QB 0» Ilibrary of congres. | UNITED STATES OF AMERICA. J THE CONSERVATION OF ■ GRAVITY AND HEAT: WITH SOME OF THE EFFECTS OF THESE FORCES OW THB PHYSICAL CONDITION OF THE EARTH; un> A BRIEF APPLICATION TO THH SOLAR SYSTEM. -♦♦♦- • • • SPRINGFIELD: SAMUEL BOWLES AND COMPANY, PRINTERS. 1864. ■J J— Entered according to Act of Congress, in the year 1864, by HENRY W. CHAPIN, In the Clerk's office of the District Court of the District of Massachusetts. • • • • » • • • \ GRAVITY AND HEAT. In advancing a few thoughts on this subject, I ask the reader's indulgence, as I introduce the plainest practical illustrations. The general appearance of the earth leads to the belief, that, at 6ome very early date in its history, it must have had a very high temperature, and, possibly, have been in a molten condition ; and many suppose that the central portion of the earth may now be in a fluid state. I shall endeavor to show that this must necessarily be the case, and, also, that the earth must, once, have been a mere mass of molten matter. At exactly what depth in the earth we should find the fluid line, (or the line where the fluid interior of the earth and the crust come in contact,) can be determined, or approximated, only by experiment. It is said that heat tends to equalize itself in matter. It tends to diffuse itself, and produce a uniform temperature m horizontal strata, and to equalize itself, in like matter of uniform density ; but it tends to concentrate in a perpendicular direction. The denser the same matter, the better are its conducting qualities. Heat has an affinity for, and is more readily conducted by, the denser strata, which, if undisturbed, usually underlie rarer strata ; thus concentrating the heat of the earth. Although heat is being conveyed from the more central portions of the earth to the surface, by the fluids and other agencies, and beyond the surface by the expansive force of the air, we find no increase of heat in the surface stratum, or in the exterior portion of the atmosphere. Effect of density, on conduction and capacity for heat. If we increase or reduce the amount of matter contained in a specified volume, we increase or reduce the amount of latent heat therein contained. This is apparent, by the unequal amount of heat evolved, when equal volumes of atmospheric air, of unequal densities, are compressed. The conducting power and capacity for heat, per cube, increase with the density. The capacity for latent heat in- creases with the density of the matter, and the capacity for sensible heat, with the density of the stratum in which it rests. If a paVti- cle of solid matter is depressed, or elevated in the atmosphere, to a denser, or rarer medium, the sensible heat increases, or decreases according to the variation in the density of the medium. This law is also made manifest, by boiling water, when under pressure, or in a vacuum, or lessening its capacity for heat, by causing it to expand bo as to form ice. The same increased capacity for heat may be seen in different substances, if they are fused while subjected to pressure. If we compress a piece of iron it becomes hot, and if the iron thus compressed was in a stratum, all the matter of which sus- tained an equal pressure, giving an equal density with the iron thus compressed, it would all be equally hot ; the permanency of the heat depending on the stability of the density of the stratum. Concentration of heat by compression and conduction. That we may realize the tendencies of heat to concentrate, and cause an in- crease of heat, as we descend in the earth, let us examine an arti- ficial stratum in a perpendicular column of sand. As there is a given amount of heat per grain, and as we find a perceptible increase in the number of grains, per inch, as we descend, we must acknowl- edge that there is a corresponding increase of heat. By casting a shaft of iron in a perpendicular position, the conditions being such, that all portions may be refrigerated, as nearly as possible at the same moment, we find that there is an increase in density and in heat, as we descend the shaft, as well as an increased conducting power in the same direction. If we continue to descend on this 6haft, through the crust, we find the same continual increase in den- sity, conducting power, and in heat, as far as we can penetrate, and as these properties increase in matter, according to the pressure, we must calculate on the same increase in the impenetrable depths. Could we continue to descend, we should arrive at a temperature holding iron in a fluid state. Cause of unequal temperatures, in different localities at the same depth. In descending through the crust, which has been more or less disturbed, the increase in density and in heat would not be as regular, and would vary in different localities, at the same depth. The strata became hardened, while subjected to more or less pres- sure than they are, in the position they now occupy, and dissimilar rock and unlike strata vary, more or less, in their densities, conduct- ing powers, and capacities for heat, when formed under equal pres- sure. These disturbances and variations cause the thermometer to indicate different degrees of temperature, in different localities, at the same depth. The 'present appearance of the crust, and the figure of the earthy are not proofs of original fluidity. Whether the surface stratum was created fluid or solid ; whether the internal heat was uniformly, or partially distributed through the crust at creation, or was placed in the position it now occupies, are questions not determined by the present limits of the melted matter, the igneous appearance of the earth's crust, or its oblate spheroidal form. If the melted nucleus occupied its present limits at creation, it may since have imparted this igneous appearance ; as it is now passing and repassing through the crust ; (as I shall endeavor to show,) and the motion of the earth on its axis would produce the oblate form, whether the surface stratum was a solid or a fluid. But the conducting powers of the strata are such, that if the portion of the earth which is now the solid crust, was in a fluid state at creation, the heat would have receded to its present limits. The earth must have been in a fluid state at creation. As the density of the earth depends on the effect of gravitation, matter must have existed prior to its condensation by gravity, and heat have been uniformly distributed through the whole mass by the con- densation. The time must therefore have existed, when the earth was in a molten condition. Since the creation, gravitation has been producing its effects on the earth, and has by its powerful and all- pervading influence increased the density of matter, unequally, in different portions of the earth, by the pressure of particle on parti- cle, causing the central portion of the earth to be the more dense. Heat, having