UC-NI 
 
 liilit 
 
GIFT OF 
 
PLAIN DIRECTIONS 
 
 FOB 
 
 THE CONSTRUCTION AND ERECTION 
 
 LIGHTNING-RODS, 
 
 BY JOHN PHIN, 
 
 EDITOR OF THE "YOUNG SCIENTIST," AND THE "AMERICAN 
 JOURNAL OF MICROSCOPY." 
 
 THIRD EDITION. 
 ENLARGED AND FULLY ILLUSTRATED. 
 
 NEW YORK: 
 THE INDUSTRIAL PUBLICATION COMPANY. 
 
 1879. - f 
 
 Copyright Secured. 
 
CA 
 
 CONTENTS. 
 
 PAGE 
 
 Preface, - - in 
 The Lightning- Kod an American Invention, - 7 
 Are Lightning-Rods Really a Protection? - - 7 
 "What the Lightning-Rod Should Do, r 8 
 The Proper Material for Lightning-Rods, - 9 
 The Proper Size of the Rod, 10 
 The Best Form of the Rod, - 11 
 Proper Arrangement of the Rod in Regard to the Building, 13 
 Barns, Ice-Houses, etc., - 16 
 Should Lightning-Rods be Painted? 17 
 The Termination of the Rod in the Air, 18 
 The Best Method of Attaching Lightning-Rods to Build- 
 ings, 21 
 The Connection of the Rod with the Ground, - 23 
 Hints to Persons Exposed to Thunderstorms, - 26 
 Lightning-Rod Swindles, 27 
 Hints on the Surveying or Examining of Lightning Rods, 
 
 for Insurance Purposes, 27 
 
 Appendix Home-made Lightning-Rods, - - - 29 
 
 256265 
 
PREFACE TO THE THIRD EDITION. 
 
 During the six years that have elapsed since this work was 
 first issued, several important discussions have been held in 
 regard to the subjects upon which it treats. The author has 
 carefully followed all that has been written in connection 
 with lightning rods, but he finds no reason to alter any of 
 his original statements and directions. Several patents have 
 also been taken out during the last few years, but none of 
 them present any improvements of importance, the old and 
 well known devices being sufficient to meet all demands. So 
 that it still remains true that perfect protection may be ob- 
 tained without infringing upon any patent. 
 
 The extensive demand which has existed for this book is 
 not the only compliment which has been paid to it. The 
 author of a somewhat pretentious volume on " Lightning 
 Protection," has, with unblushing effrontery, appropriated 
 several of our original illustrations, and has used his scissors 
 freely on the text, and all without acknowledgment. This, 
 however, was to have been expectod in a book written solely 
 for the purpose of advertising a worthless patent. The pres- 
 ent volume still remains, as when first issued, the only book 
 published on lightning rods, which has not been written for the 
 purpose of puffing some particular patent. 
 
 The author lays no claim to novelty for any of the princi- 
 ples laid down in this little treatise. They are all old and 
 well established. Many of the illustrations and methods of 
 experimental proof are, however, original, and it is hoped 
 that they will tend to render the subject clear and easily 
 understood, so that, as we have always claimed, by its aid 
 any intelligent mechanic can put up a lightning rod which 
 will not infringe any patent, and which will afford perfect 
 protection. 
 
 New York, May, 1879. 
 
PREFACE TO THE SECOND EDITION. 
 
 The favor with which the first edition of this little work has been 
 received induces the author to make a few additions of a thoroughly 
 practical nature. These additions are so important in themselves, that 
 he has deemed it best to throw them into the form of an appendix, 
 rather than to incorporate them with the body of the work. 
 
 The importance of thorough protection from the effects of lightning 
 is very generally greatly under-estimated, except perhaps in those cases 
 where the fears of property-owners have been excited by the venders 
 of rods, whose chief excellence lies in the amount of money which 
 their sale brings to the manufacturers. Having carefully watched the 
 records of the destruction of property by lightning during several years, 
 we feel quite certain that a good rod is quite as important as a fire- 
 insurance policy. 
 
 "While giving expression to a well-founded contempt for the ordinary 
 venders of lightning-rods, we would by no means be understood as 
 condemning all those who are engaged in the business of manufactur- 
 ing and erecting these valuable adjuncts to our houses. We are per- 
 sonally acquainted with dealers of thorough honesty and excellent 
 judgment; and although we may differ from them in opinion in regard 
 to certain points, such as the matter of insulation, terminal points, &c., 
 yet, since we are in perfect accord as to the necessity for a substantial 
 rod and a good ground connection, we feel that those who employ 
 these men will not be disappointed. 
 
