presents to us 
 five groups, marked by different modes of growth. First 
 we have the amphigens, so named because they increase 
 by growth on all sides, the name being derived from two 
 Greek words, amphi, around, and gennao^ to produce. 
 This mode of growth can be seen in the lichens that 
 spread out upon the surfaces of rocks, and trunks of 
 trees, and old fences. This division includes, besides 
 these lichens, tho scum-like growths that you see on 
 stagnant water (Confervse), the mushroom family (Fun- 
 gi), and the sea- weeds (Algae) that lie upon the shelves 
 and ledges of the shallow places in the sea. These are 
 all represented in Fig. 85. They are the lowest kinds of 
 
 Fig. 85. 
 
 vegetation, and are found where no other plants can 
 grow. They may be considered as pioneers of the higher 
 orders of plants, helping to weather the rock, and to 
 gather upon it the material for the growth, in time, of 
 
l'~ GEOLOGY. 
 
 other plants, and enriching also barren soils by their de- 
 cay, so as to prepare them for higher forms of vegeta- 
 tion. These plants are wholly cellular in their composi- 
 tion, while all other plants, as grasses, trees, and shrubs, 
 have tubular vessels for the circulation of the sap. The 
 latter are called, therefore, vascular plants, and the for- 
 mer cellular. 
 
 250. Acrogens. This division includes the mosses, the 
 ferns, the horsetails, and the ground-pine family. These 
 plants are pictured in Fig. 86, the tall tree-fern that 
 grows in tropical climates being represented as well as 
 the common fern, or brake, that is so familiar to us in 
 temperate climates. The plants of this class delight in 
 swamps and shady places. Their remains are found in 
 the peat of the present day, and in the coal deposits of 
 past ages. Their title comes from the fact that they in- 
 crease from the top alone, it being derived from two 
 Greek works, cikros, summit, and gennao. These, like 
 the amphigens, are of service in preparing soil for the 
 nourishment of higher orders of plants. They do a great 
 work in this respect, because they have a rapid growth, 
 and from year to year, by their decay, add to the solid, 
 nutritious material in the swamps and damp places where 
 they so luxuriantly flourish. Neither the amphigens nor 
 the acrogens aiford support to animal life to any extent. 
 
 251. Gymnogens. In this group, Fig. 87 (p. 168), we 
 have the cycads, or pineapple family, and the first pines, 
 or cone-bearing trees (conifers). They have this name 
 (gymnos, naked, and gennao) because their seeds are 
 naked instead of being inclosed in cases. They appear 
 in various kinds of soil, the dry as well as the damp. 
 From them, like the acrogens, peat and coal have been 
 largely formed. Our coal, both bituminous and anthra- 
 cite, was laid down in beds from the growth of both 
 acrogens and gymnogens far back in the past, as you 
 will see in another chapter. Their stiff, juiceless leaves, 
 scaly seeds, and hard berries afford but little nutriment 
 
KECORD OF LIFE IN THE 
 
 Fig. 86. 
 
 for animals, and therefore the record of the rocks shows 
 but scanty remains of any of the higher orders of ani- 
 mals amid those of these plants. The inference is a clear 
 one that when, in the ages past, these vegetables were 
 
103 
 
 GEOLOGY. 
 
 Fig. 87. 
 
 made to flourish for special purposes, but few of the ani- 
 mals of higher orders were brought upon the scene, be- 
 cause there was little food which such animals could ap- 
 propriate to themselves. The principle of adaptation 
 was applied to the mutual relations of the vegetable and 
 animal worlds in those ages as thoroughly as now by an 
 all- wise and omnipotent Creator. 
 
 252. Endogens. In this division of plants we have the 
 grasses, rushes, lilies, canes, and palms, as exhibited in 
 Fig. 88. Here we have a decided advance on the pro- 
 
RECORD OF LIFE IN THE HOCKS. 
 
 169 
 
 Fig. 88. 
 
 viously mentioned groups in the objects which the Crea- 
 tor had in view in introducing them. While the plants 
 of this class, like those of the former classes, add by their 
 decay to the nutritious material of the soil, their chief 
 design is to afford nutrition directly to the animal king- 
 dom. What was in the other classes only an incidental 
 object, is in this the primary one, while the primary of 
 those classes is here the incidental. The chief object of 
 
 H 
 
170 
 
 GEOLOGY. 
 
 the ainphigens, gymnogens, and acrogens was to build 
 up, as we may say, the soil of the earth, and of a part of 
 them to furnish the coal which has been stored up for 
 the use of man. They are geological in their agency 
 that is, earth-making. But the chief object of the endo- 
 gens has been to furnish food to animals that is, animal- 
 making. They are zoological in their agency. The name 
 endogens comes from endon, within, and gennao, and 
 expresses the fact that the growth is by addition in all 
 the parts of the plant equally. In the trunk or stem, for 
 example, there is in every addition a formation of new 
 fibres intermingled with those already present, and in old 
 trunks or stems the hardest part of the wood is toward 
 the surface, and the softest toward the centre. Endoge- 
 nous plants have no pith and no distinct bark. 
 
 253. Exogens. This name comes from ex, out, and 
 gennao. It indicates an entirely different mode of growth 
 from that of the endogens. There is a pith and distinct 
 bark, and the addition is in rings outside of those which 
 are already formed, the hardest part being toward the 
 centre, and the softest toward the surface. The differ- 
 ence in the modes of growth in the endogens and exo- 
 gens is exhibited by sections of stems or trunks in Figs. 
 
 89 and 90. In the 
 endogenous stem, 
 Fig. 89, you see 
 the holes occasion- 
 ed by the section 
 of the circulating 
 vessels, and be- 
 tween these is the 
 mass of woody or 
 cellular tissue which makes up the substance of the stem, 
 and forms, indeed, the walls of the vessels themselves. 
 But in the exogenous stem you see the pith, the rings 
 of wood, and the bark. The lines which radiate like the 
 spokes of a wheel from the pith to the bark are called 
 
 Fig; 89. 
 
 Fig. 90. 
 
RjfiCOED OF LIFE IN THE EOCKS. 
 
 171 
 
 medullary rays, and indicate plates of cellular or woody 
 substance. These make what is called the silver grain 
 of the wood. This division of plants includes the herbs, 
 shrubs, and timber trees, as they are seen grouped in 
 
 Fig. 91. 
 
 In this and Fig. 88 you see the differences be- 
 
 Fig. 91. 
 
 tween the two classes of plants exhibited in the trunks 
 of two trees represented as cut square off. The same 
 can be said of the exogens as was said of the endogens 
 in relation to their zoological character. The remains of 
 
172 
 
 GEOLOGY. 
 
 few of either class are found among the fossils of the far 
 past, but the record of life in the rocks shows that they 
 were more and more introduced the nearer we come 
 down to the age of man in tracing the successive ages. 
 
 254. Investigation of Vegetable Fossils. We can not 
 study fossil botany in the same manner that we do the 
 botany of the present. In the latter case we have all the 
 parts of plants in full, but in the former merely remains, 
 and sometimes only scanty ones. In many cases, there- 
 fore, in fossil botany we can only approximate to a^true 
 classification. With the scanty evidence often present- 
 ed, it is not surprising that some mistakes should have 
 been made One of these I will mention. For a long 
 time certain trunks of trees found in the coal measures 
 were put in a different family from certain roots found 
 also in these measures ; but at length it was discovered 
 that the roots and the trunks belonged to the same tree, 
 
 though in the stra- 
 ta they were found 
 separated from each 
 other. Of the many 
 points of distinction 
 in regard to vegeta- 
 ble fossils I will no- 
 tice but one, the ve- 
 nation of leaves, 
 or the mode of dis- 
 tribution of their 
 veins. The veins 
 in the leaves of en- 
 dogenous plants 
 run parallel with 
 each other, as seen 
 in Fig. 92, while in 
 "V the exogenous the 
 
 veins interlace, as seen in Fig. 93, which represents the 
 leaf of the apple. . ^ 
 
RECORD OF LIFE IN THE ROCKS. 173 
 
 255. Animal Fossils. The study of fossil zoology is 
 more satisfactory than that of fossil botany, for three 
 reasons. First, the distinctions between different kinds 
 of animals are more readily made out from the partial re- 
 mains which the rocks present to us. The reason is that 
 the differences between animals are of a more decided 
 character, and especially those which mark the grand di- 
 visions into classes, as you will soon see. Secondly, most 
 animal remains are in a better state of preservation than 
 vegetable remains. Shells, corals, scales, teeth, and bones 
 are very durable. Thirdly, more attention has been paid 
 to fossil zoology than to fossil botany by geological ob- 
 servers. 
 
 256. Protozoans. This term, derived from two Greek 
 words, protos, first, and zoon, animal, is applied to a 
 class of organisms which seem to stand on doubtful 
 ground, being half vegetable and half animal in their 
 characteristics. They are the sponges, the foraminifera, 
 and the infusoria. They have, for the most part, an in- 
 distinct organization, so that they can not be classified 
 with any of the great divisions of the animal kingdom. 
 Professor Dana therefore speaks of them as systemless ; 
 that is, as belonging to no system. And yet it would 
 seem as if some of them have a sufficiently definite form 
 to be classified, as operculina, /", polymorphina, g, and 
 nummulites, #, in Fig. 83, which are certainly very much 
 like ordinary shell-fish, though their resemblance in cer- 
 tain respects to polypes may render it improper to lo- 
 cate them with shell-fish in a definite classification. The 
 sponges have been thought by some to be on doubtful 
 ground, but it is now considered settled that they are 
 animal. The flinty diatoms, on the other hand, as stated 
 in 240, are now to be placed among vegetable organ- 
 isms, and are not, therefore, any longer to be called ani- 
 malculaa. 
 
 I pass now to the consideration of those animals that 
 can be definitely classed in systems. 
 
174 
 
 GEOLOGY. 
 
 257. Radiates. This class includes the coral animals, 
 hydras, sea-anemones, sea-nettles, echini, or sea-urchins, 
 and star-fishes. The name comes from the ray-like ar- 
 rangement which is so manifest in many of these ani- 
 mals, and exists really in all. It is from this radiate 
 form chiefly that many of them were formerly supposed 
 to be plants, and even now they are often called plant- 
 animals. Examples of them are seen in Fig. 94. Here 
 
 Fig. 94. 
 
 are represented the star-fish, the little hydra, a medusa, 
 a sea-urchin, and sea-anemones. One of the anemones is 
 divided in half, that you may see the interior. They are 
 all inhabitants of the ocean, and many of them, as they 
 are seen sometimes clustered together over a considera- 
 ble space, present, with their beautiful and varied colors, 
 the appearance of a garden under water. They are 
 
RECORD OF LIFE IN THE ROCKS. 
 
 175 
 
 pulpy in their consistence, many of them, however, hav- 
 ing a hard frame-work, as the coral animals and the star- 
 fishes. They live to a great extent on the microscopic 
 organisms which abound in the sea; and, though they are 
 more zoological than the protozoans, they are largely ge- 
 ological^ especially the coral animals, which have con- 
 tributed, and still contribute, as you have seen ( 236), 
 such quantities of limestone to the earth-making pro- 
 cesses. 
 
 258. Mollusca. This class, Fig. 95, contains animals 
 
 Fig. 95. 
 
 of a much more complicated and varied character than 
 the preceding. They are not confined to the ocean, but 
 
176 GEOLOGY. 
 
 many live in lakes, rivers, and swamps, and some even 
 on the dry land. The substance of these animals is soft, 
 as seen in the common oyster, and hence the name, which 
 comes from the Latin mollis, soft. But most of them 
 have hard shells, and so are called, in common language, 
 shell-fish ; though some, as the slugs, are wholly uncov- 
 ered. This class includes oysters, mussels, clams, snails, 
 slugs, nautili, cuttle-fishes, etc. The shells of some of 
 these animals have contributed largely to the formation 
 of the limestone of the earth, but they are more zoolog- 
 ical in their relations than the previous class. So widely 
 distributed have shell-fish always been, and so durable 
 are their shells, that their fossils are of great use to the 
 geologist in determining the relative ages of the rocks. 
 
 259. Articulata. This sub-kingdom includes insects, 
 worms, the spider and scorpion tribe, and the crab tribe. 
 These varieties are represented in Fig. 96. You have 
 here animals of extremely various character in many re- 
 spects. Nothing, for example, could be more unlike 
 than a butterfly and a lobster. Yet all these varieties 
 agree in one thing in having a covering which answers 
 to them as a skeleton, in giving firmness to the body, 
 and furnishing points of attachment to their muscles. 
 This is very obvious in such animals as crabs and lob- 
 sters, but it is equally true of insects and worms. This 
 skeleton coat of mail, as it may be called, has commonly 
 a very manifest ring-like arrangement ; and, as the rings 
 are jointed with each other, the name articulata, coming 
 from the Latin articulus, joint, is given to this division 
 of the animal kingdom. The articulata are mostly zoo- 
 logical in their relations, and are only slightly geological. 
 They live in every element in the air, the earth, and 
 the water. Some are animal-eaters, some vegetable-eat- 
 ers, and some both, and they, in their turn, are the food 
 of other animals of various kinds. 
 
 260. Vertebrata. The animals of this sub-kingdom 
 have an internal skeleton with a back-bone, so called in 
 
EECOED OF LIFE IN THE ROCKS. 
 
 177 
 
 Fig. 96. 
 
 common language, made up of vertebrae.* Through this 
 chain of bones runs a nervous extension of the brain 
 called the spinal marrow, from which nerves 
 branch out to different parts of the body. In 
 Fig. 97 you see represented a single vertebra 
 from the spinal column or back-bone of man, 
 a being its front part, and b its pointed rear 
 Fig. 97. part, which you feel on tracing the line of the 
 
 * Sometimes animals are spoken of as being in two great classes, 
 the Vertebrates and the Invertebrates, those which have and those 
 which have not vertebrae, the prefix in being a particle of negation. 
 The Invertebrates include the three great classes already spoken of 
 Radiates, Mollusks, and Articulates. 
 
 H2 
 
178. 
 
 GEOLOGY. 
 
 back-bone. You see the opening which 
 is filled with the spinal marrow. In 
 Fig. 98 you see the brain and spinal 
 marrow of man, showing how the nerves 
 branch out from the spinal marrow in 
 the vertebral column. This column dif- 
 fers much in length and arrangement 
 in different animals, being, for instance, 
 vastly longer in the serpent tlian in man, 
 and having a number of vertebrae in pro- 
 portion to its length. The vertebrata 
 have four grand divisions mammals, 
 or those that suckle their young, birds, 
 reptiles, and fishes. These are repre- 
 sented in Fig. 99. For the most part, 
 it is in this sub-kingdom that we have 
 the greatest complication of structure, 
 and with it the highest manifestations 
 of life. Intellectual qualities appear 
 here with their greatest prominence, 
 especially in those portions that ap- 
 proach to man; and in man, the highest 
 of mammals, not only is there superior- 
 ity in degree of intellect, but there are 
 superadded powers, making his intel- 
 lect different in kind as well as in de- 
 gree, thus linking him with the Infinite, and showing the 
 significance of the expression, made in the image of 
 God. Little have the vertebrata contributed of material 
 for earth-making, but they are almost wholly zoological 
 in their relations, presenting in this respect an extreme 
 contrast to the lower orders of animal life, the protozo- 
 ans and the radiates. The relations of the vertebrates 
 and the higher orders of the vegetable world, the endo- 
 gens and the exogens, are very obvious, and accordingly 
 we find in the life-record of the rocks the evidence of 
 their introduction together upon the world's arena, the 
 
 i 
 
 tig. 08. 
 
RECORD OF LIFE IN THE ROCKS. 
 
 179 
 
 Fig. 99. 
 
 full introduction of both being reserved for the age 
 which ushered in the advent of man. 
 
 261. Divisions of the Earth's History. As the record 
 of the rocks is a life-record, it seems eminently proper 
 to base the division into ages upon the changes which 
 we find in the forms of life from age to age. There are 
 other modes of division ; but, as the developments of 
 the life-record have come out, the tendency has been 
 more and more to a division on this basis. This division 
 has been made differently by different authors. The one 
 which I shall follow is that which is brought out in that 
 grand American work, Dana's Geology. He divides the 
 geological history of the world into seven periods : the 
 Azoic age, in which there was no life (a privative, and 
 zoe, life) ; the age of Mollusks ; the age of Fishes ; the 
 age of Coal-plants, or the Carboniferous age ; the age of 
 Reptiles ; the age of Mammals ; and the age of Man. 
 
180 GEOLOGY. 
 
 The last age is still in progress ; the others are in the 
 past. How long they were we know not; but that they 
 were each much longer than the age of man has thus far 
 been we have the most conclusive evidence to show. 
 
 It is proper to notice here a division of time into five 
 periods which is common in works on Geology, and in 
 relation to which there are certain terms that are in con- 
 stant use by all geologists. 1. Azoic time. This has 
 been already explained. 2. Palceozoic time. This was 
 a period in which the forms of life, as their remains 
 show, were very ancient that is, differing decidedly 
 from the present. This period includes the three ages of 
 mollusks, of fishes, and of coal-plants. Its name comes 
 from palaios, old, and zoe. 3. Mesozoic time, the fossils 
 of which differ less than those of the Paleozoic from the 
 living forms of the present, the term being derived from 
 mesos, middle, and zoe. The ages included in this period 
 are the middle ages of geological history, and cover 
 what is called the age of Reptiles, which is really, like all 
 the other grand divisions of geological time, a succession 
 of long ages. 4. Cainozoic (or, as it is sometimes called, 
 Cenozoic) time, from Jcainos, recent, and zoe. This is 
 the age of Mammals. 5. The Present age. The terms 
 primary, secondary, and tertiary are used often as mean- 
 ing the same, respectively, as Paleozoic, Mesozoic, and 
 Cainozoic. 
 
 262. Boundaries of the Ages. No age has had a sharp- 
 ly-defined limit in relation to its life-record, but each 
 age has been to some extent mingled with other ages 
 in its rise with the age that preceded it, and in its de- 
 cline with the age that followed it. Geological history, 
 as Professor Dana remarks, is like human history in this 
 respect, ages in both cases being marked by peculiarities 
 which, indistinct at first and foreshadowed in a previous 
 age, at length come out prominently to view. When 
 they thus culminate it is easy to trace them back to their 
 rise, and follow their growth, and then their decline, as 
 
AZOIC AGE. 181 
 
 they lose themselves in the rising peculiarities of another 
 coming period or age. Thus that remarkable age, the 
 coal-bearing or Carboniferous age, which was specially 
 occupied in making and storing up coal in the strata of 
 the earth's crust, was foreshadowed by the occurrence 
 of plants similar to the coal-plants in the previous age, 
 the age of Fishes. So also mammals appeared to some 
 extent long before that age in which these animals were 
 so numerous, in many cases so monstrous, as to make it 
 proper to denominate it the age of Mammals. It may be 
 remarked, in this connection, that it is not the idea to 
 give the name of a class of animals to an age because 
 they are more abundant then than they are in any other 
 age. Thus the mollusks are really not as abundant in 
 the age to which they give their name as they are after- 
 ward in the age of Reptiles, but in the age of Mollusks 
 they are more abundant than any other class. At the 
 same time, abundant as are the mollusks in the age of 
 Reptiles, the latter then surpass them in abundance, and 
 so give the name to the age. The articulates, which do 
 not give a name to any age, have steadily increased from 
 their small beginning far back at the conclusion of the 
 Azoic age on to the age of the present. 
 
 CHAPTER XIII. 
 
 AZOIC AGE. 
 
 263. Beginning of Solidification of the Earth. There 
 was a time when the earth was a liquid mass. Of 
 course, with such a degree of heat as sufficed to maintain 
 it in this condition, there was no liquid water, but the 
 heated ball was enveloped in steam. But after a time a 
 portion of the outside of the mass became solid, forming 
 a crust. Professor Hitchcock savs that it is not unlike- 
 
1 82 GEOLOGY. 
 
 ly that the time occupied in cooling the earth from its 
 melted state, sufficiently to form a crust, was longer than 
 all the time of the ages which were occupied in laying- 
 down the strata that contain fossils that is, longer than 
 all paleozoic, mesozoic, and cainozoic time. And if the 
 earth, as is supposed by many geologists, was once so 
 heated as to be in a vaporous state, the time of cooling 
 must have been vastly longer than this. But, whether 
 we reckon the azoic or lifeless age of the earth as begin- 
 ning with the first solidification of the crust, or with the 
 melted state, or extend it back to the supposed vaporous 
 or nebulous state, so called, the time that elapsed before 
 any life appeared on the earth was immense in length. 
 
 264. Floor of the Earth's Crust. It was in the solidifi- 
 cations of the Azoic age that the floor, as we may term 
 it, of the earth's crust was laid. This floor lies over the 
 melted matter which is inclosed still within the crust, and 
 which constitutes by far most of the bulk of the globe. 
 It is not an even floor, although it was laid down in hor- 
 izontal strata. It has been bent, and folded, and frac- 
 tured, and lifted up, and broken through by melted mass- 
 es forced upward from below. Although, then, its stra- 
 ta were laid before any of the fossiliferous strata, yet, 
 from these bendings and upheavals, they appear in some 
 parts of the earth upon the surface of its crust, the fos- 
 siliferous rocks skirting their prominences or partially 
 overlying them. 
 
 265. Changes in the Azoic Rocks. Vast changes oc- 
 curred in the azoic rocks during both the Azoic age and 
 the succeeding ages, for fire and water were at work 
 upon them more or less during all that time. Just as 
 soon as solidification took place on the surface of the 
 great melted ball which once constituted our earth, a 
 large part of the steam surrounding it was condensed 
 into water, which of course fell in rain. At the same 
 time, the forming crust, as is the case with all matter ex- 
 cept water, in passing from the melted to the solid state, 
 
AZOIC AGE. 183 
 
 contracted, and this contraction crumpled it into folds, 
 regular and irregular, and thus made channels and cavi- 
 ties for the water to run and dash in. Water then be- 
 gan that great work of denudation, which, as you have 
 seen in previous parts of this book, it has been carrying 
 on ever since. From that denudation in this first age 
 of the world was supplied material for the strata of the 
 grand azoic floor, which covers up the fiery deeps with- 
 in, and upon and against which the rocks of after ages 
 were laid. So great have been the changes in the azoic 
 rocks, that it is impossible to distinguish among them 
 any that can with certainty be made out to be portions 
 of the original crust that is, portions of the first solidi- 
 fication. 
 
 266. Some of the present Land formed in the Azoic 
 Age. In some quarters of the earth the azoic rocks ap- 
 pear upon the surface of the earth's crust. These, as 
 Professor Dana states, are "either, 1. Those which have 
 always remained uncovered ; 2. Those which have been 
 covered by later strata, but from which these superim- 
 posed beds have been simply washed away without much 
 disturbance ; 3. Those once covered, like the last, but 
 which, in the course of the upturnings of mountain-mak- 
 ing, have been thrust upward among the displaced stra- 
 ta, and in this way have been brought out to light." The 
 areas in which the rocks appeared above the surface of 
 the water during the Azoic age were scanty compared 
 with the whole area occupied by the land at the present 
 time. These areas were the beginnings of the conti- 
 nents, and it was by successive additions to them during 
 the succeeding ages that the continents grew to be what 
 they now are. 
 
 267. America and Europe in the Azoic Age. The azoic 
 rocks that come to the surface in North America occupy, 
 for the most part, a very long and comparatively narrow 
 strip of land extending from Nova Scotia west to the 
 base of the Rocky Mountains. This monstrous island 
 
184 GEOLOGY. 
 
 was not straight, but bent upward either way, forming 
 an elbow, and shaped much like Fig. 100. If you corn- 
 
 Fig. 100. 
 
 pare this with the shape of North America as a whole, 
 you will see why this beginning of the continent had this 
 shape, as it was completed afterward by additions. The 
 elbow extends downward, as the lower part of the com- 
 plete continent does, and the larger limb of the island 
 corresponds with the more extended side of the conti- 
 nent. Some few other comparatively small azoic areas 
 are found in North America, one of which is in Missouri, 
 and includes the noted Iron Mountains. All else was sea 
 in that quarter to the end of the Azoic age. Agassiz says 
 of the long island which was the beginning of the North 
 American continent, " We may still walk along its ridge, 
 and know that we tread upon the ancient granite that 
 first divided the waters into a northern and southern 
 ocean ; and, if our imaginations will carry us so far, we 
 may look down toward its base, and fancy how the sea 
 washed against this earliest shore of a lifeless world." 
 
 Europe was quite in contrast with America in this age. 
 There was no one great island, but several of considera- 
 ble size, and some small ones were scattered about in that 
 part of the vast azoic ocean. There was no so obviously 
 marked beginning of a continent as in the case of North 
 
AZOIC AGE. 185 
 
 America. It is with great truth, then, that Agassiz says 
 that, though America is called the New World, she is 
 really the Old World, for she is really first-born among 
 continents. 
 
 268. Thickness of the Azoic Strata. The strata of the 
 azoic rocks varies from twenty to thirty thousand feet in 
 thickness. An immensely long period was required to 
 deposit and solidify so much material, and comparative 
 quiet must have reigned during their deposit. The up- 
 heavals occurred after this was done. 
 
 269. Upheavals and Bendings. These are very exten- 
 sive, and there is much regularity in them, for the strike 
 is the same in some cases over great extents of territory. 
 The regularity is most observable in the strata of the lat- 
 ter part of the age, for in the first part the heat was so 
 great that the rocks then formed are much contorted. 
 
 270. Rocks of the Azoic Age. The rocks of this age 
 are granite, gneiss, schists, limestones, etc. They were 
 mostly deposited in beds, and then were crystallized 
 chiefly by the influence of the great heat which pre- 
 vailed in that age. Some of the granite is metamorphic, 
 but some of it was made originally as granite, having 
 been forced upward from below, as was often done at 
 different periods in the succeeding ages. One character- 
 istic of the azoic rocks is the prevalence of iron. Some 
 of the minerals which enter into the composition of some 
 of the rocks contain iron, and there are sometimes found 
 in the strata beds of iron ore of greater extent than in 
 any other age. 
 
 271. Heat and Light in the Azoic Age. The heat of 
 the forming crust in the first part of this age must have 
 been very great, and the upheavings and commotions 
 must then have been tumultuous. Hugh Miller thus de- 
 scribes what may be imagined to be the state of things 
 at that time. " Let us suppose that during the earlier 
 part of this period of excessive heat the waters of the 
 ocean had stood at the boiling point even at the surface, 
 
186 GEOLOGY. 
 
 and much higher in the profounder depths ; and farther, 
 that the half-molten crust of the earth, stretched out over 
 a molten abyss, was so thin that it could not support, 
 save for a short time, after some convulsion, even a small 
 island above the sea level. What, in such circumstances, 
 would be the aspect of the scene, optically exhibited 
 from some point in space elevated a few hundred yards 
 over the sea ? It would be simply a blank, in which the 
 intensest glow of fire would fail to be seen at a few yards' 
 distance. An inconsiderable escape of steam from the 
 safety-valve of a railway engine forms so thick a screen 
 that, as it lingers for a moment, in the passing, opposite 
 the carriage windows, the passengers fail to discern 
 through it the landscape beyond. A continuous stra- 
 tum of steam, then, that attained to the height of even 
 our present atmosphere, would wrap up the earth in a 
 darkness gross and palpable as that of Egypt of old a 
 darkness through which even a single ray of light would 
 fail to penetrate. And beneath this thick canopy the 
 unseen deep would literally " boil as a pot" wildly tem- 
 pested below; while from time to time, more deeply 
 seated, would upheave suddenly to the surface vast 
 tracts of semi-molten rock, soon again to disappear, and 
 from which waves of bulk enormous would roll outward, 
 to meet in wild conflict with the giant waves of other 
 convulsions, or to return to hiss and sputter against the 
 intensely -heated and fast-foundering mass, whose violent 
 upheaval had first elevated and sent them abroad." At 
 length, however, the earth's forming crust would cool 
 down, so that the steam atmosphere would become less 
 thick, and after a time the rays of the sun would strug- 
 gle through, forming at first a faint twilight, but gradu- 
 ally strengthening as the age advanced. At its close, 
 " day and night the one still dim and gray, the other 
 wrapped in a pall of thickest darkness would succeed 
 each other as now, as the earth revolved on its axis, and 
 the unseen luminary rose high over the cloud in the east, 
 
AGE OF MOLLUSKS. 187 
 
 or sunk in the west beneath the undefined and murky 
 horizon." So great was the heat that prevailed while 
 the azoic strata were laid down that it does not seem 
 strange that no remains of life are found in them. "As 
 well," says Agassiz, "might we expect to find the re- 
 mains of fish, or shells, or crabs at the bottom of geysers 
 or of boiling springs, as on those early shores, bathed by 
 an ocean of which the heat must have been so intense." 
 272.. State of the Surface at the End of this Age. At 
 the end of the Azoic age there was nothing like the di- 
 versity of surface that there is at the present time, there 
 being no high elevations over the comparatively small 
 portions of land which then rose above the level of the 
 universal ocean. Still, denudation had been going on 
 during all the progress of the age, and there were there- 
 fore extensive areas where there were gravel, sand, and 
 some material ground up so fine as to be mud. This 
 broken and ground material was spread not only here 
 and there over the land, but over the bottom of the seas 
 as now. In short, the earth was prepared for the com- 
 ing life of the next age. A part of this preparation was 
 the reduction of the temperature to such a point as was 
 consistent with the existence of plants and animals. 
 
 CHAPTER XIV. 
 
 AGE OF MOLLUSKS, OE SILURIAN AGE. 
 
 273. Dawn of Life. The earth having been prepared 
 during the Azoic age for vegetation, life, both vegetable 
 and animal, was now introduced upon the scene. That 
 its introduction occurred at that time is inferred from 
 the fact that the beginning of the life-record is found in 
 the rocks that were then formed, or, in other words, that 
 no fossils, no remains of life, have been found in the 
 rocks that were formed previous to that period. There 
 
188 GEOLOGY. 
 
 are, indeed, certain contents of rocks of the Azoic age, 
 from which some have argued that there were both veg- 
 etables and animals in existence then, and that they were 
 so acted upon by the mechanical and chemical agencies 
 of that early period that we now find only what was 
 produced from them. This supposition may possibly be 
 correct. If so, we have an example of that foreshadow- 
 ing that I spoke of in 262, the scanty life of the one 
 age in this case preceding the full introduction of life in 
 the other. But, at whatever time life was introduced, it 
 was done by a distinct exertion of creative power. It 
 was no result of chemical or mechanical forces already 
 existing, foivdead matter has no disposition or tendency 
 in itself to produce the seed of a vegetable or the germ 
 of an animal. All vegetables and animals have a parent- 
 age, and the beginnings of the lines of succession were 
 products of creative power. In other words, each spe- 
 cies, either vegetable or animal, was, when first intro- 
 duced upon the earth, a distinct creation. Though the 
 influence of circumstances may produce varieties in any 
 species, no species can be derived from any other spe- 
 cies. There is a disposition in some to discard this 
 view. They seem to dislike the idea of a present deity, 
 and to desire the removal of creative power as far back 
 in time as possible, as if in the dim distance they get rid 
 of some of the actual force of the power. 
 
 274. Rocks of this Age. The rocks are of considerable 
 variety hard sandstones, limestones, slates, shales, flag- 
 ging-stones, marls, and conglomerates. Some of the for- 
 mations are in part calcareous that is, they have carbon- 
 ate of lime mingled with other materials ; while in some 
 formations there is quite pure limestone, which in some 
 localities has been converted into marble. At Niagara 
 Falls we have 85 feet of limestone lying upon 80 of shales, 
 the erosion of the soft shales by the water causing a con- 
 stant undermining of the hard limestone, and therefore 
 a recession of the falls toward Lake Erie, as stated in 
 183. 
 
AGE OF MOLLUSKS. 
 
 189 
 
 275. Arrangement of the Rocks. The arrangement of 
 the rocks of this age was first thoroughly observed in a 
 region of the western part of England, which was in an- 
 cient times inhabited by a tribe called the Silures. Hence 
 this age is often called the Silurian age, and the rocks are 
 said to belong to the Silurian system, no matter in what 
 country they may be found. Local names have, after 
 this fashion, been given quite extensively by geologists 
 to different systems and formations, as you will see as 
 we proceed. The Silurian system has been very fully 
 examined in this country in the State of New York, and 
 it is presented to you in Fig. 101, in a section which was 
 drawn by Professor Hall in making his geological sur- 
 vey. The section exhibits the arrangement of the sys- 
 tem, together with the next to be noticed, the Devonian, 
 from the north side of Lake Ontario across New York 
 into Pennsylvania. I give below it the names of the dif- 
 ferent formations or groups as they have been, applied 
 from the local associations of the rocks. 
 
 Fig. 101. 
 
 1. A. Upper rocks of the Azoic 
 age. 
 
 2. B. Potsdam sandstone, lowest 
 of the rocks of the Silurian age. 
 
 3. C. Calciferous sand rock. 
 
 4. D. Black River limestone. 
 
 5. E. Trenton limestone. 
 
 6. F. Utica slate. 
 
 a. Lake Ontario. 
 
 7. G. Hudson River group. 
 
 conglomerate. 
 
 9. I. Medina sandstone. 
 
 10. K. Clinton group, 
 
 11. L/. Niagara group. 
 
 12. m. Onondaga salt group. 
 
 13. N. Helderberg series. 
 
 14. O. Hamilton group. 
 
 15. e. Tully limestone. 
 
 16. P. Portage group. 
 
 17. R. Chemung group. 
 
 18. S. Old red sandstone. 
 
 8. H. Gray sandstone and Oneida 19. T. Conglomerate of the Car- 
 
 boniferous system. 
 
 You see that the rocks all crop out here, and that, if 
 they laid horizontally, as they did when they were depos- 
 
190 GEOLOGY. 
 
 ited, the azoic rocks, A, would be underneath the whole. 
 The Silurian system ends in the Helderberg series, and 
 the Devonian lies between this and the beginning of the 
 Carboniferous system, T. The old red sandstone, S, is so 
 prominent in the Devonian system in England and Scot- 
 land that its name is there very commonly applied to the 
 whole systetn. 
 
 276. Geographical Distribution. The chief part of the 
 rocks of this system that come to the surface in the 
 United States lie along south of the continent as it was 
 begun in the Azoic age, as represented in 267. They 
 are in the great lake region, and extend along in a broad 
 belt west from Lake Michigan. A long strip of this sys- 
 tem stretches along on the east of the great Appalachian 
 coal-field, that extends from Pennsylvania down into Ala- 
 bama. The Silurian rocks are found in the west of En- 
 gland, where, as I have before said, they were first suc- 
 cessfully examined ; also in Belgium, Germany, Norway, 
 Sweden, and in Russia, in the neighborhood of St. Peters- 
 burg. 
 
 277. Copper of the Silurian Rocks. In the neighbor- 
 hood of Lake Superior trap rocks were thrust upward 
 among the Silurian rocks, and native copper is found 
 there in great abundance in veins, in both kinds of rocks 
 where they came together. It is supposed that the cop- 
 per was produced from ores in the azoic rocks lying be- 
 low, the trap, as it came up in its molten state, smelting 
 the ores as if in a vast furnace, and forcing the pure metal 
 upward, which, in its melted state, passed into openings 
 and crevices, making veins in all directions. 
 
 278. Silurian Salt. Most of the salt-springs in this 
 country issue from Silurian rocks. The extensive accu- 
 mulation of salt in the State of New York Professor 
 Dana accounts for in the following manner. He sup- 
 poses that when the saliferous (salt-bearing) beds were 
 laid down there was in that quarter a large shallow ba- 
 sin, or series of basins, \\ ith limestone, such as we have 
 
AGE OP MOLLUSKS. 191 
 
 at Niagara Falls, for a bottom. Into these basins the 
 salt water of the ocean was admitted, in some way, in- 
 termittingly. This might be from the occasional break- 
 ing away here and there of the barriers which bounded 
 in these basins from the sea, or simply from the changes 
 of the tide. The result, you see, then, would be some- 
 what like that which we have in the artificial production 
 of salt from evaporation of the waters of the ocean, as 
 noticed in 358, Part II. By evaporation over this im- 
 mense area of the basins the salt of the sea-water would 
 be deposited, mingled with the mud, which would be at 
 the same time settling as sediment. This would go 011 
 rapidly whenever the water was very low, especially 
 with the warmth of climate which prevailed in that age. 
 And such accumulations of salt going on for a long pe- 
 riod (for this salt-making, like the coal-making, did oc- 
 cupy a long time in the world's geological history) would 
 lay up in the rocks into which this mud would change 
 by solidification a vast amount of salt, such as we now 
 find in the Silurian deposits in New York. Mr. Dana 
 states that he once saw in a small coral island of the 
 Pacific a process similar to this actually going on. It 
 was an island with a lagoon in it, having no free com- 
 munication with the ocean. The waters became ex- 
 tremely salt in the hot, dry season, and fresh again in 
 the rainy months. There was a mud deposited in the 
 bottom of the lagoon from the w r ashing of the coral 
 rocks that bounded it. This calcareous mud, if solidi- 
 fied, would make a saliferous rock, like the rocks of this 
 character in the Silurian system of New York. The salt 
 is obtained from these rocks in New York by evapora- 
 ting the solution, or brine, made by the water which 
 gains access to the strata. At the great salt-works in 
 Salina and Syracuse this brine is collected by borings, 
 which sometimes extend down over 300 feet. From 35 
 to 45 gallons furnish a bushel of salt, while it requires 
 nearly ten times this quantity of sea-water to furnish this 
 amount. 
 
192 GEOLOGY. 
 
 279. Gypsum. There is also much gypsum in the 
 rocks of the saliferous 1 epoch of the Silurian age in New 
 York. It is found, not in layers, but in masses imbedded 
 in the rocks, from some of which it is supposed to have 
 been formed by a chemical process. The explanation of 
 the process is this: The sulphureted hydrogen issuing 
 from sulphur springs, which abound in New York, by be- 
 coming oxydized, produces sulphuric acid, and this, act- 
 ing upon the limestone (carbonate of lime), unites with 
 the lime, driving off, of course, the carbonic acid ( 60). 
 Wherever gypsum and salt are found together, as they 
 often have been, the salt, being soluble, may be carried 
 off by water, if circumstances allow of drainage, leaving 
 the insoluble gypsum behind. In many cases where 
 gypsum is found alone there was once salt in company 
 with it. 
 
 280. The Silurian Beach. As the land formed in the 
 Azoic age was not elevated to any great height, the land 
 which was added to it during the age of Mollusks was 
 mostly added as accumulations are now made on a wide- 
 spread beach by the waves of the sea. So much was 
 this the case, that Professor Agassiz remarks that " in 
 the Silurian period, the world, so far as it was raised 
 above the ocean, was a beach." He speaks also of cer- 
 tain marks of water movements, usually seen on beaches, 
 which are now found in the solid rocks of this age. 
 Even ripple-marks made, not merely centuries, but thou- 
 sands of centuries ago, are to be plainly seen now in the 
 rocky strata as we divide the laminae and expose fresh 
 surfaces. So there are ridges left which are manifestly 
 remains of ancient sea-shores, formed one after another 
 as the land, with the accumulation of deposits, encroached 
 upon the water. There are many of these ridges to be 
 seen extending from the neighborhood of Lake Cham- 
 plain toward the west, marking the limits of the sea at 
 successive periods in the age. They have all the irreg- 
 ularities of line and shape that are witnessed in sea- 
 
AGE OF MOLLUSKS. 193 
 
 shores of the present day. " Unstable as water" is a 
 proverb, the truth of which has been recognized from 
 time immemorial ; but the water, though itself unstable, 
 lias left stable evidences of its work every where in the 
 earth. It has left traces in rock which have lasted ages 
 upon ages longer than any chiselings of man upon mon- 
 umental granite. 
 