an affinity for the denser matter, has receded from the surface to the denser stratum. (The temperature of melted matter may be readily increased without causing it to expand, even if free from pressure.) The receding of heat from the surface to the denser stratum, caused a thickening of the fluid, and in process of time a solid, until we arrive at a depth at which matter ceases to contract by pressure, and heat ceases to recede. The expansive force of heat is overcome by pressure. With the increase of temperature, matter, at this depth, whether solid or fluid, yields to gravity, which has more force than the expansibility of heat, or the resistance of matter, causing perfect condensation at this point. That gravity produces this effect in a mass of matter, is evi- dent from the limited ability of solid matter to resist its force, to any great depth, as is made apparent by a perpendicular column of gran- ite or iron, a few miles in height, with an unlimited diameter ; the gravitating weight of which, is sufficient to crush its base. The sustaining strength of the shaft decreases if the temperature is in- creased, a slight pressure being sufficient to compress melted matter. The force of gravitation determines the density of matter.. As the density of matter, in all its forms, depends on the conditions produced by the force of gravitation, the expansive force of. heat depends on the incumbrance of gravity, and the expansive force of the matter heated. This is seen in many substances, when the com- paratively slight pressure of a portion of the atmosphere is removed from them, by placing them under an exhausted receiver. If we apply heat to water in this condition, we see how slight an in- cumbrance overcomes, in a measure, its expansive force, as, in this condition, it expands to steam with less heat. Again if we fill a hol- low tube, a few feet in length, with molten matter, when in a hori- zontal position, and then increase the pressure on the particle by placing it in a perpendicular position, its contents are increased in density, and the same matter fails to fill the tube, in its new position. If the matter contained in the tube w r as not heated, its density would not be affected by the change of position and slight increase of pres- sure. These experiments show that the density of matter and the expansive force of heat, (when taken in connection with the expan- sive force of the matter heated,) depend on gravitation and the weight of particle on particle ; and that the expansive force of heat, in matter, is more readily overcome, when the matter is heated. As the same matter contains the same heat in its new position and de- creased figure, it contains more heat per cube. The increase in density and capacity for heat is greater, in the lower extremity of the tube. Perject condensation of the fluid stratum. The force of gravity, on the crust of the earth, causes a regular increase in density, as we descend, until we arrive at a point where matter ceases to contract by pressure, or by refrigeration. This is proved, by the facts that matter cannot be annihilated by pressure, and that the contraction of matter by refrigeration decreases as the pressure is increased, its expansive force having yielded to the pressure, before congelation took place. This point must also be comparatively near the surface of the earth, as the length of the perpendicular column indicates. And, as has been shown, matter is increasing in density according to the pressure, as far as we can penetrate ; but this increase is not maintained to any very great depth, as if so, the earth would be vastly heavier than it now is. From this line inwards, the atoms come in contact, forming a perfectly condensed and uniform stratum. As this stratum is of uniform density, the fluid heat ceases to recede. Matter outside of this line is lighter, (per cube,) and retains less heat. Matter inside of this line is of uniform density and heat. Comparative density of different strata. The fluid stratum must be more dense than the solid crust, for a solid cannot rest on a fluid less dense than itself. It would sink, as would ice, on a lake that should be overloaded, and if the crust was as dense as the fluid stratum, it would itself be made a fluid by the condensation, and its temperature would be increased in intensity to that of the fluid stratum, as its powers of conduction increase with its density. The solid crust rests on the fluid stratum at that point in the earth, where the solid and the fluid are of equal density and heat. The crust floats on the melted nucleus, and decreases in density and in heat as we proceed up, and heat is not conducted from the fluid stratum to the surface, as matter decreases in density and in conducting power in that direction. The crust having been disturbed, the decrease in density is not regular ; but the power of conduction maintains a very regular decrease, owing to the intersection of veins, dikes, fissures and the like, at the time of the various disturbances. Original formation of the crust, and of surface inequalities. The fluid heat that, at creation, was distributed through that portion of matter, which is now the solid crust, has receded to the denser stratum. The refrigeration and contraction of the surface stratum took place first, that being the least dense, and the inferior strata of the crust, being refrigerated subsequently, caused a lateral pressure on the surface stratum, equal to the contraction of matter in the infe- rior strata by refrigeration, or the extra surface found in the heights and depressions, on the surface of the earth. 8 Reduction of diameter by refrigeration. If we allow the crust to be thirty, or even fifty miles in thickness, and to have contracted in congealing, as much as iron would, in the same circumstances, or as granite is said to contract, which would be one-eighth of an inch per foot, on the surface of the earth, and none at the other extremity, — viz., the fluid line, (the expansive force of heat, at that depth, having been overcome by pressure,) — the medium contraction of the crust might then have been less than one-sixteenth of an inch per foot, as some substances are known to contract less than one-eighth of an inch per foot, in congealing. Thus the earth would have been but a very few thousand feet larger in diameter, when in its fluid state, than it now is. A crust thirty miles in depth, may seem thin and unstable, while ice a foot in thickness will sustain many tons, and, a few rods in thickness, would sustain our largest structures. Refrigeration and contraction caused great disturbance. As the refrigeration of the inferior strata advanced, a mechanical advantage was gained by the heavier portions of the solid crust, over the lighter. This, together with the lateral pressure on the surface stratum, ele- vated the mountains and depressed the valleys. As the force of gravity on elevated matter decreases inversely as the square of its distance from the center of the earth, the continents and mountains as they were uplifted, became self-sustaining. As their weight de- creased by their elevation, the sustaining spherical form of the crust increased by that elevation, adding part of the weight of the mount- ains and continents to the more depressed portions, bringing an un- even pressure on many portions of the crust, causing currents and counter-currents and great changes in the solid strata, by the equal- izing process which nature maintains. The leveling forces are not reducing the surface of the earth to a plain. The changes which are now taking place are comparatively trifling, more local, and are produced mostly by the aqueous agents, which are changing the position of matter, and disturbing the equi- librium which exists in the crust. But the tendencies of nature to level the surface of the earth, by means of the aqueous agents and other forces, are counterbalanced. The removal of matter from one locality on the surface of the earth, allows as much matter to expand at the fluid line, as is caused to contract in another portion, by the addition of matter. The melted nucleus conforms to the center of pressure, as it is a perfect self-adjuster. Any portion of the crust, becoming overloaded, is crushed by the force of gravity on the super- incumbent mass, and made a fluid by the condensation ; while an equal amount of the melted matter rises, with those portions which are being made lighter, above the line of uniform density. There being less pressure it expands, has less capacity for heat, and in pro- cess of time, the fluid heat recedes from it as at creation ; restoring a uniform pressure, density, and temperature, to every portion of the crust, coming in contact with the fluid stratum. The crust of unequal thickness. Perpetual restoration of mount- ains. The crust varies in thickness, in different localities, producing this uniformity of pressure. The unequal centrifugal force, in differ- ent portions of the earth, does not affect the pressure, or the thickness of the crust, only as it affects gravity. The thickness of the crust increases as we approach the equator, as the force of gravity de- creases, on account of the spheroidal figure of the earth. The crust at the sea-level indicates a medium thickness, and the more elevated portions show an increase in thickness, equal to the elevation. If matter is removed from any locality on the surface of the earth, the melted nucleus recedes from that locality. If matter is added to any district, the melted nucleus approaches that district. The ap- proach of the fluid stratum to any point, is equal to the subsidence of that point ; and its recession from any point is equal to the up- heaval of that point, when compared with the level of the sea ; for while the melted nucleus conforms to the center of pressure, the sea maintains a level to that center. Portions of the crust the most liable to fracture. Formation of volcanoes. When large deposits of matter are being made in any locality, that locality is subsiding ; while the district from which the matter is being removed is rising, bringing a longitudinal strain on the latter, and a lateral pressure on the former. The resistance of rock strata to a crushing force, far exceeds its tension strength. Those portions of the crust which receive a longitudinal strain, are liable to fracture ; as some point near, or at the summit of those which are being uplifted ; while those portions which are receiving the greatest longitudinal strain, and are the most liable to fracture, and allow the melted nucleus to be forced up to the surface, and at times to produce volcanoes, are those lying nearly equidistant be- tween the points of greatest upheaval and depression, and are near the level of the sea. Some portion of the crust near that line and 2 10 below it, is receiving matter and is subsiding; and some portion near that line and above it, is losing matter and is being uplifted, indica- ting the line upon which faults are formed. Continual transposition of oceans and continents; the melted nu- cleus, and the crust. When large deposits of foreign matter are being made near the coast, that portion of the continent is subsiding. If the district from which matter is removed, lies contiguous to any- sea or ocean, that sea or ocean is retiring. Thus the sea is encroach- ing on the land, and the land on the sea, as alternately the solid crust is forming the bed of an ocean, the summit of a mountain, or is be- ing condensed and made a fluid : and on the other hand the melted nucleus is expanding and being refrigerated, forming the inferior stratum of plutonic rock. This rock is being formed, at points under- lying the localities where the crust is being lightened, and is laid bare by the leveling forces on the summit of some lofty mountain, and in its turn, furnishes material for aqueous strata. Older mountains not the higher. Affect of changes of level on climate. As these older mountains, in time, gradually subside, the plutonic rock is found in different localities at all the intermediate levels between these elevated positions and the ocean. The strati- fied rocks are found at all the intermediate levels between the ocean, and the summit of the lofty, and more recently formed mountains- From the position of the organic remains found in these stratified rocks, it is evident that they have at times formed the bed of the ocean. The uplifting of the crust from the level of the ocean to the line of perpetual frost, with the consequent changes in the currents of the ocean, gives to the same locality an ever-varying climate. Localities where changes of level are the most frequent and per- ceptible. Since the earth as a whole, has ceased to contract, these changes have become less rapid; but a few centuries makes them visible, in many localities on the surface of the earth. The subsi- dence may be seen at, or near, the points where large quantities of foreign matter are being deposited, as at the estuaries of some rivers, where trees are found buried in a growing posture below the level of the sea ; as well as at other points where edifices have been im- mersed. Promontories and even mountains are being submerged, and are forming islands, in those portions of a continent which are subsiding, and other mountains composed of various strata, are being formed on those portions which are losing matter and are being up- 11 lifted. The uplifting of the land is the most apparent, at points where extended high lands or mountain ranges approach, or lie con- tiguous to the sea, as may be seen on the western coast of South America. In favorable circumstances, these changes of level are the most rapid, where the surface inequalities are the most visible, as is seen in the