 281. Life in this Age. As the beach-arrangement of 
 land was prominent, so, as Agassiz remarks, the life was 
 mostly such as we find now on beaches. Mollusks were 
 abundant ; crustaceans of some kinds also, and star-fish- 
 es, sea-urchins, etc. There were corals, also, when and 
 where the circumstances were favorable to their growth. 
 I will cite two instances in contrast in this respect. In 
 forming the limestone floor of the great New York ba- 
 sins preparatory to the salt-making ( 278), the work 
 was done by coral animal s^ and other allied animals, as is 
 shown by the abundance of their remains in that rock. 
 But when the salt-beds came to be laid down these ani- 
 mals were absent, for the water was too salt for them to 
 live in, and few fossils are therefore found in these beds. 
 The same contrast was seen in the coral island observed 
 by Professor Dana. In the salt water of the lagoon 
 there were no corals nor shells, though there was a plen- 
 ty of them outside of the island in the open sea. There 
 were no insects in the Silurian age, and but few fishes ; 
 some think absolutely none. There were no land nor 
 fresh-water animals. As to vegetation, we have remains 
 only of the lowest forms of vegetation, such as sea-weeds 
 and club-mosses. No land-plants have been found ex- 
 cept in the uppermost strata. What life there was in 
 this age was very abundant during most of the period in 
 most localities. There was such a profusion, says Agas- 
 siz, " that it would seem as if God, in the joy of creation, 
 had compensated himself for a less variety of forms in 
 the greater richness of the early types." 
 
 282. Adaptation. The life on the earth at that time, 
 
 I 
 
194 GEOLOGY. 
 
 we can see from our reading of the life-record of the 
 rocks, was adapted to the circumstances of the case. 
 Though all the four grand divisions of animals were rep- 
 resented, there were few vertebrates or articulates, and 
 these were of the lower orders, because the circumstan- 
 ces of the world were not suited to those forms of life. 
 The animals were mostly marine. There were no air- 
 breathing animals, because the atmosphere was not in a 
 fit state for them. There was too much carbonic acid in 
 it, of which the air was to be relieved in after ages, as 
 will be shown you in another chapter. There were no 
 fishes, partly, at least, because they need dissolved in the 
 water which passes through their gills air that has a 
 good proportion of oxygen in it (Part II., 93). In re- 
 gard to the adaptation manifest in that age of the earth, 
 Agassiz very forcibly remarks : " Let us remember, then, 
 that in the Silurian period, the world, so far as it was 
 raised above the ocean, was a beach, and let us seek there 
 for such creatures as God has made to live on sea-shores, 
 and not belittle the creative work, or say that he first 
 scattered the seeds of life in meagre or stinted measure, 
 because we do not find air-breathing anihials when there 
 was no fitting atmosphere to feed their lungs, insects 
 with no terrestrial plants to live upon, reptiles without 
 marshes, birds without trees, cattle without grass all 
 things, in short, without the essential conditions for their 
 existence." 
 
 283. Carbonaceous Matter in Silurian Shales. There 
 was no coal formed in this age, for there was no vegeta- 
 ble growth sufficient for this purpose ; but in the shales 
 there is a considerable amount of carbonaceous matter 
 in some localities, even, in some cases, up to 20 per cent. 
 This came mostly from the sea-weeds, which, gathering 
 the carbonic acid from the air, appropriated to their own 
 growth the carbon, and gave the oxygen to the animals 
 of the sea (Part II., 95). 
 
 284. Hydrozoa and Bryozoa. In Fig. 102 we have the 
 
AGE OF MOLLUSKS. 
 
 195 
 
 1. Oldhamia. 2. Protovirgularia. 3. Graptolites. 4,5. Diplograpsus. 6. Did- 
 ymograpsus. 7. Rastrites. 
 
 Fig. 102. 
 
 frame-works of certain small animals called Hydrozoa 
 and Bryozoa, some of which contributed much to the 
 material for the formation of rocks in the Silurian age. 
 
 285. Corals and Echinoderms. In Fig. 103 we have 
 specimens of these two divisions of the Radiates, which 
 
 1. Heliolites. 
 6. Palseaster. 
 
 2. Catenipora. 3. Cyathophyllum. 4. Taxocrinus. 5. Cystid 
 Fig. 103. 
 
 had so much to do with supplying the material for the 
 limestones in the age of Mollusks. One of the most 
 
196 
 
 GEOLOGY. 
 
 beautiful of the corals is given in Fig. 104, the chain cor- 
 al, the specimen pictured being from the cliff limestone 
 
 Fig. 104. 
 
 in Iowa. The Echinoderms styled crinoids, of which 4 
 and 5, Fig. 103, are specimens, stand 
 on stems or peduncles. In Fig. 105 
 is represented the base of the frame- 
 work of one of these animals. To 
 the central piece was fastened the 
 peduncle, and the branching arms 
 of the animal were jointed to the 
 side pieces. The fragments of the 
 stems of these animals found in the 
 
 rocks were used as rosaries in the Middle Ages. They 
 
 were called St. Cuthbert's beads, and are thus noticed by 
 
 Sir Walter Scott in his Marmion : 
 
 " On a rock by Lindisfarn 
 St. Cuthbert sits, and tries to frame 
 The sea-born beads that bear his name." 
 
 286: Mollusks. In Fig. 106 you have specimens of the 
 shells of some of the varieties of Silurian mollusks. There 
 are three great classes of mollusks. 1. The Cephalopoda, 
 
 Fig. 105. 
 
AGE OF MOLLUSKS. 
 
 197 
 
 
 1. Lingula. 2. Rhynconella. 3. Pentamerus. 4. Strophomena. 5. Spirifer. 
 6. Murchisonia. 7. Orthoceras. 8. Lituites. 9. Maclurea. 
 Fig. 106. 
 
 which have arms or feet about the mouth, the name com- 
 ing from the Greek works Tcephale, head, and pous, foot. 
 The shells of this class are more often curved on one 
 plane, as 8, than spiral, as 6. In 8 we have a chambered 
 shell an arrangement that is found in almost all of this 
 class the cavity being divided by partitions into cham- 
 bers, which have a tube, called the siphuncle, running 
 through them. The use of this is explained in my Nat- 
 ural History, 554. 2. G-asteropods. The name of this 
 class comes from gaster, belly, audpous. These mollusks 
 creep on a broad disk or foot, as you see represented in 
 Fig. 107 (p. 198). The head and the broad foot, which 
 are out of the shell as the animal crawls along, can be 
 withdrawn within the shell. The common snail is an 
 example of this class. 3. The Acephals. These have no 
 heads, as the name indicates, the a being the a privative 
 of the Greek. Of these there are two divisions the com- 
 mon bivalves, as oysters and clams, which have two equal 
 valves, and those which have two unequal valves. These 
 
198 GEOLOGY. 
 
 Fig. 107. 
 
 latter have also peculiar arms, from which they are com- 
 monly called JBrachiopods, from brachion, arm, audpous. 
 The valves are symmetrical, as seen in 1, 2, 3, 4, and 5, 
 Fig. 106, which are all Brachiopods. The Brachiopods 
 were much more abundant in the Silurian age than the 
 common bivalves, but the reverse is the case at the pres- 
 ent time. The small shell, Lingula, 1, is some- 
 times found in rocks in such abundance as to 
 .give them their name, as Lingula flags and Lin- 
 gula grits. The Orthoceras, 7, is a chambered 
 shell, like the pearly Nautilus of our day, or the 
 Lituites in the figure, but as if unrolled, so as to 
 be straight. Some specimens are ten or fifteen 
 feet in length and a foot in diameter. These 
 were the monster mollusks of the Molluscan 
 age. In Fig. 108 is represented the internal 
 arrangement of the shells of these Orthocera- 
 tites. The Cephalopods, with their chambered 
 cells, were very numerous in the Silurian and 
 ^ er aneient ages, but at the present time there 
 are about half a dozen living species, and these 
 belong to the genus Nautilus. In Fig. 109 we have a 
 representation of a remarkable shell of a cephalopod from 
 the Silurian rocks of Russia. 
 
 287. Trilobites. The family of Trilobites, of which 
 there is not a species now in existence, furnished the 
 
AGE OF MOLL 
 
 Fig. 109. 
 
 chief representatives of the division of Articulates called 
 Crustaceans in the age of Mollusks. Some of the species 
 of this extensive family are shown in Fig. 110. These 
 
 1. Phacops. 2. Trinucleus. 3. Ampyx. 4. Ogygia. 5. Ilsenns. 6. Calymene. 
 7. Calymene coiled up. 
 
 Fig. 110. 
 
 animals, as you see, are divided lengthwise into three 
 lobes, and hence comes their name. They have, trans- 
 verse to these, the common ring-like divisions of the Ar- 
 ticulates. Their eyes, which were quite prominent, were 
 compound. They had the power of curling themselves 
 up like the wood-louse, as exhibited in Fig. Ill (p. 200). 
 
200 GEOLOGY. 
 
 In Fig. 110, 1 is the same with 
 6, but represented as coiled up. 
 The fossils of these animals are 
 often found in this posture in the 
 rocks, showing that the envelop- 
 ing mud or sand, which after- 
 ward became stone, caught them 
 in this condition. The size of 
 Fig. 111. these animals varied much, from 
 
 the sixth of an inch to even two feet in length. 
 
 288. Climate. The climate of the Silurian age, it is 
 supposed, was quite uniformly warm over the whole 
 earth. Mollusks are not apt to be profusely abundant 
 except in warm seas, but, as the life-record shows that 
 they Avere so in such localities as New York, it is plain 
 that tropical climes were more extensive than now. Be- 
 sides, the wide diffusion of the mollusks shows that the 
 temperature of the earth generally was more equal. That 
 the sun shone then with clearness much of the time, how- 
 ever it might have been in the Azoic age ( 271), is plain 
 from the eyes which the Creator gave to those numerous 
 inhabitants of the sea, the Trilobites. 
 
 289. Alternate Subsidences and Elevations. During 
 the different periods of this age there must have been 
 many changes in the level of the land when different 
 strata were forming. Take a single example. When 
 the great limestone floor of the New York basins (278) 
 was being laid, the water must have been of the requi- 
 site depth for the corals, and crinoids, and mollusks that 
 flourished then. For this purpose there was a subsi- 
 dence of the land, and there is evidence that this move- 
 ment extended far beyond the locality of these basins. 
 For instance, the Green Mountain region, which had pre- 
 viously been dry land, was now wholly or in part sub- 
 merged. But when, after the floor was laid, the salty 
 deposits were made, there was an elevation of the land 
 that shallow waters might prevail for the ready evapora- 
 tion of the water and the consequent deposit of the salt. 
 
AGE OF FISHES. 201 
 
 CHAPTER XV. 
 
 AGE OF FISHES, OE DEVONIAN AGE. 
 
 290. Rocks. The rocks formed in this age are, in 
 North America, in the first part of the age, limestones, 
 and afterward mostly sandstones, shales, and flags. The 
 famous North River flagging-stones were made in this 
 age. So also were the Scotch flagging-stones known 
 over Europe as the Caithness flags of commerce. The 
 Devonian system of England and Scotland has the gen- 
 eral name of Old Red Sandstone, red sandstone being 
 there the principal rock of the system. The name De- 
 vonian was given to this system because its rocks were 
 early investigated by Murchison in Devonshire, England. 
 
 291. Extent of the System in this Country. The De- 
 vonian rocks cover a large area in the interior of this 
 country, extending along south of the addition which 
 was made in the age of Mollusks to the continent as it 
 was begun in the Azoic age. Lake Erie is included in 
 this space. Lake Michigan bounds it on the west, and 
 a long, narrow arm of it extends from a little below this 
 lake far to the northwest. This area extends broadly 
 down the west side of the Appalachian coal formation 
 two thirds of its length, tapering, however, as it goes. 
 This immense Devonian field has a broad eastern branch 
 extending from Lake Erie to within a short distance of 
 the Hudson River. It is this part of the field, reaching 
 down into Pennsylvania, which is represented in the sec- 
 tion given in Fig. 101, beginning in N, the Helderberg 
 series, and ending in S, the Old Red Sandstone. Perhaps 
 some of this large extent of territory has had some of 
 the Devonian strata covered by other rocks of a later 
 
 12 
 
202 \ GEOLOGY. 
 
 formation, but, if so, they have been denuded by the ac- 
 tion of water. 
 
 292. Devonian System in Europe. Devonian rocks are 
 found in most of the countries of Europe. In Germany 
 they cover a larger space than the Silurian. This sys- 
 tem is very marked in England, and also in Scotland, 
 where the genius of the lamented Hugh Miller has given 
 it a deep but melancholy interest. In Russia, south of 
 St. Petersburg, it covers an area of 150,000 square miles. 
 In connection with the Devonian of Russia, I will men- 
 tion an interesting example of geological investigation. 
 It was doubted for some time whether the red sand- 
 stone of Devonshire was of the same period with that 
 of Hereford, because the strata of Devon contained cer- 
 tain shells which were not found in the rocks of Here- 
 ford, while the latter contained fishes that were not found 
 in those of Devon. Sir R. Murchison settled this ques- 
 tion by finding in Russian strata both the shells of De- 
 von and the fishes of Hereford. You see what this shows 
 that the rocks in Russia, in Devon, and in Hereford 
 belong to the same epoch, and that the fact that the 
 fishes and shells were not found together in both Devon 
 and Hereford was owing to some local causes. 
 
 293. Coral Formations. I have stated in 290 that 
 the strata of this age first laid down were limestones. 
 The corals had a great agency in providing material for 
 these. Indeed, the upper Helderberg period was, Pro- 
 fessor Dana states, " eminently the coral-reef period of 
 the Palaeozoic ages." Near Louisville, Kentucky, at the 
 Falls of the Ohio, there is a grand display of the lime- 
 stone of this period, very much like a coral reef of the 
 present time. At all seasons when the water is not high 
 a series of ledges is exposed, and the softer parts of the 
 rock having been worn away, the harder corals stand out 
 in bold relief, and many of them branch out precisely as 
 if they were living. There are honey-comb, cup-shaped, 
 star-like, and other forms mingled with the joints, stems, 
 
AGE OF FISHES. 203 
 
 and heads of criooids. Among them is seen a species 
 of the family Favosites, having a beautiful honey-comb 
 structure, and appearing in 
 masses in some cases of not 
 less than five feet in diameter. 
 A species of this family is rep- 
 resented in Fig. 112. The ele- 
 Fig.ii2. g ant cbain cora ] } Fig. 104, is 
 
 also present in this locality. 
 
 294. Variety in Rock-making at the same Period. 
 Different kinds of rock-making were sometimes going on 
 at the same time over different parts of the Devonian 
 area itf' this country, and the same is true of other coun- 
 tries also. Thus, at one period, while corals,* crinoids, 
 etc., were accumulating limestones over a large area in 
 the Western States, over New York there were exten- 
 sive flats forming and solidifying into sandstones, and 
 shales, and flags. Here are found ripple-marks and 
 shrinkage cracks, showing that the flats were sometimes 
 covered with shallow water, and sometimes drying in 
 the sun. The ripple-marks in the flags are so even and 
 extensive that it is obvious that the sea swept over wide- 
 spread flats. While this was going on in New York, 
 there was at the West, where the corals and crinoids 
 were building limestone, an interior sea of vast extent, 
 and of suitable depth for these animals to flourish in. 
 
 295. Devonian Vegetation. In the age of Fishes there 
 was not only more marine vegetation than in the age of 
 Mollusks, but land vegetation appeared, and before the 
 middle of the age had passed it had covered the com- 
 paratively small portions of the continents that had fairly 
 risen above the ocean and remained so. At the close of 
 the age the State of New York, although it had been 
 previously submerged, formed a part of the land which 
 was thus covered. The plants, as we approach the con- 
 clusion of this age, become more and more like those of 
 the next age, thus exemplifying that foreshadowing of 
 
204 GEOLOGY. 
 
 which I have spoken in 262. Indeed, there has actu- 
 ally been found some coal in some of the rocks, in addi- 
 tion to the carbonaceous shales, which appear now as 
 they did in the Silurian system. 
 
 296. Animal Life. As there was a considerable ad- 
 vance upon the previous age in the forms of vegetable 
 life, there was a corresponding one in those of animal 
 life. Few, if any, vertebrates existed in the Silurian age, 
 but now they abounded in the form of fishes. Some rep- 
 tiles also appeared, though not in much variety. There 
 is no evidence of the existence of any insects, or birds, 
 or mammals. 
 
 297. Mollusks. Of the Mollusks there was a^ abun- 
 dant a variety of species as in 
 
 the previous age. Of the Bra- 
 
 Fig. 113. 
 
 chiopods, the genus Stri- 
 gocephalus, of which Fig. 
 113 represents one spe- 
 cies, was introduced at 
 this period. Of the Ce- 
 phalopods, the genus Cly- 
 menia was introduced, of 
 which Fig. 114 represents 
 one species. Thirty- five 
 species, which is nearly 
 
 all under this genus, have been found in the rocks of one 
 locality in Bavaria. 
 
 298. Crustaceans. The Trilobites, whose species were 
 numbered by the hundreds in the Silurian age, now 
 amounted to a dozen or two. But there are some very 
 extraordinary Crustaceans, which, beginning to appear 
 in the age of Mollusks, were now very abundant. They 
 
AGE OF FISHES. 
 
 205 
 
 were singular in their formation, combining in one ani- 
 mal the qualities of various kinds of animals. " King- 
 crab-like," says- Page, " in their carapace and organs of 
 mastication, lobster-like in their prolonged and segment- 
 ed bodies, furnished with broad, paddle-like swimming 
 limbs, and frequently with huge prehensile claws, they 
 present the zoologist with an entirely distinct family, if 
 not with the elements of a new and separate legion. 
 Some of the species are of great size three, four, and 
 six feet in length and seem to have been the scaven- 
 gers of their period, living on the lower forms and garb- 
 age of the sea-shore." One of these is pictured in Fig. 
 115, lying on his back. In the same rocks in which are 
 
 Fig. 115. 
 
 the remains of these Crustaceans there are found patches 
 of spawn-like appearance, which, though they have been 
 supposed by some to be berries of some plant, are now 
 generally regarded as the egg-packets of these animals. 
 The eggs are flattened, and they have more or less of a 
 concentric arrangement, as seen in Fig. 116 (p. 206). 
 
 299. Fishes. That you may understand the record 
 which these animals have made of themselves in the 
 rocks of this and other ages also, I will here notice the 
 
206 GEOLOGY. 
 
 Fig. 116. 
 
 classification of fishes. Agassiz discovered that there is 
 such a relation between the form of the scale and the in- 
 ternal organization of the fish, that those which have sim- 
 ilar scales are similar in their general character. This 
 discovery is of great importance in studying the palaeon- 
 tology of fishes, because the scales are so often preserved 
 in the rocks when the other structures of fishes have per- 
 ished. It is on this account that while the classification 
 of Cuvier answers admirably for living forms, that of 
 Agassiz is altogether better for the fossils. The four or- 
 ders of Agassiz are as follows: 1. Placoids. The name 
 comes from a Greek word ?j pte, a broad plate. The skin 
 in this order is covered with broad, irregular plates of 
 enamel, as in the shark family. The skeleton is soft and 
 cartilaginous, much of the firmness of the animal depend- 
 ing upon the external covering, which may be considered 
 in part as an external skeleton. In Fig. 117, 1, is repre- 
 sented one of the plates, and at 2 one of the prickly tu- 
 bercles of the ray-fishes, which belong to the same order. 
 2. Ganoid. This term comes from ganos, splendor. 
 Fishes of this order are covered in a regular manner 
 with scales of horn or bone, having a thick outer layer 
 of enamel, which is hard and bright. Such a scale is fig- 
 ured at 3. The sturgeon and trunk-fish belong to this 
 order. 3. Ctenoid. This name, from kteis, a comb, in- 
 dicates scales, 4 and 5, which are toothed or jagged on 
 the posterior margin. The perch is an example of this 
 order. 4. Cycloid. The term comes from kufdos, a cir- 
 
207 
 
 Fig. 117. 
 
 cle. The scales, 6, have a simple and smooth margin, 
 and their outer surface is often variously ornamented. 
 In this order are the salmon, the carp, and the pike. 
 
 I shall have occasion to refer to these orders hereaf- 
 ter. Suffice it to say now that the placoids and ganoids 
 had their greatest developments in the Palaeozoic ages, 
 and that there are few of them at the present time, while 
 the ctenoids and cycloids came on at a later age, and 
 abound in the waters of the present period. Four fifths 
 of the present fishes belong to the ctenoid and cycloid 
 orders, the remaining fifth consisting of placoids, with a 
 small number of ganoids. 
 
 300. Coccosteus, Pterichthys, and Cephalaspis. The 
 fishes of the Devonian age whose names I have here 
 given are ganoids, having very peculiar characteristics. 
 The Coccosteus, or "berry-bone," 1, Fig. 118 (p. 208), has 
 the largest part of the body incased in a box-like cover- 
 ing of bony plates, upon which there are berry-like projec- 
 tions. The Pterichthys, or " wing-fish," 2, which Hugh 
 Miller, its discoverer, termed the characteristic organism 
 of the old red sandstone, is so extraordinary that Agassiz 
 says of it that " it is impossible to find any thing more 
 eccentric in the whole creation." On the head was a 
 
208 
 
 GEOLOGY. 
 
 Fig. 118 
 
 strong helmet with two circular holes in front for the 
 eyes. The chest and back were covered by a curiously- 
 constructed cuirass formed of plates, and the tail was 
 sheathed in a flexible mail of bony scales. The arms are 
 also covered with plates. There are peculiarities in the 
 jointing of the different parts of this bony covering, and 
 in the contrivances for securing lightness with strength, 
 which are very curious. Hugh Miller says of it that, 
 " with its inflexible cuirass and its flexible tail, and with 
 its two arms, that combined the broad blade of the pad- 
 dle with the sharp point of the spear, it might be regard- 
 ed, when in motion, as a little subaqueous boat mounted 
 on two oars and a scull." He farther says that " when, 
 in laying open the rock in which it lies, the under part is 
 presented, as usually happens, we are struck with its re- 
 semblance to a human figure, with the arms expanded, 
 as in the act of swimming, and the legs transformed^ as 
 in the ordinary figures of the mermaid, into a tapering 
 tail." The correctness of this description can be seen in 
 Fig. 119. The Cephalaspis, or "buckler-head," 3, Fig. 
 118, is so called from the shield-like shape of the bony 
 head-plate, which is all in one piece. 
 
AGE OF FISHES. 
 
 209 
 
 Fig. 119. 
 
 301. Asterolepis. This is another of the ganoids of 
 the Old Red Sandstone. It equaled in size the largest of 
 alligators. The helmet on its head was made of strong 
 bony plates, ornamented with star-like markings, and its 
 body was covered with a mail of scales which looked as 
 if they had been carved in the most delicate manner. It 
 is stated by Hugh Miller that helmets of this creature 
 " have been found in the flag-stones of Caithness large 
 enough to cover the front skull of an elephant, and strong 
 enough to have sent back a musket bullet as if from a 
 stone wall." But what was most strange of all is that, 
 although the Asterolepis was a fish, it had in the arrange- 
 ments of its jaws and teeth the complete characteristics 
 of a reptile. Here is an example, in another form, of the 
 foreshadowing spoken of in 262. We see, in this age 
 of Fishes, stamped unmistakably upon some of these an- 
 
210 GEOLOGY. 
 
 imals characteristics of the reptiles which are to abound 
 so largely in one of the following ages as to give it its 
 name. When such mingling of the characteristics of two 
 or more classes of animals occurs in one animal, it is said 
 to be a comprehensive type. Such types were quite com- 
 mon in the forming ages of the world, but as it advanced 
 to its fully-developed condition, in preparation for the ad- 
 vent of man, the classes of animals became more distinct- 
 ly defined, and at the present time such comprehensive 
 types are rare exceptions so rare as to be regarded .as 
 great curiosities in nature. One of these is the duck- 
 billed Platypus of Australia, noticed in 133 in my Nat- 
 ural History. 
 
 302. Tails of the Ancient Fishes Nearly* all the fishes 
 
 whose remains are found 
 in the earlier strata of the 
 earth's rocks had unilobed 
 tails, as seen in Fig. 120 
 that is, the spinal column 
 Fi s- 12 - ran into the upper lobe of 
 
 the tail, the lower being so small 
 
 as not to be counted as a lobe. 
 
 In the later strata, on the oth- 
 er hand, the tails are bilobed, 
 
 Fig. 121, in the great majority 
 
 of the fossils. At the present 
 
 time the only family of fishes * Fig. 121. 
 
 that has the unilobed tails is the Shark family. 
 
 303. Abundance of Devonian Pishes. In estimating 
 the abundance of ancient fishes from their fossils, we are 
 to consider how uncommon a thing it must be for fishes 
 to become enveloped in sand or mud, in comparison, for 
 example, with shells. Keeping this in view, the great 
 number of species that have been made out from the fos- 
 sils in some quarters, especially in Great Britain and Eu- 
 rope, indicates that fishes must have been very abundant 
 in the Devonian age. In some cases great numbers must, 
 
AGE OF FISHES. 211 
 
 from some cause, have been suddenly destroyed and bur- 
 ied at the same time, for Hugh Miller states that there 
 are strata in Scotland where they lie as thickly as her- 
 rings do on the fishing-banks in the time of the fisher- 
 man's harvest. And often there is positive proof of their 
 having been suddenly killed and buried in their contorted 
 attitudes. Undoubtedly, in such cases, the fishes were 
 overwhelmed with the material in which they were en- 
 veloped by some great convulsion, and then they became 
 fossilized in the rock into which this material was con- 
 verted by solidification. 
 
 304. United States at the End of this Age. I have 
 given you in 267 some idea of the beginning of the 
 continent of North America in the Azoic age, and in 
 276 some idea of the additions which were made in 
 the Silurian age. During the Devonian age additions 
 were made on the south and southwest, carrying out the 
 plan already begun, as indicated in Fig. 100. Agassiz 
 has stated what these additions were. He says that so 
 much was added that at the conclusion of the age there 
 were above the water within the United States "the 
 greater part of New England, the whole of New York, 
 a narrow strip along the north of Ohio, a great part of 
 Indiana and Illinois, and nearly the whole of Michigan 
 and Wisconsin." Besides this, from upheavals at the 
 close of this period, there were, in place of the Rocky 
 Mountains at the West, and of the Appalachian chain, 
 which now stretches as a rocky wall from New England 
 to Alabama, detached islands and reefs amid shallow 
 waters. One of the upheavals that occurred at the con- 
 clusion of the Devonian age raised the high ground on 
 which the city of Cincinnati now stands. Of this hill 
 Agassiz says, " The granite did not break through, 
 though the force of the upheaval was such as to rend 
 asunder the Devonian deposits, for we find them lying 
 torn and broken about the base of the hill ; while the Si- 
 lurian beds, which should underlie them in their natural 
 
212 GEOLOGY. 
 
 position, from its centre and summit. This accounts for 
 the great profusion of Silurian organic remains in that 
 neighborhood. Indeed, there is no locality which forces 
 upon the observer more strongly the profusion and rich- 
 ness of the early creation, for one may actually collect 
 the remains of Silurian shells and Crustacea by cart-loads 
 around the city of Cincinnati. A naturalist would find 
 it difficult to gather along any modern sea-shore, even 
 on tropical coasts, where marine life is more abundant 
 than elsewhere, so rich a harvest, in the same time, as he 
 will bring home from an hour's ramble in the environs 
 of that city." 
 
 305. Scenery of this Age. During most of the Devo- 
 nian age the scenery must have been exceedingly tame 
 and monotonous. " Over dark and shallow seas," says 
 Hugh Miller, " mud-banks of vast extent occasionally 
 raised their flat, dingy backs, and remained hardening in 
 the hot sun until their oozy surfaces had cracked and 
 warped, and become hard as the sun-baked brick of 
 Eastern countries ; and then, ere the seeds of terrestrial 
 plants, floated from some distant island, or wafted in the 
 air, had found time to strike root into the crevices of the 
 soil, some of the frequent earth-tremors of the age shook 
 the flat expanse under the water out of which it had 
 arisen, and the waves rippled over it as before." And 
 when vegetation obtained any where a foothold upon the 
 land, as was the case quite extensively in the latter part 
 of the age ( 295), it was comparatively scanty, and 
 there was none of that variety of surface which we have 
 now, for there were no lofty mountains nor large rivers. 
 Besides, there were no birds nor four-footed beasts to 
 enliven the scene. 
 
AGE OF COAL. 213 
 
 CHAPTER XVI. 
 
 THE CARBONIFEROUS AGE, OR AGE OF COAL. 
 
 306. Propriety of the Name. Nothing has been made 
 more plain by the investigations of geologists than that 
 thousands of centuries ago there was an age, and that a 
 very long one, devoted expressly by the Creator to the 
 formation and storing up of coal for the future use of 
 man. It seems eminently proper, therefore, to call this 
 the Age of Coal, or the Carboniferous Age. Observe 
 that all the other ages that transpired during the forma- 
 tion of the earth were marked by the predominance of 
 certain classes of animals, and are named accordingly; 
 but this is named from a mineral production which came, 
 as you have seen in 42, from certain chemical changes 
 in vegetable substances. Animals of most of the various 
 classes were abundant in this age, but no class was espe- 
 cially predominant over all the others, so that it is im- 
 possible to derive a name from that source. There 
 seems to be no room for choice, then, but we are driven 
 to the name which has been adopted by universal con- 
 sent. 
 
 307. Localities of Coal. There are more and larger 
 beds of coal in North America than in any other part of 
 the world. Great Britain comes next in order. The 
 coal there is mostly bituminous, more or less, while in 
 this country there are large quantities of the anthracite, 
 or non-bituminous coal. Pennsylvania has a larger area 
 of coal in proportion to its whole area than any other 
 part of the world. There is coal in Spain, France, Bel- 
 gium, and Germany. Russia exhibits over a wide area 
 some of the rocks of the coal period, but has very little 
 coal. 
 
214 GEOLOGY. 
 
 308. Amount of Coal. The amount of coal in the prin- 
 cipal coal-fields in the world has been estimated by Pro- 
 fessor H. D. Rogers as follows : 
 
 Belgium 36,000,000,000 tons. 
 
 France 59,000,000,000 
 
 British Isles 190,000,000,000 
 
 Pennsylvania 316,000,000,000 
 
 Appalachian coal-field 1,387,000,000,000 
 
 Indiana, Illinois, and Kentucky 1,277,000,000,000 
 
 Iowa, Missouri, and Arkansas 739,000, 000, 000 
 
 Total amount in North America.... 4, 000, 000, 000,000 
 The anthracite of this country was first introduced into 
 use in blacksmithing by Judge Obadiah Gore, a Con- 
 necticut blacksmith, in Wilkesbarre, a few years less than 
 a century ago; but it did not come into common use 
 until between thirty and forty years since. In 1820 the 
 amount worked in Pennsylvania was only 380 tons. Its 
 use, however, from that time increased rapidly, and in 
 1847 that state furnished over three million of tons, be- 
 sides two million of bituminous coal. The United States 
 produced in 1857 ten and a half million of tons ; and if 
 our annual consumption should be twelve million of tons, 
 it is calculated that there is coal enough in North Amer- 
 ica to last us 333,333 years. 
 
 309. Extent of Coal-fields. Coal-fields vary much in 
 extent, the largest in the world being in North America. 
 The most extensive of all is the Appalachian. This oc- 
 cupies parts of Pennsylvania, Ohio, and Virginia, the 
 eastern portion of Kentucky and Tennessee, and extends 
 down into Alabama. It covers an area of 80,000 square 
 miles, 60,000 of this being available. This is about ten 
 times as great a space as that occupied by all the pro- 
 ductive coal-fields of Great Britain. Then there is the 
 Indiana, Illinois, and Kentucky coal-field, covering a 
 space of 50,000 square miles, and the Iowa and Mis-souri 
 coal-field, 60,000. The New England coal-field occupies 
 an area of only about 600 square miles. 
 
 310. Arrangement of the Coal-strata. The coal is in 
 
AQE OF COAL. 215 
 
 strata or seams of various degrees of thickness, between 
 strata of different kinds of rocks. Sometimes the layers 
 are almost as thin as paper, and, on the other hand, they 
 are sometimes 30, 40, and even 60 feet thick. Seldom, 
 however, do they exceed eight feet in thickness. The 
 lower part, or floor, as we may term it, of the coal for- 
 mation is limestone ; but the upper part, where the beds 
 of coal lie between strata of rock, is made up of sand- 
 stones, conglomerates, shales, and limestones. It is this 
 upper portion that is commonly called the coal-measures. 
 The rocks between which the coal is laid down do not 
 differ from many rocks in other formations, but are to be 
 distinguished from them only by their fossils. It is their 
 life-record that indicates their proximity to coal. This 
 fact is of great practical use in searching for localities of 
 coal, and a disregard of it has sometimes occasioned 
 needless expense. On this point Professor Hitchcock 
 remarks : " No geologist would expect to find valuable 
 beds of coal in the oldest crystalline rocks, but in the' 
 fossiliferous rocks alone ; and even here he would have 
 but feeble expectations in any rock except the coal for- 
 mation. What a vast amount of unnecessary expense 
 and labor would have been avoided had men who had 
 searched for coal been always acquainted with this prin- 
 ciple, and able to distinguish the different rocks ! Per- 
 pendicular strata of mica and talcose schists would then 
 never have been bored into at great expense in search 
 of coal ; nor would black tourmalin have been mistaken 
 for coal, as it has been." Commonly, the rock that lies 
 directly under a bed of coal is clayey in its character, 
 and is called the under-day. From its composition, and 
 from the fact that roots of certain carboniferous plants 
 are often found in it, it is inferred that it was the dirt- 
 bed in which the plants grew that furnished the mate- 
 rial for the formation of the coal. The amount of rock 
 in the strata of the coal-measures preponderates vastly 
 over the amount of coal, the proportion being generally 
 fifty or more feet of rock to one of coal. 
 
216 GEOLOGY. 
 
 311. Sub-carboniferous Period. That first part of the 
 Carboniferous age in which the limestone floor was laid 
 down for the coal-measures to rest upon is called by ge- 
 ologists the sub-carboniferous period. The prefix sub 
 being the Latin for under, you see the propriety of the 
 term. This floor was laid down over a very large area 
 in this country. The same thing is found in other coun- 
 tries where coal was made in this age. The thickness 
 of this formation varies much in different localities, in 
 some amounting to more than 6000 feet. As this lime- 
 stone was made from the remains of marine animals, 
 crinoids, corals, etc., long ages must have been occupied 
 in constructing this foundation of the coral-fields. The 
 strata of the proper carboniferous rocks, the rocks of the 
 coal-measures, are conformable with the sub-carbonifer- 
 ous. 
 
 312. Sub-carboniferous Period in this Country. The 
 circumstances under which the sub-carboniferous lime- 
 stone was formed in the United States have been admi- 
 rably brought out by Professor Dana, and I will attempt 
 briefly to make the principal of them clear to you. In 
 the Niagara period of the Silurian age there was a for- 
 mation of limestone over a large portion of the interior 
 of the United States. This was made by the deposition 
 of the remains of marine animals. While this was going 
 on all the interior part of the country was a sea, not very 
 deep, but of sufficient depth for these animals. This 
 sea might be considered as an extension upward of the 
 present Gulf of Mexico. It was cut off from direct com- 
 munication with the Atlantic Ocean by a low barrier of 
 land stretching from the north downward, which had 
 been made to emerge in order to shut in this great inte- 
 rior sea. A similar condition of things existed in the 
 Devonian age, when, in the Upper Helderberg period, 
 the corals were so busy in laying down limestone 
 ( 293). A similar arrangement existed also in the sub- 
 carboniferous period, except that the interior sea was 
 
AGE OF COAL. 217 
 
 smaller than in the Devonian, as it was smaller then than 
 in the Silurian. It grew smaller from the additions 
 which were made in successive periods to the perma- 
 nent land of the continent. There was another point of 
 difference in the sub-carboniferous sea the crinoids 
 were predominant, so that Dana speaks of it as the Cri- 
 noidal sea, while in the Devonian it was the corals that 
 did most of the work, and in the Silurian, brachiopods, 
 corals, and crinoids were about equally present. 
 
 313. How Coal was Made. All the coal in the world 
 has been formed from trees and other plants. Proof of 
 this has been adduced in 41, and need not be dwelt 
 upon now. The coal is the result of a decomposition, to 
 a greater or less degree, of the woody fibre or substance 
 of the wood. When wood is burned in the open air all 
 the carbon is dissipated by gaseous combinations ; but 
 when the combustion is effected with the air mostly ex- 
 cluded, the carbon is retained to a considerable extent, 
 making charcoal. For a full explanation of this I refer 
 you to Part II. The same changes that occur in the 
 combustion that produces charcoal may occur, under cer- 
 tain circumstances, without the phenomenon of combus- 
 tion. If, for example, the decomposition take place slow- 
 ly under water, the chemical changes are essentially the 
 same as when what is ordinarily called combustion is 
 seen. If you observe what the composition of wood is, 
 you can see how this can be. Wood is composed of 
 carbon, hydrogen, and oxygen, the elements which are 
 engaged in ordinary combustion ; and it is by the slow 
 action of these upon each other that the slow combus- 
 tion under water goes on. Very properly, then, is this 
 process called eremacausis, this term being made from 
 two Greek words, erema, slowly, and kausis, burning. 
 The same thing occurs in the decay of vegetable matter 
 in the open air, the slow combustion in this case being, 
 however, carried out in full, as in the ordinary burning 
 of wood, the carbon, oxygen, and hydrogen all forming 
 
 K 
 
218 GEOLOGY. 
 
 gradually new combinations, as they do quickly in com- 
 mon combustion. Heat is more or less an agent in ef- 
 fecting eremacausis, as it is in effecting the combustion 
 which is sudden and attended with palpable phenomena. 
 
 314. Condensation of Coal by Pressure. While the 
 coal is forming it is subjected more or less to pressure 
 by the masses of matter which accumulate above it, and 
 form the rocky strata. It is therefore condensed, in- 
 stead of being light and porous, like charcoal, or the 
 coke which is obtained in the making of gas. In peat 
 we have an example of the looseness of coal formation 
 when subjected to but little pressure. 
 
 315. Bituminous and Non-bituminous Coal. Anthra- 
 cite, or non-bituminous coal, is almost pure carbon, but 
 bituminous coal contains considerable hydrogen and ox- 
 ygen. It is the hydrogen, in connection with the car- 
 bon, that produces its flame when it is burned. The 
 flame is really the burning of the carbureted hydrogen, 
 which in our gas-works is evolved from bituminous coal 
 by a low degree of combustion, and is then passed about 
 by pipes to be burned in our houses. The flame which 
 plays over an anthracite fire when it is not wholly kin- 
 dled is the burning of a different gas, which I have no- 
 ticed in Part II., 67. It is supposed that anthracite 
 coal was once bituminous, and that it was freed from its 
 bituminous qualities by a process essentially the same 
 with that by which we make gas in our gas-works, the 
 difference being simply that we have left in the one case 
 a solid non-bituminous coal, and in the other a porous 
 one common coke. 
 
 316. How the Coal was Deposited. You are now pre- 
 pared to see how the coal was deposited in beds or 
 strata between strata of rocks. In the first place there 
 was a growth of plants of various kinds, varying in size 
 from small mosses to enormous trees, in the dirt-bed of 
 which I have spoken in 310. This was, for the most 
 part, a swampy growth, and that, too, as you will soon 
 
AGE OF COAL. 219 
 
 see, of a most luxuriant and profuse character. Trees 
 and shrubs dropped their leaves and fruit year after year, 
 and at length died themselves, while other trees and 
 shrubs took their places ; and thus growth and decay 
 went on, perhaps, through many slowly-moving centu- 
 ries, till enough of these vegetable remains was accumu- 
 lated to make a coal-bed. At length a subsidence of the 
 land took place, the water flowed over it, covering up all 
 this accumulation of vegetable substance, and under the 
 water and the detritus which the water brought in, the 
 decomposition occurred which resulted in the produc- 
 tion of coal. The detritus went on accumulating, at the 
 same time slowly solidifying from below upward, till at 
 length the subsidence ceased, and there succeeded an el- 
 evation, so as to bring the surface again into the swampy 
 condition for a new growth, preparatory to another bed 
 of coal. The set of processes thus described was in 
 some cases many times repeated, there being often many 
 beds of coal between the strata of rock. In Kentucky 
 there are from fifteen to twenty separate coal-beds in 
 the strata, and in Nova Scotia, at a locality called the 
 Joggins, there are seventy-six coal-seams, some of them 
 being very thin. The process was essentially the same 
 for each of these, the periods of elevation and subsidence 
 being longer for the thick seams than for the thin ones. 
 Though there were alternate subsidence and elevation, 
 " the sinking condition," remarks Hugh Miller, " was the 
 general one ; platform after platform disappeared, as 
 century after century rolled away, impressing upon them 
 their character as they passed ; and so the coal-meas- 
 ures, where deepest and most extensive, consist, from 
 bottom to top, ofthese buried platforms, ranged like the 
 sheets of a work in the course of printing, that, after be- 
 ing stamped by the pressman, are then placed horizon- 
 tally over one another in a pile." 
 