warmer climates. Visible effects of upheaval and depression. Location of volcanoes defined. The effects of this upheaval and depression are indelibly stamped, in various ways, on the solid crust ; as is seen in the various fractures of cleavage, dislocation and the like. Fractures which were produced in the surface stratum, near, or at the summit of an uplift, are usually represented by a rent : those underlying the same locality in the inferior, hotter, and more plastic strata, by a fold. Before the faults were disturbed, they represented a line near the level of the ocean. But if erosion and denudation were very unequal on opposite sides of the continent, they may represent a somewhat higher altitude. As volcanoes are formed on those lines where the changes of level are the most frequent, and where the crust receives the greatest longitudinal strain, they are found more or less in belts or bands. Localities exposed to frequent fluctuations. It is not my purpose to describe the geographical or geological features of the earth ; to note the increase of heat as we descend through the crust, or to point out the localities where changes have been the most frequent, or disturbances the most violent. These have been done by many observers, with more or less care and minuteness. I propose to con- fine myself to the origin and cause of these conditions and disturb- ances, and indicate the portion of the , crust, the conditions of the elements, and the season of the year in which they are more likely to occur. As the currents of seas and oceans are subjected to more frequent fluctuations than inland streams are, islands, peninsulas, and the like are subjected to more frequent fluctuations in their upheaval and depression, than is the case with the main land ; as the peninsula of Italy very plainly indicates. It has been suggested by writers on physical geography, that those inland tropical seas, which are receiv- ing a constant influx of salt water through their straits, might be filling up with salt, from the almost constant evaporation from their surfaces. As previously shown, any extended portions of land, sea, or ocean, which are receiving large deposits of foreign matter, whether 12 of Salt, coral, or any other substance, are subsiding. There may be exceptions to this, however. A point may be uplifted, when receiv- ing slight deposits of foreign matter, if it is located nearly equidistant between two points, each of which are receiving an excess of matter, and are subsiding. The uplift would be produced, by the solidity of the crust, before it is sufficiently overloaded to cause subsidence, as some coral islands in the central portion of the Pacific ocean may possibly indicate. Some localities are being uplifted when receiving deposits, if the district, as a whole, is losing an excess of matter, as is seen in some valleys, lake and volcanic regions. Lakes thus situated are gradually filling up, as is the case with Lake Geneva. Other localities are being depressed while being lightened, if the surrounding district is receiving an excess of matter, as some islands, peninsulas, capes, promontories, and similar localities may indi- cate. Familiar examples. That the heavier portions of the crust should be subsiding and the lighter rising, is in accordance with the effect produced on an arch, the equilibrium of which is disturbed by light- ening or overloading any portion of its span. The heavier portion subsides, causing the lighter to rise. It is evident, that the uplifted portions of the crust would be sus- tained in their elevated positions, as they lose a portion of their weight in being elevated, and as a part of their weight is added to the more depressed portions of the crust, in consequence of that elevation. That portions of the crust are being uplifted, and that a part of their weight rests on the valleys and more depressed por- tions, is manifest from the frequent landslides. If it were not so, landslides would be unknown ; and if a part of the weight of the more elevated portions did not rest on the more depressed, perpen- dicular gravel and earth banks would be a familiar feature in our landscape. The uplifts are bounded by depressions. Their vicissitudes are equal. As the crust floats on the melted nucleus, and the inequalities on the surface poise each other, great mountain chains must be bal- anced by a deep sea, or a vast extent of low, level plain. Astronomy teaches that the diameter of the earth is invariable : the upheavals and depressions must, therefore, be equal. These motions counter- balance the effect of the leveling forces, and maintain an equilibrium in the inequalities on the surface of the earth. 13 General derangement of landmarks. The leveling forces are not producing any very perceptible effect on the rocks which project above the line of perpetual frost, as is evident from their jagged ap- pearance, but at a slightly inferior level they are working with great energy ; as is seen in the heaving of the surface, owing to the alter- nate freezing and thawing, and in the action of glaciers and torrents ; removing large quantities of matter, undermining precipices, forming overhanging cliffs, and at times frightful avalanches of rock and earth. As the particles of rock and earth are removed, they seek an inferior level and are increased in weight, and by being trans- ported to a greater or less distance, they are deranging, in a greater or less degree, the geographical landmarks. The cause of earthquakes. Although the crust has an arching and self-sustaining form, its sustaining strength is limited, by the same limited ability existing in the arch and in the perpendicular column. As the diameter of the column was unlimited, it may rep- resent the crust of the earth. The solidity and sustaining strength of the crust are such, that it resists this gradually leveling process of overloading and lightening for a while, before yielding to a new position. This resistance causes the changes of level and the trans- ition in the density of matter, to be more or less paroxysmal, rending the solid crust, producing shocks or earthquakes by the fracture and concussion, at times forming new, or reanimating old volcanoes, causing great energy and activity at the vents. The motions and fractures are unlike at different altitudes. The disturbance produced by the fracturing of the crust varies with the nature of the soil, the face of the country, and the height above the level of the sea, at which the fractures occur. The motions imparted to the crust on the line upon which faults are formed, are very com- plicated and violent, as a portion of the crust on this line is being uplifted, and a portion depressed. When the crust yields to the £ accumulating forces and becomes fractured, it frequently opens and closes again. These fractures and complicated motions disturb the % solid crust, in various ways that we from time to time experience. The unobstructed motion of matter at the vents may, in a measure, counteract the disturbing effect of the concussion on the surrounding crust. Slight secondary forces are sometimes introduced by the ad- mission of fluids into the fractures of the crust, forming steam, gasses, and the like. 14 The conditions, localities, times and seasons most conducive of earthquakes. Earthquakes, or the fracturing of the crust, more fre- quently take place, when the disturbing forces are the most intense and act the most in unison ; as when the earth is in that part of its orbit nearest the sun and moon, or when the sun and moon act in conjunction, with a high tide resting on the portion about to be de- pressed ; *or when there is a sudden decrease in the pressure of the atmosphere on the continent, or on a portion of the continent and ocean. While the pressure would be greatly reduced on the land, (the portion which is being elevated,) the waters of the surrounding ocean would flow in, on account of the greater pressure elsewhere, and keep up the weight on those portions being depressed ; viz : — those portions of the crust lying below the ocean. There are also atmospheric tides which correspond with the tides of the ocean. When these tides are at their maximum, at a given point on the ocean, (other things being favorable,) the ebb in the atmospheric tide causes the barometer to be at its minimum, on the adjoining conti- nent. As the sun passes the equator twice yearly, and the spring tides are the highest when the sun is in that vicinity, earthquakes are most frequent when the sun is near the equinox. As the land on the surface of the earth is more largely situated in the northern hemisphere, and has the least amount of ice, snow, and moisture resting upon it, when the sun has its most northern declination ; and as the disturbing effect of the leveling forces have been accumulating during the year, and the vertex of the tidal-wave in a measure follows the course of the sun, in its journey north and south, earthquakes frequently occur when the sun returns to the summer solstice. Effect of centripetal and centrifugal forces on density. Irrespect- ive of the conditions which control the expansive force of heat, a permanent increase or decrease in gravity would cause a permanent increase or decrease in the density of matter. When the distance is \ diminished between the sun and any of the planets, the centripetal and centrifugal forces are increased. As these forces act in direct opposition to each other on matter, the tendency is to increase, or reduce the density of the bodies, according as these forces are in- creased or reduced. This may be demonstrated by matter under our immediate control. The extreme eccentricity of the orbits of comets and their tenuity of substance, causes some of their disks to 15 be sensibly reduced as they approach the sun. As the distance be- tween the sun, moon, and earth is continually varying, and as the matter of the earth is alternately approaching, and receding from, the moon, by its motion on its axis, the density of the earth is very slightly affected by these varying influences. The slight effects of these disturbing forces are made visible, by their accumulation at the vents, and cause continual motion in the melted matter there. Volcanoes will always exist on the earth. The reason of their over- flowing at different altitudes, and more frequently near the level of the sea. As the artisan may not be able to braze up the last aperture in the thin shell of a hollow metallic globe a few inches in diameter, on account of the continually varying pressure of the air resting on the inner and outer surfaces, so nature fails to refrigerate the melted matter in the vents, and close up the last apertures in the crust, on account of the constant transposition of the matter in the vents, caused by the ever-varying pressure against its inner and outer sur- faces. If the fluid stratum could be in a state of perfect rest, the uniform pressure of the solid crust resting upon its surface, would force it up through every vent and fissure, to a height nearly equal to that of the the fluid stratum before any refrigeration and contrac- tion took place. On account of its continual motion it may be car- ried still further upward by inertia, and forms cones above that point. As the melted nucleus conforms to the center of pressure, and the sea maintains a level to that center, the height to which the fluid would rise above the surface of the earth, should be calculated from the level of the sea, volcanoes being more likely to overflow at the sea-level, and less likely on the higher points, where the crust is thicker. The crust varies in thickness in different localities, owing to the variation in density, in the force of gravity, and the unequal sustaining strength of the spherical form of the crust in different dis- tricts and elevations. These inequalities and paroxysmal transitions in the density of matter, and the unequal egress of the fluid at the vents, giving different degrees of momentum, cause the melted mat- ter to overflow or stand in the vents at different heights, as regards the level of the sea. Origin of unlike igneous rock. As unlike matter in dissimilar inferior strata is being condensed and made a fluid, at different times, by the transposition of matter on the surface, various substances may be ejected from the same volcanoes or fissures, at different times. 16 While granite may be the basis of condensed matter, the various trap rocks may be the product of different fused strata. To determine the weight of the earth, we should calculate the medium density of the crust, and the density of the fluid stratum. There must he a melted nucleus. Frozen localities may remain congealed. That the crust is thin, and the interior of the earth a fluid, is evident from the limited ability of refrigerated matter but a few miles below the surface, to resist the superincumbent mass of the crust, as is indicated in the base of the perpendicular column. If we take the intensity of the stratum of equitable temperature in con- nection with the centralizing tendency of the crust, it shows that the interior stratum must be intensely hot. Although heat tends to dif- fuse a uniform temperature in horizontal strata; when the density becomes sufficiently reduced to admitof freezing, the power of con- duction has become nearly or quite obliterated, so that it may remain for ages congealed, before being thawed by conduction, as many per- manently frozen wells and various localities indicate. The internal heat is sufficiently intense to fuse the crust. That we may better realize the transitions through which the heat and matter of the earth are capable of passing, let us take fifty parts of matter and subject forty-nine parts, more or less, in a crucible, to