 317. Impurities of Coal. Coal varies much in its pu- 
 rity, as every one who has burned coal must have no- 
 
220 GEOLOGY. 
 
 ticed from year to year. The impurities came in part 
 from the woody substance from which the coal was 
 made. There was silex, which is one of the chief of the 
 impurities, in some of the plants of the Coal age. But 
 impurities came chiefly from the detritus which was laid 
 down upon the coal-beds, for there would, of course, be 
 more or less admixture of this with the coal. There is 
 more or less iron pyrites (sulphuret of iron) in coal, and 
 to this is owing the sulphur smell which a coal fire gives 
 out. When there is much of it in coal it detracts much 
 from its value, causing it to crumble on exposure to the 
 air, and to emit strong fumes when burned. 
 
 318. Rate of Formation of Coal. Some calculations 
 have been made in regard to the time required for the 
 formation of beds of coal. Taking some observations 
 of Liebig as to the rapidity of vegetable accumulation, 
 it has been calculated that it would require 170 years to 
 make one inch thickness of anthracite coal, and there- 
 fore 122,400 years to accumulate a stratum of 60 feet. 
 This is based upon the ordinary growth of the present 
 time ; but, as you will soon see, the growth of the Car- 
 boniferous age was probably much more rapid than it is 
 now, and this, of course, must reduce the time. But, at 
 any rate, the time must have been very long for the ac- 
 cumulation of even a bed of ordinary thickness. And 
 when we come to take into the account the formation 
 of the rocky strata as well as the coal-beds, our arithme- 
 tic must give out, for the whole system, from the sub- 
 carboniferous upward, through all the strata, has a thick- 
 ness, in some cases, of from 12,000 to about 15,000 feet 
 that is, nearly three miles. 
 
 319. Plants. The remains of plants are found in great 
 abundance in the coal-measures, though none appear in 
 the great sub-carboniferous limestone floor which is be- 
 neath them. The plants were of various sizes. Many 
 of them were prodigious in size, compared with similar 
 kinds of plants at the present day. The vegetation of 
 
AGE OF COAL. 
 
 221 
 
 Fig. 122. 
 
 that age was to a large extent, in point of size, a forest 
 vegetation, and yet but few of the plants which at the 
 present time are of the same family with the largest that 
 existed then are a little taller than a man. The remains 
 found are of various kinds trunks, 
 branches, pieces of bark, cones, 
 leaves, etc. The impressions of 
 leaves upon the laminae of rock are 
 sometimes very beautiful, as seen in 
 Fig. 122. Here we have a carbon- 
 aceous representation of the stem 
 and leaves that is, the carbon of 
 the plant in the decomposition of 
 the vegetable substance is left upon 
 the stone. " The shaly beds," says 
 Dana, "often contain the ancient 
 ferns spread out between the lay- 
 ers with all the perfection they 
 would have in a herbarium, and so abundantly that, 
 however thin the shale be split, it opens to view new im- 
 pressions of plants." The experiments of Professor Gop- 
 pert, of Breslau, go far to explain the various conditions 
 in which we find the remains of plants in the rocks of 
 the coal-measures. He placed fern-leaves in clay, and 
 when they had become dry exposed them to a red heat, 
 and thus obtained striking resemblances to the fossil 
 ferns in the rocks. According to the degree of heat, the 
 leaves were found to be either brown, shining, black, or 
 entirely lost, the impression alone remaining. In this 
 latter case the carbon of the leaves, being diffused in the 
 clay, stained it black, thus showing that the color of the 
 coal-shales is derived from the carbon of the plants in- 
 closed in them. I will now proceed^lQ^notice some of 
 the plants of this age. 
 
 320. Calamites. This is a name given to a family of 
 plants that belong to the same tribe with the horse-tails, 
 cat-tails, and rushes of the present day. Two species 
 
222 GEOLOGY. 
 
 are represented in Fig. 123, b being the same with a, but 
 
 Fig. 13a 
 
 showing remains of its roots. The plant is jointed and 
 hollow, the surface being deeply fluted. While the 
 rushes and cat-tails of the present day are quite small, 
 some specimens of these ancient plants have been found 
 20, and even 40 feet in length, and three feet in diameter. 
 Portions of the trunks of these trees, for so they may be 
 called, have been found standing upright in coal mines, 
 penetrating the sandstone layers above the coal. 
 
 321. Sigillaria and Stigmaria. These were for a long 
 time supposed to be two distinct plants, but they have 
 been found to belong to the same plant, the Sigillaria be- 
 ing the trunk, and the Stigmaria the lower part of the 
 trunk, with the roots. The Stigmaria, Fig. 124, is never 
 found any whea^but in the under clay spoken of in 
 310. The trunks of the plant are generally found lying 
 horizontally, but sometimes they are erect. They vary in 
 length from five to sixty feet, and in diameter from a 
 few inches to five feet. 
 
AGE OF COAL. 
 
 223 
 
 Fig. 124. 
 
 322. Lepidodendron. This is a name which has been 
 given to a tribe of carboniferous plants that were much 
 like the club-mosses of the present day ; but they were 
 lofty, woody trees. One was found in a coal mine in 
 England that was 40 feet long, and so enormously large 
 at the base as to measure 13 feet in diameter. 
 
 323. Ferns. There was a great abundance of ferns in 
 the Carboniferous age. A very large number of species 
 have been found in the coal strata. In Figs. 125, 126, 
 
 Figs. 125, 126. 
 
 127, and 128 (p. 224) are represented some fossil ferns. 
 The two first are from the coal-measures of Rhode Isl- 
 
224 
 
 GEOLOGY. 
 
 Ffg. 127. 
 
 Fig. 128. 
 
 and. Many of the ferns were trees resembling the tree- 
 ferns now found in some tropical countries, growing to 
 the height sometimes of even 40 and 50 feet. It is stated 
 by Hitchcock that over 250 species of ferns have been 
 found in the coal strata of Europe, and yet the native 
 species in Europe at the present time do not exceed 50. 
 As ferns are now far more abundant in tropical than in 
 temperate regions, the life-record of the coal-measures 
 seems to show that the climate in Europe and this coun- 
 try during the coal period was tropical. 
 
 324. Conifers. The Conifers, or cone-bearing plants, 
 were very abundant. These are Gymnogens, or dicotyl- 
 edonous plants (Fig. 87), related to the pines and yews. 
 Most of the other plants of this age were Acrogens 
 (Fig. 86), the Ferns, the Equisetacea3, or cat-tail family, 
 and the Lycopodiacese, or club-mosses. The Amphigens 
 (Fig. 85) were represented in sea-weeds and a few mush- 
 rooms. It is doubtful whether there were my Endo- 
 gens (Fig. 88), and there were none of the Exogens 
 (Fig. 91), the chief foresktrees and shrubs of the present 
 day. 
 
 325. General View of Carboniferous Vegetation. In 
 Fig. 129 you have grouped together many of the differ- 
 ent kinds of plants of the Carboniferous age. On the 
 right, in the foreground, is the Sigillaria, with Stigmaria 
 
AGE OF COAL. 
 
 225 
 
 Fig. 129. 
 
 roots, and next to it the beautiful tree-fern. On the left, 
 standing up loftily, is a Lepidodendron, and by it lies 
 prostrate a Calamites, there being also in the rear of it, 
 in the background, one inclining of a much larger size. 
 The smaller plants fill up the intervals between these, 
 
 K2 
 
226 GEOLOGY. 
 
 There were few, if any flowers in all this vegetation, but 
 " what was wanting in blossom," says Page, * was more 
 than compensated for by the profusion of light, symmet- 
 rical, feathery fronds, and by the tall, pillar-like stems 
 which rose, each one boldly carved with its own pecul- 
 iar pattern. The trunks of a modern forest are rough 
 and gnarled; those of the period now under review 
 sprang up like the sculptured shafts of a medieval tem- 
 ple, graceful in proportion, and rich in ornament through 
 the endless repetition of flutings, spirals, zigzags, loz- 
 enges, ovals, and other geometrical designs these de- 
 signs being the persistent leaf-scars of a vegetation sim- 
 pler in structure and more 
 primitive in plan." An exam- 
 pie of the leaf-scars of which 
 he speaks is represented in 
 Fig. 130, the scars left by the 
 fallen leaves being seen at a, 
 while at b is the surface of 
 the wood brought to view by 
 the removal of the carbon- 
 Fig - m ized bark. You observe the 
 
 regularity with which these scars are arranged. The 
 modes of this regularity differ in different plants, thus 
 affording a rich variety. 
 
 326. Causes of the Rank Carboniferous Vegetation. 
 In order to understand how the rank vegetation of that 
 age was produced, you must recur to what I said of the 
 chemistry of the atmosphere in Part II. You there 
 learned that from the carbonic acid gas which is sup- 
 plied to the air from the lungs of animals, from fires, and 
 from various chemical decompositions, the leaves gather 
 in the most of the carbon which is incorporated in the 
 plants in their growth. Now it is supposed that there 
 was much more carbonic acid in the atmosphere up to 
 the beginning of the coal-making age than there was at 
 its close. Some estimate it as having been six times as 
 
AGE OP COAL. 227 
 
 much as it is at the present time. Here, then, there was 
 in the air a large surplus of one of the three materials 
 of which plants are chiefly composed, and it was appro- 
 priated in producing the profuse vegetation. And as 
 this vegetation was for the purpose of making coal, we 
 may say that the material for the coal was kept in the 
 atmosphere in a gaseous state, by being combined with 
 oxygen, until the earth, during a lapse of long ages, was 
 put into a fit condition to bring forth an exuberant veg- 
 etation. When this was effected the Creator introduced 
 the requisite plants, and the transfer was made from the 
 atmosphere through them to the coal-measures. Such 
 a transfer from the gaseous to the solid state of such a 
 quantity of matter seems at first thought strange, but it 
 is no more so Jthan the transformation which we see con- 
 tinually in the case of water. This rises in the vaporous 
 or gaseous state into the atmosphere by evaporation, 
 and anon we see some of it again in the shape of solid 
 ice on the surface of the earth. 
 
 327. Climate of the Carboniferous Age. The climate 
 of the earth was very different in that age from what it 
 is now. It was warm in all quarters, and very equally 
 so. We know this because we find very widely distrib- 
 uted the remains of plants and animals similar to those 
 which now flourish in warm climates. The climate was 
 so warm in the arctic regions that rank vegetation was 
 present there, and coal was laid down. With such prev- 
 alent warmth there must have been great moisture in 
 the air, and this favored rank growth, notwithstanding 
 there probably was from this moisture less of clear sun- 
 shine than there is now. 
 
 328. Carboniferous Scenery. Though the vegetation 
 of that age was so rich, the scenery was tame and mo- 
 notonous. Forests, with their tangled undergrowth, 
 mostly swampy, spread over vast platforms, in some 
 cases almost continental in extent. There were no such 
 elevations as we see at the present day to relieve the 
 
228 GEOLOGY. 
 
 eye, but one wide wilderness stretched far away, varied 
 only by slight undulations. We may get some idea of- 
 the nature of this scenery from some localities on our 
 earth, but none at all of its extent. Especially extensive 
 were the platforms in the earlier part of the Carbonifer- 
 ous age, for the beds of coal then laid down are found 
 to be much vaster in extent than those of the later coal- 
 measures. In this country these early beds cover a large 
 portion of the continent. Each of the successive plat- 
 forme of luxuriant vegetation, after having maintained 
 the same level for hundreds, or even thousands of years, 
 was submerged in water gradually (Hugh Miller thinks 
 in some cases suddenly), that each bed of coal might be 
 packed down with layers of rock above it. The wide 
 wilderness of vegetation thus became a wide waste of 
 waters. 
 
 329. Animals. So highly charged with carbonic acid 
 gas was the atmosphere of the coal-making age, that an- 
 imals which require such air as we now have on the 
 earth could not exist. There were, therefore, no mam- 
 mals or birds, and none of the higher kinds of insects. 
 There were cold-blooded animals, as fishes and reptiles, 
 the latter finding their appropriate localities in the stag- 
 nant pools, swamps, and thick, damp forests of that age. 
 Cold-blooded animals live an inactive, lazy life, as com- 
 pared with the warm-blooded, and therefore do not re- 
 quire so much oxygen.* There was, of course, an abund- 
 ance of Mollusks, Crustaceans, and Radiates, especially 
 when the platforms were submerged, and the limestone 
 strata were forming. The tameness and monotony of 
 
 * It would seem at first thought that the life of fishes is generally a 
 very active one ; but it is not so, for the fish needs to make but little 
 effort in its motions, for two reasons. First, it is of nearly the same 
 specific gravity with the element in which it moves, and is therefore 
 obliged to make but a slight effort in any upward movement. It is 
 in strong contrast with birds in this respect. Secondly, most fishes 
 have an air-bladder, which they can compress or enlarge at pleasure, 
 as they wish to fall or rise. See my Natural History, Chapter xx. 
 
AGE OF COAL. 
 
 229 
 
 the carboniferous scenery were heightened by the ab- 
 sence of all running and flying animals. As to sounds, 
 " there was no music in the groves," says Dana, " save, 
 perhaps, that of insect life and the croaking Batrachian." 
 330. Coral Animals. The reef-making animals, some 
 varieties of which you see in Fig. 131, were busy wher- 
 
 ^^ w 
 
 1. Syringopera. 2. Lythostrotion. 3. Aulopora. 4. Amplexus. 5. Clisiophyl- 
 lum. 6. Ptilopora. 7. Archimedopora. 
 
 Fig. 131." 
 
 ever limestone was forming. They had a large work to 
 do, then, in the sub-carboniferous period, when the great 
 limestone floor was laid down for the coal-measures, and 
 afterward, also, in the case of those strata over the coal- 
 beds which are composed of limestone. 
 
 331. Crinoids and Sea-urchins. These animals abound- 
 ed in connection with the corals, the crinoids being much 
 more abundant than the corals in the limestone of the 
 sub-carboniferous period. Indeed, whole strata are com- 
 posed of the calcareous remains of the crinoids. Two 
 
230 GEOLOGY. 
 
 varieties are represented in Fig. 132, at 1 and 2. There 
 
 Fig. 132. 
 
 is also one variety of sea-urchin at 3, and the plates and 
 spine of another variety at 4. Fig. 133 represents a slab 
 of limestone from Iowa, in which are seen remains of cor- 
 
 Fig. 133. 
 
AGE OF COAL. 
 
 231 
 
 als, crinoids, etc., brought out in relief by the long-con- 
 tinued action of the weather upon the stone. 
 
 332. Articulates. Of the Crustaceans, but few of those 
 singular animals, the Trilobites, which numbered about 
 six hundred species in the Silurian, were present in the 
 Carboniferous age, and these were the last of that tribe. 
 New tribes appeared, of which one was very much like 
 the horse-shoe of the present day. Minute Crustaceans 
 swarmed in myriads in stagnant waters, as their remains 
 in the rocks now show. Of insects there have been 
 found some wing-cases of beetles. Insects of the cock- 
 roach tribe nourished then, and there were also some 
 scorpions. 
 
 333. Reptiles and Fishes. Some reptiles appeared in 
 this age, foreshadowing the succeeding one, in which 
 they were to be so abundant and large as to give the 
 name of Reptilian to it. The remains of some have been 
 found, and tracks have been discovered which evidently 
 belonged to reptiles, no remains of which have as yet 
 appeared in the rocks. Fig. 134 represents two of the 
 
 tracks of such a reptile, which 
 were found near Pottsville, in 
 Pennsylvania, by Dr. Isaac Lea, 
 of Philadelphia. In one part of 
 the slab there is the impression 
 of a tail. These marks, mingled 
 with ripple-marks and impres- 
 sions of rain-drops, making out 
 a most interesting record of that 
 age so far distant in the past 
 eternity, have been before no- 
 ticed in 210. Some of the 
 fishes of this age foreshadow 
 the succeeding Reptilian age, 
 by combining some of the reptilian characteristics with 
 those of fishes. Of such reptile fishes there is at the pres- 
 ent time but one known genus, the Lepidosteus, or gar- 
 
 Fig. 134. 
 
232 GEOLOGY. 
 
 pike of North America. Of this Hugh Miller says that 
 " it would almost seem as if it had been spared, amid 
 the wreck of genera and species, to serve us as a key by 
 'which to unlock the marvels of the ichthyology of those 
 remote periods of geologic history appropriated to the 
 dynasty of the fish." This wonderful animal has an ar- 
 mor of bony scales, covered with hard enamel like that 
 of teeth, so that it would be difficult for any shot to take 
 effect on it ; and as his teeth are very formidable, it has 
 been said of him by the fisherman that " he can hurt ev- 
 ery thing, and nothing can hurt him." It is very agile, 
 darting through the water even up the rapids of Niaga- 
 ra. It can bend its head freely in all directions, like a 
 serpent, which no other fish can do, for its vertebra have 
 the ball and socket arrangement of serpents instead of 
 the cup arrangement of fishes. In this fish we have the 
 only living type of the prevailing family of fishes in the 
 Coal period. Some of the fishes of that family were 
 such monsters in size, compared with the gar-pike, that 
 the sublime language of Job about the Leviathan could 
 be properly applied to them. Hugh Miller says of them, 
 "If the gar-pike, a fish from three to four feet in length, 
 can make itself so -formidable from its great strength and 
 activity, and the excellence of its armor, that even the 
 cattle and horses that come to drink at the water's side 
 are scarce safe from its attacks, what must have been the 
 character of a fish of the same reptilian order from thirty 
 to forty feet in length, furnished with teeth thrice larger 
 than the largest alligator, and ten times larger than the 
 bulkiest Lepidosteus, and that was covered from snout 
 to tail with an impenetrable mail of enameled bone ?" 
 
 334. Mollusks. Of these there was a great abundance 
 and variety. The Brachiopods were largely represented. 
 Of the genus Productus there were many species, one of 
 which is represented in Fig. 135. It is called Productus 
 spinulosus, from the long, slender spines that project from 
 the shell. Of another genus of the Brachiopods, Spirifcr, 
 
AGE OF COAL. 
 
 233 
 
 Fig. 135. 
 
 there were also many spe- 
 cies. One of them is repre- 
 sented in Fig. 136, show- 
 ing the spiral support from 
 which it takes its name, a, 
 as it is in the shell, and #, 
 a part of it taken out. The 
 strange Orthoceratites, 
 which, like the Crustacean 
 Trilobites, were abundant 
 in the Silurian age, now, 
 like them, appeared with 
 but few species, and, be- 
 fore the age had passed, 
 became extinct. 
 
 Fig. ISO. 
 
 335. Permian Period. The Carboniferous age ended 
 with what is called the Permian period, in which no coal 
 was formed. This period has its name from a portion 
 of Russia which was in ancient times the kingdom of 
 Perraia. Here the rocks of that period cover an area 
 TOO miles long and 400 broad. Until quite recently, it 
 was supposed that there are no Permian strata in this 
 country ; but they have been discovered in Illinois, Kan- 
 sas, and some parts of the slope of the Rocky Mountains. 
 In this period nearly all the country east of the Mississip- 
 pi was dry land, and therefore all the Permian deposits 
 were made on the west of it, with the exception of a small 
 part of Illinois. In Europe there are Permian strata in 
 Central Germany, and in England in the neighborhood 
 of the coal regions, in addition to the extensive area cov- 
 
234 GEOLOGY. 
 
 ered by them in Russia. In this country the rocks are 
 limestones, sandstones of various colors, shales or marls, 
 gypsum beds, and conglomerates. In the Permian stra- 
 ta of Europe the limestones are mostly found to be mag- 
 nesian. Why this is so the researches of geologists have 
 as yet not been able to determine ; and Phillips remarks 
 in regard to it that " we must be content to shelter our 
 ignorance under the statement that, from some unknown 
 cause, the waters of the sea were then decomposed in 
 such a way as to permit very generally the precipitation 
 of united magnesian and calcareous carbonates." 
 
 336. North America at the Close of this Age. Two 
 thirds of the North American Continent was above the 
 level of the ocean at the close of the Carboniferous age. 
 This was the eastern part, while the western was occu- 
 pied by a large interior or mediterranean sea, such as in 
 the Silurian and Devonian ages extended over much of 
 the eastern part also. The Rocky Mountains, as well 
 as, indeed, the Alleghanies, did not yet exist. The bor- 
 ders or fringes of the continent on the south and east 
 were yet to be added, and also a large portion of the 
 western part of the continent. Florida, that great work 
 of the coral animals, was yet to be constructed. Al- 
 though so much was done, long ages upon ages were yet 
 to be passed before the continent would be completed. 
 
 337. Disturbances in the Coal-measures. The strata 
 of the Carboniferous age have been subjected to upheav- 
 als, foldings, fractures, etc., like all other strata, some of 
 them being very extensive, even mountainous. If it were 
 not for these, few of the beds of coal lying between the 
 thousands (318) of feet of strata would have come with- 
 in the reach of man in his minings. Most of these up- 
 heavals and flexures occurred at the close of the age, in 
 the interval between Palaeozoic and Mesozoic time. The 
 results are so observable in this country, all along the re- 
 gion of the Appalachian chain, that the change produced 
 at that time has been called the Appalachian revolution. 
 
AGE OF COAL. 235 
 
 Where the flexures are most decided the strata were met- 
 amorphosed gneiss, granite, and other crystalline rocks 
 being produced showing that great heat was present at 
 that time in such localities. The same changes took place 
 in the coal-measures of other countries. The movements 
 in the bending and folding of the strata were not con- 
 fused, but occurred in certain lines, according to some 
 systematic plan of the Creator. They were probably 
 very slow perhaps to the extent of some yards, or even 
 feet only, in a century else such bend ings without frac- 
 tures as are often found could not have been produced. 
 It is believed that, besides the metamorphosis of strata 
 which laid up at that time for the use of man such quan- 
 tities of building material, there were separated and de- 
 posited in this metamorphic process many of the precious 
 and other metals, and also many of the precious gems. It 
 has also been observed that the coal is most debitumin- 
 ized where the disturbances of the strata were the great- 
 est. This is probably to be attributed to two causes 
 the action of great heat in such localities, and the oppor- 
 tunity of escape for gaseous products given by the frac- 
 tures made in the disturbances. Denudation is often 
 connected with the faults, bendings, etc. This is exem- 
 plified in Fig. 68, p. 140. These denudations were some- 
 times vast, the thickness of strata removed amounting 
 even to many thousands of feet. 
 
 338. Palaeozoic Life-record. You have now been 
 made acquainted to some extent with the changes in life 
 which occurred in the three Paleozoic ages the Siluri- 
 an, Devonian, and Carboniferous. While the grand di- 
 visions marked out by the Creator are preserved from 
 the beginning, showing that the same general plan exist- 
 ed from the outset as now, the predominant forms of 
 life, especially of animal life, are very different from each 
 other in the different ages, and very different from those 
 which appear at the present time. All the four divisions 
 of animals began in the first of the Palaeozoic ages, the 
 
236 GEOLOGY. 
 
 ">^^ 
 
 SilurialTpbut "the vertebrates did not appear till the lat- 
 ter part of it, and then in small numbers, and only in the 
 low form of fishes. Reptiles did not appear till the lat- 
 ter part of the Devonian, the age of Fishes, and were not 
 in their greatest abundance till after the Paleozoic time 
 was past. There were no Mammals in the Paleozoic 
 ages. Many species of animals which flourished in those 
 ages, perhaps largely, at length vanished, never to ap- 
 pear again ; for it is a remarkable fact, that any species 
 which conies to an end is never again brought upon the 
 stage. For example, the Trilobites, of which there were 
 hundreds of species in the Silurian age, all dwindled 
 away one after another, till, in the Carboniferous age, the 
 last of the species disappeared, and none of all of them 
 has ever again been revived. At the close of the Car- 
 boniferous age, in the midst of the disturbances that oc- 
 curred, every species of animal and plant was destroyed, 
 though many species belonging to the same genera with 
 those of this age existed in the after ages. This uni- 
 versal destruction of the life of the Carboniferous age is 
 one of the great marks of distinction between this and 
 the following age. 
 
 CHAPTER XVII. 
 
 AGE OF REPTILES. 
 
 339. Names. We now pass from Paleozoic to Meso- 
 zoic time, or the Medieval age of the earth, the age of 
 Reptiles. It- is divided into three periods, the Triassic, 
 Jurassic, and Cretaceous. The Triassic is so called on 
 account of an obvious threefold division which the sys- 
 tem of rocks presents in Germany, though it is not seen 
 in other quarters of the world. The term Jurassic comes 
 from the Jura Mountains of Switzerland, where the for- 
 mation or system of strata designated by this name is 
 well developed, and has been particularly examined. 
 
AGE OF RE 
 
 The term Oolitic is sometimes appli< 
 monly it is confined to one portion only of the Jurassic 
 period, in which one of the limestones formed is oolitic 
 in its structure. The term Cretaceous, from the Latin 
 word creta, chalk, is applied to the closing period of the 
 Reptilian age, because the chalk of England and Europe 
 is one of the rocks of the system belonging to that pe- 
 riod. In this country we have the system, but the chalk, 
 which is so prominent in those countries, is left out here. 
 
 340. Triassic Rocks. The rocks of this period are 
 mostly sandstones, shales, conglomerates, and sometimes 
 some limestones. So prominent are the red sandstones 
 that the whole system is called the New Red Sandstone, 
 in distinction from the Old Red Sandstone of the Devo- 
 nian age. In the valley of the Connecticut the material 
 for the rocks of this formation was derived from the 
 crystalline rocks in the neighborhood, chiefly by the ero- 
 sive action of water. The freestone of Connecticut and 
 New Jersey, so much used in building, comes from this 
 formation. In the western part of this country the Tri- 
 assic rocks are sandstones and marls of a brick-red color, 
 often having gypsum in them. The red color, so preva- 
 lent in the sandstones, though varying much in shade, is 
 owing to the presence of oxyd of iron. The life-record in 
 the rocks of this formation is scanty, because they are 
 not well suited to the preservation of fossils. 
 
 341. Localities. In the eastern part of this country 
 the Triassic rocks are surface rocks along between the 
 Appalachians and the Atlantic coast. In the Connecti- 
 cut Valley they extend from the Sound at New Haven 
 up to the northern part of Massachusetts. There stand 
 up in the midst of them Mount Holyoke, Mount Tom, 
 East and West Rock, and other Trappean elevations, 
 imparting variety and grandeur to the scenery. In the 
 West this system is extensively spread over part of the 
 slopes of the Rocky Mountains. The Triassic system is 
 developed in various parts of Europe and in England. 
 
238 GEOLOGY. 
 
 342. Triassic Salt. While in this country the chief 
 source of salt is in the Silurian formation ( 278), in En- 
 gland and Europe it is in the Triassic system, which is 
 often, for that reason, called the Saliferous system. The 
 rocks in connection with which the salt is found are sim- 
 ilar in both formations, but the manner in which the 
 salt was produced could not be the same in both cases. 
 The evaporating process which it is supposed, as stated 
 in 278, produced it in the Silurian formation in New 
 York, could not in any way accumulate masses of rock 
 salt 40 yards in thickness, or a mountain of salt 600 feet 
 high and 1 200 broad, such as is found at Cordova, in Spain. 
 It is supposed that volcanic agency operated in such 
 cases, as salt is common in what is thrown out from vol- 
 canoes, and salt-springs sometimes rise to the surface 
 from granitic rocks, showing that there are sources of 
 salt lying deep in the earth. The purity of the rock- 
 salt, it is thought, indicates its volcanic origin, for if it 
 were deposited from a solution it would have impurities 
 mingled with it. 
 
 343. Plants of the Triassic Period. Though the plants 
 which were peculiar to the Carboniferous age were not 
 present, as the Sigillaria and the Lepidodendrons, yet 
 there were Cycads as there were then, and Ferns, Equi- 
 seta, and Conifers in new forms. Trunks of conifers of 
 considerable size have been met with in the sandstones. 
 Some coal has been found in this formation in some lo- 
 calities, made, of course, out of the vegetation of which I 
 have spoken. Triassic coal has been discovered in Vir- 
 ginia and North Carolina in this country, in Australia, 
 and in various parts of Asia. 
 
 344. Animals. The excess of carbonic acid that ex- 
 isted in the atmosphere previous to the Carboniferous 
 age was removed from it by the rank vegetable growth 
 of that period, so that when the Triassic period came on 
 the air was fitted for air-breathing animals. They ac- 
 cordingly were introduced upon the scene. Not only 
 
AGE OF REPTILES. 
 
 239 
 
 were reptiles, and among them the monstrous Saurians, 
 introduced, but also birds and mammals. The mammals 
 were not, however, in great abundance, and were of the 
 lower orders, the marsupial, which at the present day 
 are so common in Australia. The fishes were all ganoids 
 and placoids, as in the Palaeozoic ages, but there was an 
 approach in their tails to the bilobed character of the 
 present day ( 302), and some were wholly of this mod- 
 ern fashion. Of the Mollusks, a family called 
 Ammonites, which figured largely in the two 
 other periods of the 
 Reptilian age, now ap- 
 peared. One species, 
 the Ammonites 'nodo- 
 sus, is represented in 
 Fig. 137. Among the 
 radiated animals of this 
 period was a crinoid of 
 singular beauty, called 
 the Lily Encrinite, Fig. 138. 
 
 345. Reptiles. Lizards, Saurians, Batra- 
 chians, many of them gigantic in size, were Fi s- 13S - 
 abundant, though not so abundant, and strange, and 
 monstrous as they were in the following period, the mid- 
 dle one of the age of Reptiles. One of the most remark- 
 able of these animals was the Labyrinthodon, pictured in 
 Fig. 139 (p. 240). Though having a head of three or four 
 feet in length, and teeth three inches long, and being 
 about the size of an ox, with his long hind legs, he was 
 very much like a frog. All of his skeleton has never 
 been discovered, but from his skull and some other bones 
 Professor Owen, by his knowledge of the adaptation of 
 bones to each other, like Cuvier, has reconstructed in his 
 mind the whole frame of the animal, and the result is the 
 singular form which you have in the figure. The tracks 
 which you see in the figure have been observed alone, in 
 Triassic rocks, and have, until recently, been supposed 
 
 Fig. 137. 
 
240 
 
 GEOLOGY. 
 
 Fig. 139. 
 
 to belong to another animal, whose remains, however, 
 had never been discovered. The name of Cheirotheri- 
 um was given to this supposed animal because the tracks 
 were so much like the print of a hand, the word being 
 derived from two Greek words, cheir, hand, and therion, 
 beast. It is now pretty well ascertained that these 
 tracks were all made by the Labyrinthodon. This name 
 is given to this animal from the structure of its teeth. 
 In Fig. 140, at a, is a tooth half its natural size, and at b 
 
 Fig. 140. 
 
 is part of a transverse section magnified twenty diame- 
 ters. You see that the turnings on this surface have a 
 labyrinthine arrangement, and hence the name given to 
 the animal. At c is one of these turnings very highly 
 magnified. 
 
 346. Tracks. The tracks of Triassic animals have 
 been observed by geologists in various quarters, but most 
 largely by Professor Hitchcock, of this country, in the 
 red sandstones of the Connecticut River Valley, where 
 
AGE OF REPTILES. 
 
 they abound. Before he began 
 his observations in 1835, these 
 tracks had been noticed for full 
 forty years by persons who 
 were not aware of their great 
 geological interest. Some are 
 tracks of birds, some of reptiles, 
 and some of animals that had in 
 combination the characteristics 
 of both birds and reptiles rep- 
 tilian birds, as they may be call- 
 ed. In Fig. 141 is represented 
 a slab of sandstone found near 
 Mount Holyoke. The large 
 tracks show that the animal 
 which made them on the mud, 
 now hardened into rock, had a 
 foot 20 inches long and 
 21 wide. It is supposed 
 that he was a Batra- 
 chian, a toad-like animal, 
 and yet he must have 
 been of the size of an ele- 
 phant. There are tracks, 
 a , of some smaller ani- 
 mal, and much of the sur- 
 face shows also the im- 
 pressions of rain-drops 
 as distinctly as if they 
 were made yesterday. 
 One of the largest of the 
 birds of that period was 
 the Brontozoum gigan- 
 teum, whose track is 
 given in Fig. 142 (p. 
 242). Its feet were from 
 14 to 20 inches long, its 
 L 
 
 241 
 
242 
 
 Fig. 142. 
 
 stride, as shown by the tracks, from four to six feet, and 
 it is supposed that it reached a height of 14 feet. A 
 very singular track is represented in Fig. 143. An im- 
 pression like a brush extends back from the foot. It is 
 supposed that the heel was covered with ridges, which 
 made these lines. 
 
 347. A Stone Fossil Book. A book with stone leaves 
 has been deposited by Professor Hitchcock in the Am- 
 herst Ichnological Cabinet. It is a book of five leaves, 
 nineteen inches long by eight in width, each leaf being 
 about an inch thick. The impressions of the tracks of 
 an animal are on all the leaves, corresponding in position 
 
AGE OF REPTILES. 
 
 243 
 
 throughout. The explanation is this : Five successive 
 layers of mud had been laid down of this thickness, each 
 one having partly dried before the succeeding one was 
 laid. The animal treading upon the upper one made an 
 impression through the whole five layers, which after- 
 ward solidified into rock, and so were preserved through 
 long ages to the present time. Dr. Hitchcock ingenious- 
 ly mounted the leaves in such a way that the book can 
 be readily opened or shut. 
 
 348. Trap Rocks. Masses of these rocks have come 
 up among the Triassic rocks in the eastern part of this 
 country, many of them being lofty enough to be called 
 mountains. As examples of these, there are, in Massa- 
 chusetts, Mounts Tom and Holyoke ; in Connecticut, 
 East and West Rock at New Haven, and the Hanging 
 Hills of Meriden ; in New Jersey, Bergen Hill, and vari- 
 ous other elevations. I have already told you, in 230, 
 how these masses are formed. The effect which the 
 fused rock, as it was thrust upward, produced upon the 
 sandstone is plainly to be seen in many localities. The 
 difference between the sandstone close by the trap and 
 that which is away from it is as distinct as that between 
 a brick so burned as to be very hard and one which has 
 the ordinary hardness. The ridges and dikes of trap are 
 arranged with some system, extending in certain general 
 directions as mountains do. This may be seen in Perci- 
 
244 
 
 GEOLOGY. 
 
 val's map of them in his Geological Survey of Connecti- 
 cut. The eruptions of trap are not wholly confined to 
 Triassic rocks, but appear to some extent on either side 
 of the area occupied by them, making ridges and dikes 
 among the other rocks. 
 
 Fig. 144. 
 
 349. Plants of the Jurassic Period. The climate of the 
 
AGE OF EEPTILES. 
 
 245 
 
 earth was quite universally warm and genial, as is shown 
 by the wide diffusion of certain plants and animals, even 
 into the arctic regions. The vegetation, therefore, was 
 luxuriant, consisting largely of cycads, conifers, and tree- 
 ferns, with some palms, lilies, etc. There were also equi- 
 setums and club-mosses. In Fig. 144 is represented the 
 vegetation of this period. In many localities the luxuri- 
 ant vegetation was packed down in beds of coal, as in 
 the Carboniferous period. There are localities of this 
 kind in Europe, in Great Britain, in China, in India, and 
 in Virginia in this country. Coal can be made of vege- 
 table fibre at any period if those circumstances are pres- 
 ent which I have stated to be necessary in the chapter 
 on the Coal-making age. 
 
 350. Portland Dirt-bed. In the island of Portland, 
 and in some of the adjoining counties of England, there 
 have been found the remains of an ancient forest of the 
 Oolitic, or Jurassic period, lying between the strata. 
 This so-called Portland dirt-bed is composed of a bluish 
 loam, which contains stumps and roots of trees petrified, 
 as represented in Fig. 145. There are strata of rock 
 
 Fig. 145. 
 
 above and below ; those below, A, being mostly marine 
 limestone, and those above, C, being, on the other hand, 
 fresh-water limestone. The rocky strata and the dirt- 
 bed, you see, are all parallel, but not horizontal. They 
 were horizontal when they were formed, but have all in 
 some way been tilted up together. This tilting, howev- 
 er, is only found in some localities, the horizontal posi- 
 
246 GEOLOGY. 
 
 tion being retained in others. Now, in all the region 
 where this arrangement is found, there must have been, 
 in the first place, deposits of a marine character, for the 
 Portland stone, A, is filled with marine shells. After- 
 ward these beds were covered with lake or river mud, 
 which became dry land, and was the scene of a forest veg- 
 etation. Then the land sank down, and was submerged, 
 with its load of forest growth, beneath fresh water in 
 place of the salt water which was there before the dirt- 
 bed was laid. From this water the limestone strata, C, 
 were deposited upon the dirt-bed, B, this being demon- 
 strated by the shells in the stone, which are of the kinds 
 that are found only in fresh water. The tilting, which 
 is to the amount of 45 degrees, was not done till all the 
 fresh-water limestones, C, were laid down. 
 
 351. Animals. Animal life had advanced on its forms 
 in the previous age, though the fishes were still only ga- 
 noid and placoid, and the mammalia were still of the mar- 
 supial type. Insects appeared more largely than before, 
 because there was more food for such animals in the veg- 
 etation. " There were," says Page, " burro wers among 
 the decaying timber of the pine forests; leapers among 
 the leaves and herbage of the cycas grove; hunters along 
 the river-bank and across its sunny waters ; and gaudy 
 flutterers over the flowers of the lily and the palm-tree. 
 All the great orders of insect life beetles, cockroaches, 
 dragon-flies, grasshoppers, and ants are abundantly rep- 
 resented." The Crustaceans were numerous, those which 
 were similar to shrimps and lobsters being especially prev- 
 alent. The higher orders of Mollusks abounded. There 
 were still Crinoids, though they were on the wane. Cor- 
 als were abundant wherever the formation of limestone 
 was going on. Sea-urchins also were numerous, one of 
 which is represented in Fig. 146. But the reptilian de- 
 velopment was the great feature of this middle portion of 
 the age of Reptiles. There were reptiles for the ocean, 
 the river and estuary, the muddy shore, and the land ; 
 
AGE OF REPTILES. 
 
 247 
 
 and many of them, were 
 monstrous in size and 
 extraordinary in char- 
 acter. 
 
 352. Ammonites and 
 Belemnites. Of the 
 Mollusks, these are the 
 most prominent and 
 
 They belong to the class called Cephalopods 
 ( 286). The Ammonites, which began in the Triassic 
 period, were now very abundant, their beautiful shells 
 
 peculiar. 
 
 ^~^ -sff^-'"'^^ '^^ i 
 
 1. Ammonite!? Jason. 2. A. Communis. 3 A. Bucklandi. 4, 5, 6. Belemnites. 
 7. Belemnoteuthis. 
 
 Fig. 147. 
 
 appearing in hundreds of forms, with every variety of 
 
248 GEOLOGY. 
 
 ornamentation. It was now the " reign of the Ammon- 
 ites ;" but they have long ago passed away, and the 
 only present representative of the class is the Nautilus 
 of the Southern Ocean. Some of these ancient Am- 
 monites were monsters, being even three feet in diame- 
 ter. On the left of Fig. 147 (p. 247) are three species. 
 On the right of the figure are the Belemnites, in different 
 degrees of preservation. These belong to the Cuttle-fish 
 tribe. At 7 is one with its crown of arms, with which 
 it took its prey. The animal probably sailed along with 
 its long, conical shell pointed downward, and now and 
 then rose quickly to grasp some fish swimming above it, 
 darting down to the bottom to devour it. Like the cut- 
 tle-fish of the present day, the Belemnite had an ink-bag, 
 and used it for the same purpose to discolor the water 
 to aid it in escaping from its enemies. From the ink- 
 bag of a Belemnite found at Lyme Regis, in England, a 
 pigment was obtained like that which is now prepared 
 from the cuttle-fish under the name of India ink. 
 
 353. Ichthyosaurus. This animal, whose skeleton is 
 represented in Fig. 148, combined in itself the character- 
 
 Fig. 148. 
 
 istics of a porpoise, a fish, and a crocodile. Its large 
 head was pointed like that of a porpoise, and it had pad- 
 dles or flippers like the Porpoise family. It was like a 
 fish in having no neck, the head and body being contin- 
 uous in outline. It was also like a fish in the arrange- 
 ment of its spinal column. Its teeth and jaws were like 
 those of a crocodile. Its eye was very large, its socket 
 being eighteen inches in diameter. It was so construct- 
 ed that the animal could see equally well in and out of 
 the water. Its jaws were so long that, when fully open- 
 ed, their extremities would be seven feet apart. It was, 
 
AGE OF REPTILES. 
 
 249 
 
 in some cases, even thirty feet in length. One of its pad- 
 dles contained over a hundred bones, giving this instru- 
 ment great elasticity and power. Thirty species of this 
 animal have been discovered. 
 
 354. Flesiosauras. This animal, of which you see the 
 skeleton represented in Fig. 149, had the general plan of 
 
 Fig. 149. 
 
 the Ichthyosaurus, but differed from it in several mate- 
 rial particulars) It was fitted for more brisk motion. 
 Its head was flat and serpent-like. It had a very long 
 neck, its paddles were large but slender, and its tail 
 short. In swimming, it probably used its paddles more 
 and its tail less than the Ichthyosaurus. The greatest 
 difference, hpwever, is in the size of the head. The 
 length of the Plesiosaurus was about 17 feet. Both ani- 
 mals had the power of creeping on land. 
 
 355. Pterodactylus. The Pterodactyl is the most ex- 
 traordinary of the animals of this period. It had the 
 head and neck of a bird, the mouth of a crocodile, the 
 
250 GEOLOGY. 
 
 wings of a bat, and the body and tail of a mammal. It 
 was, in some cases, of such enormous size that it meas- 
 ured from tip to tip of the spread wings 18 or 20 feet. 
 Although the general appearance of its wings was like 
 the bat, the arrangement was different. Instead of four 
 extended toes enveloped in skin, as in the bat, the fifth 
 toes only were lengthened, and the skin extended along 
 the side of the body and legs. Its eyes were enormously 
 large, so that it probably could seek its prey in the night. 
 In Fig. 150 (p. 249) you see the skeleton as it was found 
 in one case, and in Fig. 151 it is represented as complete 
 
 Fig. 151. 
 
 and in order, so that you see the relative position and 
 size of the various parts. 
 
 356. A Question in Comparative Anatomy. In Fig. 
 152 we have the Ichthyosaurus, Plesiosaurus, and Pter- 
 odactyl as they are" supposed to have appeared in the 
 scenes of the Jurassic age. It has been commonly sup- 
 
AGE OF REPTILES. 
 
 posed that the Pterodactyl was a flying animal, as here 
 represented, and that it lived on insects as the bats do, 
 although, perhaps, at the same time, it would dive down 
 occasionally into the water for fishes, to mingle them 
 with its insect food. Agassiz expresses, on the contra- 
 ry, the opinion that it was an aquatic animal, preying 
 upon fish and other animals in the water. This opinion 
 he bases upon two facts. First, the teeth are conical, 
 sharp, and separated from each other, and are, indeed, 
 such as are common to animals that live on aquatic prey, 
 and such as would not be required for the capture and 
 destruction of insects. Secondly, there is nothing in the 
 frame-work of the breast of the animal to indicate that 
 
252 
 
 GEOLOGY. 
 
 it had those powerful muscles which flying animals al- 
 ways have. Instead of the projecting keel which birds 
 have for the attachment of their large flying muscles, it 
 has a thin, flat breast-bone, like that of the sea-turtle of 
 the present day. For the full exposition of the subject 
 of arrangements for flying, I refer you to my Natural 
 History, 199 and 200. It may be added to the rea- 
 sons which Agassiz has given for his opinion that there 
 were, so far as we know, no insects of sufficient size to 
 be food for so large an animal. But, after all, there was 
 in the Pterodactyl an apparatus which might be used, to 
 some extent, in flying, though there were no muscles 
 competent to sustain flight for any length of time. "We 
 must therefore conclude that it probably rose into the 
 air occasionally, very much as the flying-fish now does, 
 with, perhaps, a somewhat longer range of flight. 
 
 357. Dinosaurs. There is a class of Jurassic land rep- 
 tiles called Dinosaurs, the name coming from two Greek 
 works, deinos, terrible, and sauros, lizard. Two of these, 
 Megalosaur and Hyla3osaur, are represented in Fig. 153. 
 
 Fig. 153. 
 
 Another is the Iguanodon, so called because it was like 
 the Iguana family of the present day, a notice of which 
 
AGE OF EEPTILES. 253 
 
 you will find in my Natural History, 326. These mon- 
 strous animals, being 25 or 30 feet in length, roamed, el- 
 ephant-like, over the river plains or through the forests, 
 the Iguanodon browsing upon shrubs and trees, and the 
 Megalosaur and Hylseosaur devouring crocodiles and 
 tortoises. 
 
 358. Cretaceous System. In Europe and Asia the se- 
 ries of rocks belonging to this system is characterized by 
 the presence of sands and sandstones in the lower part, 
 and chalk in the upper part. In this country there is no 
 chalk in the series, but there are beds of sand, clay, marl, 
 and different kinds of limestone. Sandy strata of various 
 kinds and colors predominate. Some are solid, and oth- 
 ers are more or less loose in their structure some so 
 much so that they can be crumbled by the hand. There 
 is a dark green variety called the Green-san^ the great- 
 est part of which, sometimes even to 90 per cent., is sili- 
 cate of iron and potash. There is also a little phosphate 
 of lime in it. It is prized as a fertilizer in New Jersey 
 and other parts of this country, its virtue in this respect 
 coming from the potash and the phosphate. In England 
 the Green-sand gives its name to the whole of the lower 
 part of the Cretaceous series, because it is so prominent 
 in it. Chalk, which is so prominent a part of the series 
 in England and Europe, is, like limestone and marble, a 
 carbonate of lime, but loosely put together in compari- 
 son with them. The chalk is varied in character by the 
 different kinds of impurities that are apt to be mingled 
 with it, and their different proportions. 
 
 359. Localities. In this country the Cretaceous sys- 
 tem comes to the surface over a vastly larger area than 
 the other two series of Mesozoic rocks, the Triassic and 
 Jurassic. It, in fact, made a very large addition to the 
 North American continent in the west and southwest, 
 chiefly west of the Mississippi, though quite largely in 
 the states bordering on the Gulf of Mexico. In the east 
 it appears here and there from New Jersey down to 
 
254 GEOLOGY. 
 
 South Carolina. It is very prominent in England, the 
 famous Dover Cliffs being composed of the chalk, and it 
 appears on the other side of the Channel, in France. It 
 also shows itself in other portions of France, and in vari- 
 ous parts of Europe. 
 
 360. Source of the Chalk. Chalk is a marine deposit, 
 and it is supposed that it was made in water some two 
 or three hundred feet deep. It was made chiefly by 
 those minute animals called Foraminifera, the shells of 
 some of whose species are represented in Fig. 83, p. 157. 
 The evidence on this point is decisive. The observations 
 of Ehrenberg and others with the microscope show that 
 chalk is made up of shells, the foraminifera furnishing by 
 far the largest proportion of them. Ehrenberg states 
 that a cubic inch of chalk often contains over a million 
 of these microscopic organisms. Whenever you make 
 a mark with chalk upon the blackboard, you really de- 
 posit there a quantity of the shells of these organisms ; 
 and if your eyes could be suddenly endowed with a high 
 magnifying power, that white line would appear to you 
 like part of the wall of a grotto covered over with shells. 
 Indeed, the fact that the carbonate of lime has in any 
 case the form of chalk is owing to the aggregation of 
 these shells, they being so small that they give to the 
 rock formed from them a soft and porous character. 
 This character is not given to the rock under any ordi- 
 nary circumstances when it is formed from corals or 
 shells of any size. These same foraminifera are busy at 
 the present day taking from the water of the ocean car- 
 bonate of lime to form their shells, and these, being left 
 on the sea's bottom, have been found in some localities 
 to compose almost wholly the sand that has been brought 
 up in deep soundings. The material for chalk is then 
 being deposited, and the chalk w r hich may thus be made 
 may at some future period be raised to the surface, and 
 constitute a part of the dry land of our earth. 
 
 361 . Flint in the Chalk. In England, and other coun- 
 
AGE OF REPTILES. 
 
 255 
 
 tries where chalfc abounds, flint is found in it to a con- 
 siderable depth. Sometimes it appears in layers, but 
 commonly in nodules or lumps, of various sizes and 
 shapes. The nodules are sometimes irregular and gro- 
 tesque, and when so are quite a favorite ornament in cot- 
 tage gardens in England. Covered with whitewash, 
 they are used as edges to the borders. One of these 
 forms you see in Fig. 154. Sometimes these nodules 
 
 Fig. 154. 
 
 take such a form as to be called fossil mushrooms. In 
 such cases the flint was depos- 
 ited upon and in certain com- 
 pound polypes of these forms, 
 or, in other words, they are pet- 
 rifactions of the frame-work of 
 these animals. Two of these are 
 seen in Fig. 155. Such forms 
 are called Ventriculites. 
 362. Fossils in the Flint. There are some very inter- 
 esting minute fossils in the flint nodules. Some of these 
 I will notice. There are certain vegetable fossils called 
 Xanthidia, which, like the diatoms, were formerly sup- 
 posed to be animal. There are many species of them. 
 In Fig. 156 (p. 256), at 2, you see represented a chip of 
 flint, which is so thin that the Xanthidia can be seen by 
 transmitted light. The five spots mark the frame-works 
 of five of them. The figure below exhibits one of these 
 
 Fig. 155. 
 
256 
 
 GEOLOGY. 
 
 Fig. 156. 
 
 largely magnified. It is supposed that 
 each of them furnished a nucleus around 
 which the flint, dissolved in the water 
 of the ocean, gathered and solidified. 
 In the upper part of Fig. 157, at a, c, 
 and $, are shell prisms that are found 
 in flint, those at a being the most com- 
 mon form. They are magnified ten 
 times, as indicated.* The origin of 
 these prisms, which are composed of 
 carbonate of lime, is curious. They 
 come from the shells of certain bi- 
 valves of that period. Now shells are 
 ordinarily made with laminaB or layers, one placed upon 
 another, as you may see in an oyster. But the shells of 
 these strange bivalves are composed of prisms, or many- 
 sided columns packed together, and extending from the 
 inside to the outside. In the figure, at 5, we have a 
 piece of flint, with a piece of one of these shells imbed- 
 ded in it. Some of the shell has been dissolved and re- 
 moved, so that you see in the recess the little columns 
 standing up all around, and on the floor of the cavity 
 are the minute depressions in the flint made by their 
 ends. In the specimen of which this figure is a repre- 
 sentation there was a roof of flint over the recess, but 
 this was carefully ground off in order to show the ar- 
 rangement. In the lower part of the figure you see rep- 
 resented a great variety of flinty spicula which come 
 from sponges, and are found in the flint nodules. They 
 are all much magnified, one of them, , even a hundred 
 times. This is very rarely found. The most common 
 of these spicules are #, A, &, and p. The spindle-shaped 
 one, with raised rings, o, is by no means uncommon. 
 The one resembling it, but having a triradiate summit, 
 
 * Throughout Fig. 157 the character X means multiplied or mag- 
 nified, the numeral annexed showing to what degree the object is 
 magnified. 
 
AGE OF REPTILES. 
 
 257 
 
 Fig. 157. 
 
 n, occurs more rarely. At m is the form which prevails 
 in patches of silicious network. It is supposed that the 
 spicula of sponges and the shells of the little diatoms 
 
258 GEOLOGY. 
 
 furnished a large portion of the flint for the nodules in 
 the chalk. The sponges abounded at that period, and 
 had an agency in regard to silicious matter similar to 
 that which corals have had in relation to limestone, and, 
 to some extent at least, they have that agency still. 
 
 363. Animals of the Cretaceous Period. I have al- 
 ready spoken of the Foraminifera and the Sponges. The 
 corals were not so abundant as in the Jurassic period. 
 The sea-urchins were very numerous, and the preserva- 
 tion of their beautiful remains is one of the marked fea- 
 tures of the period of the Chalk. The Crinoids, or En- 
 crinites, were decidedly on the wane. The Crustaceans 
 were on the increase, and approached in character to the 
 crabs and lobsters of the present day. The fishes ex- 
 hibited a great change. Though some of the placoids 
 and ganoids of former ages still remained, the ctenoids 
 and cycloids, which are now the prevailing orders, first 
 appeared in the Cretaceous age. The great reptiles of 
 the Jurassic period were passing away, for this was the 
 concluding period of the Reptilian age. The higher 
 mollusks appeared in great profusion. There was a re- 
 markable change in the forms of that great tribe of mol- 
 lusks, the Ammonites. Before this the coil of their cham- 
 bered cells was close and on one plane, as seen in Fig. 
 147 ; but now the coil was more or less open in many 
 of the species, sometimes with fantastic variations, or it 
 was spiral. Examples are given in Fig. 158, where we 
 have, 1. Ancyloceras, incurved like a crosier. 2. Scaph- 
 ites, curved like the prow of a skiff. 3. Crioceras^ curled 
 like a ram's-horn. 4. Hamites, bent like a hook ; and, 5, 
 Turrilites, running in a spiral round a straight axis. 
 
 364. Uplifts at the Close of the Reptilian Age. While 
 there were some disturbances during the progress of this 
 age, there were great and extensive ones at its close, in 
 the interval of passage from Mesozoic to Cainozoic time, 
 just as there were at the close of Paleozoic time, as no- 
 ticed in 337. Some of the great chains of mountains 
 
AGE OF REPTILES. 
 
 L>59 
 
 Fig. 158. 
 
 rose into existence in this interval the Rocky Mount- 
 ains, the Andes, portions of the Alps, etc. The same up- 
 lifting continued into the next age, so that these mount- 
 ains, and the Himalayas, Pyrenees, Appenines, etc., were 
 then fully raised. The evidence in regard to the rising 
 of mountains during both these periods is twofold. 1st. 
 The rocks of the cretaceous system lie high up on their 
 sides ; 2d. The marine rocks of the tertiary system that 
 is, of the age of Mammals, flank their sides below at a 
 different slope. Take, for example, the Rocky Mount- 
 ains. The cretaceous rocks are found lying sloped high 
 up upon them. This proves that the sea, from whose 
 waters the materials of the cretaceous rocks were depos- 
 ited, stood over the region where these mountains now 
 are, and that these rocks were raised up after the Creta- 
 ceous age had passed. Then the tertiary rocks were de- 
 posited from waters which flowed about the base of the 
 mountains. But how do we know that the raising of 
 them was not completed till some time in the Tertiary 
 age ? If it was completed, the rocks of the tertiary sys- 
 tem would, of course, not be sloped up the sides of the 
 
260 GEOLOGY. 
 
 mountains at all ; but if it was not, they would be thus 
 sloped in proportion to the degree of raising in the ter- 
 tiary, and such sloping is actually found to exist. All 
 this is simply an illustration of what is explained with 
 figures in 226. In this uplifting of strata in the forma- 
 tion of mountains, remains of animals which once lived 
 in the sea have been raised to very great heights. They 
 have been found imbedded in the strata in the Alps at 
 the height of six or eight thousand feet, and in the An- 
 des, according to Humboldt, at the height of fourteen 
 thousand feet that is, over two miles and a half. 
 
 365. Destruction of Life at the End of this Age. As at 
 the end of Palaeozoic time ( 338), so now at the end of 
 Mesozoic time, there was nearly, if not quite, a universal 
 destruction of life. In both cases this was owing to the 
 great disturbances that occurred. It is supposed that 
 after the Cretaceous period was completed, in the move- 
 ment which raised the mountains, of which I have spoken 
 in 364, there was a general elevation of the land of the 
 northern regions, and that the severe cold which was 
 thus produced was at least a prominent agency in the 
 destruction of life at this period. Hugh Miller makes 
 these two gaps or breaks the basis of a division of the 
 life of the world into three dynasties : the dynasty of the 
 Fish, extending from the Azoic age to the end of Palae- 
 ozoic time, when the first break occurs ; the dynasty of 
 the Reptile, from this period to the end of Mesozoic time, 
 when the second break occurs ; and the last, the dynas- 
 ty of the Mammal, which, commencing after the second 
 break, continues at the present time. 
 
 366. New Creations. During all the progress of the 
 ages, whenever a new species of plant or animal ap- 
 peared, there was a new creation, as already intimated 
 in 273. And as the life-record of the rocks shows that 
 there have been continually extinctions of species, and 
 introductions of new species in their places, creative pow- 
 er has been continually exerted in the domain of life upon 
 
AGE OF MAMMALS. 261 
 
 our earth. But this power was specially active when, 
 in the great and extensive changes effected at times in 
 the earth's crust, as was often the case, life was largely 
 destroyed. And when the destruction was complete in 
 the two gaps that have been mentioned, there succeeded 
 an entirely new creation of plants and animals. 
 
 CHAPTER XVIII. 
 
 AGE OF MAMMALS. 
 
 36V. Transition from Mesozoic to Cainozoic Time. 
 We now come to a period in the earth's history in which 
 there is a decided resemblance to the present time in 
 the general surface of the earth, and in its vegetables 
 and animals. The surface had become diversified with 
 numerous mountains, valleys, and rivers, though by no 
 means as largely as now, for this diversification was com- 
 pleted only when man was to be ushered upon the scene. 
 The endogens and exogens, the great sources of food for 
 man and beast, were quite predominant in the vegeta- 
 tion of the earth. In the animal kingdom, the marsupi- 
 als, which are allied at the same time to reptiles and to 
 birds, gave way to mammalia of the higher orders. In 
 the previous ages the most striking displays of animal 
 life were mostly in the ocean, in huge fishes, and mol- 
 lusks, and reptiles ; but now the land was to surpass the 
 sea in this respect. 
 
 368. Divisions of Cainozoic Time. A common division 
 of the Cainozoic age is into the Tertiary and Post-terti- 
 ary the Tertiary occupying the time, up to the Glacial 
 period, when, as you will see, the agency of ice was ap- 
 plied over a large portion of the earth to produce im- 
 portant results, and the Post-tertiary, extending thence 
 on to the advent of man. The term tertiary is an old 
 geological term, which the progress of discovery has 
 shown to be inapplicable. It was adopted when it was 
 
262 GEOLOGY. 
 
 supposed that the crystalline rocks were the first form- 
 ed in all cases, which were therefore called primary, or 
 primitive, the secondary being those which were be- 
 tween the primary and tertiary in relative age. But 
 when it was found that the so-called primary rocks were 
 formed in various ages, some of them quite recently, this 
 classification was given up ; but the name tertiary has 
 been retained, by common consent, as a matter of con- 
 venience. Indeed, the three terms are used still to some 
 extent, as mentioned in 261, primary having, however, 
 a different meaning attached to it from what it had for- 
 merly, it being applied to the palaeozoic rocks instead of 
 those which are originally crystalline. Lyell has divided 
 the strata of the Tertiary age into three series, according 
 to the percentage of shells found that are the same with 
 those that exist now. 1. Eocene, the term being derived 
 from two Greek words, eos, dawn, and Jcainos^ recent. 
 When the name was adopted it was supposed that from 
 five to ten per cent, of the species found in the strata 
 were identical with species found at the present time, 
 and therefore the period in which these strata were 
 formed was very properly considered as the dawn of the 
 present life of the earth. But Dana states that it has 
 been discovered that the species of this period are all 
 extinct. 2. Miocene, the term coming from meion, less, 
 and Jcainos. Here from ten to forty per cent, of the spe- 
 cies found are living species at the present time. 3. Pli- 
 ocene, from pleion, more, and Jcainos. Here the percent- 
 age of living species is greater than in the miocene, it 
 being from fifty to ninety per cent. These three series 
 are often called ancient tertiary, middle tertiary, and 
 modern tertiary. 
 
 369. Tertiary Deposits. In the previous ages the stra- 
 ta of rocks were mostly marine that is, deposited from 
 the waters of the sea as sediment, or laid down by coral 
 and other animals that lived in the sea. But now many 
 of the strata were either lacustrine that is, deposited 
 
AGE OF MAMMALS. 263 
 
 in lake bottoms ; or estuary that is, deposited from the 
 waters of a branch of the sea, where there was a min- 
 gling of salt and fresh waters. Some deposits occurred 
 in interior (mediterranean) seas. There was, during a 
 part of the Tertiary age, such a sea in Europe of immense 
 extent, with vast irregular islands in it. There was oft- 
 en in this age an alternation of marine and fresh-water 
 deposits, as shown by the fossils found in the strata. 
 This is the case with the basin, so called, in which the 
 city of Paris lies. First in order we have plastic clay, a 
 fresh-water deposit. Then upon this are strata in which 
 there is a vast quantity of marine shells. This is the cal- 
 caire grossier, which is, for the most part, a granular yel- 
 lowish limestone. It is regularly bedded and jointed, so 
 that it is easy to quarry it, and it is the grand building- 
 stone of Paris. Over 500 species of marine shells have 
 been discovered in these strata. By some changes of 
 the land in some way, there was at length fresh water 
 over all that region, and in the deposits made from it 
 upon the calcaire grassier there are, accordingly, found 
 remains of fresh-water animals and plants. Again the 
 sea water was let in, and we have a marine group of 
 strata, to be followed again by fresh water and its char- 
 acteristic deposits. In these last fresh-water beds the 
 most peculiar rock is the millstone, a flinty rock full of 
 cells and winding cavities, occasioned, it is supposed, by 
 the escape of gas from the bed of the lake up through 
 the deposit while it was hardening. 
 
 370. Areas of the Deposits. The deposits of strata in 
 this age were not made over areas of almost continental 
 extent, as was the case in the previous periods. There 
 were elevations of land here and there over the spaces 
 now occupied by the continents, of such size and arrange- 
 ment that there were lakes, and estuaries, and inland seas, 
 and on the floors and shores of these the deposits were 
 made. As these elevations multiplied and increased dur- 
 ing the progress of the age, the areas of deposition were 
 
264 GEOLOGY. 
 
 less in extent in the latter than in the first part of the 
 age. The more the areas became divided, the more di- 
 versified and complicated were the deposits. 
 
 371. Tertiary Rocks. Most of the rocks of this age are 
 less firm than those of previous ages, but some of them 
 are very hard. They are, shell-rocks of various kinds, 
 shell-beds, or mixtures of shells and earth, sandstones, 
 marls, clays, beds of sand, compact limestones, conglom- 
 erates, buhrstones, etc. The lowest of the tertiary rocks 
 in Europe were made to a large extent from materials 
 derived from the denudation of the chalk formation. 
 For this purpose, the cretaceous strata were upheaved 
 from the sea in which they were formed, so that the de- 
 nuding water could act upon the chalk cliffs. A slow 
 process it was for the water to wear away sufficient 
 amounts of these emerged strata to form the lower ter- 
 tiary strata of Europe, and a long age was required to 
 do it. 
 
 372. Nummulitic Formation. I have already noticed 
 in 239 those small shell-animals of the tribe Foramin- 
 ifera, the shells of which have formed such immense 
 quantities of rocky strata in Europe, and Asia, and Afri- 
 ca. In Fig. 159, at 1 and 2, are representations of nurn- 
 
 Fig. 159. 
 
 mulites as they are found in the rocks, and at 3 is a sec- 
 tion of one, showing its cells. The resemblance of these 
 fossils to pieces of money has given occasion to many su- 
 perstitious legends in regard to them among the Ger- 
 mans, and they are very commonly called the devil's 
 
AGE OF MAMMALS. 265 
 
 money. The nummulites of different beds are of differ- 
 ent species and of various sizes, some of them reaching 
 the size of an inch and a half in diameter. There are, 
 of course, other shells mingled with the nummulites, 
 though some strata are almost entirely nummulitic. 
 " The nummulitic formation," says Lyell, " with its char- 
 acteristic fossils, plays a far more conspicuous part than 
 any other tertiary group in the solid frame-work of the 
 earth's crust, whether in Europe, Asia, or Africa. It oft- 
 en attains a thickness of many thousand feet, and extends 
 from the Alps to the Carpathians, and is in full force in 
 the north of Africa, as, for example, in Algeria and Mo- 
 rocco. It has also been traced from Egypt, where it was 
 largely quarried of old for the building of the Pyramids, 
 into Asia Minor, and across Persia by Bagdad to the 
 mouths of the Indus. It occurs not only in Cutch, but 
 in the mountain ranges which separate Scinde from Per- 
 sia, and which form the passes leading to Caboul ; and it 
 has been followed still farther eastward into India, as far 
 as eastern Bengal and the frontiers of China." In the 
 Swiss Alps nummulitic strata are found 10,000 feet above 
 the level of the sea, and in Thibet at the height of 16,500 
 feet. They enter into the composition of the central and 
 loftiest parts not only of these mountains, but of the Py- 
 renees, the Carpathians, and Himalayas. Where, there- 
 fore, these great mountain chains now are, the sea stood 
 during that long age, when those little animals, the 
 nummulites, were accumulating these vast masses of 
 rock to be raised in after ages into lofty mountains by 
 some of the processes noticed in 226. Though there 
 are some nummulites found in the strata of the same pe- 
 riod in this country, they did not play here the magnifi- 
 cent role in rock-making which they did in Europe, Asia, 
 and Africa. 
 
 373. Tertiary Plants. In the earlier parts of the Ter- 
 tiary period the climate of the earth was more uniform- 
 ly mild than in the latter, and therefore in the strata of 
 
 M 
 
266 GEOLOGY. 
 
 that time we find in the northern portions of the earth 
 the remains of such plants as would naturally flourish in 
 warm climates. There are palm-like leaves and fruits, 
 leguminous seeds of arboreal growth, twigs arid leaves 
 of mimosa, laurel, and other plants, all allied to what 
 now grow in southern latitudes, and quite in contrast 
 with the plants now found in the same localities. Asso- 
 ciated with the twigs, leaves, and fruits found in the 
 strata are beds of lignite, or brown coal, indicating a 
 great abundance in the vegetation. From the high lati- 
 tude to which warm weather extended in that period, 
 Agassiz remarks that the Tertiary age may be called the 
 geological summer. 
 
 374. Strata of Diatoms. There are found here and 
 there in the Tertiary system strata which are made up 
 of what" were formerly supposed to be infusorial animals. 
 The diatoms, however, which compose by far the largest 
 proportion of the rock, are now ascertained to be vege- 
 table, and not animal. I have already noticed these 
 plants, and the strata which they have formed, in 240, 
 and will not dwell on them here. As these diatomaceae 
 are so exceedingly minute, a very long age must have 
 been required for the accumulation of thick beds of silex 
 from their remains, such as are found about Richmond, 
 in this country, and in Bilin, in Bohemia. As it takes 
 187 millions of them to make a single grain, it could have 
 been only by the contributions of countless generations 
 of them that a stratum of from 14 to 30 feet in thickness 
 was laid down. 
 
 375. Tertiary Animals. So far to the north was the 
 climate warm in the Tertiary age, that as it was with 
 plants, as stated in 373, so it was with animals such 
 kinds of animals as now flourish in tropical climates were 
 then in high northern latitudes, crocodiles, turtles, gigan- 
 tic sharks, pachydermatous quadrupeds, etc. The earli- 
 est remains of birds are found in the strata of the Eo- 
 cene period, the dawn of the Tertiary. So also serpents 
 
AGE OF MAMMALS. 
 
 267 
 
 first appear in the Tertiary strata. Not a species offish, 
 or reptile, or bird, or mammal of the Tertiary period 
 is in existence at the present time. These classes of an- 
 imals are in contrast with mollusks in this respect, for 
 many of the latter, as you saw in 368, coming into ex- 
 istence in the Miocene and Pliocene periods of the Ter- 
 tiary, are living still in the midst of the mollusks of the 
 present period that were created long ages after them. 
 
 376. Fishes. The remains of fishes abound in the ter- 
 tiary strata. The most intef esting are the Shark family, 
 which flourished in great numbers both in Europe and 
 America. Some of them were monstrous in size. In 
 Fig. 160 is represented the tooth of the Carcharodon 
 
268 GEOLOGY. 
 
 megalodon, the largest species of shark, which must have 
 been 100 feet in length. The sharks of the present time 
 are large, and are justly very much feared, but they are 
 " mere pigmies," says Hitchcock, " compared with those 
 that swam in the seas which washed the shores of North 
 and South Carolina in the Eocene and Miocene periods." 
 These terrific monsters, besides being much larger than 
 the sharks of the present age, were much more numerous 
 than now. 
 
 377. Reptiles. Some eighteen or twenty species of 
 crocodiles flourished in the Tertiary period, while there 
 are only seven or eight at the present time. The croco- 
 diles whose remains are found in the London clay were 
 like those which are now living in the island of Borneo. 
 There were about seventy species of turtles and tortois- 
 es in the Tertiary period. Dana speaks of the remains 
 of one which was 20 feet in length, and whose feet must 
 have been as large as those of a rhinoceros. 
 
 378. Mollusks. Up to the Tertiary period the mol- 
 lusks were all of species that do not exist at the present 
 time, but in this period the geologist reckons the chro- 
 nology of the strata by the relative percentage of extinct 
 and existing shells in them. To do this the general clas- 
 sification of Lyell ( 368) is adopted, and subdivisions, 
 more or less numerous, are made under it. In some cases 
 a stratum of rock is composed almost wholly of shells, 
 perhaps almost entirely of one kind. Sometimes there 
 
 is much variety in adja- 
 cent strata. As an illus- 
 tration, I will give you 
 the arrangement of a clift' 
 on the bank of the James 
 River, Va., represented 
 in Fig. 161. We have 
 here, 1. Six feet of sand 
 and clay. 2. One foot of 
 reddish clav. 3. A band 
 
AGE OP MAMMALS. 269 
 
 'of small pebbles a few inches thick. 4. A layer of sand 
 three feet thick, containing shells called Chama and Ve- 
 nus difformis. 5. A stratum four feet thick, consisting 
 mostly of a compact mass of Chama and Area centena- 
 ria. 6. A stratum two feet thick, mostly of large Pec- 
 tens. 7. Another stratum of Chama, with Area centena- 
 ria, Panopea reflexa, about six feet in depth. 8. A sec- 
 ond layer of Pectens, with Ostrea compressirostra, one 
 foot thick. 9. Another stratum of Chama three feet 
 thick. 10. A stratum of Peetens and Ostrea five feet 
 thick. When the shells are very perfect we know that 
 the animals that inhabited them lived and died on the 
 spot, and that the strata were formed very gradually in 
 still water. We make a different inference when the 
 shells are much broken up. On the York River, in Vir- 
 ginia, there is a porous rock, in some places forty feet 
 in height, which is made up almost wholly of comminu- 
 ted shells. Here was no still water, but there were the 
 rush of the tide and the breaking of the surf during all 
 the time that this rock was being deposited. 
 
 379. Indusial Limestones. Another example, in addi- 
 tion to those already mentioned, of the contributions of 
 small animals in the work of rock-making we have in the 
 indusial limestones in the ancient province of Auvergne, 
 in the central part of France. The agent in this case 
 was the larva of a species of fly, allied to the common 
 caddis-worm of the angler of the present day. We find 
 now that the larvae or grubs of different species use va- 
 rious materials for their indusia, or covers, some gluing 
 together small bits of wood, others choosing grains of 
 sand, and others still the shells of 
 small mollusks. One of the last 
 is seen in Fig. 162. The animal 
 is in a tube which it has con- 
 structed for itself of minute shells, 
 and, living in this, it thrusts its 
 head and a portion of its body 
 
270 GEOLOGY. 
 
 out in search of its food.* "It is evident," says Mr.' 
 Eley, an English geologist, " that the larger of the an- 
 cient lakes of Auvergne was inhabited by a species of 
 this family, and that they swarmed in it in a remarkable 
 manner ; for their cases, incrusted with a calcareous mat- 
 ter, are seen to form there thick layers of limestone 
 called indusial, from this strange origin which altern- 
 ate with the more usual kinds of marl through a thick- 
 ness of several hundred feet." These indusial strata are 
 eight or ten feet thick, and extend over an area of many 
 square miles. When you are told that one of the cases 
 or tubes contains over a hundred shells, and ten or twelve 
 tubes may be counted in a single cubic inch of rock, you 
 may have some idea of the countless myriads of minute 
 mollusks which must have formerly lived and died in ev- 
 ery part of this region, and of the length of time required 
 for the formation of the strata constructed chiefly from 
 their shells. 
 
 380. Mammals. Animals of this class were specially 
 prominent in the scenes of this age. Tapir-like pachy- 
 derms flourished largely in the early part of the age, but 
 as we come to its latter portions in the examination of 
 the strata, we find the mammals more like those of the 
 present age. Still, there is not a single species of all 
 those that have this resemblance which is not now ex- 
 tinct. There are some localities that are peculiarly rich 
 in remains of the mammals of the Tertiary. In the Up- 
 per Missouri region, in this country, among other re- 
 mains, there have been found those of three species of 
 camel, a rhinoceros as large as the Indian species, a mas- 
 todon, an elephant, a wolf larger than any species of the 
 present day, four or five species of the Horse family, etc. 
 It seems strange to us that some of these animals should 
 exist in such a locality, so far from the haunts of similar 
 animals in the present period ; but more strange still is 
 
 * For a full description of the habits of these animals, see my Nat- 
 ural History, 459. 
 
AGE OF MAMMALS. 271 
 
 it to think of monkeys as being in England, and yet re- 
 mains of them are found in that locality as far back even 
 as the strata of the Eocene. 
 
 381. Cetacea. The most remarkable of the Cetaceans 
 of this age is the Zeuglodon cetoides, a tooth of which 
 is seen represented of its natural size in Fig. 163. The 
 
 tooth is yoke-shaped, and hence the name given to the 
 animal, which is derived from two Greek words, zevglon, 
 a yoke, and odons, tooth. Its remains were first noticed 
 by Dr. Harlan, of Philadelphia, who in 1832 described a 
 vertebra weighing 44 pounds, which was brought from 
 the Washita. He referred the animal to which it be- 
 longed to a new genus, which he called Basilosaurus 
 that is, king of the Saurians, supposing it to be reptilian 
 in character. It has since, however, been proved to be- 
 long to the whale tribe. Its vertebra were formerly so 
 abundant in the State of Alabama that they were used 
 very commonly in making walls. Some of them are a 
 foot and a half in length, and a foot in diameter. Lyell 
 saw the vertebral column of one skeleton which extend- 
 ed on the ground nearly 70 feet. 
 
GEOLOGY. 
 
 382. Pachydermata. The most prominent of the mam- 
 mals of the early Tertiary were the pachydermatous 
 quadrupeds. Some of these animals are represented in 
 Fig. 164. The one on the right is the Palaeotherium. 
 
 Fig, 164. 
 
 This is intermediate in shape and character between the 
 tapir and rhinoceros of the present day. There are about 
 twelve species, varying much in size, the largest being 
 of the size of a rhinoceros, the smallest about as large as 
 a sheep. The other two animals, the Anoplotherium in 
 the middle, and the Ziphodon on the left, were lighter in 
 their construction, though having the same general char- 
 acter with the Pala30therium. These are representatives 
 of a large class of mammals that flourished in that age 
 in the forests, on the plains, and by the lake and river- 
 swamps. They were curious creatures, uniting in them- 
 selves the peculiarities of two or more animals of differ- 
 ent, even often of opposite character, such as tapir, sea- 
 cow, hog, rhinoceros, ass, camel, and antelope. 
 
 383. Cuvier's Investigations. The remains of these 
 pachydermata have been found in great abundance in 
 the strata of what is called the Paris basin. Four fifths 
 of the fifty species of quadrupeds whose remains are 
 found there belong to this tribe, which is represented in 
 the present age by only four species, so different are the 
 prevalent forms of animal life now from what they were 
 
AGE OF MAMMALS. 273 
 
 in the Eocene of the Tertiary. Guvier was the first to 
 develop the true character of the remains in the Paris 
 basin. Soon after he had investigated the fossil ele- 
 phants (to be noticed hereafter), some bones found in 
 the quarries of Montmartre, near Paris, were brought to 
 him for examination. He at once instituted comparisons 
 between these and the bones of various animals of the 
 present age, in order to ascertain the character of the 
 animals to which the fossil bones belonged. He soon 
 decided that they were pachyderms ; and at length, with 
 his knowledge of the relations of bones to each other and 
 to other parts of the frame, he was able, from a few bones, 
 such as those of the head, the jaws, some teeth, and a few 
 of the vertebra?, to fill out the deficiencies, and he drew 
 the outlines of two animals as he supposed them to have 
 been, the Pala30therium and Anoplotherium, represented 
 in Fig. 164. He presented the subject to the French 
 Academy, averring that the fossil bones belonged to ani- 
 mals of a creation previous to the present animal crea- 
 tion, and he therefore called the larger animal Pala3othe- 
 rium, from two Greek words, palaios, ancient, and theri- 
 on, animal. These views were received variously by sci- 
 entific men, some disbelieving, many doubting, and those 
 only believing who had paid some attention to compara- 
 tive anatomy. As the investigation proceeded, complete 
 skeletons of the animals were after a while found in the 
 strata, and the outlines made by Cuvier were shown to 
 be correct, and his views were universally adopted. 
 
 384. Dinotherium. Farther along in the Tertiary than 
 the pachyderms of the Paris basin appeared a monstrous 
 pachyderm of a singular composite character, called the 
 Dinotherium, represented in Fig. 165 (p. 274). Its re- 
 mains have been found in various parts of Europe, the 
 most perfect being a fine skull found in Germany. The 
 figure gives the animal as it was restored by Professor 
 Kaup from the scanty remains which have been obtain- 
 ed. As none of the bones of the limbs have as yet 
 M2 
 
274 
 
 GEOLOGY. 
 
 Fig. 165. 
 
 been found, there is some difference of opinion among 
 naturalists as to the true character of the animal, some 
 supposing it -to be much like an elephant, and others al- 
 lying it to the dugong, a swimming pachyderm, for the 
 description of which I refer you to my Natural History, 
 195. There is, in truth, in this strange animal, a mix- 
 ture of the peculiarities of the elephant, hippopotamus, 
 tapir, and dugong. If it be a quadruped, it is the largest 
 of all the quadrupeds that ha^e lived on the globe, being 
 larger than even the mammoth and mastodon, hereafter 
 to be noticed. It was probably eighteen feet long. Its 
 skull is nearly four feet in length, its upper jaw being 
 shaped like that of the elephant, for the attachment of a 
 trunk. It had two enormous tusks on the lower jaw, 
 curving downward like those of the walrus. It proba- 
 bly lived chiefly in the water, like the hippopotamus. Its 
 diet, as we know by its teeth, was vegetable, and it un- 
 doubtedly used its tusks to tear up the roots of aquatic 
 plants by a rake-like action from the beds of rivers and 
 lakes. Perhaps, too, it used its tusks as hooks for draw- 
 ing its huge unwieldy body up banks, and even along 
 upon the ground if it had no real legs. 
 