an intense fluid heat, and then add the remainder. It would all become a fluid. If the crust encircling the fluid stratum should be broken up and pushed into the melted mass, it would be melted, (as heat tends to diffuse a uniform temperature in horizontal strata,) and the earth would return to its fluid state. In process of time the heat would return to its present limits, and the earth would assume its present condition. If, after being thus melted, the heat could not recede to its present position, it could not now maintain its present limits. If it was thus melted, the matter composing the crust would be ex- panded, the inequalities of the surface would be leveled, and the sphere enlarged, but the surface of the earth would not be very materially increased, when we consider the undulations and surface wrinkles of the present formation. Conservation of Gravity and Heat. In establishing the law of the conservation of gravity and heat, it becomes necessary to show that heat disappears from, or increases by the cube in two bodies, as they approach or recede from each other, in the same 17 ratio as tha force of gravity increases, or decreases in those bodies. Gravity is a constant force, and heat its equivalent when resisted. When two bodies are attracted towards each other, the equivalent of the force of gravity is found in their accelerated motion. When that motion is resisted by any force, matter is condensed and heat made visible. If we should remove a particle of matter from any point on the surface of the earth, a portion of the fluid stratum underlying that point would expand, and retain less heat per cube. The solidity of the crust might resist a sudden transition, but the final result would not be effected by the delay. The melted nucleus would be dimin- ished by the removal. If the matter thus removed was elevated to the upper atmosphere, (as might be represented by attaching a body to a balloon,) the loss of heat in a portion of the fluid stratum under- lying the point from which the matter was removed, would be the same, and heat would have vanished from that point by the cube, as gravity would, by the square of the distance ; and the elevated body would rest in a medium of air, less dense than that from which it was removed. As the tendency of heat, in every stratum or me- dium, is to diffuse a uniform temperature in a horizontal direction, the temperature of the elevated body would be reduced in intensity, to that of the medium in which it rests, and the frosts of a perpetual winter might rest upon it. But if the body elevated has a fixed form, that has not allowed it to expand in an equal ratio with the loss of gravity, heat has not been vanishing by the cube, as has gravity by the square of the distance. This can be made very apparent, if we imagine the body elevated a second time, and this time beyond the influence of the earth. In this last removal, while gravity has been vanishing inversely as the square of the distance, heat has not been vanishing by the cube, as there has been no con- veying currents or conducting mediums, and chiefly as the body has not been expanding. We therefore find that in elevating the body and thereby causing gravity to vanish, we have not removed the force of cohesion from the particles. As matter must have been created prior to the condensing effect of gravity on the same, giving it form, gravity must have condensed matter before cohesion took effect in the particles. As gravity pro- duced its effects first, it must vanish first. As cohesion originally fixed its firm grasp on the particles of solid matter by refrigeration, 3 18 when the matter was under the condensing effect of gravity, heat must be restored to the solid matter, to cause cohesion to vanish, after the condensing effect of gravity shall have been removed. As gravity has vanished from the elevated body, if we should restore the previously refrigerated heat and fuse the elevated body, cohesion and heat would vanish as has gravity, and matter would disappear by the cube, in an equal ratio. The more rare the same substance, the greater is its capacity for latent heat per pound. As matter existed prior to its condensation by gravity, it might exist if gravitation should be removed. Gravity has been constantly pro- ducing its effects on the earth since the creative act, and that we may better understand its original, as well as its present effects, and as we are led to believe by Holy "Writ* that the force of gravitation may have been suspended or removed from a limited amount of mat- ter, let us for a moment consider the effect, if the force of gravitation should be miraculously removed from the matter composing the earth. If it should be gradually removed, heat would be uniformly diffused through the whole mass,| and matter would expand. The prophecy in regard to the final consummation of all things would be literally fulfilled. The heat refrigerated from the solid crust, when under the condensing effect of gravity, would be restored. The elements would " melt with fervent heat and be dissolved," and the expansion of matter would cause the earth to "pass away with a great noise." Gravity, cohesion, and heat would vanish, and matter would disap- pear by the cube, in an equal ratio. While gravitation has the power to condense the rarest nebular matter and produce heat, on the other hand, heat has the power to expand the same matter to its original condition, if ever gravitation should be removed. Formation of a planet from nebulous matter. As the projectile forces have not been suspended, if we should restore gravitation to the particles of matter from which it has been removed, nature, with her present laws, would restore the present density, figure, and physi- cal condition of the earth, but not its geographical positions. Matter would be condensed and heat evolved. That portion of matter lying - * Exodus xiv. 22 ; II. Kings vi. G; Matthew xiv. 2G-29, and similar passages. f If it was removed rapidly, fragments of solid matter corresponding to me- teoric matter, might bo hurled into the surrounding space. 