 385. Tertiary Mountain-making. There was, as you 
 have already seen, considerable mountain-making during 
 the Tertiary period, and therefore much change of eleva- 
 tion and flexure of the strata, with more or less of frac- 
 
AGE OF MAMMALS. 275 
 
 tures. The Rocky Mountains, which began to be raised 
 at the close of the Cretaceous age, did not reach then- 
 full height till late in the Tertiary period. The Pyrenees 
 and Carpathians were lifted up in the Eocene part of the 
 Tertiary. It was during the Tertiary age that the Alps, 
 Appenines, the Caucasian range, and the Himalayas at- 
 tained, very nearly at least, to their present altitude. On 
 the completion of this period the mountains of the earth 
 were very generally raised to their full height. 
 
 Observe that these mountains, which were raised thus 
 late, comparatively, in the course of the formation of the 
 continents, are many of them of very great height. Com- 
 pare them with the Alleghanies, that were raised, as is 
 supposed, at the close of the Carboniferous age. The 
 contrast is still greater if you compare them with the 
 Laurentian Hills, so called, in Canada, which were the 
 mountains in the Azoic age on that long island, the germ 
 of the North American continent, spoken of in 267. 
 These first mountains of the earth are nowhere more 
 than 1500 or 2000 feet above the level of the sea. The 
 reason of this difference between the older and more re- 
 cently formed mountains is thus given by Agassiz in 
 speaking of the Laurentian Hills. " Their low stature, 
 as compared with that of more lofty mountain ranges, is 
 in accordance with an invariable rule, by which the rela- 
 tive age of mountains may be estimated. The oldest 
 mountains are the lowest, while the younger and more 
 recent ones tower above their elders, and are usually 
 more torn and dislocated also. This is easily understood 
 when we remember that all mountains and mountain 
 chains are the result of upheavals, afll that the violence 
 of the outbreak must have been in proportion to the 
 strength of the resistance. When the crust of the earth 
 was so thin that the heated masses within easily broke 
 through it, they were not thrown to so great a height, 
 and formed comparatively low elevations, such as the 
 Canadian hills, or the mountains of Bretagne and 
 
276 GEOLOGY. 
 
 But in later times, when young, vigorous giants, such as 
 the Alps, the Himalayas, or, later still, the Rocky Mount- 
 ains, forced their way out from their fiery prison-house, 
 the crust of the earth was much thicker, and fearful in- 
 deed must have been the convulsions which attended 
 their exit." 
 
 With the raising of so many mountains, the great sys- 
 tems of rivers alluded to in 165 were begun; but, as 
 they were not completed till the next age, I will defer 
 the consideration of this subject till I come to speak of 
 that age. 
 
 386. Tertiary Volcanoes. There are evidences that 
 volcanic agencies were at work during the Tertiary age 
 in various parts of the earth. Such evidences have been 
 found in the West India islands, in Central America, in 
 parts of the Andes, and on the eastern continent in 
 France, Italy, Spain, Greece, and the island of Sicily. 
 The most interesting and striking evidences are found in 
 the ancient provinces of Auvergne, Velais, and Vivarais, 
 in the centre of France. Many hundreds of cones are 
 seen there, and the streams of lava which issued from 
 them can be traced, in many cases, as distinctly as those 
 which in this present age so recently have flowed from 
 Vesuvius or Etna. Some of these cones are represented 
 in Fig. 166. Many of them have been preserved with 
 
 remarkable distinctness. This is owing to their loose, 
 porous structure, which at first thought would be con- 
 sidered as rendering them very destructible. The ex- 
 planation is, that all the rain which falls is absorbed at 
 
AGE OF MAMMALS. 
 
 277 
 
 once by the porous mass, so that there are no rills run- 
 ning down the sides of the cones to wear them away. 
 The highest of the volcanoes is Mont Dor, in Auvergne, 
 which was several thousand feet above the surrounding 
 platform, and retains now the shape of a flattened cone, 
 broken on its summit into several rocky peaks, probably 
 from occasional earthquakes in ages long gone by, and 
 the continued influence of rain through not merely many 
 centuries, but many ages. 
 
 387. Basins. From the disturbances which occurred 
 in the Tertiary period, there are strata found in some lo- 
 calities so arranged in flexures as to form what are called 
 basins. Among the most noted of these are the basins 
 of London and Paris. In Fig. 167 is represented, in a 
 
 Fig. 167. 
 
 rude way, that of London. At 4 we have the chalk ly- 
 ing upon green sand, 5. Upon the chalk lies the plastic 
 clay, so called because in France, where it is less mixed 
 with other materials, it is extensively used in pottery. 
 Here there are in it beds of flint and pebbles alternating 
 with sands and clay. Upon it lies the London clay, 2, 
 upon which the city of London stands. It varies from 
 two to six hundred feet in thickness, is of a dark color, 
 tough in texture, and having mixed with it here and 
 there earth of a green color, white sand, and masses of 
 clayey limestone. At 6 is the River Thames. At 1, 1 
 are caps of marine sand, which are found on many of the 
 hills in the valley of the Thames. This sand probably, 
 when first deposited, formed a continuous bed over the 
 region, but has been excavated with a part of the Lon- 
 don clay, an example of the denuding agency of water. 
 
278 GEOLOGY. 
 
 With such a basin arrangement of strata as we have 
 here and at Paris, you can see how artesian wells can be 
 successful in both of these localities, as noticed in Part 
 I., 120, to which I refer you for the explanation of their 
 operation. 
 
 388. Tertiary Continent-making. In the Tertiary age 
 a great work was done in the building up of the conti- 
 nents. But it was not so much by the laying down of 
 deposits, though these were vast in thickness and over 
 extensive areas, as it was by elevating strata already 
 made, and crumpling them up in various quarters into 
 mountains. The work of this period is thus summed up 
 by Dana. " There was, 1, the finishing of the rocky sub- 
 stratum of the continents ; 2, the expansion of the conti- 
 nental areas to their full limits, or their permanent recov- 
 ery from the waters of the ocean ; 3, the elevation of 
 many of the great mountains of the globe, or consid- 
 erable portions of them, through a large part of their 
 height." He says, also, that " the mass of the earth 
 above the ocean's level was increased two or three fold 
 between the beginning and end of the Tertiary period." 
 In this country there was a mere fringe added* along its 
 eastern and southern edge, but in the west, beyond the 
 Mississippi, there was an addition of vast extent. Tho 
 North American continent, with its triangular shape, had 
 now its great triangular skeleton of mountain ranges, 
 as Agassiz calls it, completed, shutting in that immense 
 area, the Mississippi Valley. The Laurentian Hills on the 
 north, making the base of the triangle, came into being 
 in that first long, dark age of the world, the Azoic age ; 
 the range of Alleghanies, making the eastern limb, were 
 raised probably at the close of the Carboniferous period; 
 and the Rocky Mountains, the western limb, were thrust 
 up in the Tertiary age. The continent was now essen- 
 tially completed, the only great works yet to be done 
 being the filling up of a narrow gulf which extended to 
 where the city of St. Louis now is, from the material 
 
AGE OF MAMMALS. 279 
 
 brought down from wide regions by the Mississippi and 
 Missouri rivers, and the building up of the peninsula of 
 Florida by the coral animals, which are at the present 
 time building as busily as ever. 
 
 389. Post-tertiary Period. This period extends from 
 the conclusion of the Tertiary to the advent of man. 
 The building of all the continents was now, as I have just 
 said of North America, essentially completed that is, 
 the land had now reached its present bounds, and its 
 grand ranges of prominences were raised to their des- 
 tined heights. But there needed to be a greater diver- 
 sification of surface than had as yet been effected a di- 
 versification for the most part in detail. Hills and val- 
 leys were to be made ; stones of various sizes were to-be 
 scattered over the surface ; rivers were to be extended 
 and multiplied ; and terrace-like formations were to be 
 made along rivers, and lakes, and seas. Moreover, it 
 was necessary that much rock should be broken and 
 ground up, to make a sufficient quantity of fertile earth 
 for man and the accompanying races of animals. All 
 this was done by the agency of water in its two forms, 
 liquid and solid, as you will see as I proceed. 
 
 390. Divisions. This period has been variously di- 
 vided. As the system is developed in this country, it 
 is divided by Dana into three epochs. First is the Gla- 
 cial, when, in the higher latitudes, the land was raised 
 much above its present elevation, and arctic cold pre- 
 vailed over a large portion of the earth from either pole 
 toward the equator, producing glaciers and icebergs. 
 The second is the Champlain^ so named because the 
 beds of this epoch are well developed at Lake Cham- 
 plain. In this epoch there was r in strong contrast with 
 the Glacial, a depression of the surface below its present 
 level, and there were deposits of three kinds river-bor- 
 der, lacustrine, and marine, or sea-border. As the land 
 sank down, the glaciers and icebergs melted, and the wa- 
 ters swept over the varied surface of the land, producing 
 
280 GEOLOGY. 
 
 great changes in the disposition of its loose materials. 
 The third epoch was the Terrace period. Now there 
 was gradual elevation of the land till it reached its pres- 
 ent level, the waters all the time actirrg upon the mate- 
 rials laid down in the Champlain epoch, especially in the 
 rivers. This action made terraces skirting rivers, lakes, 
 bays, etc., which fact has given the epoch its name. It 
 is a transition epoch, for it is separated by no well-de- 
 fined line from the succeeding age, the age of Man. 
 
 The same division can be made essentially in Europe. 
 I will speak of each epoch separately. 
 
 391. Glacial Epoch. In this epoch, the summer heat, 
 which prevailed over the now temperate regions during 
 the Tertiary age, was s'ucceeded by arctic cold. The cap 
 of ice which now covers each pole extended then far to- 
 ward the equator. In this country, all New England, 
 New York, and other parts in the same latitudes were 
 covered by it. In Europe, those parts that have now 
 glaciers far up in the valleys of their mountains were 
 then covered with them as Greenland is now. Ice reign- 
 ed then all over Great Britain. The change in tempera- 
 ture was a gradual one, produced, as it is supposed, by 
 the elevation of all the land in a body at the north to 
 a much higher level than it has at the present time. 
 The glaciers of that period moved down in the valleys 
 as the glaciers of the present time do. One moved down 
 the valley of the Connecticut, another down the valley 
 of the Hudson, etc. They produced results similar to 
 those which are produced by glaciers at the present day, 
 described in 190. Many of them were thicker and lar- 
 ger than present glaciers, and produced, therefore, larger 
 results. There were then, as now, icebergs wherever 
 the glaciers reached to water instead of terminating on 
 land. 
 
 392. Drift. As a consequence of the action of glaciers 
 and icebergs in the Glacial period, there is scattered over 
 all the northern parts of America, Europe, and Asia wKif 
 
AGE OF MAMMALS. 281 
 
 is called drift. It is various in its composition, the ma- 
 terial being sand or gravel, or boulders of various sizes. 
 Sometimes the boulders are mingled with the sand and 
 gravel, and sometimes they are separate. When the ma- 
 terials of drift are in manifest layers, and to some extent 
 sorted, the finer and coarser alternating, and the frag- 
 ments are rounded and smoothed, it is called modified 
 drift. Water has in this case acted upon the materials, 
 and laid them in beds. Now of all this material which 
 we call drift, none was produced where it lies, but it 
 was transported to its localities, and for the most part 
 from the north toward the south. There are two theo- 
 ries in regard to its transportation the one attributing 
 the result to glaciers, and the other to icebergs called 
 respectively the glacier and the iceberg theory. But the 
 facts show conclusively that neither could alone accom- 
 plish all the work, and that both must have been more or 
 less in operation. The drift must have produced great 
 changes on the surface, filling up valleys here and there, 
 making lakes to overflow, and altering the courses of riv- 
 ers. A marked instance we have of the latter change 
 in the case of the Niagara River. There is decisive evi- 
 dence that the bed which it flowed in, from the whirl- 
 pool onward, until the Glacial epoch was then filled up 
 with drift, and the water opened for itself a new gorge 
 through solid rock, through which it has run to the pres- 
 ent time. The drift is by no means confined to the val- 
 leys and plains, but extends high up on the sides of 
 mountains, and is found even on the tops of some of 
 them, as Mount Holyoke and Mount Tom, in Massachu- 
 setts. It is at the height of 2000 feet in the Green 
 Mountains, 3000 on Monadnock, and even 6000 on 
 Mount Washington. 
 
 393. Boulders. These are angular, or more or less 
 rounded, according to the amount of friction to which 
 they have been subjected by water and other stones. 
 They vary much in size, and while they commonly do 
 
282 GEOLOGY. 
 
 not exceed a cubic foot, they sometimes reach thousands 
 of cubic feet in size, and thousands of tons in weight. 
 The boulder on which the colossal statue of Peter the 
 Great stands in St. Petersburg is a mass of granite 
 weighing 1500 tons. A boulder at Whittingham, Vt., a 
 town in the Green Mountains, is 43 feet long and 32 in 
 average width, contains 40,000 cubic feet, and weighs 
 3400 tons. The distances to which boulders have been 
 transported have been much investigated. The ordinary 
 distances are from 20 to 40 miles, but they have often 
 been carried 60, or even 100 miles. Hitchcock speaks 
 of some boulders found in Ohio and Michigan which 
 came from the ancient azoic rocks of Canada, and calcu- 
 lates that they must have been brought from a distance 
 of from 400 to 600 miles. These distances are discov- 
 ered by comparing the boulders with the rocks of the 
 country, thus tracing them back to the sources from 
 which they came. Sometimes great boulders have been 
 carried across deep valleys. Thus the monstrous one in 
 Whittingham was transported across a valley 1000 feet 
 deep, and another on the Hoosac Mountain, in Massa- 
 chusetts, came across a valley 1300 feet deep. 
 
 Sometimes many square miles are almost covered with 
 boulders of various sizes. This is often seen in the hilly 
 parts of New England. A singular circumstance in re- 
 gard to the disposition of boulders, first pointed out by 
 Hitchcock, is the arrangement of them in long trains. 
 There are two nearly parallel trains in Massachusetts, 
 extending from between Canaan and Lebanon, one of 
 them to a distance of 20 miles and the other 10. They 
 are from 300 to 400 feet in width, and are about half a 
 mile apart. It is a singular fact that they cross two 
 ranges of mountains which are 100 feet higher than the 
 source from which the stones came. The boulders are 
 most of them large, one of them weighing over 2000 
 tons, and their angles are but little rounded, showing 
 that they have been subjected to but little friction. Did 
 
AGE OF MAMMALS. 283 
 
 two enormous icebergs float side by side slowly over 
 that region, dropping their freight of stones as they 
 melted away? This is the only supposition we can 
 make, but this is not at all satisfactory. 
 
 394. Glacial Markings. In speaking of the effects of 
 glaciers in 190, I referred to various markings made 
 by them on the rocks of ftieir beds. Similar markings 
 are found on the sides of mountains, and on the faces of 
 rocks where the glaciers and icebergs of the Post-ter- 
 tiary age moved along. We find them every where in 
 the tracks of boulders. There is great variety in them. 
 Sometimes there are deep furrows, and sometimes mere 
 scratches. Sometimes there are lines as delicate as if 
 made by the tool of an engraver, and sometimes the sur- 
 face of a stone susceptible of polish is as smooth as it 
 would be if it were artificially polished in the shop of 
 a manufacturer. Sometimes rocky ridges have been 
 rounded and smoothed, giving them an undulating ap- 
 pearance, like the roches montonnees, or embossed rocks 
 seen in the Alps, the result of the action of glaciers of 
 the present time, as represented in Fig. 42. It is evi- 
 dent that most of these markings must have been made 
 by glaciers, and not by icebergs. While icebergs can 
 plow up dirt, and sand, and gravel, and crush rocks, it 
 requires the firm, slow, steady movement of the glacier, 
 holding its rocky tools imbedded in the ice, to make the 
 regular parallel grooves and lines, and the polished sur- 
 faces. And, in proof of the correctness of this view, we 
 find a striking resemblance between the efiects of mod- 
 ern glaciers on the rocks and those marks which appeal- 
 where the glaciers of the Post-tertiary age were supposed 
 to be. Still there is some coarse and irregular work, as 
 we may term it, which must have been done by icebergs, 
 as, for example, the making of furrows and valleys on 
 the summits of some of the lesser mountains. 
 
 The glacial markings are found abundantly on high 
 mountains as well as in valleys and on plains. On the 
 
-284 GEOLOGY. 
 
 Green Mountains they are found at the height of GOOD 
 feet. 
 
 395. Champlain Epoch. As the land elevated in the 
 Glacial epoch subsided, and water rose over it, the 
 Champlain epoch was ushered in. It found a vast quan- 
 tity of material which had been broken up by the ice of 
 glaciers and icebergs, and transported by them from the 
 sources from which it was obtained, mostly in southern 
 directions, and to greater or less distances. The -finer 
 portions of this, the gravel, and sand, and mud, the mov- 
 ing waters of this epoch carried about and laid down in 
 widely-extended strata. These formations are alluvial, 
 the term being derived from the Latin word alluo^ to 
 wash. Boulders never are found lying upon these beds, 
 for they were scattered by the glaciers and icebergs be- 
 fore these strata were laid down. They are often envel- 
 oped and covered up by the strata. They are often also 
 found on elevations in the neighborhood of Champlain 
 strata. In such cases there may have been once some of 
 the finer material of the drift mingled with them, and this 
 may have been washed away, the water not being able to 
 remove the boulders themselves. As the land subsided or 
 sunk down extensively in this epoch, some of the deposits 
 occurred on very high elevations. Hitchcock mentions 
 beaches of these deposits at great heights in the Green 
 and the White Mountains, one at the Franconia Notch 
 being 2665 feet above the level of the sea. The subsi- 
 dence of the land at the north during this epoch, lessen- 
 ing the amount of it above the surface of the water, and 
 so removing the arctic cold, which the raising of the land 
 in the Glacial period had produced ( 391), melted, of 
 course, the glaciers of the temperate regions. This cre- 
 ated at the outset of this epoch a great flow of waters 
 over the continents, which carried with them large quan- 
 tities of the smaller materials of the drift. The deposi- 
 tion of these was much modified by the lakes and rivers 
 which already existed, and, in return, also made many 
 
AGE OF MAMMA 
 
 changes in them. It is difficult, in many 
 guish the deposits of this period from those of the suc- 
 ceeding one, but it may be remarked in the general that 
 the river-plains and sea-beaches of the Champlain epoch 
 are at the present day elevated plains and beaches that 
 is, existing at higher levels than the terraces made in the 
 succeeding period. 
 
 396. Terrace Epoch. As you have seen, there have 
 been, in the course of the formation of the continents, 
 many extensive subsidences of land, letting the water 
 prevail for a time where it had been dry land before. 
 The last of these general submergences occurred in the 
 Champlain epoch. In the next epoch, the Terrace pe- 
 riod, the movement of the land was upward a move- 
 ment of emergence which went on until the land ac- 
 quired a comparatively settled condition that is, one 
 from which it has not varied, to any great degree, since 
 the advent of man. During this upward movement of 
 the Terrace epoch there was, to a considerable extent, a 
 rearrangement of the strata laid down in the Champlain 
 epoch. In this rearrangement the formation of terraces 
 was so common that this has given the name to the pe- 
 riod. The term terrace is applied to banks of loose ma- 
 terials skirting the sides of valleys about rivers and 
 lakes, having a level surface on the top, and fronting on 
 the river or lake with a more or less steep escarpment. 
 As they are often quite numerous, j*ising above each 
 other like the seats of an amphitheatre, but differing 
 much in width and in the lines of their edges, they give 
 great variety and beauty to the scenery, especially when 
 the habitations of men are built upon them, which is oft- 
 en done, or when, as is sometimes the case, they are used 
 as the dwelling-places of the dead. Not only do they 
 vary in width and in line of edge, but the variety is oft- 
 en increased by the action of rain with the currents 
 caused by it on their level-topped surfaces. You see in 
 Figs. 168 and 169 (p. 286) sections of two series of ter- 
 
286 
 
 GEOLOGY. 
 
 Fig. 169. 
 
 races. In Fig. 168, at the right hand, is represented a 
 section of the bed of the Connecticut River, lying in the 
 alluvial loam. Here there are seven terraces of various 
 widths, the upper one having a considerable excavation 
 in it from the continued action of rain. In Fig. 169 is 
 represented a set of terraces at another locality on the 
 Connecticut, where the arrangement is somewhat differ- 
 ent. 
 
 397. How Terraces were Formed. Terraces resulted 
 from the action of water on the modified drift as the land 
 was rising from its subsided condition in the Champlain 
 epoch. In other words, they were formed by the natu- 
 ral drainage of the country during that rise. Of course, 
 various circumstances had a play in their formation, giv- 
 ing them variety in their shape and arrangement. The 
 
AGE OF MAMMALS. 287 
 
 operation of the chief of these circumstances is stated by 
 Dana after this manner. Every river has its channel 
 and its flood-plain, the latter being overflowed whenever 
 a freshet occurs, as stated in 174. Now if, when the 
 land was rising, the rise was chiefly in the interior of a 
 continent, the coast being little changed, the rivers run- 
 ning toward the sea would have their slope increased, 
 and so greater force would be given to the descending 
 water. The result of this would be, that not only would 
 the channel be deepened, but a part of the flood-plain 
 would be at a lower level. This is indicated in Fig. 170, 
 
 A 
 
 Fig. 170. 
 
 where a is the bed of the river, and b the flood-plain, in 
 the Champlain period. The change thus effected by the 
 erosive power of water is represented by the dotted line. 
 This would leave the river as seen in Fig. 171, with b for 
 
 the flood-plain, and a terrace, c. As soon as the river by 
 this process attained its former slope, this process would 
 stop. Then, if the same rising went on, another similar 
 result would occur. And so with a succession of risings, 
 or perhaps with one continued rising, several terraces 
 might be made, as represented in Figs. 168 and 169. 
 There are many circumstances which vary the results of 
 this process, and make the terraces irregular in height 
 and form. There are also other processes that have pro- 
 duced terraces, but these I will not stop to describe. 
 
 398. Sea-beaches. I have spoken of the beaches which 
 were made in the Champlain epoch. When these are 
 found in the neighborhood of terraces they lie at a high- 
 
288 GEOLOGY. 
 
 er level, though, as they were formed earlier than the 
 terraces, they extend down under them, and are there- 
 fore, geologically speaking, lower. They often form a 
 sort of upper terrace in the series, making a fringe along 
 the sides of the hills that shut in a valley. Though ir- 
 regular in form, they have a certain general level, if ob- 
 servation be made of one for any considerable length 
 along the hills that it skirts. They consist mostly of 
 sand and gravel, all the stones in them being rounded, 
 thus showing the influence of long-continued water fric- 
 tion. It is supposed that they are beaches left by the re- 
 tiring sea, as the submergence of the Champlain period 
 passed away. 
 
 399. Niagara River. Great changes occurred in this 
 river during the Post-tertiary period. Just previous to 
 the beginning of this epoch the river ran in entirely a 
 different bed from what it now runs in from the whirl- 
 pool on to its outlet in Lake Ontario. The evidence is 
 this: The west bank of the gorge at the whirlpool 
 shows the beginning of a deep ravine filled with drift in 
 the form of gravel and sand, and this ravine can be 
 traced on to Lake Ontario. The inference is clear, there- 
 fore, that the water ran through this passage of four 
 miles to the lake until it was filled up with drift in the 
 Glacial period ; and this bed being filled up, the w r ater 
 sought, and, to a great extent at least, made for itself, 
 by its erosive power, another passage, the one in which 
 it now runs. But this is not all. The water has effect- 
 ed in this passage, as I have before stated in 183, the 
 removal of the falls from the neighborhood of Queens- 
 town back seven miles to their present position. The 
 process by which this has been done has been explained 
 in 183 ; but the story of the changes which have been 
 effected in the Niagara River is not all told yet. The 
 still waters of a lake once lay over all the neighborhood 
 where the falls now are, for there are lake deposits there, 
 as shown by the fossils which the strata contain. The 
 
AGE OF MAMMALS. 289 
 
 tooth and other bones of a mastodon found in these de- 
 posits show that they were laid down in the Champlain 
 epoch, for this animal flourished at that time. 
 
 400. Length of the Post-tertiary Age. If we can not 
 make some approximation to an estimate of the length 
 of time consumed by the Post-tertiary period, by calcu- 
 lations from the rate of progress in the recession of the 
 Falls of Niagara, we can, at least, see that the age was a 
 very long one. The recession is still going on, and va- 
 rious observations have been made in regard to it, and 
 estimates have been based on those observations. The 
 results, as worked out by different observers, vary great- 
 ly. Some estimate the recession as high as three feet in 
 a year, which undoubtedly is far beyond the fact. Lyell 
 estimates it as averaging one foot a year. This, which 
 Dana says is certainly large, would give over 31,000 
 years for the whole recession. Mr. Desor, another ob- 
 server, inferred from the data which he ascertained that 
 it was " more nearly three feet a century than three feet 
 a year." Taking it at three feet a century, the whole 
 would require over a million of years. 
 
 401. Post-tertiary Rivers. Rivers are a part of the 
 grand apparatus for the circulation of water on the earth. 
 Evaporation carries up water in the atmosphere from 
 over the whole surface, from the land as well as the sea, 
 and the vapor thus dissolved in the air is condensed into 
 rain, or snow, or hail, in order to be brought back to the 
 earth. Falling, it gathers in little streams, which, uniting 
 together, make the great rivers that run to the ocean. 
 Now, in order to have very large rivers, two things are 
 necessary a considerable extent of land to afford room 
 for the union of many streams in one, and the presence 
 of great mountains, to condense the vapor rapidly with 
 their tall, cold peaks. Neither of these conditions was 
 present when the continents began to form. When that 
 long island, with its low mountains, the germ of the 
 North American continent, was lifted up in the Azoic 
 
 N 
 
290 GEOLOGY. 
 
 age from amid the waters, no such rivers as the Missis- 
 sippi or the St. Lawrence were upon it. And the grand 
 river systems of the earth were not fully formed till after 
 the continents were expanded to their full limits, and 
 the mountain ranges spoken of in 385 were raised up 
 in the Tertiary age. The Post-tertiary age then was, as 
 stated by Professor Dana, " the era of the first grand 
 display of completed river systems of the first Amazon, 
 Mississippi, Ganges, Indus, Nile," etc. 
 
 402. Terminal Moraines of the Ancient Glaciers. The 
 glaciers of the Post-tertiary age had terminal moraines, 
 like those of the present time ( 190). They have, of 
 course, been much altered by the fluviatile operations, 
 that is, the operations of moving water, which produced 
 such great effects during the long ages of the Champlain 
 and Terrace periods, and hence it is that I notice them 
 here. The alterations alluded to are so great that the 
 resemblance of the remains of these ancient moraines to 
 those found at*the foot of the glaciers of the present day 
 is not obvious to the common observer. It is only the 
 practiced eye of the skillful geologist that can discover 
 it. Agassiz, Guyot, and others have investigated this 
 subject by extended observations in some of the locali- 
 ties where the vast glaciers of the Glacial period lay, es- 
 pecially in Switzerland and the island of Great Britain, 
 and have traced out the moraines with signal success, in 
 spite of the obliteration of their distinctive marks by 
 causes which have been acting upon them for ages. 
 They are, for the most part, semicircular in shape, the 
 concavity being toward the direction from which the gla- 
 cier moved downward. Sometimes there are several 
 of these semicircular walls, one placed within another. 
 Each of these is a moraine, the outer one having been 
 formed first, and the others one after another, as the gla- 
 cier retreated or became shortened ( 1 89). In the pass- 
 ing away of the Glacial age there was, of course, a con- 
 stant diminution of the extent of the glaciers, and conse- 
 
AGE OF MAMMALS. 291 
 
 quently many concentric moraines were formed. I have 
 spoken of the moraines as walls, but many of them are 
 broad and extensive, some of them being now the sites 
 of cities. The cities of Berne and Zurich stand on mo- 
 raines. Agassiz mentions a moraine through which a 
 river had made for itself a passage, and a village occu- 
 pies the moraine on both sides of the river. 
 
 These ancient moraines, like those found at the pres- 
 ent time, are made up of boulders, pebbles, gravel, and 
 sand, indiscriminately mixed together. But their com- 
 position is concealed from view by the soil which has ac- 
 cumulated upon their surface in the many centuries, even 
 long ages, that have passed since their formation, and 
 the consequent vegetation that has sprung up upon it. 
 " Time," says Agassiz, " which mellows and softens all 
 the wrecks of the past, has clothed them with turf, grass- 
 ed them over, planted them with trees, sown his seed, 
 and gathered in his harvests upon them, until at last they 
 make a part of the undulating surface of the country." 
 
 403. Soil made in the Post-tertiary Period. Soil is 
 merely comminuted rock. Nothing but the lowest or- 
 der of vegetation can grow on solid rock, and that in the 
 scantiest manner. The rock must be broken and ground 
 up into soil in order to be the basis of a full vegetation. 
 The various agencies by irhich this is done have been 
 brought to your view in various parts of this book. They 
 have been at work at all times since the first rocks of the 
 Azoic age were formed, but at some periods more than 
 at others. They were especially at work in the Post-ter- 
 tiary period. Quite a large portion of the soil now cul- 
 tivated was produced then, and we may say that it was 
 one of the great objects of the Creator, in the operations 
 of that period, to provide soil for the gardens and fields 
 of man, who was to come upon the scene of action in the 
 following age. The rocks were broken and ground up 
 for this purpose by the glaciers and icebergs of the Gla- 
 cial period, and the work of grinding and sorting was 
 
292 GEOLOGY. 
 
 continued on through the Champlain and Terrace peri- 
 ods, the water making piece rub against piece, great and 
 small, thus furnishing the small particles that were to be 
 the nutritious part of the soil which it was to spread 
 over the country. Hugh Miller, in speaking of the soil 
 which was thus furnished to Scotland, holds the follow- 
 ing language: "It is but a tedious process through which 
 the minute lichen, or dwarfish moss, settling on a surface 
 of naked stone, forms, in the course of ages, a soil for 
 plants of greater bulk and a higher order ; and had Scot- 
 land been left to the exclusive operation of this slow 
 agent, it would be still a rocky desert, with perhaps here 
 and there a strip of alluvial meadow by the side of a 
 stream, and here and there an insulated patch of mossy 
 soil among the hollows of the crags ; but, though it might 
 possess its few gardens for the spade, it would have no 
 fields for the plow. We owe our arable land to that ge- 
 ologic agent which, grinding down, as in a mill, the up- 
 per layers of the surface rocks of the kingdom, and then 
 spreading over the eroded strata their own debris, form- 
 ed the general basis in which the first vegetation took 
 root, and in the course of years composed the vegetable 
 mould. ' A foundering land under a severe sky, beaten 
 by tempests and lashed by tides, with glaciers half chok- 
 ing up its cheerless 'valleys, ad with countless icebergs 
 brushing its coasts and grating over its shallows, would 
 have seemed a melancholy and hopeless object to human 
 eye had there been human eyes to look upon it at the 
 time ; and yet such seem to have been the circumstances 
 in which our country was placed by Him who, to " per- 
 form his wonders," 
 
 "Plants his footsteps in the sea, 
 And rides upon the storm," 
 
 in order that, at the appointed period, it might, accord- 
 ing to the poet, be a land 
 
 "Made blithe by plow and harrow." 
 404. Post-tertiary Animals. There are three points 
 
AGE OF MAMMALS. 293 
 
 worthy of remark in relation to the animals of this pe- 
 riod. 1. Their great size. The elephants, bears, lions, 
 horses, hyenas, etc., were much larger than the species 
 of these animals existing at the present time. Perhaps 
 the difference is greater in the sloths than in any other 
 class of animals, as you will soon see. 2. The division as 
 to the general character of prevalent species in the dif- 
 ferent continents was much the same as now. Thus, in 
 the eastern continent, the Carnivorous animals predom- 
 inated ; in North America, the Herbivorous ; in South 
 America, the Edentates; and in Australia, the Marsu- 
 pials, or pouched animals. 3. Animals that were in 
 character like those which now have their habitat in 
 warm climates lived then in the regions that are now 
 temperate, and in some cases even up to the arctic re- 
 gions, as in the case of the elephant and rhinoceros of 
 Siberia. Owen says of England at this period, "Gigan- 
 tic elephants of nearly twice the bulk of the largest indi- 
 viduals that now exist in Ceylon and Africa roamed 
 here in herds, if we may judge from the abundance of 
 their remains. Two-horned rhinoceroses of at least two 
 species forced their way through the ancient forests, or 
 wallowed in the swamps. The lakes and rivers were 
 tenanted with hippopotamuses as bulky, and with as for- 
 midable tusks as those of Africa." Besides these, there 
 were tigers larger than those of Bengal, and " troops of 
 hyenas larger than the fierce Hyena crocuta of South 
 Africa, which they most resembled, crunched the bones 
 of carcasses relinquished by the nobler beasts of prey, 
 and doubtless themselves often waged a war of exterm- 
 ination on the feebler quadrupeds." 
 
 I will now go on to notice some of the animals that 
 were peculiar to this period. 
 
 405. Post-tertiary Elephants. Elephas primigenus, 
 the great Siberian mammoth, was a third taller than the 
 largest of elephants of the present time, and was twice 
 as heavy. The skeleton of this animal is represented 
 
294 GEOLOGY. 
 
 in Fig. 172, and the animal itself is seen in Fig. 173, 
 
 Fig. 173 
 
 at the left side. You observe that the tusks are very 
 
AGE OF MAMMALS. 295 
 
 much longer than in elephants of our time, and that 
 they are curved upward and backward with a broad 
 sweep. This animal had long black hair, mingled with 
 which there was a coat of reddish-brown wool. Such a 
 covering undoubtedly fitted it to bear a colder climate 
 than it could bear with the ordinary covering of ele- 
 phants. At the same time, it is clear, from the fact that 
 so many animals of the same kinds with those that now. 
 flourish in warm regions then existed in northern lati- 
 tudes, that the climate of the far north was, at least, 
 much less cold than it is now. Indeed, the woolly cov- 
 ering of the mammoth of Siberia simply indicates that 
 the climate there was only so much cooler than it is 
 where elephants are accustomed to live now, that this 
 additional covering was required for its comfort, and yet 
 it was not so cold as absolutely to forbid the existence 
 of animals of that nature, as is the case in that region at 
 the present time. Besides, if arctic cold reigned there 
 as it does now, the vegetation could not have been suffi- 
 cient for the sustenance of any number of these enor- 
 mous quadrupeds. The remains of the mammoth show 
 that great herds lived there. The tusks which are found 
 furnish a large part of the ivory in the market. The Li- 
 akhow Islands, lying off the north coast of Asia, are com- 
 posed to a great extent of mammoth bones, cemented 
 together by sand and ice, and in the year 1821 as much 
 as 20,000 pounds of fossil ivory was obtained from the 
 island of New Siberia, some of the tusks weighing near- 
 ly 500 pounds. The mammoth lived in herds in En- 
 gland. Its remains have also been found in North Amer- 
 ica, but not much below the latitude of 40. Below this 
 level in this country another species of elephant nour- 
 ished, and was very abundant in the South, in the Valley 
 of the Mississippi. On the island of Malta there have 
 been found the bones of a pigmy elephant which was 
 about the size of a calf. 
 
 406. The St. Petersburg Skeleton. There is a skele- 
 
296 GEOLOGY. 
 
 ton of a mammoth in the Imperial Museum at St. Peters- 
 burg, the story of which is interesting, both on account 
 of the circumstances under which it was obtained, and 
 the influence which it had upon palaeontological re- 
 searches. The story is this: In the year 1799 a Siberi- 
 an fisherman saw a rounded mass projecting from an ice- 
 bank near the mouth of the River Lena. The summer 
 weather so thawed it year after year that in 1803 the 
 enveloping ice was all melted, and the nucleus of this 
 mound-like projection was found to be an enormous ele- 
 phant. Though it had been there not merely centuries, 
 but ages, it was perfectly preserved, so that dogs and 
 wolves fed upon it as upon fresh meat. In the next 
 year, 1804, the fisherman cut off the tusks, which weigh- 
 ed 360 pounds, and sold them. In 1807 an English trav- 
 eler, Mr. Adams, hearing the story, visited the spot, suc- 
 ceeded in collecting all the bones except those of one 
 foot, which were supposed to have been carried off by 
 wolves, and recovered also the tusks. He also found 
 some of the hair and wool, and parts of the skin. The 
 name Mammoth, which was given to this elephant, is a 
 Siberian word meaning earth-beast, the idea of the na- 
 tives being that the mammoths live somewhere under 
 ground, and die whenever they come to the surface and 
 feel the influence of the sun. 
 
 407. Cuvier's Views. The discovery of the Siberian 
 elephant was the occasion of many speculations. At 
 first it was thought that it was transported to this high 
 latitude from India by some accident, and similar re- 
 mains found shortly after in Italy, Germany, etc., were 
 supposed to belong to Carthaginian elephants brought 
 into Europe by the armies of Hannibal ; but Cuvier soon 
 solved the mystery. He contended that an Indian ele- 
 phant carried to Siberia could not be changed in the 
 transportation, but would remain an Indian elephant still; 
 and as the bones of the Siberian mammoth showed that 
 it differed essentially in some respects from either spe- 
 
AGE OF MAMMALS. 297 
 
 cies of elephant existing at the present time, he averred 
 that it was another species. He averred, farther, that 
 the mammoth was a species belonging to a previous age 
 and now extinct, the proofs of which soon became very 
 abundant from the investigations that were prompted by 
 the teachings of Cuvier. It was shortly after this that 
 the discoveries were made at Montmartre, as noticed in 
 383, and these awakened a general interest in palaaon- 
 tological investigations. 
 
 408. Mastodons. These animals, one species of which 
 is represented at the right of Fig. 173, differed so decid- 
 edly from the mammoths as to constitute another genus. 
 This genus is now extinct, while that of the mammoths, 
 or elephants, still exists, there being now two living spe- 
 cies, the Indian and the African elephant, for descriptions 
 of which I refer you to my " Natural History," page 80. 
 The teeth of the mastodon differ very much from those 
 of the mammoth, having the enamel raised up in conical 
 eminences, as seen on the right of Fig. 174, instead of the 
 
 Fig. 1T4. 
 
 arrangement in ridges of the mammoth, as represented 
 at the left of the figure. The Mastodon giganteus, an 
 entire skeleton of which is in the Palaeontological Gal- 
 lery of the Britisji Museum, considerably exceeded in 
 size the largest elephant of the present time. Its bones 
 
298 GEOLOGY. 
 
 are found only on the North American continent, and 
 are very abundant in some parts, especially in a saline 
 morass in Kentucky called the Big Bone Lick. There 
 is a tradition prevailing among the Indians that there 
 existed men of gigantic stature at the same time with 
 the colossal animals to which these bones belonged, and 
 that both were destroyed by the thunderbolts of the 
 Great Being ; but this, like many other traditions, is un- 
 founded, for no bones of man have been found in connec- 
 tion with those of the mastodons. There have been five 
 entire skeletons of this animal dug up in this country. 
 The best one was obtained from a marsh near Newburg, 
 New York, and was set up by Dr. Warren, in Boston. 
 When found, its posture was such as we would expect 
 an animal to have that sunk in mire. Remains of its 
 last meal, lying between its ribs, showed that it lived, in 
 part at least, on spruce and fir-trees. The skeleton is 11 
 feet high, and its length to the beginning of the tail is 
 17 feet. The tusks are 12 feet long, over two feet of 
 them being imbedded in the bone of the skull. 
 
 Remains of a mastodon of a different species from the 
 North American one have been found in South America. 
 
 409. Mylodon. In the pampean or prairie formation 
 of South America, and in the caves of Brazil, have been 
 found the remains of certain huge animals allied to the 
 existing Sloth family. There are only three species of 
 this family at the present time, and they are of moderate 
 size ; but of the monsters that belonged to it in the Post- 
 tertiary age there are many species. Of the three spe- 
 cies of one genus, Mylodon, the skeleton of one, Mylodon 
 robustus, is represented in Fig. 175. The sloths of the 
 present day live in the trees of dense forests, the foliage 
 being their food. The sloths of the olden time lived on 
 the same kind of food, as is shown by their teeth ; but 
 they were too heavy to climb, and they obtained the fo- 
 liage by breaking down or uprooting trees. In doing 
 this, the Mylodon put itself, probably, in the attitude rep- 
 
AGE OF MAMMALS. 
 