19 nearest the surface, not being perfectly condensed by gravity, would be refrigerated and form the crust. Ages must have elapsed since the force of gravitation was imparted to the matter composing the earth. As a year is not sufficiently long, to refrigerate the ruins of some stately mansion that has been de- stroyed by fire, and years often elapse in the refrigeration of matter, a few feet in thickness, ejected from a volcano at a single eruption ; what ages must have elapsed in the refrigeration of the solid crust of the earth : epochs during which the temperature has been grad- ually decreasing on the surface. As all portions have retained heat equal to their density and capacity, and to the density of the stratum in which they are found, the interior stratum being perfectly con- densed is intensely hot, and in the economy of nature it must be so, in order to maintain motion in the fluids and vitalize all nature. On account of the centralizing tendency of the crust, if the interior stratum was not intensely hot, the surface stratum would be intensely cold. The constant transposition of the fluids tends to equalization of heat ; as is shown by the direction and temperature of the prevailing currents. The denudating and transporting forces of the currents of the ocean, give the continents their form. The currents in the atmos- phere tend to equalize its temperature, and its conducting power and capacity for latent heat increase, by the cube, with its density, thereby increasing the refrigerating forces. Hence a dense atmosphere as indicated by the barometer, on a still clear evening, facilitates the deposit of dew, or the appearance of frost. In consequence of the centrifugal force and spheroidal figure of the earth, the tendency originally must have been, to form the ine- qualities on the surface of the earth, nearly parallel with the equator. But the unequal temperature and equalizing tendencies of the air and water, in different portions of the earth, cause constant transpo- sition of the fluids at the poles and equator, maintaining sea-commu- nication in a transverse direction, from the vicinity of pole to pole, giving form and outline to the continents, and determining in the main the direction of mountain chains. Currents moving in a northerly and southerly direction, (as the Gulf stream,) move more or less in curves, owing to the rotation of the earth on its axis ; and always tend to flow in a line determined by a composition of these forces, wearing a'way all intervening barriers in the course of time. 20 On account of the centralizing tendency of the crust, if the inter- nal fires should become extinct, the pulsations of the globe would cease. The sun would continue to give motion to the atmosphere, but the earth might be transformed into a sterile waste. The unequal temperature and density of water in the earth, a cause of springs. If we apply heat to the lower extremity of a column of water, the equalizing tendency is again made visible by two currents, the warm current ascending, conveying the heat in an opposite direc- tion from that in which it is conveyed by conduction, and the cold, descending, showing that the internal heat produces motion and causes springs, and that artesian wells would overflow at, or above, the surface of the earth, if it was a perfect sphere, as water stands the highest in the ascending limb. The variation in height of the water in two contiguous columns, depends on the length, and on the unequal temperature, or weight, per cube, of the water in the respec- tive columns. Their temperature may be made such as to cause a variation in their heights, of a foot in every twenty-three feet, or over four feet per hundred. Water often descends into the ground warmer and less dense than it returns. By* descending a few feet into the earth, we find our- selves below the influence of the impinging of the sunbeams on the surface, and arrive at a stratum of invariable temperature, which absorbs this extra heat. As the water becomes more dense, it con- tinues to descend, and takes the place of that below, which has been made less dense by the internal heat, and is in its turn expanded, and again returned to the surface in the form of a spring. If its transit to the surface is very direct and quick, it may return hot. If the temperature of the descending column is reduced to that of the stratum of invariable temperature, through which it passes, the tem- perature of the ascending column may be reduced nearly as low, and the water be returned to the surface, cooler and more dense than when it left. Thus while the water of a refreshing shower may enter the ground warm and insipid, it may be returned to the sur- face a cool and invigorating spring. The undulating surface and impervious structure of some of the inferior strata are such, that natural drainage, (which is usually assigned as the cause of springs, whether from natural or artificial apertures,) is an important agent in their production. These two forces may act separately or unitedly, in the production of springs. 21 As water free to move, does not sensibly conduct heat, and is but slightly compressible, it may be found with its density increased by pressure, and still indicate a very high or a very low temperature, if the pressure is such that it cannot expand to steam or ice. As cold water is heavier than warm, and salt water heavier than fresh, when the distribution of water at the equator is equal to the evaporation, the colder and heavier waters of the polar regions may move towards the equator in an undercurrent, and when the evapo- ration is nearly constant, or greater than the distribution, the hotter, Salter, and heavier waters may sink to an equal depth and move in an opposite direction. tfttJ &mu www* % THE SOLAR SYSTEM. Having noticed a few of the effects of gravitation on the earth, I shall very briefly consider its condensing effects on the Solar System ; as matter throughout the universe is equally attracted by gravitation, and obeys the same mechanical laws. The effect of gravitation on the density and peculiar motion of the moon. As the force of gravitation decreases as the distance increases, and the density of matter depends on the force of gravitation, the inferior limb of the moon must be denser than the superior limb. The distance between the sun and moon being far greater than the distance between the earth and moon, the unequal attraction of the earth on the opposite limbs of the moon, greatly exceeds that of the sun on its opposite limbs. The preponderance of gravity on the denser portion causes the moon to be a balanced figure, exposing only its loaded or denser limb to the earth. This explains the singular phenomenon of the apparent uniform rotation of the satellites on their axes, with each revolution in their orbits, (as is supposed to be the case with the satellites of Jupiter,) although the length of their orbits and times of revolution are unequal. The balanced position of the moon is the more stable, when its denser portion is turned towards the earth and sun, as when the moon is in opposition to the sun. But the unequal orbital motion of the moon, and varying, angular position of the sun, with its unequal gravitating influence on the opposite limbs of the moon, pauses the oscillations called the librations of the moon, in latitude as well as in longitude, as the moon is balanced towards the center of the earth, and its path varies 24 from the ecliptic. On account of the balanced condition of the moon and inclination of its orbit, its polar axis is inclined to the ecliptic. The conditions of the crust, and the unequal amount of land and altitudes in the two hemispheres, depend on gravitation. The thick- ness, density, conducting power and temperature, of the crust of the earth, at the surface, depend on the force of gravitation. On ac- count of the feeble force of lunar gravity on the surface of the moon, owing to its diminutive size, when compared with the earth, its crust must be very thick and rare, and its density and surface temperature much less than that of the earth : for the same reason, its atmosphere must be very rare. As the unequal refrigeration and contraction of the interior and exterior portion of the crust, caused the inequalities on the surface of the earth, and as rarer matter con- tracts more in congealing, the contraction and formation of a rare and thick crust must cause great surface inequalities, as the disk of the moon indicates. The crust of the earth is the lightest, as well as rarest, and thickest, at the equator. The greatest surface inequalities are therefore found in the warmer climates, as is seen in the altitude of table lands and mountain ranges. The crust being the rarest, lightest, and most elevated, where it is the least affected by gravita- tion, more than one-half of the land and the greater altitudes, are located in the northern hemisphere. For with the inclination of the earth on its axis and motion in its orbit, the south pole approaches nearer to the sun, than the north pole, subjecting it to more powerful attraction. The unequal influence of the sun on the opposite limbs of the earth, increases as the distance between them decreases. The variation in the force of gravitation in the two hemispheres, is exceed- ingly slight, and the variation in the altitudes is also very trifling, when compared with the mass of the earth. The density and physical condition of the planets are determined by the force of gravitation. The decrease in the density of the planets, as the force of gravitation on them decreases, indicates a similarity of substance. If exactly similar, the ratio between their density and distance from the sun would not be regular, as the force of gravitation varies with their mass, figure, surface temperature, and the gravitating influence of each on the other, (as the effect of the moon on the earth,) as well as with their distance from the sun. The density and conducting power of the crust of the earth would be increased, and its thickness would be reduced, if the force of 25 gravity should be increased. The crust of the larger planets must, therefore, be very thin and dense, causing a high surface temperature, which would rapidly convert the surface fluids into a vapory envelope, greatly reducing the density of those planets when taken as a whole. The loss of gravity must cause the surface of the exterior envelope of vapor, to be very rare, with a correspondingly low temperature, as is the case with our upper atmosphere. The reflective power of vapor is greatly increased in this condition, and far exceeds that of land and water. That their outer envelopes are in this condition, is indicated by their great reflective powers, as well as by their variable surfaces. The rapid motion of these planets on their axes, causes their equatorial diameters largely to exceed their polar diameters. When > fluids are very sensibly elevated by centrifugal force, it is a law in mechanics that they will form more or less in ridges at right angles with the axis of rotation. Light reflected from deep ravines and elevated ridges, would cause the surface to appear variegated, and ridges formed of vapor must undergo frequent changes by condensation. The physical disturbing forces, on these planets, must have great energy, caused in part by the rapid evaporation and condensation, which would give unceasing activity to the leveling forces ; and also by their rapid rotation on their axes, and the mass, and unequal revolutions of their moons. These, together with the near approach of the fluid line to their sur- faces, would cause volcanic action on a very grand and extensive scale. »The immense volumes of dark and heated vapor that ascend at times, would reduce the reflective power of the overhanging vapor on a very large extent of surface. At other times, eruptions would cause a vast extent of surface to be covered with molten matter. The heat ascending from such extensive fields of melted lava would disperse, in a measure, and illuminate the vapor hanging over an immense extent of surface. These convulsions may cause the more permanent spots on the disk of Jupiter ; those which do not always disappear with a reconstruction of the belts. As unlike density and temperature admit of different chemical combinations, the unlike density and temperature of the planets may cause their various colors. The expansive force of heat is the most apparent where matter is the least encumbered with gravitation. * A high surface temperature 4 26 would, therefore, greatly inflate the outer envelope, as the larger masses indicate. The same expansive force may be perceptible on some of the comets, as they approach the sun. Heat the equivalent of gravitation. Light the effect of heat. The immense power of gravitation in the sun, causes the line of uniform density to be located so near the surface, that the refrigerating forces are insufficient for congelation, except now and then the formation of comparatively small spots or thin, floating islands, on some portion the least affected by gravitation, as some point on the equator ; and they are soon liquified by a relative change of position. The expan- sive force caused by their rapid liquifaction, may account for the lofty protuberances which have been seen projecting from the surface of the sun. The expansive force of heat and powerful condensing effect of gravitation on the surface of the sun, must cause the exterior en- velope to be very dense, highly heated gas ; as it were a very dense blaze, reflecting light accordingly. The naturally depressed condition of the floating islands, accounts for the apparent openings, where there is a visible island. That the gas overhanging the edge or shore of these islands, is to some extent illuminated by the melted nucleus, producing the penumbra, is indi- cated by its disappearing, when any two or more contiguous islands intercept the light. The faculse may be caused by the accumulation of the floating specks in clusters, owing to their mutual attraction, thereby increas- ing the brightness of the surrounding surface, just before the visible formation of an island. When the island first disappears, its perfect fluidity may also cause increased brightness. That the sun must reflect light, is made apparent by the fact that matter sufficiently condensed is hot and luminous, and as the tem- perature of a stratum depends on its density, the light of the sun must be as permanent as gravitation. "spare moments." April, 1863. LIBRARY OF CONGRESS 003 536 992 2