 299 
 
 Fig. 175. 
 
 resented in the figure, supporting itself on its two hind 
 legs and its massive tail, as on a tripod. As it had pow- 
 erful claws, it undoubtedly sometimes dug up the earth 
 around trees preparatory to uprooting them. The ani- 
 mal was of about the size of a rhinoceros or hippopota- 
 mus. Its skull has two plates of bone with cells between 
 them, as is the case with the skull of man ; but in the 
 mylodon the cellular portion is very large, separating the 
 plates of bone considerably. The reason of this undoubt- 
 edly is, that the animal, in tearing down trees, was very 
 liable to have them fall down upon his pate, as his un- 
 wieldy form prevented any thing like nimble efforts in 
 getting out of harm's way. If in such an accident the 
 skull were fractured, the break would not be apt to ex- 
 
300 GEOLOGY. 
 
 tend beyond the cellular portion to the inner plate or 
 table, and so the monster's brain would be safe, suffering 
 only a concussion, from which it would speedily recover. 
 The evidences of such a fracture Professor Owen found 
 in one skull, and they were such as to show that the 
 fracture was healed, and that therefore the animal sur- 
 vived the accident. 
 
 410. Megatherium. This animal was another of those 
 Post-tertiary South American sloths. Its name, derived 
 from two Greek words, megas, great, and them, wild 
 beast, indicates its enormous bulk. The skeleton of one 
 of the dozen species of this genus is represented in Fig. 
 176. The length of this animal was about twelve feet, 
 
 Fig.l 
 
 and its height was eight. It was exceedingly massive, 
 its thigh bone being twice as thick as that of the ele- 
 phant, and the other bones are in like proportion. The 
 width of the tail at its upper part was two feet. Its 
 fore foot was more than three feet long, and one foot in 
 width, and the toes were armed with enormous claws. 
 It lived upon leaves and twigs, which it gathered as the 
 
AGE OF MAMMALS. 
 
 301 
 
 Mylodon did, by pulling down trees, as represented in 
 the case of one species in the front part of Fig. 177. 
 
 Fig. 1T7. 
 
 Another genus of the Sloth-like family of the Post-terti- 
 ary period was the Megalonyx, the name (megas, great, 
 and onux, nail) being given to it on account of its large 
 claws. The first species known was found in Virginia, 
 and this name was suggested by President Jeiferson. 
 Its size was about that of an ox, but it was much more 
 solidly and heavily built. 
 
 411. Glyptodon. This genus, embracing several spe- 
 
302 GEOLOGY. 
 
 cies, all of which were gigantic, was allied to the arma- 
 dilloes of the present day. One species is represented 
 in the rear part of Fig. 177. This animal had a shell 
 somewhat like a turtle. This solid coat of mail is com- 
 posed of innumerable plates joined together by serrated 
 or notched sutures. Looked at from within, they are 
 hexagonal, but externally they form a mosaic of rosette- 
 like figures. Remains of this shell were first found in 
 company with bones of the megatherium, and were sup- 
 posed to belong to that animal. But the truth was soon 
 discovered on finding an entire shell, which is now in the 
 museum of the College of Surgeons in London. This 
 shell is nine feet in length, and the curve, measured 
 across, is seven feet. It is large enough to cover over a 
 large number of the armadilloes of the present day. 
 
 412. "Whales. These animals appeared in localities in 
 the Post-tertiary period far away from their present hab- 
 itats. The sea in that age extended up as an arm where 
 the St. Lawrence now runs, and covered the present lo- 
 cality of Lake Champlain. Whales and seals flourished 
 there at that time, and their remains have been found 
 among other spots in the neighborhood of Montreal. In 
 Fig. 178 you have a representation of the bones of the 
 
 Fig. ITS. 
 
 head of a small whale, similar to the existing white 
 
AGE OF MAMMALS. 303 
 
 whale of the Northern Sea, as they were dug up on the 
 borders of Lake Champlain, 60 feet above its waters, 
 and 150 above the level of the sea at the present time. 
 
 413. Kirkdale Cave. The bones of animals of the 
 Post-tertiary age have been found to some extent in 
 caverns in Great Britain, on the Continent of Europe, 
 and in Brazil, in South America. The European caves 
 were dens of cave-bears, so called because they dragged 
 their prey into these caves. In England they were the 
 dens of hyenas. In South America they were occupied 
 by wolves and certain panther-like animals. The most 
 famous cave in England is the Kirkdale Cave, in York- 
 shire, the mouth of which was accidentally discovered 
 by some workmen in 1821, in quarrying stone on the 
 slope of a limestone hill. I transcribe an account of it 
 given by Agassiz. " Overgrown with grass and bushes, 
 the mouth of this cave in the hill-side had been effectual- 
 ly closed against all intruders, and it was not strange 
 that its existence had never been suspected. The hole 
 was small, but large enough to admit a man on his hands 
 and knees ; and the workmen, creeping in through the 
 opening, found that it led into a cavern, broad in some 
 parts, but low throughout. There were only a few spots 
 where a man could stand upright ; but it was quite ex- 
 tensive, with branches opening out from it, some of 
 which have not yet been explored. The whole floor 
 was strewn,.from one end to the other, with hundreds 
 of bones, like a huge dog-kennel. The workmen won- 
 dered a little at their discovery, but, remembering that 
 there had been a murrain among the cattle in this re- 
 gion some years before, they came to the conclusion that 
 these must be the bones of cattle that had died in great 
 numbers at that time, and, having so settled the matter 
 to their own satisfaction, they took little heed to the 
 bones, but threw many of them out on the road with the 
 common limestone. Fortunately, a gentleman living in 
 the neighborhood, whose attention had been attracted 
 
304 GEOLOGY. 
 
 to them, preserved them from destruction ; and a few 
 months after the discovery of the cave, Dr. Buckland, 
 the famous English geologist, visited Kirkdale to exam- 
 ine its strange contents, which proved, indeed, stranger 
 than any one had imagined, for many of these remains 
 belonged to animals never before found in England. The 
 bones of hyenas, tigers, elephants, rhinoceroses, and hip- 
 popotamuses were found mingled with those of deer, 
 bears, wolves, foxes, and many smaller creatures. The 
 bones were gnawed, and many were broken, evidently 
 not by natural decay, but seemed to have been snapped 
 violently apart. After the most complete investigation 
 of the circumstances, Dr. Buckland convinced himself, 
 and proved to the satisfaction of all scientific men, that 
 the cave had been a deu of hyenas at a time when they, 
 as well as tigers, elephants, rhinoceroses, etc., existed in 
 England in as great numbers as they now do in the wild- 
 est parts of tropical Asia or Africa. It was evident that 
 the hyenas were the lords of this ancient cavern, and the 
 other animals their unwilling guests, for the remains of 
 the latter were those which had been most gnawed, bro- 
 ken, and mangled ; and the head of an enormous hyena, 
 with gigantic fangs, found complete, bore ample evidence 
 to their great size and power. Some of the animals, such 
 as the elephants, rhinoceroses, etc., could not have been 
 brought into the cave without being first killed and torn 
 to pieces, for it is not large enough to admit them. But 
 their gnawed and broken bones attest, nevertheless, that 
 they were devoured like the rest ; and, probably, the hy- 
 enas then had the same propensity which characterizes 
 those of our own time, to tear in pieces the body of any 
 dead animal, and carry it to their den, to feed upon it 
 apart." 
 
AGE OF MAN. 305 
 
 CHAPTER XIX. 
 
 AGE OF MAN. 
 
 414. Boundaries of this Age. In the ages of the far 
 past, as you have already seen, there is no exact line di- 
 viding one age from another. So it is with the present 
 age, and the Post-tertiary that preceded it. It has been 
 the common idea that the advent of man is fixed by the 
 chronology of the Bible at about 6000 years ago, and 
 the researches of geology have been thought to coincide 
 with this ; but recently there have been some researches 
 which seem to put the introduction of man farther back 
 than this. The question is yet undecided, but if the re- 
 sult indicated should be arrived at definitely, it would 
 not show that the Bible is false, as some would have it, 
 but merely that the common view of its early chronolo- 
 gy is wrong. As to the conclusion of the present age, 
 geology leaves us entirely in the dark. The Bible does 
 indeed point to a time when the affairs of this world 
 shall be concluded, and the earth cease to be the habita- 
 tion of the human race, a vast change being indicated 
 by the announcement that " the heavens shall pass away 
 with a great noise, and the elements shall melt with a 
 fervent heat; the earth also, and the works that are 
 therein, shall be burned up." But the geologist, though 
 he sees in the operations that are now going on eviden- 
 ces of great future changes in the arrangement of the 
 earth's surface, finds nothing which could enable him to 
 predict any such radical change as the Bible plainly, 
 though in general and indefinite terms, points out. 
 
 415. Earth now and in Former Ages. The contrast 
 between the state of the earth in the present age and in 
 any of the former ages is very great, and the farther we 
 
306 GEOLOGY. 
 
 go back in the comparison the more striking does it ap- 
 pear. To say nothing of that period or age when the 
 earth was in a fused condition, look at the Azoic age 
 as compared with the present. When the extent of 
 land was small, and there was no life either on land, or 
 in water, or air, there were no high mountains, and no 
 rivers of any size. It was a dull, monotonous world, 
 compared with the variegated earth which we have now, 
 with its continents, islands, mountains, lakes, and rivers, 
 all swarming with busy and noisy life. A strong con- 
 trast can be made out in regard to the ages that follow- 
 ed, especially in relation to the changes of various kinds 
 that were necessary in making the requisite additions to 
 the continents, such .as flexures, upheavals, denudations, 
 deposits, elevations, subsidences, etc. Disturbances, it is 
 true, are occurring in this age, many of them precisely of 
 the same character ; but they are not so great, nor so 
 wide in their range. For example, glaciers and icebergs 
 are at work now; but their work is not continent-wide, 
 as it was in the Glacial age, when ice reigned supreme 
 over a large portion of the earth, in order to prepare it, 
 as you have seen, for man. So, in the formation of peat, 
 we have the same thing essentially as was the grand 
 business of the Carboniferous age ; but it is a small op- 
 eration compared with the coal-making of that period. 
 The Post-tertiary period was the nearest in character to 
 the present, especially the Terrace epoch, for the conti- 
 nents were then finished, and all the grand general work 
 of diversification of the surface was completed, only the 
 minor diversification, as it may be termed, remaining to 
 be done. 
 
 416. Completion of the Earth. Although changes, and 
 those of no small extent, are now going on in the crust 
 of the earth, yet, in a certain sense, it may be regarded 
 as having been completed at the time when man was in- 
 troduced upon it. This conclusion is seen to be true if 
 we consider certain prominent facts, viz., that the conti- 
 
AGE OF MAN. 307 
 
 nents had their germs, and grew gradually by accretions, 
 after a regular plan, to their present dimensions ; that 
 after their proper size was reached great operations were 
 instituted to diversify the surface, and to grind up some 
 of the rocks into soil for the use of man ; that the prep- 
 arations of the earth's crust, even down to minute cir- 
 cumstances, so far as they are understood, can be seen 
 to look toward the consummation arrived at in the age 
 of Man ; and, finally, that man, appearing after a succes- 
 sion of animals extending through long ages, differs 
 from them all in the possession of qualities that ally him 
 with the Infinite, and therefore show him to be the fit- 
 ting end of such a consummation. The earth was made 
 for man. Accordingly, he has a general control over 
 the powers of earth, being commissioned " to subdue it, 
 and have dominion over the fish of the sea, and over the 
 fowl of the air, and over every living thing that moveth 
 upon the earth." Mind gives him this control, even 
 where physical circumstances, as weight and strength of 
 muscle, are sufficient to overpower him in any direct ef- 
 fort. He is the lord of this lower creation, acting as the 
 vicegerent of the Creator. 
 
 417. Changes now Transpiring. The changes which 
 have taken place during the age of Man, and are now 
 going on, have been quite fully noticed in Chapter X., 
 and I shall only give a summary of them here. The 
 rocks are every where subjected to weathering, which 
 wears them away by piecemeal,%nd the rivers are car- 
 rying away the detritus of the rocks, lodging it in deltas 
 or on flood-plains. The tendency of all this is to fill up 
 the depressions, and to make the land encroach upon the 
 space occupied by the water. Then there is evidence 
 that over extensive areas of the floor of the sea deposits 
 are being laid down of the same materials that now com- 
 pose rocks made in former ages. Besides, there are the 
 coral animals busily engaged in building extensive reefs. 
 There is, therefore, great land-building going on, and the 
 
308 GEOLOGY. 
 
 result must inevitably be, that the level of the ocean will 
 rise, unless there be some movements of the land to coun- 
 teract it. Elevations in the land or depressions in the 
 floor of the sea would do this. That elevations have 
 occurred within this age, and are occurring now, we 
 have the clearest evidence, as shown in Chapter X. It 
 may be that the heaving of volcanoes, adding to the 
 land, may occasion some corresponding depressions in 
 the floor of the sea in their neighborhood. At any rate, 
 in some way the general level of the ocean in relation to 
 the land is maintained about the same from century to 
 century. The preservation of this equilibrium in the 
 midst of constant changes is secured by the same all- 
 wise and all-powerful Providence that preserves the uni- 
 versal constitution of the atmosphere, as noticed in 85, 
 Part II. This appears very wonderful when we reflect 
 that the earth is essentially a molten ball covered with a 
 hard crust, which has vent-holes communicating with the 
 internal fires, and contains vast quantities of water in its 
 depressions. 
 
 418. Present Activity of the Agencies Producing 
 Change. The causes of the present changes in the earth 
 were brought to view in 172, and were there stated to 
 be the same as have been in action in the different ages 
 of the earth's formation. All of them have been in op- 
 eration from the first except one, that is, life, which was 
 introduced upon the stage after the long periods of the 
 Azoic age were passed? An interesting question arises 
 in regard to the degree of activity of these agencies at 
 the present time. Lyell and some others claim that they 
 are as active now as they ever were ; but the evidences 
 in favor of the opposite opinion are very decisive. They 
 surely are not as strongly at work now as they were 
 when they raised up the lofty mountains, or when, in the 
 Azoic age, the crust of the earth was solidifying at the 
 first, and the germs of the continents were forming. 
 
 419. Historic and Human Periods. What is called the 
 
AGE OF MAN. 309 
 
 Human period covers the whole age of Man, but the His- 
 toric period does not. What purports to be the early 
 history of many of the old nations is made up of tradi- 
 tions, which are far from being reliable. Real history, 
 with the exception of the inspired history of the Bible, 
 goes but a little way back in the case of any ancient na- 
 tion. " Milton did not scruple to declare," says Hume, 
 " that the skirmishes of kites or crows as much merited 
 a particular narrative as the confused transactions and 
 battles of the Saxon Heptarchy." But the study of the 
 remains of a people may be carried far back into the 
 past, beyond the beginning of that degree of civilization 
 which is necessary to authentic history, and may give us 
 valuable results. It is by such study alone that we can 
 acquire a knowledge of ancient nations in their savage 
 or barbaric state. 
 
 420. Stone, Bronze, and Iron Ages of Man. In mark- 
 ing the progress of man by means of the remains of his 
 implements, weapons, ornaments, etc., the materials 
 which he has used in making them have been consid- 
 ered as denoting three stages. In the first and rudest 
 condition we have the Stone age, when stone was the 
 material from which were shapen such implements as 
 hammers, axes, chisels, and arrow-heads. In Fig. 179 (p. 
 310) are represented some of these early stone imple- 
 ments gathered from various quarters, all of them exhib- 
 iting a striking similarity, but some of them being a lit- 
 tle more elaborate than the others. Those at 1 and 2 
 are from the Valley of the Somme, in France ; at 3, 4, 
 and 5, from England ; at 6, 7, and 8, from Canada ; and 
 at 9 and 10, from Scandinavia. Quite an advance upon 
 this is the Bronze age, for there are more thought and 
 skill shown in melting metals together for the making 
 of implements than in the bare shaping of stone. Cop- 
 per was the chief metal of this age. Last of all comes 
 the Iron age, in which the excellence of iron above all 
 other metals for the manufacture of tools and weapons is 
 
310 
 
 GEOLOGY. 
 
 Fig. 179. 
 
 recognized, the advance in thought and contrivance hav- 
 ing enabled man to discover the art of preparing it, by 
 various smelting processes, for this purpose. It is curious 
 to notice how each of these ages has its peculiar style 
 of ornaments, dwellings, etc. There is no literature, and 
 therefore no history, in so rude a condition as that of the 
 Stone age, and almost none in the Bronze; but when a 
 nation or tribe is so far advanced in the arts as to work 
 iron, there is a literature, small at first, but increasing 
 with every advance in the arts of civilization. 
 
 421. Animals. In the age just previous to the age of 
 Man brute force held sway in the animal kingdom. It 
 was fitting, therefore, that as the reign of intellect in the 
 world was ushered in, such monsters as the megatheri- 
 ums, mammoths, mastodons, etc., should drop out of ex- 
 istence, and that the animals so useful to man, and so 
 easily controlled by him, as the ox, the horse, the sheep, 
 etc., should appear upon the earth in such abundance. 
 The line of separation between this and the Terrace pe- 
 riod in regard to animals is not a fixed and definite one. 
 It is not so even in regard to the Mammalia. Some ex- 
 isting now began their existence in the Terrace period, 
 
AGE OF MAN. 311 
 
 but there is a difference of opinion as to how many of 
 them did so. There are more of insects and birds in the 
 present age than in any previous one, but not so many 
 mammals as in the Mammalian age, or reptiles as in 
 the Reptilian age. Some animals have become extinct 
 within the memory of man. Outlines of three of them 
 are given in Fig. 180 (p. 312). The shortest one, the 
 Dodo, which lived in Mauritius and other adjoining isl- 
 ands, was a heavy, clumsy bird, covered with loose, 
 downy feathers, and having imperfect wings. It weighed 
 about fifty pounds. The earlier voyagers saw it, and 
 made sketches of it; but after the possession of the isl- 
 and of Mauritius by the French in 1712 it was no longer 
 known, and one or two heads and feet of this bird are 
 all that remain of it in the cabinets of Europe. The tall- 
 est figure is an outline of the Dinornis elephantoides of 
 New Zealand, exceeding the ostrich in size. The name 
 comes from two Greek words, demos, terrible, and ornis, 
 bird. The outline on the right represents another spe- 
 cies, the Dinornis ingens. Bones have been found in 
 Madagascar similar to those of these birds, and quite as 
 large, and with them some egg-shells. The bird to 
 which they belonged has been called ^Epiornis maxi- 
 mus. Its egg was over a foot in diameter, and equaled 
 148 hen's eggs and 50,000 humming-bird's eggs in size. 
 422. Man One Species. Although some few physiolo- 
 gists hold an opposite opinion, the evidence is very de- 
 cided that all the varieties of the human race belong to 
 one species, as is declared in the Bible. As this evi- 
 dence is brought out quite fully in my " Human Physiol- 
 ogy," I will not go into details here. Suffice it to say 
 now, that the resemblance, we may say identity, of the 
 races of men in all essential physical characteristics, and 
 especially in those which are mental, is unmistakable, 
 and that all the varieties can be accounted for from the 
 influence of circumstances, which, indeed, acting also 
 upon other animals inferior to man, but every where ac- 
 
GEOLOGY. 
 
 Fig. ISO. 
 
 companying him, as dogs, horses, etc., have produced in 
 them somewhat similar results. 
 
 423. Man's Place in Nature. The grand difference be- 
 
AGE OF MAN. 313 
 
 tween man and other animals is one of kind, and not of 
 degree only. He is not merely the highest of a series 
 of animals, as some assert, but he possesses certain qual- 
 ities that do not belong in any degree to the animals be- 
 low him. He stands in some respects alone. In phys- 
 ical structure he is, indeed, allied to other animals, be- 
 cause he lives amid the same material circumstances, 
 and has similar bodily wants. These relations with oth- 
 er things make it also necessary that he should have 
 similar instincts, and, to some extent, similar thoughts 
 and reasonings, for brutes do have a lower order of 
 reasoning that is, they draw simple inferences. But 
 here the resemblance stops. There is a certain depart- 
 ment of mind which belongs exclusively to man, and sep- 
 arates him by an impassable gulf from other animals. It 
 is the power of abstract or general reasoning that distin- 
 guishes the mind of man from that of the brute. No 
 brute, however much he may know, can ever himself 
 either discover, or receive by instruction, any general 
 principle. It is this power that gives man the knowl- 
 edge of the existence of a great First Cause, and of the 
 difference between right and wrong, and that introduces 
 him into a sphere of thought and feeling which he occu- 
 pies in common with the angels, and with the Creator 
 himself. It is this which makes him " a living soul" It 
 is from this that he is said to be created in the image of 
 God. From this come all his endless contrivance in im- 
 plements and machinery, his attainments in science, and 
 his construction of language. This subject, thus briefly 
 noticed here, is fully treated in my " Human Physiology." 
 424. A Supposition. It is the idea of some that, as 
 man is the present culmination of the animal kingdom, 
 there is still to be an onward progress, and that some 
 other being of a higher order even than man will, after 
 a while, appear upon the scene. There would be some 
 reason for this expectation if there had been a regular 
 gradation from the first dawn of life in the Silurian age, 
 
 O 
 
314 GEOLOGY. 
 
 evolving man at last at the summit of the series, the dif- 
 ference between him and the highest of other animals 
 being only in degree. But there is no such regularity 
 of gradation, and man is not merely the highest in grade 
 of all animals, but he differs from them in the possession 
 of mental attributes, that ally him with the Infinite, and 
 force upon us the conviction that the earth was made for 
 him, and that he alone is the end of its creation. 
 
 CHAPTER XX. 
 
 CONCLUDING OBSERVATIONS. 
 
 425. Geology and Astronomy Compared. In Astrono- 
 my we take into consideration systems of planets which 
 are at immense distances from each other, but in Geol- 
 ogy our view is confined to a single planet, and that a 
 comparatively small one. In the study of Astronomy 
 we have only the vast and the grand before us, and 
 there is nothing small, or even moderate in size, much 
 less minute ; but in Geology we have a combination of 
 the vast and the small, so that the study has more of 
 the elements of interest in it than Astronomy presents. 
 While conceptions of grandeur are sufficiently awaken- 
 ed by some of the extended movements of continent- 
 making, much of the subject lies directly under our feet, 
 and invites the most familiar examination. The interest 
 is enhanced when we see that even operations so minute 
 as to call for the microscope in their investigation have 
 been concerned in laying down strata of immense extent 
 and thickness, in the building up of continents, and that 
 these operations are in some degree still going on. Be- 
 sides, the fact that it is our earth that we examine in 
 its vast stony leaves that all those multiform processes 
 which have occupied long ages were constructing a hab- 
 itation for us, gives to the study an interest which does 
 not attach to the study of other planets. 
 
CONCLUDING OBSERVATIONS. 315 
 
 426. Record of the Rocks and History. In reading 
 history as written by men there is always more or less 
 doubt about its reliability. It is even so with the histo- 
 ry of recent times, but more especially with that of times 
 long gone by, as already alluded to in 419; but the 
 record which the Creator has left in the rocks is a true 
 history. When Geology first unfolded its leaves to the 
 world, it was the idea of some that the animal and vege- 
 table forms found in the strata were the mere images of 
 living things imprinted there, and not actual remains. 
 This most unworthy idea of the Deity's work of creation 
 is not now entertained by any one, but the history folded 
 up in the rocks is universally recognized as a true life- 
 record of past ages. We may sometimes err in read' 
 ing it, or may even fail to decipher it ; but, nevertheless, 
 there is no mistake in this record written by the Infinite 
 and the True. 
 
 427. The Two Divine Records of the Creation. There 
 are two authentic records of the creation of the earth, 
 the one contained in the Bible, and the other inscribed 
 on the rocks. Some scientific men, who do not absolute- 
 ly deny the truth of the Bible, seem to think that the 
 record developed by their discoveries has a certain and 
 indisputable claim on their faith, which the other record 
 has not. But both are equally authentic, though the ev- 
 idences of authenticity are different in the two cases. It 
 is just as well established that the Bible is a divine rec- 
 ord, the authors being merely agents of the Deity, as 
 that the record in the rocks was made by divine power, 
 heat, water, light, electricity, etc., being the agents by 
 which it was made. These two records can not, then, 
 be inconsistent with each other, though they may be ap- 
 parently so, from a wrong interpretation of the one or 
 the other. In interpreting the account of the earth's cre- 
 ation in the Bible, we must remember that it does not 
 purport to be a scientific account, and therefore common, 
 and not scientific expressions are used. Judged of in a 
 
316 GEOLOGY. 
 
 reasonable manner, it is plain that this account, which is 
 so universally admired for its sublimity, has remarkable 
 coincidences with the record in the rocks. These have 
 been admirably traced out by Hugh Miller, Dana, and 
 others, and I will not dwell upon them here. They are 
 such that every candid mind must conclude, in view of 
 them, with Dana, that " no human mind, in the early age 
 of the world, unless gifted with superhuman intelligence, 
 could have contrived such a scheme." It might have 
 been done by some very wise man of the present time, 
 with the aid of all the knowledge which the researches 
 of Geology could give him, though not with such re- 
 markable skill and sublimity ; but to do it previous to 
 the acquisition of this knowledge would be an impossi- 
 bility. The conclusion, then, is inevitable, that Moses 
 was guided by superhuman power in making the ac- 
 count, or, in other words, was divinely inspired. 
 
 Many geologists think it out of place to notice at all 
 the record in the Bible ; but if it be true that the Deity 
 has given us a written record, it is our duty to examine 
 it thoroughly and candidly, and a reasonable reference 
 to it in a scientific work can not be out of place. It is 
 the dictate of science as well as religion to notice it, and 
 therefore it is done by such eminent men as Dana, Hitch- 
 cock, Hugh Miller, etc. 
 
 428. The Days in the Mosaic Record. That the days 
 which Moses says were occupied by the Creator in the 
 creation were long ages is evident from a comparison of 
 the order of events in that narrative with that revealed 
 by the record of the rocks. But perhaps it is objected 
 that the plain reading of the account would lead any one 
 to believe that the six days of the creation were days of 
 twenty-four hours each. So it would, if not interpreted 
 by the knowledge which Geology has given us, just as 
 we should infer from the language of the Bible that the 
 sun actually rises and sets, as the ecclesiastical court that 
 imprisoned Galileo believed, until Astronomy taught us 
 
CONCLUDING OBSERVATIONS. 317 
 
 otherwise. In regard to the word day, we continually 
 use it in various senses, and Dana states that it is used 
 in five different senses in the Mosaic account of the cre- 
 ation. " < These are,' he says, (1 .) The light' God called 
 the light day,' v. 5 ; (2.) the ' evening and the morning' 
 before the appearance of the sun; (3.) the 'evening and 
 the morning' after the appearance of the sun ; (4.) the 
 hours of light in the twenty-four hours (as well as the 
 whole twenty-four hours), in verse 14 ; and, (5.) in the fol- 
 lowing chapter, at the commencement of another record 
 of creation, the whole period of creation is called ' a day.' 
 The proper meaning of ' evening and morning' in a his- 
 tory of creation is beginning and completion; and in 
 this sense darkness before light is but a common meta- 
 phor." It is a significant fact, I add, that the word day 
 is applied to the three first periods of creation, when as 
 yet the sun had not appeared. There could have been 
 then no such division as our day ; and, indeed, it is ex- 
 pressly stated that this division was introduced in the 
 fourth period or day of creation, for it is said of the 
 lights in the firmament, " Let them be for signs, and for 
 seasons, and for days, and years." 
 
 429. Traditions and Superstitions. There have been 
 many traditions and superstitions in regard to creation, 
 and the origin of various fossils that were accidentally 
 found in the rocks before geology was knowu as a sci- 
 ence. I have here and there referred to some of these. 
 There is an interesting English legend in regard to fos- 
 sil ammonites. These abound in the neighborhood of 
 Whitby, in Yorkshire, and it was a common belief there 
 that they are petrified snakes. The story of their petri- 
 faction is this : As the snakes were so numerous as to 
 prove a great annoyance to the inhabitants, they im- 
 plored their patron saint, St. Hilda, to intercede for their 
 destruction, whereupon she not only prayed their heads 
 off, but prayed them also into stone. Sir Walter Scott 
 thus records the legend in his Marmion : 
 
318 GEOLOGY. 
 
 " And how the nuns of Whitby told 
 How, of countless snakes, each one 
 Was changed into a coil of stone 
 When holy Hilda prayed. 
 Themselves within their sacred bound, 
 Their stony folds had often found." 
 
 So lately was this superstition current, that the author 
 of a modern scientific work relates that a sharp dealer, 
 who was requested by his customers to supply them 
 with some of the creatures that had escaped that part 
 of St. Hilda's prayer which de- 
 stroyed their heads, affixed to 
 the fossils some heads of plaster 
 of Paris suitably colored. He 
 had a thriving trade till it was 
 upset by some officious geolo- 
 gist. But even now the fossils 
 are sold in Whitby with the ex- 
 tremity of the last whorl filed 
 into the shape of a snake's head, 
 Fi s- 181 - as represented in Fig. 181. 
 
 430. Use of Geology to the Poet and the Painter. Ge- 
 ology is of service to the poet in adding largely to his 
 fund of facts such as are eminently fitted to awaken the 
 sublimest thoughts and feelings, and to give a wide range 
 to the flights of his imagination. It is of use to the paint- 
 er of scenery as anatomy is to the painter of the human 
 form, for it gives us, as we may say, the anatomy of the 
 earth. Besides, it supplies him with many valuable and 
 interesting hints as to the objects upon the earth's surface. 
 
 431. Plan in Earth-development. You have seen, in 
 the course of your study in this book, that the Creator 
 worked from the beginning after a plan, in developing 
 the continents on the crust of the earth, and if we could 
 go down into the depths of the ocean, and examine the 
 irregularities of its floor, we should undoubtedly see the 
 same thing there. What the geologist has shown us in 
 
CONCLUDING OBSERVATIONS. 319 
 
 regard to this plan is like what we see as we look upon 
 a potter as he makes some vessel. We see the general 
 plan developed very soon after he begins to turn the ball 
 of clay, and the minutiae of the plan appear more and 
 more as he proceeds. Just so the investigations of geol- 
 ogists have shown how the continents, at the very com- 
 mencement of their formation, had a shape which looked 
 toward what they now are, and how they were gradual- 
 ly developed, and at length were finished in all the mi- 
 nutiae of their diversification. And I may remark here 
 that each continent had its own plan. While, for exam- 
 ple, the North American continent, as you saw in 267, 
 began with the formation of one long island, Europe was 
 at first a group of islands, which were afterward united 
 together. There was a plan, also, in regard to the ani- 
 mals of the earth. This is seen in the preservation of 
 the four grand divisions of animals from the beginning, 
 through all the changes of genera and species; in the 
 gradual advance from the lower up to the higher forms, 
 through the ages of the earth's growth ; in the introduc- 
 tion of particular forms for special purposes, at certain 
 periods, and in certain localities; and in the final con- 
 summation of the animal kingdom, in which, after all its 
 long line of successions, there was an adaptation of it to 
 the wants of man, who was constituted its ruler. The 
 same may be substantially said of the vegetable kingdom. 
 432. Time in Geological Processes. I have here and 
 there, in previous chapters, given some illustrations of the 
 great lengths of time required for the formation which 
 make up the crust of the earth. You will recollect the 
 calculation of Liebig, noticed in 318, in regard to the 
 formation of coal. Calculations have also been made in 
 regard to the deposition of the strata of rocks, and the 
 estimates for all the formations, from the Azoic down, 
 reach a sum total of over fifty million of years. The es- 
 timates are based upon the rate at which rocks are de- 
 posited and solidified in lakes and seas at the present 
 
320 GEOLOGY. 
 
 time. There is nothing in science which so well im- 
 presses the mind with the truth of the declaration of the 
 Bible, that " one day is with the Lord as a thousand 
 years, and a thousand years as one day." 
 
 433. Minute Agencies. I have brought to your notice 
 in this book many examples of extensive operations in 
 the construction of the earth by minute agencies. It is 
 a very small thing for a coral animal to separate from 
 the water a little carbonate of lime and appropriate it to 
 itself; but multitudes of these animals, at work in the 
 same locality, year after year, for centuries and even 
 ages, lay down thick masses of limestone rock. The case 
 is even stronger with the diatoms, microscopic vegetable 
 organisms which separate silex from its solution in the 
 water and deposit it in thick beds. A large portion of 
 the crust of the earth is, in fact, the result of the aggre- 
 gate labor of minute animals and vegetables. 
 
 434. Disintegration of the Rocks. In the preparation 
 of the earth for the use of man, the disintegration of the 
 rocks has been a prominent process. The soil which he 
 cultivates is, as you have seen, a result of this disintegra- 
 tion. The mud that is carried down the rivers, and de- 
 posited in deltas or on flood-plains, is comminuted rock 
 gathered by the waters from mountains and hills. The 
 ice, in glaciers and icebergs, is continually grinding up 
 the rocks to add to the soil of the earth. A vast work 
 has been done in the past by water, in both its liquid 
 and solid forms, in this preparation of the earth for veg- 
 etation. This was done largely, as you have seen, in the 
 Glacial period ; but the work has always been going on, 
 for water has always been in motion. 
 
 435. Reconstruction. In the building up of the earth 
 there has been a vast amount of reconstruction. The 
 rocks of which the crust of the earth is composed are 
 made, to a very great extent, of materials derived from 
 the ruins of rocks previously made ; and often the ma- 
 terials have been used over and over again. Disintegra- 
 
CONCLUDING OBSERVATIONS. 321 
 
 tion, then, has not been of use solely or chiefly in pre- 
 paring the soil for vegetation. Its principal use has 
 been to procure the proper arrangement and condition 
 of the earth's crust. You have seen how largely, in 
 some cases, denudation has been carried on. This is 
 chiefly for the purpose of removing the material to local- 
 ities where it is required. It is by this reconstruction, 
 so extensively prosecuted, that the proper diversification 
 of the surface of the earth has been effected. 
 
 436. Mechanical, Chemical, and Vital Agencies. In all 
 these disintegrations and reconstructions you see a great 
 interplay of mechanical, chemical, and vital forces. I 
 will cite here a single example. Carbonate of lime, in 
 the forms of limestone, chalk, and marble, enters largely 
 into the structure of the crust of the earth ; but water is 
 continually dissolving some of this as it finds it in the 
 rocks, and so the ocean is kept supplied with it. This is 
 a chemical operation, the carbonic acid in the water en- 
 abling it to dissolve considerable of the carbonate of 
 lime. Then, following it to the ocean, shell-animals there 
 gather it to make their shells, or coral animals to make 
 their skeletons. This is a vital operation, for in the bod- 
 ies of these animals, by a vital power, the carbonate of 
 lime is separated from the water in which it is dissolved, 
 and is deposited in a solid form. Then, by a mechanical 
 operation, these shells and skeletons become massed into 
 solid rock. 
 
 437. The Atmosphere. One of the most signal exam- 
 ples of the interplay above referred to is seen in the re- 
 lations which the atmosphere bears to the earth that it 
 envelops like a robe. Before the Carboniferous age it 
 was a very different atmosphere from what it is now. 
 It was then highly charged with carbonic acid gas, which 
 is carbon, or charcoal, united with oxygen. Now this 
 excess of carbon in the air was brought down in the 
 Carboniferous age, and lodged in the bowels of the earth, 
 as coal, in immense stores, for the future use of man. 
 
 O2 
 
322 GEOLOGY. 
 
 Observe how the mechanical, chemical, and vital forces 
 were in operation here. The carbon of the air was made 
 a part of the wood in the enormous vegetation of the 
 Carboniferous era, through the vital and chemical action 
 of the leaves (81, Part II.). Then, by chemical and 
 mechanical operations together, this wood was accumu- 
 lated under strata and changed into coal. The same op- 
 erations are going on now, but not to any thing like the 
 extent that they did in the Coal-making age. For ages, 
 then, we may say, the coal which mankind are now burn- 
 ing was stowed away in the atmosphere, unseen in its 
 gaseous union with oxygen, and at the proper time it 
 was brought down, and stowed in solid form in the bow- 
 els of the earth, ready for man's use. 
 
 438. Circulation of Matter. You see that by the forces 
 which I have mentioned a large portion of the matter in 
 the world is in constant motion, water being the chief, 
 but not the only agent by which the motion is kept up. 
 More of it was in circulation in former ages, when the 
 continents were in process of formation, than there is 
 now, when they are, in a certain sense, completed. There 
 is enough of it now remaining quiet to give " the founda- 
 tions of the earth" stability, and the great object of the 
 present circulation of matter is to keep up the operations 
 necessary to make the earth a fit habitation for man. 
 
 439. Exertion of Creative Power. It is the notion of 
 some that the Creator put a certain amount of matter 
 into this ball that we call earth, and then left it, under 
 the operation of certain laws or tendencies, to work out 
 all the results which we see. In other words, the ma- 
 chinery, mechanical, chemical, and vital, was wound up, 
 so to speak,, in the beginning, and has not been touched 
 since by the creative hand. That there have been no 
 additions to the matter in this world since it was first 
 launched into space is probably true ; but that creative 
 power has often been exercised in giving new properties 
 and tendencies to matter there is the most decisive evi- 
 
CONCLUDING OBSEEVATIONS. 323 
 
 dence. Geology reveals the foot that there was once a 
 long age in which there was no life, vegetable or animal, 
 upon the earth. After this was passed life was created 
 that is, by creative power there were given to portions 
 of matter properties which matter of itself can never orig- 
 inate. In fact, every new species was an independent 
 creation. To assert, as some have done, that there never 
 was any creative power exerted, and that all we see is 
 the result of the fortuitous concourse of atoms, is a folly 
 w r hich does not merit a moment's notice. 
 
 440. Development Theory. There is a class of un- 
 founded theories that have been broached from time to 
 time in regard to the origin of species, all of them bear- 
 ing essentially the same character. Among these, one 
 recently brought out by Darwin, called the development 
 theory, is just now attracting much notice. He supposes 
 that, at the outset, there was " a breathing of life into a 
 few forms, or one form," and that all the living forms 
 which we see were evolved from this beginning by what 
 he calls " natural selection in the struggle for existence." 
 He admits, therefore, a divine creation of life at the first, 
 but claims that the development of all living forms after 
 this was directed by chance and Nature. All species, in 
 his view, came from mere varieties that were started in 
 this " struggle." In evolving thus one species from an- 
 other, it is supposed that there were intermediate forms, 
 and that much time was required for the passage through 
 the gradations. Unfortunately for this part* of the the- 
 ory, geology steps in with a most complete refutation 
 from its life-record in the rocks. Not a single interme- 
 diate form has been found in all this record. If they 
 had ever existed they must have been found, and that 
 abundantly in the midst of the multitude of species that 
 appear. The changes demanded by this theory in con- 
 verting one species into another are great changes. The 
 matter is well stated by Page thus : " Given the scales, 
 fins, and gills of a fish what the conditions, and what 
 
324 GEOLOGY. 
 
 the amount of time necessary to transmute them into the 
 scutes, paddles, and lungs of a marine reptile ? Given 
 the scutes, membranous forearms, and stomach of a flying 
 reptile what the phases of change, and what the amount 
 of time required for their transformation into the feath- 
 ers, wings, and gizzard of a bird ? Or, given the four 
 hands, with partially opposable thumbs, the low facial 
 angle, and the jabbering, half-reasoning of a monkey 
 what the force of conditions, and what the term of time 
 for their development into the two-handed dexterity, the 
 erect aspect, and the eloquent ratiocinations of a philoso- 
 pher of the nineteenth century ?" 
 
 There are many fundamental objections to this theory, 
 but this is not the place for a full notice of them. 
 
 441. Creation of Man. Such writers as Darwin and 
 Huxley seem to think of creation as only a creation of 
 material forms, and do not indulge in the least the idea 
 of a spiritual creation. But, in truth, the grand event in 
 the successive creations of which this earth has been the 
 scene is the creation of a living SOUL. Man is not a mere 
 congeries of living organs, endued with certain proper- 
 ties, but a spiritual existence connected with such a con- 
 geries. Now, that this soul was created as really as the 
 congeries of organs with which it is united appears from 
 two facts : 1. It has certain attributes which, as stated 
 in 423, show that it is to some extent different, not 
 merely in degree, but in kind, from the mind of brutes, 
 and therefore had an independent origin. Not only is 
 there no proof that the mind of man was generated from 
 the mind of a monkey, as claimed by Huxley, but there 
 is positive proof to the contrary in this radical differ- 
 ence. 2. This proof is enhanced by the fact that there 
 is no difference in brain that corresponds at all with this 
 mental difference. This utterly refutes the materialistic 
 doctrine that mind is a mere product of matter, and that 
 the differences of mind come from differences in material 
 organization ; for, if this were so, we should rightly ex- 
 
CONCLUDING OBSERVATIONS. 325 
 
 i 
 
 pect (as I have stated in my "Human Physiology," 523) 
 that, as the mind of man is specifically different from that 
 of the highest of the inferior animals, there would be a 
 specific difference in the brain. The fact that there is no 
 such difference shows that the mind of man is, in a cer- 
 tain sense, independent of material organization, and was 
 a separate creation, though their connection establishes 
 an intimate mutual dependence in man's present exist- 
 ence in this world. What folly, then, is the doctrine of 
 a " science, falsely so called," which places man only a 
 little above the monkeys, when the Creator has declared 
 in his Word that he " made him a little lower than the 
 angels," and a true science agrees with the declaration ! 
 
QUESTIONS. 
 
 [The numbers refer to the pages.] 
 
 CHAPTER I. 
 
 9. What is said of the forms of minerals? In what sense are all 
 minerals solid ? Illustrate the relation which heat has to the forms 
 of matter. 
 
 10. What are the three kinds of substances that are not mineral? 
 State what is said about the lifeless period of the earth. 
 
 11. What is said about the introduction of life ? What of the dif- 
 ferent results of chemical and of vital action ? Explain what is called 
 decay. Give in full the illustration in regard to the egg. 
 
 12. What is said of mineral matter in regard to organic substances? 
 Of what materials have many rocks been made ? What is said of 
 carbonate of lime ? What of the flinty rocks ? 
 
 13. Give examples of simple minerals. What metals are never 
 found uncombined with other elements? What metals are found 
 both native and in combination ? With what are they combined ? 
 What is said of oxygen ? Of hydrogen ? Of chlorine ? Of sulphur 
 and carbon ? What is said of the different degrees in which miner- 
 als are compound ? Mention the composition of mica and of lapis 
 lazuli. 
 
 14. What is said of granite as a mixture of mineral compounds ? 
 State the relations of Mineralogy, Chemistry, and Geology. 
 
 CHAPTER II. 
 
 14. What takes place in crystallization ? What are familiar exam- 
 ples of crystals ? What is the arrangement of the crystals of mica ? 
 
 15. What is said of perfect and imperfect crystallization? What 
 is an octahedron ? What is said of the sizes of crystals? 
 
 16. State fully the difference between the mode of crystallization 
 and of vital growth. What is said of crystals with curved lines ? 
 What of spherical forms in some rocks ? What of the arrangements 
 of crystals ? 
 
 17. What is said of the manner in which mineral matter is depos- 
 ited in living substances? What vegetable substances assume crys- 
 
328 QUESTIONS. 
 
 talline forms ? Under what circumstances do they do this ? What 
 is said of forming crystals by deposit from solution ? 
 
 18. Explain the formation of frost and dew. Give examples of 
 the conversion of liquids and gases into crystals. What is said of the 
 production of crystals by the influence of heat ? What of the water 
 of crystallization ? What is an amorphous mineral ? What a di- 
 morphous mineral ? 
 
 19. What is said of the arrangement of crystals? What of the 
 crystals of common salt? What arrangements are there in rocks 
 that are somewhat like crystallization ? What is cleavage ? What 
 are some of its different modes ? 
 
 20. What is said of cleavage in quartz? What are primary forms? 
 How many are there ? Into how many classes are they divided ? 
 What are the crystals of the first class ? What is a rhomb ? What 
 an octahedron ? What a dodecahedron ? 
 
 21. Show how the cube may be converted into the octahedron by 
 cleavage. Show how the octahedron can be converted into the cube. 
 What are secondary forms ? In what two ways are they produced 
 in nature ? Illustrate the mode by addition. 
 
 22. What is said of constancy in the forms of crystals? What of 
 symmetry ? 
 
 22. Illustrate the analogy between the symmetry of the mineral 
 and that of the living world. 
 
 CHAPTER III. 
 
 23. What are the four grand elements of which animal and vege- 
 table substances are composed ? What is said of the diffusion of car- 
 bon ? What constitutes the diamond ? 
 
 24. How can the diamond be proved to be pure carbon ? How 
 does it differ from charcoal and anthracite ? What is said of the col- 
 oring of diamonds? What are the qualities of diamonds? What is 
 said of their size ? What are the meaning and origin of the word 
 carat ? 
 
 25. What is said of the cost of diamonds ? What of the art of cut- 
 ting them ? What of the expense of the process ? What of the uses 
 of the diamond ? 
 
 26. What are the chief localities in which diamonds are found ? 
 What is said of the modes of collecting them ? What is the compo- 
 sition of graphite ? What are its properties ? What its uses ? How 
 is it prepared for use in pencils ? What is the difference in com- 
 position between bituminous and non-bituminous coal ? What gas is 
 produced from bituminous coal ? 
 
 27. What is the blue flame of imperfectly burning anthracite ? How 
 
QUESTIONS. 329 
 
 is illuminating gas obtained from bituminous coal ? What is coke ? 
 How is it supposed that anthracite coal was produced? How is it 
 like coke ? How does it differ from it ? What is its ordinary com- 
 position ? From what does redness in the ash come ? What is said 
 of slag ? Why do oyster-shells thrown into a coal fire remove the 
 slag or clinker ? What is said of certain uses to which anthracite is 
 sometimes applied ? 
 
 28. What is said of the varieties of bituminous coal? What of the 
 mineral called jet ? What is lignite ? What proofs are there that 
 coal is of vegetable origin ? 
 
 29. How does carbon as it is in wood differ from carbon as it is in 
 coal ? Give the comparison in relation to its combination in wood. 
 Give in full what is stated in regard to the change in producing coal. 
 What is peat, and how is it made ? 
 
 30. What is said of the depth and extent of peat beds ? What of 
 the diffusion of coal in the earth ? What is amber ? What are its 
 properties ? What its uses ? What is said of specimens of it and 
 imitations of them ? 
 
 31. How are the different kinds of bitumen produced ? What is 
 said of asphaltum ? What of petroleum ? 
 
 32. What of naphtha ? What is the composition of carbonic acid 
 gr-s? What are its qualities? From what sources is it supplied to 
 the atmosphere? How is its undue accumulation in the atmosphere 
 prevented ? What is said of localities where it is produced in large 
 amount ? State in full what is said of its agency in relation to lime- 
 stone. What is said of the natural production of illuminating gas in 
 some localities ? 
 
 CHAPTER IV. 
 
 33. What is said of the crystallization of sulphur? What of its lo- 
 calities ? From what ores is much of our sulphur obtained ? What 
 are some of its uses ? 
 
 34. What is the common iron pyrites, and why is it so called? 
 What are the forms of its crystals ? What mistake is often made 
 about it? How is it distinguished from gold? What use is made of 
 it ? What are the two other kinds of iron pyrites mentioned ? What 
 is said of copper pyrites ? What is copper glance? What is said of 
 a sulphuret of a very compound character? 
 
 35. What is galena? What is said of it? In what parts of the 
 United States is it found abundantly ? What is said of the sulphuret 
 of silver ? What of the sulphuret of antimony ? What of the sulphu- 
 rets of arsenic ? 
 
 36. What of the sulphuret of mercury ? What of the sulphuret of 
 
330 QUESTIONS. 
 
 zinc ? Give the names and composition of the three vitriols. How 
 does a sulphate differ from a sulphuret? How are these three sul- 
 phates produced from the sulphurets of the same metals ? What is 
 copperas ? What are its uses ? What is said of sulphate of lead ? 
 
 37. What is the composition of gypsum ? What are its properties? 
 What is said of some of its forms ? What is anhydrous gypsum ? 
 What is said of the gypsum found in the Mammoth Cave of Ken- 
 tucky ? State the case related by Prof. Hitchcock, and the mode of 
 detecting the- error indicated. 
 
 38. What is said of the sulphates of magnesia and soda? What 
 of the sulphate of baryta ? What of sulphuric and sulphurous acids ? 
 What of sulphureted hydrogen ? 
 
 CHAPTER V. 
 
 39. What are native metals ? To what is the term ores usually ap- 
 plied ? In what different senses is it used ? What is said of the po- 
 sitions and associations of ores ? 
 
 40. Illustrate the simplest method of obtaining metals from ores. 
 Illustrate the other method mentioned. What is the gangue of an 
 ore ? What is the process termed washing ? Illustrate the operation 
 of fluxes. What are the most common ores of iron ? What is said 
 of them as colorers of rocks and soil ? 
 
 41. What is said of meteoric iron? What of magnetic iron ore? 
 What of hematite ? What of brown iron ore ? 
 
 42. What of chromic iron ? What of carbonate of iron ? Under 
 what circumstances is native copper found ? What is said of finding 
 silver with it ? Where are famous copper mines ? What is said of 
 the copper region of Lake Superior ? 
 
 43. How was the copper produced in that region ? What is said 
 of the oxyds of copper ? How many carbonates of copper are there ? 
 What is said of the one called malachite ? What of the silicate of 
 copper? What of native lead? What is red lead? What white? 
 What chrome yellow ? What is said of tin and its ores ? 
 
 44. What is said of zinc and its ores ? What of antimony and its 
 compounds ? What of the ores of cobalt ? What of nickel and its 
 ores ? What of bismuth and its compounds ? 
 
 45. What is said of the ores of manganese ? What are the proper- 
 ties of mercury ? What is related of its discovery ? Why is it called 
 quicksilver ? How is its purity estimated by the miners ? What are 
 its uses ? 
 
 46. In what various conditions and combinations is silver found ? 
 In what states is gold found ? What is the only compound that has 
 yet been met with ? How is gold distinguished from iron and copper 
 
QUESTIONS. 331 
 
 pyrites ? In what different forms is native gold found ? What is 
 said of some of its localities ? 
 
 47. What is said of the amount of gold obtained from Australia and 
 the United States ? What of the modes of obtaining gold ? What 
 of the sorting of gold by natural operations ? Explain the operation 
 by which a "pocket" of gold is formed. 
 
 48. Describe the manner of effecting a large "washing" in the 
 search for gold. What are the quantities of gold that make it so use- 
 ful ? What is said of gilding ? What of the alloys of gold ? With 
 what is platinum generally found associated ? What are its proper- 
 ties? 
 
 49. What is said of the metals found in company with platinum ? 
 
 CHAPTER VI. 
 
 49. What are oxy-salts ? What are haloid salts, and why are they 
 so called ? 
 
 50. What is saltpetre ? What is said of its production in nature 
 in different localities ? Of what use is it in the composition of gun- 
 powder? What is said of the nitrate of soda? What is the compo- 
 sition of common salt ? What is said of its diffusion in the earth ? 
 Under what circumstances is water in seas or lakes exceedingly salt ? 
 Where are there famous salt mines ? What is said of the mines of 
 Cracow ? Where are there hills of salt ? How is salt obtained in 
 this country ? 
 
 51. What is the composition of borax? What is said of the most 
 noted locality of it? Under what circumstances is boracic acid 
 evolved ? What are the different forms of carbonate of lime ? What 
 is said of its diffusion in the earth ? How is it distinguished from oth- 
 er minerals that resemble it? What effect does heat produce upon 
 it? What is hydraulic lime ? 
 
 52. What is marl? What calcareous tufa? What fact is stated 
 about chalk ? To what is the name calcareous spar applied ? What 
 is said of some of its varieties ? 
 
 53. What is oolitic marble ? Explain the formation of stalactites 
 and stalagmites. What is said of Weyer's Cave ? What of the mag- 
 nesian carbonate of lime? 
 
 54. State in full what is said of fluor spar. What is said of apa- 
 tite ? What of the salts of magnesia ? 
 
 55. What is said of the chlorid of ammonium ? What is the com- 
 position of common alum ? What is said of other alums? What of 
 the feather alum ? What of the phosphates of alumina ? 
 
332 QUESTIONS. 
 
 CHAPTER VII. 
 
 66. What are most of the earthy minerals ? What is a silicate ? 
 What is said of the compound character of most earthy minerals ? 
 What are some of them which are very simple ? What proportion 
 does silica constitute of the earth's crust ? What is quartz ? What 
 is said of silica in mica and feldspar ? 
 
 57. What are the properties of silica? What is said of its different 
 forms and conditions ? What of its being colored ? What is said of 
 flint ? What of the three varieties of quartz ? 
 
 58. What is said of the crystals of quartz ? What of rock crystal ? 
 What of the amethyst ? What of other crystals of quartz ? 
 
 59. What is chalcedony ? What is said of the variety called car- 
 nelian? What of the agate? What of the onyx? What of the cat's 
 eye ? What is the composition of opal ? What is said of its varie- 
 ties ? What is said of silica in solution ? 
 
 60. What are the two states in which silica exists? State in full 
 what is said of the changes from the one state into the other. Ex- 
 plain petrifaction with silica. 
 
 61 . What is said of the silicates of magnesia ? What of the varie- 
 ties of talc ? What of serpentine ? What gave this name to it ? 
 What is verd antique ? What is said of chlorite ? 
 
 62. What is said of pyroxene ? What of hornblende ? What of 
 its two remarkable varieties, asbestos and amianthus? What is the 
 composition of alumina ? What is said of its base ? What is emery ? 
 
 63. What is sapphire ? What is said of clay ? What of the min- 
 eral called spinel ? What of the silicates of alumina ? What of feld- 
 spar ? What are its varieties in color and appearance ? 
 
 64. What is kaolin ? What is said of albite ? What of labrador- 
 ite ? What is the composition of mica ? What are its qualities ? 
 What its uses ? 
 
 65. What is said of garnet? What of tourmaline ? What of the 
 composition of topaz ? What of its use in jewelry ? 
 
 66. What is said of the composition of lapis lazuli ? What are 
 beryls and emeralds ? What is said of their size and their value ? 
 What of zircon? 
 
 CHAPTER VIII. 
 
 76. What is the relation of mineralogy to geology ? What is the 
 derivation of the word geology ? In what senses does the geologist 
 use the term rock? How many elementary substances are there? 
 Name those which enter in any extent into the composition of the 
 rocks. What is said of the amount of oxygen in the earth's crust ? 
 
 68. What is said of sulphur as a component of rocks ? What of 
 
QUESTIONS. 333 
 
 hydrogen ? State in full what is said of compounds existing in the 
 rocks. What examples are given of incomplete crystalline structure 
 in rocks ? 
 
 69. What is said of the structure of sandstone ? What of rocks 
 composed of a single mineral ? What is a pudding-stone ? What a 
 breccia ? 
 
 70. What is said of stratified and unstratified rocks? Give in full 
 what is said of silicious, argillaceous, and calcareous rocks. How is 
 sulphuric acid used as a test in examining rocks ? 
 
 71. What is the composition of granite? What is syenite? What 
 porphyritic granite ? What is said of the colors of granite ? What 
 is said of its dissemination in the earth ? 
 
 72. What is said of the uses of granite ? What of the presence of 
 pyrites in it ? What of the selection of granite for building ? State 
 in full what is said of gneiss. 
 
 73. What is said of the terms slate, shale, and schist? What of 
 mica schist? Of hornblende slate? Of talcose slate ? Of clay slate? 
 What is granite rock? What is said of its varieties? What of its 
 uses? 
 
 74. State in full what is said about sandstones. What is the mean- 
 ing of the word trap ? 
 
 75. What is greenstone ? What basalt ? What trachyte ? What 
 clinkstone ? What is said of the term porphyry ? What of the term 
 amygdaloid? What form do the trappean rocks tend to assume? 
 What examples are given of this? 
 
 76. Describe the ordinary structure of the trappean columns. What 
 is said of the basaltic dike in North Carolina ? 
 
 77. What of Titan's Piazza? State in full what is said of the trap- 
 pean rocks in this country. What is lava ? What are the two classes 
 of lava ? 
 
 78. What is scoria? What is pumice? What its uses? What 
 are obsidian and pitchstone ? What is said of the resemblance of 
 lavas to the trappean rocks ? 
 
 CHAPTER IX. 
 
 79. What is said of the substances of which the earth is composed? 
 If the surface of the earth were not diversified, what would be the ar- 
 rangement of the water and the air? Give in full what is said of 
 the weight of the earth. What estimates are given of the increase of 
 condensation toward the centre? 
 
 80. Explain what is represented by Fig. 31. 
 
 81. Show how much this figure exaggerates the amount of equato- 
 rial bulging. What influence has this bulging upon the earth's rev- 
 
334 QUESTIONS. 
 
 olution ? What is meant by the crust of the earth ? In what ways 
 has knowledge of it to great depths been obtained ? 
 
 82. What is said of the foundation of this crust? What of its 
 thickness? What is the proportion of land and water on its surface? 
 What is said of the elevations on the earth's crust? What of the de- 
 pressions ? What of the shallows of the ocean ? What of bodies of 
 water between certain portions of land ? 
 
 83. What comparison is made between the equatorial bulging and 
 the mountainous elevations ? What between the elevations and de- 
 pressions ? What is said of the ocean near Newfoundland ? What 
 of the general arrangement of the land? What of its divisions? 
 What of the position of the Atlantic and Pacific Oceans ? 
 
 84. What is said of a certain arrangement of the waters noticed by 
 Guyot ? What of the arrangement of the mountains ? 
 
 85. What is said of their relation to the oceans ? What of varia- 
 tions in the arrangements of chains of mountains ? What as to their 
 prevailing directions ? State in full what is said of volcanoes. What 
 is a plateau ? 
 
 86. What are called lowlands ? Give examples of extensive low- 
 lands. What relations have mountains to plateaus and lowlands? 
 What are table-lands ? Give examples of extensive plateaus. How 
 do these compare in arrangement with what we often see on a small 
 scale ? 
 
 87. State in full what is said of rivers. What is said of lakes? 
 How do mountains affect the fertility of regions? How are winds 
 produced ? Give what is said of the prevalent winds. 
 
 88. State in full what is said of the influence of mountains on the 
 fall of rain, and the consequent difference between America and Eu- 
 rope. What would have been the condition of North America if the 
 Rocky Mountains were on its eastern side and the Appalachians on 
 the western ? What is said of the circulation of water ? 
 
 89. What is said of systematic currents? What comparison is 
 made in regard to the circulation of water ? What is said of the di- 
 versification of the earth's surface ? What of the treasures in the 
 earth's crust ? 
 
 CHAPTER X. 
 
 90. What is said of the apparent discrepancy between the Scripture 
 account of the creation and the ideas of geologists ? In what sense is 
 the word present used in the title of this chapter ? What are the 
 agents of change in the earth ? 
 
 91. State in full what is said of the aqueous and igneous agencies. 
 Illustrate the influence of different degrees of rapidity in the flow of 
 water on the removal of materials. 
 
QUESTIONS. 335 
 
 92. State in full what is said of deposits in rivers and on their bor- 
 ders. 
 
 93. Explain the mode of improving rivers illustrated by Fig. 35. 
 
 94. What is said of deposits in lakes ? State the facts in regard to 
 the Lake of Geneva. What is said of the lakes of our country? 
 
 95. What is a delta, and why is it so named ? Describe the mode 
 of its formation. What is said of bars and islands formed in connec- 
 tion with deltas ? 
 
 96. Why is there no delta at the mouth of the Amazon ? Give in 
 full what is said of the sediment deposited from the Ganges in the 
 Bay of Bengal. What is said of Louisiana, and of the amount of 
 matter brought down by the Mississippi ? 
 
 97. What is said of the extent of deltas? What of the consolida- 
 tion of sediment from rivers into rock ? Give examples of the en- 
 croachment of water upon land. 
 
 98. What is said of the mechanical action of water upon rock? 
 What is said of " Pulpit Rock ?" 
 
 99. Illustrate the erosive work which water does by rubbing one 
 solid against another. What is said of pot-holes? Give the state- 
 ment in regard to Niagara Falls. 
 
 100. What is said of the canons of Colorado ? What of the erosion 
 by the River Simeto ? State in full what is said of the constancy of 
 the action of water in erosions. 
 
 102. How does frost disintegrate rocks ? How do the results differ 
 in hard and soft rocks? What is a talus, and how is it formed? 
 What is said of the sorting of fragments in a talus ? State in full 
 what is said of the chemical action of water on rocks. 
 
 103. Explain weathering. What is said of the Druidical monu- 
 ments ? What of the weathering of hard and of soft rocks? What 
 of weathering in the soil ? 
 
 104. Give the statement about the boulder. What is said of the 
 Loggan stones ? How do the present effects of glaciers and icebergs 
 compare with their effects in past ages ? Why is a glacier said to be 
 a river of ice? 
 
 105. Of what is a glacier made? What are lateral and medial 
 moraines ? Give in full what is said about the termination of a gla- 
 cier. 
 
 107. What is said of the markings and other effects of glaciers ? 
 
 108. Describe the formation of terminal moraines. How are ice- 
 bergs produced ? What is said of their height ? What proportion 
 of an iceberg is above the surface of the water ? 
 
 109. How extensive are some icebergs? What is stated of their 
 numbers ? What is said of their dropping fragments of rock ? What 
 of their dragging and stranding? 
 
336 QUESTIONS. 
 
 110. State in full what is said of the leveling operations of water. 
 What is said of the agency of heat ? 
 
 111. Of what benefit to the earth are volcanoes ? What is the dis- 
 tinction between extinct and active volcanoes ? How is it supposed 
 that an eruption is produced ? Describe the phenomena of an erup- 
 tion. 
 
 112. When was the first eruption of Vesuvius that is on record? 
 What was its condition just before this ? State in full what is said 
 of the burial of Herculaneum and Pompeii. What happened to Ve- 
 suvius in 1822 ? What is the size of Etna ? What is said of its erup- 
 tion in 1669 ? 
 
 113. What does Mantell say of one of Etna's eruptions? 
 
 114. Describe the crater of Kilauea. Where is Tomboro? Give 
 Lyell's description of the effects of one of its eruptions. 
 
 115. Give the facts in regard to Graham's Island. What is said 
 of other volcanic islands ? 
 
 116. Give the statement about an island near Iceland. 
 
 117. How may changes in the temperature of the earth's crust 
 cause earthquakes ? Give Prof. Dana's illustration. What is said of 
 the two vibrations produced by an earthquake ? State the effects of 
 earthquakes. 
 
 118. What is said of solfataras ? What of hot springs? Describe 
 the geysers of Iceland. 
 
 119. Explain their operation. 
 
 120. State in full what is said of sand being moved by wind. 
 
 121. What is said of gradual alterations of levels ? Give the state- 
 ment about the Temple of Jupiter Serapis. 
 
 122. What does Hugh Miller say about the old coast-lines of Scot- 
 land ? State the evidences of a gradual change of level in Sweden 
 and Norway. 
 
 1 23. What is said of organic agencies ? What of changes made by 
 man? 
 
 CHAPTER XI. 
 
 123. What is said of the succession of changes in the construction 
 of the earth's crust ? 
 
 124. What is said of the development of life upon the earth ? Why 
 will what you have learned of present changes help you to understand 
 changes in the past? How does the geologist arrive at his conclu- 
 sions? By what comparisons as to composition does he determine 
 the origin of rocks ? 
 
 125. State the case of the shells found in rock. State the observa- 
 tion made about different rocks that contain shells. State the rea- 
 soning about the pudding-stone. 
 
QUESTIONS. 337 
 
 126. What observations are made by the geologist in regard to 
 tracks, ripples, etc. ? State the case of the slab found in Pottsville. 
 What are the two grand classes of rocks ? What is the construction 
 of stratified rocks ? Why are they called aqueous rocks ? Why fos- 
 siliferous rocks ? 
 
 127. What are metamorphic rocks ? What is the derivation of the 
 name ? What proof is mentioned that heat is the chief agent of met- 
 amorphism ? What is said of the appearance and the formation of 
 unstratified rocks ? 
 
 128. What is the usual difference in position of the stratified and 
 the unstratified rocks ? What is said of trappean rocks ? What is a 
 stratum ? What a stratification ? What are laminae ? What is said 
 of them as seen in shales and micaceous sandstones? 
 
 129. What is said of the deposition of laminae ? How is the term 
 formation used? What are joints and master-joints? 
 
 130. What is said of the regularity of these divisions in the rocks? 
 What is stated about the cliffs of Cayuga Lake? What is cleavage 
 in rocks ? 
 
 131. What is said of the order of succession in the strata? Give 
 the comparison of Phillips. What remarkable fact is stated about 
 the chalk formation ? What is said of flexures of strata? What of 
 the circumstances under which they were produced ? State the 
 comparison in regard to ice. 
 
 132. Illustrate the mode of producing the flexures. What fact 
 bearing on this is related by Lyell ? 
 
 133. What is said of upheavals of strata accompanied by fracture? 
 What of chasms, caverns, and natural bridges ? Illustrate the man- 
 ner in which strata are brought to view by upheavals. 
 
 134. What is true of strata found in a vertical position? Show 
 how strata may be supposed to be horizontal when they are far from it. 
 
 135. Explain dip and strike. Show what anticlinal and synclinal 
 lines are. 
 
 136. Show in detail how strata may be laid down on a map when 
 they outcrop. 
 
 137. Show how the thickness of the strata in the above case may 
 be ascertained. 
 
 138. What is said of the extent of knowledge that can be acquired 
 by such observations as have been detailed ? 
 
 139. Show what are conformable and unconformable strata. What 
 are faults ? 
 
 140. What is denudation ? What is said of the extent of the re- 
 sults effected by it ? State the case illustrating denudation occurring 
 with a fault. 
 
 141 . State the case of the great fault spoken of by Mr. Lesley. 
 
 F 
 
338 QUESTIONS. 
 
 142. Point out the different modes in which mountains have been 
 made. 
 
 143. Mention the three ways in which valleys have been made. 
 Of what materials are volcanoes constructed ? Give the facts in re- 
 gard to Fusiyama. 
 
 145. Indicate the mode of formation of volcanic cones. How are 
 irregularities in their form caused ? What is said of the formation 
 of trappean rocks ? 
 
 146. How is a sunk dike formed ? How a raised dike ? What com- 
 parison is made by Hugh Miller in speaking of the trap dikes about 
 Edinburg ? What is said of East and West Kocks in New Haven ? 
 What does Hugh Miller say about trap scenery ? How were the trap 
 rocks formed? 
 
 147. What is said of the commotion attending their formation ? 
 What is the statement of Hugh Miller and v the criticism upon it? 
 What is said of the pillar-like form often assumed by the trap rocks ? 
 What are veins? What is said of veins in granite? 
 
 148. State what is said of the granite boulder of which a section is 
 given. How do veins differ from dikes ? 
 
 149. What is the vein-stone or gangue ? What is said of the man- 
 ner in which dikes and veins are formed ? What is a lode ? What 
 is drift ? In what parts of the continents does it appear ? By what 
 means was it transported to its localities ? How can it be ascertained 
 where it came from in any case? 
 
 150. What traces of the passage of drift are found? What is said 
 of alternate elevations and subsidences of the earth's crust? What 
 prolonged subsidence is spoken of by Lyell ? What is said of the sub- 
 sidences and elevations of the Coal age ? 
 
 151. By what means are pebbles, sand, and earth produced from 
 rocks ? What is soil ? What may be said of the additions to it from 
 decay ? Is the preparation of soil by disintegration of rock to be re- 
 garded only as a destructive process ? How may earth-worms and 
 ants be considered as geological workers ? 
 
 152. Describe the work of the earth-worms. Describe that of the 
 ants. 
 
 154. Indicate the manner in which coral reefs are built. To what 
 climates are coral animals confined ? Why are there none on the 
 western coast of South America? What is the extent of the reef on 
 the coast of New Holland ? Explain the difference between fringing 
 and barrier reefs. How was Florida made ? 
 
 155. What are atolls and lagoons ? Show how an atoll is formed 
 by means of Figs. 81 and 82. 
 
 156. What is said of the number of coral islands in the Pacific 
 Ocean ? What of the depth to which they reach in the water ? What 
 
QUESTIONS. 339 
 
 of the time occupied in their formation ? What is- said of the forma- 
 tion of limestone rocks from shells ? 
 
 157. What is said of the foraminifera ? What of the agency of 
 minute animals, in comparison with large ones, in forming the earth's 
 crust ? What is stated about the nummulites ? What is oaze, and 
 what is said of it ? 
 
 158. Of what are the limestone strata quarried near Paris com- 
 posed? What did Ehrenberg find in chalk? Mention the observa- 
 tions of Soldani. What is said of silicious shells ? What of the 
 white clay about Richmond ? 
 
 159. What of the tripoli of Germany? What is supposed to be the 
 origin of the flint-stones found in chalk ? What is said of the extent 
 of the agency of silicious animalcules and plants in forming rocks ? 
 What is the nature of diatoms ? What is said of the formation of 
 seas, lakes, and rivers ? What is said of plan in the construction of 
 the earth ? 
 
 160. What is said of life in the different ages of the earth ? What 
 of making out the order of succession in the rocks by the life-record ? 
 
 161. What is said of the resemblances of present living forms to 
 those of the past ? What is the nature of the evidence from the life- 
 record as to the relative ages of the strata ? What is said of the cor- 
 respondence of the evidence in different countries ? Illustrate this 
 by reference to the coal formation. 
 
 162. What are fossils ? What is the origin of the term ? In what 
 different degrees are fossils preserved ? What is said of petrified fos- 
 sils? What of casts of living substances made by some mineral? 
 Why may coal, strictly speaking, be considered a fossil ? State what 
 is said of the preservability of different fossils. 
 
 163. Give in full what is said of the abundance of fossils. Explain 
 the principles on which Cuvier and others have investigated fossils. 
 
 164. Show how these principles are applied by most people to a 
 limited extent. How is skill acquired in applying them ? What is 
 said of their application to vegetables ? What is the derivation of the 
 word Palaeontology? What is said of the general plan of living 
 structures ? 
 
 165. What are the Acrogens, and why are they so named? What 
 are the Gymnogens, and what is the derivation of their name ? What 
 purpose have these and the Acrogens served? 
 
 167. What relations had the Acrogens and Gymnogens to animal 
 life? 
 
 169. What are the Endogens ? What is their chief purpose ? 
 
 170. What is meant by a geological, and what by a zoological 
 agency ? Explain the meaning of the term Endogens. How does 
 the mode of growth in an Exogen differ from that of an Endogen ? 
 
340 QUESTIONS. 
 
 What is the difference in their stems ? What is the use of the Exo- 
 gens ? What is said of the presence of the Endogens and Exogens in 
 the life-record ? What difficulty is there in the study of fossil botany? 
 What error is mentioned as having risen from the scantiness of the 
 evidence ? What is said of the veins in the leaves as furnishing a 
 ground of distinction in the classification of vegetable remains ? 
 
 173. Why is the study of fossil zoology more satisfactory than, that 
 of fossil botany ? Give in full what is stated about Protozoans. 
 
 174. What are the classes of Radiates ? Why are they so called ? 
 State what is said of them. 
 
 176. Why are Mollusks so called? What does this division in- 
 clude ? How far are Mollusks zoological in their relations ? Why 
 are they of great value in geological investigations ? Why are the 
 Articulata so named ? What does this 4ivision include ? What is 
 said of the relations of the Articulata ? What of the variety of their 
 character ? 
 
 177. What are the characteristics of the Vertebrata ? 
 
 178. What is said of the spinal marrow of the Vertebrates ? What 
 are the four grand divisions of this portion of the. animal kingdom ? 
 What is said of the intellectual qualities of the Vertebrata ? What 
 of their relations, geological and zoological ? What of their relations 
 to the higher orders of the vegetable world ? 
 
 179. What is said of the mode of division of the earth's history ? 
 What is Dana's division ? 
 
 180. Give the division of time into five periods, explaining their 
 names. How definite are the boundaries of the ages ? What is said 
 of foreshadowing ? 
 
 181. What examples of foreshadowing are cited ? What is said of 
 the idea on which the ages are named? 
 
 CHAPTER XIII. 
 
 181. What is said of the fused state of the earth? 
 
 182. What of the time occupied in cooling the earth sufficiently to 
 form a crust ? What of the length of time before life appeared on the 
 earth? State in full what is said of the floor of the earth's crust. 
 What were the changes that attended the beginning solidification of 
 the earth's crust? 
 
 183. What agency had denudation in this beginning of the forma- 
 tion of land ? Give Dana's statement in regard to the land formed 
 in the Azoic age. What is said of the extent of the lands that then 
 appeared above the surface of the waters ? 
 
 184. What was the shape of North America in the Azoic age? 
 What does Agassiz say of this island ? How was Europe, in contrast 
 with North America, in this age ? 
 
QUESTIONS. 341 
 
 185. What is said of the thickness of the Azoic strata ? What of 
 the upheavals and flexures of them ? What of the rocks of this age ? 
 What of the temperature of the forming crust? 
 
 186. Give Hugh Miller's description of the commotions attending 
 its formation. 
 
 187. Why could not life exist in this age ? What was the condition 
 of the surface of the land at the end of it ? 
 
 CHAPTER XIV. 
 
 *- 187. Why is it inferred that life was introduced at the beginning 
 of the Silurian age ? 
 
 188. Why is it supposed by some that life was introduced before 
 this ? What reason have we for saying that life was created ? What 
 is said of species ? What are the rocks of this age ? What is said of 
 the rocks at Niagara Falls ? 
 
 189. Why is this called the Silurian age? What is the arrange- 
 ment of the Silurian system in New York ? 
 
 190. What is the geographical distribution of the Silurian rocks, so 
 far as ascertained? State the origin of the copper of Lake Superior. 
 What is said of the salt springs in this country ? 
 
 191. State Dana's way of accounting for the great accumulation 
 of salt in the State of New- York. Trace the comparison in regard 
 to the lagoon. How is the salt obtained from the springs in New 
 York? 
 
 192. How was the gypsum, which abounds in the Silurian forma- 
 tion in New York, produced ? Where gypsum and salt are found to- 
 gether, how are they separated? State in full what is said of "the 
 Silurian beach." 
 
 193. What is said of the traces left by water ? State in full what 
 is said of life in the Silurian age. 
 
 194. What was the condition of the atmosphere in this age ? Show- 
 how the animal world was adapted to it. Give what Agassiz says of 
 this adaptation. What was the source of the carbonaceous matter in 
 the Silurian shales? 
 
 195. What are the Hydrozoa and Bryozoa of this age? What is 
 said of the corals and echinoderms? 
 
 196. What of the chain coral ? What of the crinoids ? 
 
 197. Name the three classes of Mollusks, and state what is said of 
 each. 
 
 198. What are the Brachiopods, and what is said of them ? What 
 is said of the Lingula? Of the Orthoceras? What of the Cephalo- 
 pods in this age, in contrast with the present ? 
 
 199. What is said of the Trilobites? 
 
342 QUESTIONS. 
 
 200. What evidence is there that the climate of this age was quite 
 warm over most of the earth ? What evidence is there that the sun 
 shone clearly then ? 
 
 CHAPTER XV. 
 
 201. What were the rocks formed in the Devonian age? Indicate 
 the extent of the Devonian system in this country. 
 
 202. What is its extent in Europe ? Detail the interesting exam- 
 ple of geological investigation mentioned. How prominent were the 
 coral formations in this age ? Mention the remarkable display of De 
 vonian corals in Kentucky. 
 
 203. What two elegant corals are mentioned as being found in that 
 locality ? What different kinds of rock-making were going on at the 
 same time in the Devonian age ? What is said of Devonian vegeta- 
 tion? 
 
 204. What of Devonian animals ? What of Mollusks ? What of 
 Trilobites ? 
 
 205. What of Crustaceans ? 
 
 206. What is the discovery of Agassiz in regard to the classifica- 
 tion of fishes? Of what value is this to geology? Name the four 
 orders of Agassiz, and state what is said of each. 
 
 207. What is said of the comparative prevalence of these orders in 
 different ages ? Describe the Coccosteus. 
 
 208. Describe the Pterichthys. What is said of the appearance of 
 its remains in the rock ? Why is the Cephalaspis so named ? 
 
 209. Describe the Asterolepis. 
 
 210. What are comprehensive types ? What is said of their compar- 
 ative prevalence in different ages ? What is said of the tails of ancient 
 fishes ? What of the abundance of fishes in the Devonian age? 
 
 211. What of the state in which their remains are often found? 
 What was the condition of the North American continent at the end 
 of the Azoic age ? What at the end of the Silurian ? What addi- 
 tions were made to it in the Devonian ? What results did upheavals 
 in the west and the east produce at the close of this age ? What re- 
 sults where the city of Cincinnati now stands ? 
 
 212. What does Agassiz say of the abundance and richness of Silu- 
 rian remains found in that locality ? What is said of the scenery of 
 the Devonian age ? 
 
 CHAPTER XVI. 
 
 213. How does the name of the age of coal differ from the names 
 of the other ages? What peculiar propriety is there in the name ? 
 
QUESTIONS. 343 
 
 214. What is the estimated amount of coal in all the coal-fields of 
 North America? What of all in Great Britain ? In Belgium ? In 
 France ? What facts are stated about the introduction of anthracite 
 into full use in this country ? What estimate is made of the length 
 of time the coal of this country will last? What statements are 
 made about the extent of coal-fields ? 
 
 215. Describe the arrangement of the carboniferous strata. What 
 are called the coal-measures ? In what way do the rocky strata in 
 these measures differ from other rocks ? Of what practical value is 
 the knowledge of this difference ? What does Hitchcock say on this 
 point ? What is the under-day, and what is said of it ? What is the 
 proportion of coal to rock in the coal-measures ? 
 
 216. What is the sub-carboniferous period? What is the thickness 
 of the floor of the coal-measures laid in this period ? Of what was 
 it made ? What is the relative position of the sub-carboniferous and 
 carboniferous strata ? What similarity of arrangement was there in 
 the Silurian and Devonian ages and the sub-carboniferous period? 
 
 217. In what two respects did this arrangement differ in the sub- 
 carboniferous period from that of the Silurian and Devonian ages ? 
 What is the difference between the burning of wood and the making 
 of charcoal ? Explain the chemistry of the formation of coal. Why 
 is this process called eremacausis ? What is said of the decay of veg- 
 etable matter ? 
 
 218. What is said of the agency of pressure in making coal ? What 
 is the difference between bituminous and non-bituminous coal ? What 
 is the flame of bituminous coal ? What that of imperfectly burning 
 anthracite ? How is it supposed that anthracite was produced from 
 bituminous coal ? How does it differ from coke ? What is said of 
 the vegetable growth from which coal was formed ? 
 
 219. What is said of the accumulation of material for a coal-bed? 
 Describe what took place after all the material was deposited. What 
 is stated about the number of coal-beds ? What does Hugh Miller 
 say of the alternate subsidences and elevations of this age ? 
 
 220. What is said of the impurities of coal? What of the calcula- 
 tions as to the time required for the formation of the coal-measures ? 
 What of the plants whose remains are found in them ? 
 
 221. What is said of the remains of leaves found in the rocks? 
 State the experiments of Professor Goppert. 
 
 222. What is said of the Calamites ? What of Sigillaria and Stig- 
 maria ? 
 
 223. What of the Lepidodendron ? What of the Ferns ? 
 
 224. What of the Conifers ? 
 
 225. What is the general view given of carboniferous vegetation ? 
 
 226. What does Page say of the beauty of this vegetation ? What 
 
344 QUESTIONS, 
 
 is said of leaf-scars ? What was the peculiar condition of the atmos- 
 phere up to the Carboniferous age ? 
 
 227. What change was made in it during that age ? How was it 
 done? State the comparison made in regard to this transfer from 
 the gaseous to the solid state. What is said of the climate of this 
 age ? What was the character of Carboniferous scenery? 
 
 228. What is said of the extent of the successive platforms of vege- 
 tation ? What change occurred in the scene when the accumulated 
 material was submerged for conversion into coal ? What is said of 
 the animals of this age ? 
 
 229. What is said of the coral animals ? What of the crinoids , 
 and sea-urchins ? 
 
 231. What of the Crustaceans? What of the Reptiles? State 
 the facts about the Pottsville reptile. What is said of the fishes ? 
 
 232. State in full what is said of the Lepidosteus and of the gar- 
 pike of the present age. What is said of the Mollusks ? What of 
 the Productus spinulosus ? 
 
 233. What of the Spirifer ? From what does the Permian period 
 get its name ? What is said of the Permian strata in this country ? 
 What of them in Europe ? 
 
 234. What are the Permian rocks in this country? What is said 
 of the Permian limestones of Europe? What was the condition of 
 North America at the end of the age of Coal ? What is said of the 
 disturbances of the coal-measures ? 
 
 235. What is said of the connection of metamorphosis with these 
 disturbances ? What of their being systematic ? What of their rate 
 of movement ? What of certain valuable results of metamorphosis at 
 this time ? What of the debituminization of coal ? What of denuda- 
 tion ? What of the differences of the forms of life in different ages ? 
 
 236. When did vertebrates first appear ? When reptiles ? What 
 class of animals did not appear till after Palaeozoic time ? What is 
 said of the disappearance of animals ? What of the destruction of 
 life at the close of the Carboniferous age ? 
 
 CHAPTER XVII. 
 
 236. What are the divisions of the age of Reptiles? Whence 
 conies the term Triassic ? Whence Jurassic ? 
 
 237. What is said of the term Oolitic ? What of the term Creta- 
 ceous ? What is stated about the Cretaceous system in this country ? 
 State in full what is said of the Triassic rocks. What is said of the 
 localities in which they are the surface rocks ? 
 
 238. Why is this system often called in Europe the Saliferous sys- 
 tem? How is the production of salt there in contrast with its pro- 
 
QUESTIONS. 345 
 
 duction in this country? What is said of Triassic plants? What of 
 Triassic coal ? How did the atmosphere differ from what it was up 
 to the Carboniferous age ? What animals were consequently now 
 introduced ? 
 
 239. What kinds of mammals were introduced ? What kinds of 
 fishes ? What is said of the Mollusks ? What is the Lily Encrinite ? 
 What is said of the Keptiles ? Describe the Labyrinthodon. 
 
 240. What is said of the name Cheirotherium ? What of the teeth 
 of the Labyrinthodon ? 
 
 241. What of the tracks of Triassic animals? What of the slab 
 represented in Fig. 141 ? What of the Brontozoum giganteum ? 
 
 242. What of the track represented in Fig. 143 ? What of the 
 stone fossil book ? 
 
 243. What are some of the notable localities of trap rocks in this 
 country ? As they were thrust up, what effect resulted in the adja- 
 cent rocks? What is said of their systematic arrangement? 
 
 245. What is said of the vegetation of the Triassic period ? State 
 the facts about the Portland dirt-bed. 
 
 246. Give in full what is said of the animals of this age. 
 
 247. What were the most prominent of the mollusks of this pe- 
 riod? What is the class to which they belong, and what are the 
 characteristics of the class ? 
 
 248. What is said of the Ammonites? What of the Belemnites? 
 What of the Ichthyosaurus ? 
 
 249. What of the Plesiosaurus ? 
 
 250. What of the Pterodactyl ? What has been the common opin- 
 ion about the nature of this animal ? What is Agassiz's opinion, and 
 what are his reasons for it ? 
 
 252. What is probably the truth about the flying of the Pterodac- 
 tyl ? What is said of the Dinosaurs ? 
 
 253. What are the rocks of the Cretaceous system in Europe and 
 Asia? What in this country? What is said of the Green-sand? 
 What of chalk? What of the localities of the Cretaceous system ? 
 
 254. How was chalk formed ? Of what is it constituted as shown 
 by the microscope ? What is said of chalk-marks ? What is the act- 
 ual difference between chalk and other forms of carbonate of lime? 
 What is said of deposits of chalk now going on ? 
 
 255. What is said of the presence of flint in chalk? What of the 
 Xanthidia? 
 
 256. What of the shell prisms in flint? What of the flinty spicula 
 from sponges ? 
 
 258. What of the agency of sponges in the Cretaceous period ? 
 What of the animals of that period ? What of the change in the 
 forms of the Ammonites? 
 
 P2 
 
346 QUESTIONS. 
 
 259. What is said of the formation of mountains at the close of the 
 Reptilian age, and in the age after it ? Give in full what is said of 
 the evidence in regard to this. 
 
 260. What is stated about the heights at which animal remains are 
 found in the mountains raised at that time ? What is said of the de- 
 struction of life at the end of this age ? What is Hugh Miller's divi- 
 sion of the life of the earth ? What is said of new creations ? 
 
 CHAPTER XVIII. 
 
 261. In the age of Mammals, how was the condition of the earth 
 more like its present condition than it was in the previous ages? 
 What is meant by Cainozoic time ? What are its divisions ? 
 
 262. What is said of the terms primary, secondary, and tertiary ? 
 Give in full what is said of Lyell's division. Of what kinds, mostly, 
 were tertiary deposits? 
 
 263. What is said of Tertiary mediterranean seas ? State in full 
 what is said of the Paris basin. What is said of the areas of Tertiary 
 deposits ? 
 
 264. What are the Tertiary rocks? What is said of some of the 
 Tertiary strata of Europe ? What is said of Nummulites ? 
 
 265. State in full what is said of the Nummulitic formation. 
 
 266. What is said of Tertiary plants ? Give in full what is said of 
 diatoms. What is said of Tertiary animals ? 
 
 267. What comparison is made between Tertiary animals and those 
 of the present age ? What is said of the fishes ? 
 
 268. What of the reptiles? What of the mollusks? Give the 
 statement about the arrangement of a cliff in Virginia. 
 
 269. State some of the inferences drawn from the condition of 
 shells in strata. State in full what is said of indusial limestones. 
 
 270. What is said of the Mammals of this age ? 
 
 271. What is said of the whale called Zeuglodon cetoides ? 
 
 272. To what class did the most prominent of Tertiary mammals 
 belong? Describe those which are represented in Fig. 164. What 
 comparison is made between the pachydermata of the present time 
 and those whose remains were found in the Paris basin ? 
 
 273. What is said of Cuvier's investigations ? To what conclusion 
 did he come? How were his views received? State in full what is 
 said of the Dinotherium. 
 
 275. Indicate the extent of Tertiary mountain-making. Give in 
 full the comparison between the Tertiary mountains and those made 
 in earlier ages. 
 
 276. What is said of systems of rivers ? What evidences are there 
 of the working of volcanic agencies in the Tertiary period ? What is 
 the explanation of the distinctness of some of the cones in France? 
 
QUESTIONS. 347 
 
 277. What is the name of the highest of these cones, and what is 
 said of it ? How were basins, so called, formed in the Tertiary pe- 
 riod ? What is the arrangement of the London basin ? 
 
 278. How do artesian wells operate in such basins? What is said 
 of Tertiary continent-making? What proportion of the land was 
 brought above the surface of the water in this period? What addi- 
 tions were made to North America ? What is said of the condition 
 of this continent at the end of this period ? 
 
 279. What is the Post-tertiary period ? What was to be done in it 
 to the continents ? Into what three epochs is it divided ? What was 
 done in the first ? What in the second ? 
 
 280. What in the third ? Indicate the extent of the reign of ice in 
 the Glacial epoch. What is supposed to have been the cause of the 
 cold ? What is said of the glaciers of this period ? 
 
 281. What is drift? What modified drift? What are the two 
 theories about drift ? What is the truth in regard to them ? What 
 changes were produced by the drift ? What change in the Niagara 
 River ? What is said of the heights at which drift is found ? 
 
 282. What is said of the shape and size of boulders ? What of the 
 distances to which they have been carried? What examples are 
 given of the transportation of them across deep valleys ? What is 
 stated about the distribution of boulders ? 
 
 283. What is said of glacial markings ? What of the roches mon- 
 tonnees ? What of the work done by iceberes, and that done by gla- 
 ciers ? What of the localities of the glacial markings ? 
 
 284. What general change in the land occurred in the Champlain 
 epoch ? What resulted from this change ? What is the character of 
 the formations of this epoch ? How are boulders situated in relation 
 to these formations ? What is said of the elevated heights to which 
 these formations sometimes reached ? What is said of the wide dis- 
 persion of the smaller materials of the drift ? 
 
 285. What are the river-plains and sea -beaches of the Cham- 
 plain epoch now ? What is said of the subsidence of land in this 
 epoch ? What of the movement in the Terrace epoch ? What effect 
 was produced by this on the Champlain strata? To what is the 
 term terraces applied ? What is said of the arrangement of ter- 
 races ? 
 
 286. Describe what is represented in Figs. 168 and 169. State in 
 the general how terraces were formed. 
 
 287. Explain by Figs. 170 and 171 the manner in which they were 
 commonly made. 
 
 288. What is said of sea-beaches ? Describe in full the changes 
 that occurred in the Niagara River in the Post-tertiary period. 
 
 289. What calculations have been made about the time occupied 
 
. , 
 
 348 - QUESTIONS. 
 
 in the recession of Niagara Falls? How are rivers formed? What 
 two things are needed to make large rivers ? 
 
 290. When were the grand river systems of the earth formed? 
 What is said of the alterations in the terminal moraines of the an- 
 cient glaciers ? What of the results obtained in their investigation ? 
 
 291. What cities are built on moraines? What is the composition 
 of the Post-tertiary moraines ? What is said of the present conceal- 
 ment of their character ? What is soil ? By what agencies has it 
 been made ? What is said of their operation in the Post-tertiary pe- 
 riod? 
 
 292. What does Hugh Miller say of the preparation of soil in Scot- 
 land in that period? 
 
 293. What three points are worthy of remark in regard to Post- 
 tertiary animals ? What is said of the animals of England of that 
 period ? 
 
 294. How did the Siberian mammoth differ from the elephants of 
 the present time ? 
 
 295. Give in full what is said of the covering of the mammoth in 
 relation to the question of climate. What is said about vegetation in 
 reference to this ? What is said of the abundance of mammoths in 
 certain localities, and of the supply of ivory from their tusks ? What 
 is stated about the mammoths of this country ? 
 
 296. Give the history of the St. Petersburg skeleton. State the 
 speculations about it, and the views of Cuvier. 
 
 297. What is said of the mastodons? How do their teeth differ 
 from those of the mammoth ? What is said of the Mastodon gigan- 
 teus? 
 
 298. What is the Indian tradition about mastodons ? What is sta- 
 ted about the Newburg mastodon ? "What is said of the Mylodon ? 
 
 299. What is said of the structure of the Mylodon's skull? 
 
 300. What is said of the Megatherium ? 
 
 301. What of the Megalonyx? 
 
 302. What of the Glyptodon ? What of the whales of that period ? 
 
 303. Where have caves been found containing bones of Post-ter- 
 tiary animals ? Describe the Kirkdale cave. What was the suppo- 
 sition of some quarrymen about it ? 
 
 304. State in full the results of Dr. Buckland's examination of this 
 
 CHAPTER XIX. 
 
 305. What is said of the beginning of the age of Man ? What 
 about its conclusion ? 
 
 306. Point out the contrast between the earth now and in the Azoic 
 age. What is said of the contrast between the present age and the 
 
QUESTIONS 
 
 ages following the Azoic ? How was the Post-tertiary period the most 
 like the present ? 
 
 307. What facts show that the earth was essentially completed 
 when man was introduced ? What is said of his control over the 
 earth ? Give the summary of the changes now going on in the earth. 
 
 308. What is said about the preservation of the equilibrium of land 
 and ocean at the present time ? What of the comparative activity 
 of agents of change now and in former ages ? 
 
 309. What is the distinction between the historic and the human 
 period ? What is said of history ? What of the study of the remains 
 of a people ? What is said of the Stone age of man ? What of the 
 specimens of stone implements represented in Fig. 179 ? What of the 
 Bronze age ? 
 
 310. What of the Iron age ? What of literature in relation to these 
 ages ? What change was made in regard to the animals of the earth 
 when the age ofJMan began ? 
 
 311. Mention some of the animals that have become extinct during 
 the age of Man, and state what is said of them. What is said of the 
 evidence that man is one species ? 
 
 313. Of what nature is the grand difference between man and 
 other animals ? In what respects is man like other animals, and why? 
 What power has the human mind which the brute mind has not? 
 Mention the various results of the possession of this power. What 
 supposition has been entertained by some in regard to future prog- 
 ress? How is this seen to be unfounded? 
 
 CHAPTER XX. 
 
 314. Give the comparison between the study of Astronomy and 
 that of Geology. 
 
 315. What is said of the comparative reliability of history and the 
 record of the rocks ? What erroneous idea was entertained by some 
 in the infancy of geology ? What is said of the authenticity of the 
 two records of creation ? What of apparent inconsistencies between 
 them ? What of the proper mode of interpreting the Mosaic record ? 
 
 316. What is said of the coincidences between the two records? 
 What is said to show that the account of Moses was divinely inspired ? 
 What is said of the propriety of noticing the record of the Bible in a 
 work on geology ? What were the days of the Mosaic record ? What 
 objection to the view taken is mentioned, and what is said about it ? 
 
 317. What are the various senses in which the word day is used in 
 the Mosaic account? What significant fact is stated about the use 
 of the word ? Relate the English legend about ammonites. 
 
 318. Relate the imposition practiced in regard to this legend. Of 
 
350.- QUESTIONS. 
 
 what use is geology to the poet and the painter? What is said of a 
 plan in the formation of the earth ? 
 
 319. Give the comparison in regard to the potter. Illustrate the 
 fact that the continents were constructed each on its own plan. What 
 facts show that the Creator had a plan throughout in regard to the 
 animals of the earth ? What is said of time in geological processes ? 
 
 320. What is said of minute agencies in the formation of the 
 earth's crust ? What of disintegration of the rocks ? What of the ex- 
 tent to which reconstruction has been carried on in the formation of 
 the earth's crust ? 
 
 321. What have been the two purposes of disintegration ? Which 
 is the principal one ? How has diversification of the earth's surface 
 been effected ? Show the interplay of mechanical, chemical, and vi- 
 tal forces in the case of carbonate of lime. What was the state of the 
 atmosphere before the Carboniferous age ? What change was effect- 
 ed in it then, and with what result? 
 
 322. Show how the interplay above referred to is "illustrated in the 
 making of coal in the Carboniferous age. What is said of the circu- 
 lation of matter ? What has been the notion of some in regard to 
 the creation of the earth ? What is the truth on this point? 
 
 323. What is said of the creation of life ? What of the notion that 
 there has been no creation at all ? State the development theory. 
 How does geology show this to be false ? 
 
 324. How does Page state the changes implied in this theory? 
 What is the grand creation of the Deity on this earth ? What two 
 facts show that the soul of man was a distinct creation ? 
 
 325. If mind were entirely dependent upon matter, what ought we 
 to find in the brain of man ? What is said of the doctrine that places 
 man onlv a little above the monkevs? 
 
GLOSSARY. 
 
 [The numbers refer to the paragraphs where the terms are explained.] 
 
 Acephal 286 
 
 Acrogens 250 
 
 Amorphous 21 
 
 Amphigens 249 
 
 Amygdaloid 152 
 
 Anhydrous 60 
 
 Anticlinal 219 
 
 Aqueous (rocks) 211 
 
 Arenaceous 145 
 
 Argillaceous 145 
 
 Atoll 238 
 
 Azoic 261 
 
 Bilobed 302 
 
 Bort -35 
 
 Brachiopod 286 
 
 Cainozoic 261 
 
 Calcareous 145 
 
 Cenozoic 261 
 
 Cephalopod 286 
 
 Cleavage 24, 212 
 
 Coal-measures 310 
 
 Comprehensive (type) 301 
 
 Conformable (strata) 222 
 
 Cretaceous 339 
 
 Ctenoid 299 
 
 Cycloid 299 
 
 Deliquesce 97 
 
 Denudation 224 
 
 Devonian 290 
 
 Dimorphous 21 
 
 Dip (of strata) 218 
 
 Dodecahedron 25 
 
 Dune 205 
 
 Endogens 252 
 
 Eocene 368 
 
 Eremacausis 313 
 
 Exogens 253 
 
 Faults 223 
 
 Ferruginous 113 
 
 Flux , 69 
 
 Fossiliferous 211 
 
 Fossils 245 
 
 Gangue 69 
 
 Ganoid 299 
 
 Gasteropod 286 
 
 Gymnogens 251 
 
 Haloid.... 95 
 
 Hydrocarbon 46 
 
 Indusial 379 
 
 Joints (in rocks) 212 
 
 Jurassic 339 
 
 Lacustrine 369 
 
 Lagoon 238 
 
 Lamination 212 
 
 Lode 231 
 
 Massive (minerals) 105 
 
 Master-joints 212 
 
 Mesozoic 261 
 
 Metamorphic 211 
 
 Miocene 368 
 
 Nebulous state 263 
 
 Nummulite 239 
 
 Octahedron 13 
 
 Oolite 102 
 
 Organized (substances) ...... 3 
 
 Outcropping 220 
 
 Paleontology 247 
 
 Placoid 299 
 
 Pliocene 368 
 
 Primary (forms) 25 
 
 Protozoans 256 
 
 Rhomb 25 
 
 Saliferous 278 
 
 Secondary (forms) 26 
 
352 
 
 GLOSSARY. 
 
 Silurian 275 
 
 Stratification 212 
 
 Strike of strata 218 
 
 Sub-carboniferous 311 
 
 Synclinal 219 
 
 Talus 185 
 
 Tertiary , 368 
 
 Trappean 
 
 Trend 
 
 Triassic 
 
 Tufa 
 
 Unilobed 
 
 Water of crystallization. 
 Weathering 
 
 .... 152 
 .... 162 
 
 .... 339 
 .... 195 
 .... 302 
 .... 20 
 .. 187 
 
INDEX. 
 
 [The numbers refer to the paragraphs.] 
 
 Acephals 286 
 
 Acrogens 250 
 
 Adaptation 282 
 
 JEpiornis maximus 421 
 
 Agate 114 
 
 Ages, boundaries of 262 
 
 Ages of Man, Stone, Bronze, 
 
 and Iron 420 
 
 Aiguille de Dree 146 
 
 Alabaster 60 
 
 Albite 129 
 
 Alge 249 
 
 Alum 109 
 
 Alumina 126 
 
 Alumina, phosphates of. 110 
 
 Alumina, silicates of 128 
 
 Amber 45 
 
 Amethyst 113 
 
 Amianthus 125 
 
 Ammonites 344, 352, 363 
 
 Ammonium, chlorid of. 108 
 
 Amorphons minerals 21 
 
 Amygdaloid 152 
 
 Anoplotherium 382 
 
 Anticlinal lines 219 
 
 Antimony 84 
 
 Antimony, sulphuret of. 54 
 
 Anthracite 39 
 
 Anthracite, how produced.... 315 
 Anthracite, introduction of... 308 
 Ants, as geological workers.. 235 
 
 Aqueous rocks 211 
 
 Arenaceous rocks 145 
 
 Argillaceous rocks 145 
 
 Arsenic, sulphurets of 55 
 
 Articulate 259, 332 
 
 Asbestos... .. 125 
 
 Asphaltum 46 
 
 Asterolepis 301 
 
 Astronomy, Geology com- 
 pared with 425 
 
 Atmosphere, relation of to 
 
 coal 437 
 
 Atolls 238 
 
 Auvergne, volcanoes of 386 
 
 Azoic time 261 
 
 Azoic age, heat and light in 271 
 
 Azoic age, land of. 266, 267 
 
 Azoic age, rocks of 270 
 
 Barrier reefs 237 
 
 Baryta, sulphate of. 62 
 
 Basalt 152 
 
 Basilosaurus 381 
 
 Basins 387 
 
 Belemnites 352 
 
 Beryls 135 
 
 Bismuth 87 
 
 Bitumen 46 
 
 Black Jack 57 
 
 Boracite 107 
 
 Borax 99 
 
 Boulders 393 
 
 Brachiopods 286 
 
 Breccia 143 
 
 Brontozoum giganteum. 346 
 
 Bryozoa 284 
 
 Buhrstone 150 
 
 Cainozoic time 261 
 
 Cainozoic time, divisions of. . 368 
 
 Calamites 32 
 
 Calcaire grossier 369 
 
 Calcareous rocks 145 
 
354 
 
 INDEX. 
 
 Calcareous spar 101 
 
 Carbon, diffusion of 29 
 
 Carbonic acid 47 
 
 Carbureted hydrogen 48 
 
 Carcharodon 376 
 
 Caruelian 114 
 
 Caverns , 216 
 
 Cenozoic time 261 
 
 Cephalaspis 300 
 
 Cephalopods 286 
 
 Chain coral 285 
 
 Chalcedony 114 
 
 Chalk 100 
 
 Chalk, flint in 361 
 
 Chalk, source of 360 
 
 Chalk, what composed of 239, 383 
 
 Champlain epoch 395 
 
 Changes in the earth, agents 
 
 of 172 
 
 Cheirotherium 345 
 
 Chlorite 123 
 
 Chrome yellow 75 
 
 Chrysoberyl 135 
 
 Cleavage 24, 212 
 
 Clink-stone 152 
 
 Coal 38 
 
 Coal, origin of. 41 
 
 Coal, diffusion of 44 
 
 Coal, localities of 307 
 
 Coal, how made 313 
 
 Coal, how deposited 316 
 
 Coal, plants in 319 
 
 Coal, rate of formation of.... 318 
 Coal, why called a mineral... 42 
 Coal age, vegetation of ..325, 326 
 
 Coal age, climate of. 327 
 
 Coal age, scenery of 328 
 
 Coal age, animals of 329, 334 
 
 Coal age, North America at 
 
 close of 336 
 
 Coal-fields 309 
 
 Coal-measures 310 
 
 Coal-measures, disturbances 
 
 in 337 
 
 Coast-lines of Scotland 207 
 
 Cobalt 85 
 
 Coccosteus ... .. 300 
 
 Colorado, canons of 184 
 
 Columnar trap 153, 154 
 
 Confervaj 249 
 
 Conformable strata 222 
 
 Continent-making in the Ter- 
 tiary period 388 
 
 Copper, native 77 
 
 Copper, oxyds of 78 
 
 Copper, carbonates of 79 
 
 Copper, silicate of 80 
 
 Copper of Silurian rocks ..... 277 
 
 Coral reefs 237 
 
 Corals 236 
 
 Corals in age of Coal 330 
 
 Corals in Cretaceous period.. 363 
 
 Corals in Devonian age 293 
 
 Corals in Jurassic period 351 
 
 Corals in Silurian age 285 
 
 Creation, the two records of. 427 
 
 Creative power 439 
 
 Cretaceous period, animals of 363 
 
 Cretaceous system 358, 359 
 
 Crinoids in Coal age 331 
 
 Crinoids in Cretaceous period 363 
 Crinoids in Jurassic period... 351 
 
 Crinoids in Silurian age 285 
 
 Crust of the earth, floor of... 264 
 Crust of the earth, treasures 
 
 in 170 
 
 Crystallization 13 
 
 Crystallization, contrasted 
 
 with vital growth 15 
 
 Crystallization, modes of 19 
 
 Crystallization, water of. 20 
 
 Crystals, arrangements of.. 16, 22 
 Crystals, primary forms of... 25 
 Crystals, secondary forms of. 26 
 Crystals, constancy in forms 
 
 of 27 
 
 Crystals, symmetry in 28 
 
 Crystals, sizes of. 14 
 
 Ctenoids 299 
 
 Cuvier, investigations of. 247, 383 
 Cycloids 299 
 
 Decay fi 
 
 Deliquescence 97 
 
355 
 
 Deltas 177, 179 
 
 Denudation 224, 225 
 
 Deposits, consolidation of.... 180 
 
 Development theory 440 
 
 Devonian age, corals in 293 
 
 Devonian age, crustaceans in 298 
 Devonian age, mollusks in... 297 
 Devonian age, vegetation in 295 
 Devonian age, abundance of 
 
 fishes in 303 
 
 Devonian age, scenery of.... 305 
 
 Devonian age, rocks of 290 
 
 Devonian age, United States 
 
 at end of 304 
 
 Devonian system 291, 292 
 
 Diamonds 30-36 
 
 Diatoms 240, 374 
 
 Dikes 229 
 
 Dimorphous minerals 21 
 
 Dinornis elephantoides 421 
 
 Dinosaurus 357 
 
 Dinotherium 384 
 
 Dip 218 
 
 Dodo 421 
 
 Dolomite 104 
 
 Drift 232, 392 
 
 Druidical monuments 187 
 
 Dunes 205 
 
 Dutch white 63 
 
 Earth as a whole 156 
 
 Earth, form of 157 
 
 Earth, crust of 158 
 
 Earth, ages of 171 
 
 Earth, completion of 416 
 
 Earth now and in former ages 415 
 Earth, stages in construction 
 
 of 209 
 
 Earth, plan in construction of 242 
 
 Earth, solidification of 263 
 
 Earth's surface, elevations 
 
 and depressions in 160, 233 
 
 Earth's surface, how diversi- 
 fied 169 
 
 Earth development, plan in.. 431 
 
 Earth's crust, floor of. 264 
 
 Earth's history, divisions of.. 261 
 
 Earthquakes 200,201 
 
 Earth-worms as geological 
 
 workers 235 
 
 Ehrenberg on chalk 239 
 
 Elevations 233 
 
 Emeralds 135 
 
 Emery 126 
 
 Endogens 252 
 
 England, post-tertiary ani- 
 mals of. 404 
 
 Eocene i 368 
 
 Epsom salts 61 
 
 Eremacausis 313 
 
 Etna 196 
 
 Exogens 253 
 
 Faults 223,225 
 
 Feldspar 129 
 
 Ferns in coal strata 323 
 
 Fingal's Cave 153 
 
 Fishes 299 
 
 Fishes of age of Coal 333 
 
 Fishes of Tertiary period 376 
 
 Fishes, tails of 302 
 
 Flexures of rocks 214 
 
 Flint, fossils in 362 
 
 Flint in chalk 361 
 
 Flood-plain 174 
 
 Fluor spar 105 
 
 Fluxes 69 
 
 Foraminifera 239 
 
 Fool's gold 50 
 
 Formation 212 
 
 Fossils 245-247 
 
 Fossils, animal 255 
 
 Fossils, vegetable 254 
 
 Fossil book in stone 347 
 
 Fossiliferous rocks 126 
 
 Franconia Notch 395 
 
 Fringing reefs 237 
 
 Fungi 249 
 
 Galena 52 
 
 Gangues 69 
 
 Ganoids 299 
 
 Garnets 131 
 
 Gar-pike 333 
 
356 
 
 INDEX. 
 
 Gasteropoda 186 
 
 Geological evidence, nature 
 
 of 210, 244 
 
 Geysers 203, 204 
 
 Giant's Causeway 153 
 
 Glacial period 368, 391 
 
 Glacial markings 394 
 
 Glaciers 188-190 
 
 Glance, copper 51 
 
 Glauber's salt.. 61 
 
 Gneiss , 148 
 
 Graham's Island 199 
 
 Granite 146, 147 
 
 Graphite 37 
 
 Green-sand 358 
 
 Green-stone 152 
 
 Gold 91-93 
 
 Goppert, experiments of. 319 
 
 Grotto del Cane 47 
 
 Gulf Stream 168 
 
 Gymnogens 251 
 
 Haloid salts 95 
 
 Hamburg white 63 
 
 Heat, agency of. 193 
 
 Heat, relation of to forms of 
 
 matter 2 
 
 Hematite 74 
 
 Herculaueum 195 
 
 Historic period 419 
 
 Hornblende 125 
 
 Human period 419 
 
 Hydrozoa 284 
 
 Hyla3osaur 357 
 
 Icebergs 191 
 
 Iceland spar 101 
 
 Icononzo, natural bridge at .. 216 
 
 Ichthyosaurus 353 
 
 Iguanodon 357 
 
 Indusial limestones 379 
 
 Iridium 94 
 
 Iron, ores'of 70 
 
 Iron, meteoric 71 
 
 Iron, carbonate of 76 
 
 Iron mountains -73 
 
 Islands, volcanic , 199 
 
 Joints 212 
 
 Jupiter Serapis, Temple of.. 206 
 Jurassic period, plants of.... 349 
 Jurassic period, animals of... 351 
 
 Kaolin 129 
 
 Kilauea, Crater of 197 
 
 Kirkdale Cave 413 
 
 Labradorite \ 119 
 
 Labyrinthodon 345 
 
 Lagoons 238 
 
 Lakes 166 
 
 Lakes, deposits in 176 
 
 Lamination 212 
 
 Land, arrangement of. 161 
 
 Land, proportion of to water. 159 
 
 Lapis lazuli 134 
 
 Laurentian Hills 385, 388 
 
 Lead 81 
 
 Lead, oxyds of 81 
 
 Lead, sulphuret of 52 
 
 Lead, sulphate of 59 
 
 Lepidodendron 322 
 
 Lepidosteus 333 
 
 Levels, alterations of 206 
 
 Life introduced by the Cre- 
 ator 15 
 
 Life in different ages 243 
 
 Life, dawn of, in the earth... 273 
 Life, plan in structures of.... 248 
 
 Life-record in the rocks 243 
 
 Life-record, Palaeozoic 338 
 
 Lily Encrinite 344 
 
 Lime, carbonate of. 100 
 
 Lime, silicates of 119 
 
 Limestone 100 
 
 Lingula 28G 
 
 Lisbon, earthquake at 201 
 
 Lithodomes 207 
 
 Loggan stones 187 
 
 London basin 387 
 
 Lowlands 164 
 
 Magnesia, salts of. 107 
 
 Magnesia, silicates of 120 
 
 Magnesia, sulphate of 61 
 
INDEX. 
 
 357 
 
 Magnesian carbonate of lime 104 
 
 Magnetic iron ore 71 
 
 Mammals 260 
 
 Mammals of Tertiary period 380 
 Mammals of Triassic period 344 
 Mammoth Cave of Kentucky 16 
 
 Mammoths 405 
 
 Man, creation of 441 
 
 Man, changes made by 208 
 
 Man one species 422 
 
 Man's place in nature 423 
 
 Manganese 88 
 
 Marble . 102 
 
 Master-joints 212 
 
 Mastodons 408 
 
 Matter, circulation of. 438 
 
 Matter, forms of. 2 
 
 Megalonyx 410 
 
 Megalosaur 357 
 
 Megatherium 410 
 
 Mercury 89 
 
 Mercury, sulphate of. 56 
 
 Metamorphic rocks 211 
 
 Mesozoic time 261 
 
 Mica 130 
 
 Microscopic animals in rock 339 
 
 Minerals, forms of. 1 
 
 Minerals in living substances 17 
 Minerals, simple and com- 
 pound 9 
 
 Mines, salt 98 
 
 Minium 81 
 
 Miocene 368 
 
 Mollusks 258 
 
 Mollusks in age of Coal 334 
 
 Mollusks in Cretaceous pe- 
 riod 363 
 
 Mollusks in Devonian age ... 297 
 
 Mollusks in Silurian age 286 
 
 Mollusks in Tertiary period.. 378 
 
 Moraines 188, 190, 402 
 
 Moraines, cities built on 402 
 
 Mosaic record, authenticity 
 
 of 427 
 
 Mosaic record, days in 428 
 
 Mountain-making in Tertiary 
 period 385 
 
 Mountains, arrangement of.. 162 
 
 Mountains, how made 226 
 
 Mountains, relation of, to 
 
 fertility 167 
 
 Mylodon 409 
 
 Naphtha 46 
 
 Nautilus 286 
 
 Niagara Falls, recession of... 183 
 Niagara River, changes in 392, 399 
 
 Nickel 86 
 
 Nummulites 239 
 
 Nummulitic formation 372 
 
 Oaze 239 
 
 Obsidian 155 
 
 Olivine 152 
 
 Onyx 114 
 
 Oolite 102 
 
 Opal 115 
 
 Ores 66-68 
 
 Organic agencies 207 
 
 Organized substances 3 
 
 Orpiment 55 
 
 Orthoceras 286 
 
 Osmium 94 
 
 Oxysalts 95 
 
 Pachydermata of Tertiary 
 
 period 382 
 
 Pala30therium 382 
 
 Palaeozoic time 261 
 
 Palisades 154 
 
 Peat 43 
 
 Pebbles 234 
 
 Permian period 335 
 
 Petrifactions 118 
 
 Petroleum 46 
 
 Pitchstone 155 
 
 Placoids 299 
 
 Plateaus 164 
 
 Platinum 48 
 
 Plesiosaurus 354 
 
 Pliocene ,...." 14 
 
 Pompeii 195 
 
 Porphyry 152 
 
 Portland dirt-bed ... ,.. 350 
 
358 
 
 INDEX. 
 
 Post-tertiary period 368, 389 
 
 Post-tertiary period, divisions 
 
 of 390 
 
 Post-tertiary period, animals 
 
 of 404 
 
 Post-tertiary period, length of 400 
 Post-tertiary period, rivers of 401 
 
 Potosi, situation of., 164 
 
 Primary forms of crystals.... 25 
 
 Protogine 146 
 
 Protozoans 256 
 
 Pterichthys 300 
 
 Pterodactyl 355, 356 
 
 Pudding-stones 143 
 
 Pulpit Rock 182 
 
 Pumice 155 
 
 Pyramids, of what rock built 239 
 
 Pyrites, iron 50 
 
 Pyrites, copper 51 
 
 Pyroxene 124 
 
 Quartz 113 
 
 Quartz rock 150 
 
 Quito, situation of 164 
 
 -Radiates 257 
 
 Realgar 55 
 
 Reconstruction 435 
 
 Red lead 81 
 
 Reptiles of age of Coal 333 
 
 Reptiles of Tertiary period .. 377 
 Reptiles of Triassic period... 345 
 Reptilian age, destruction of 
 
 life at close of. 365 
 
 Reptilian age, uplifts at close 
 
 of 364 
 
 Rhodium 94 
 
 Richmond, white clay of. 240 
 
 Ripple marks 210 
 
 Ripple marks on Silurian 
 
 beach 280 
 
 Rivers, amount of deposits 
 
 from 178 
 
 Rivers, deposits in 174 
 
 Rivers, improvement of 175 
 
 Rivers of post- tertiary period 401 
 Rivers, systems of 165 
 
 Roches montonnees 394 
 
 Rock, definition of 138 
 
 Rocks, disintegration of. 434 
 
 Rocks, elementary substances 
 
 in 139 
 
 Rocks, kinds of 140-145, 211 
 
 Rocks, order of succession of 21-3 
 Rocks, regularity of form in.. 23 
 Rubies 126, 127 
 
 Salt mines 98 
 
 Salt of Triassic system 342 
 
 Saltpetre 96 
 
 Salt springs 98 
 
 Sand 234 
 
 Sand moved by wind 205 
 
 Sandstones 151 
 
 Sapphire 126 
 
 Satin spar 60, 101 
 
 Schists 149 
 
 Scoria 155 
 
 Sea-beaches 398 
 
 Secondary forms of crystals.. 26 
 
 Serpentine 122 
 
 Shales 149 
 
 Shells in rocks 239, 246, 258 
 
 Shells, silicious 240 
 
 Sigillaria 321 
 
 Silica 112 
 
 Silica in solution 116 
 
 Silica in two states 117 
 
 Silica, petrifactions with 118 
 
 Silicates Ill 
 
 Silicious rocks 145 
 
 Silurian age, climate of....;.. 288 
 
 Silurian age, life in 281 
 
 Silurian age, subsidences and 
 
 elevations in 289 
 
 Silurian beach 280 
 
 Silurian copper 277 
 
 Silurian salt 278 
 
 Silurian shales, carbonaceous 
 
 matter in .^-283 
 
 Silurian system, distribution 
 
 of 276 
 
 Silurian system, rocks of..... 274 
 Silver 00 
 
INDEX. 
 
 359 
 
 Silver, sulphuret of 52 
 
 Slates 149 
 
 Smalt 85 
 
 Soapstone 121 
 
 Soda, borate of 99 
 
 Soda, nitrate of 97 
 
 Soda, sulphate of 61 
 
 Soil made in post-tertiary pe- 
 riod 403 
 
 Soil, what it is 234 
 
 Solfataras 202 
 
 Sphinx, what made of 239 
 
 Spicula in flint nodules 362 
 
 Spinel 127 
 
 Stalagmites and stalactites... 103 
 
 Stigmaria 321 
 
 Strata 212 
 
 Strata at different angles 217 
 
 Strata, conformable and un- 
 
 conformable 222 
 
 Strata, flexures of 214 
 
 Strata, mapping of. 220 
 
 Strata, measuring of 221 
 
 Strata, upheavals of. 216 
 
 Stratification 212 
 
 Stratified rocks 144 
 
 St. Petersburg skeleton 406 
 
 Strike 218 
 
 Sub-carboniferous period 311 
 
 Subsidences 233 
 
 Sugar, crystallization of. 18 
 
 Sulphur 49 
 
 Sulphurets 50-57 
 
 Sulph ureted hydrogen 64 
 
 Sulphuric and sulphurous 
 
 acids 63 
 
 Syenite 146 
 
 Synclinal lines 219 
 
 Talc 121 
 
 Talus 126 
 
 Terrace epoch 396 
 
 Terraces, how formed 397 
 
 Tertiary period 368 
 
 Tertiary period, deposits of.. 369 
 Tertiary period, mountains 
 made in ... .. 385 
 
 Tertiary period, pachyder- 
 
 mata of. 382 
 
 Tertiary period, plants of 373 
 
 Tertiary period, rocks of 371 
 
 Time in geology 432 
 
 Tin 82 
 
 Tomboro 198 
 
 Topaz 126, 133 
 
 Tourmaline.. 132 
 
 Tracks as evidences in -geol- 
 ogy 210 
 
 Tracks in Triassic rocks 346 
 
 Trachyte 152 
 
 Trap rocks 152-154, 348 
 
 Trap rocks, how formed.. 229, 230 
 
 Trap scenery 229 
 
 Triassic period 339 
 
 Triassic rocks 330 
 
 Triassic plants 343 
 
 Triassic salt 342 
 
 Triassic animals 344 
 
 Trilobites 287 
 
 Trilobites of age of Coal 332 
 
 Tufa 195 
 
 Turquois 119 
 
 Unconformable strata 222 
 
 Under-clay 310 
 
 Unstratified rocks 144, 211 
 
 Valleys, kinds of 227 
 
 Venice white 63 
 
 Ventriculites 361 
 
 Veins 231 
 
 Verd-antique 122 
 
 Vertebrates 260 
 
 Vesuvius 195 
 
 Viesch, glacier of 388 
 
 Vitriols 58 
 
 Volcanoes 163, 194 
 
 Volcanoes, formation of 228 
 
 Volcanoes of the Tertiary pe- 
 riod 386 
 
 Water as a leveler 192 
 
 Water changing locality of 
 materials .. 173 
 
360 
 
 INDEX. 
 
 Water, chemical action of.... 186 
 
 Water, circulation of 168 
 
 Water encroaching on land.. 181 
 Water, erosive power of.. 182, 184 
 Water, proportion of land to 159 
 
 Weathering 187 
 
 Whales of post-tertiary period 412 
 White lead... . 81 
 
 Xanthidia... 362 
 
 Zaffre 
 
 Zeuglodon cetoides 
 
 Zinc 
 
 Zinc, sulphuret of.. 
 
 Ziphodon 
 
 Zircon 
 
 85 
 
 381 
 
 83 
 
 57 
 
 382 
 
 136 
 
 THE END. 
 
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