 At the same time, we would reiterate the statement which has been 
 made in the body of the work, to the effect that amongst the scientific 
 men of the present day there is no difference of opinion in regard to 
 the general principles which should govern us in the construction and 
 erection of lightning-rods. It is true that in a recent utterance, Prof. 
 Henry, of Washington, whose scientific reputation stands very high, 
 has gone back at least a century in his views. Fortunately, however, 
 since some of his most important statements contradict the experience 
 of every tyro in electrical experimentation, his opinions upon this 
 subject cannot carry much weight But with this single exception, we 
 believe that scientific men are in perfect accord in regard to everything 
 connected with lightning-rods. 
 
 In this little book we have endeavored to be sound and reliable, 
 and we have not aimed at novelties, though perhaps a few new meth- 
 ods of illustration and of proof, relating to general principles, and of 
 arrangement as regards the rod itself, have been introduced. In a 
 word, we have held steadily in view the diffusion of sound practical 
 information, and not the manufacture of a reputation for brilliancy 
 and ingenuity. 
 
PREFACE. 
 
 THERE are few subjects concerning which less is known by the public at 
 large than the principles that should govern the construction of Lightning- 
 Rods. Nor does this apply to the mere public alone. The authors of our 
 popular scientific books, and the editors of many of those papers that attempt 
 to give scientific instruction, are equally at fault; their directions being any- 
 thing but accurate. This assertion may perhaps be characterized as " vague " 
 and " sweeping;" but unfortunately it can, if necessary, be easily sustained by 
 numerous pointed illustrations. And yet the question of protection from 
 lightning is confessedly a very important one, and has engaged the attention 
 of some of the most enlightened governments on earth. On several different 
 occasions has a committee of the French Academy examined the subject at 
 the instance of the government. Neither have the British left this question 
 unexamined, as their piles of Blue-Books testify. The propriety of making 
 such earnest investigations is obvious from the following record: In 1864, 
 Boudin presented to the French Academy of Sciences a table showing that in 
 France, during the period of 29 years, 2,238 persons were killed by lightning, 
 and 6,714 struck without being killed. It is thus seen, that, during each of 
 these years, 77 persons lost their lives, and 232 were injured. Among those 
 struck by lightning, between the years 1835 and 1852, 67 per cent, were males, 
 10 per cent, females, and 23 per cent, unknown. From 1854 to 1863, 26.7 per 
 cent, of females, and 73.3 per cent, of males, were struck. 
 
 At sea the damage done to shipping has been equally marked. A writer in 
 Nicholson's Journal of the Progress of Science calculates the loss by lightning, 
 in Great Britain alone, at 50,000 sterling annually, and Sir William Snow 
 Harris believes that this estimate is under the mark. During the five years 
 between 1810 and 1815, the British Navy lost by lightning no less than forty 
 sail of the line, twenty frigates, and twelve sloops and corvettes. Indeed, it 
 has been proved beyond all controversy that, in Europe at least, the danger 
 of being killed by lightning is far greater than the danger of being killed by a 
 railroad accident ; or, in other words, that out of the entire population the 
 percentage of those killed by lightning is greater than the percentage of the 
 passengers who are- killed on railroads. 
 
 And yet, in the face of this melancholy record, it remains an undoubted 
 truth that life and property may, with certainty, be protected from injury by 
 lightning. There are many instances where buildings furnished with rods 
 have been struck by lightning and injured; but, so far as our experience 
 extends, the rods .have been defective in every case. In the British Navy, 
 where the very perfect system of protection devised by Harris has been 
 adopted, injury by lightning has become a thing almost unknown. Harris, 
 in his work on Frictional Electricity, tells us that, in the British Navy, damage 
 by lightning has happily ceased, but that in the Merchant Navy, where no 
 
iv PREFACE. 
 
 adequate means are taken to check it, it unfortunately still continues. We 
 regard his testimony upon this point as worthy of acceptance. 
 
 In view of these facts, it is obviously of the utmost importance that the 
 public generally should be fully informed in regard to the principles upon 
 which lightning-rods ought to be erected. It unfortunately happens that the 
 information given in regard to this subject by most of our text-books on 
 Natural Philosophy is exceedingly meagre, and as for special treatises there 
 is not a single one, now before the public, in the English language. It is 
 true that we have a few pamphlets and one small book ; but they can hardly 
 be dignified with the name of treatises on the subject, since they are all 
 written in the interest of some particular patent, and were never intended to 
 give such information as would enable an ordinarily intelligent mechanic to 
 erect a lightning-rod for himself. 
 
 In this country, our people appear to have derived most of their information 
 from a class of wandering mechanics known as "Lightning-Rod Men." The 
 object of these men, wo are sorry to say, seems in many cases to be to make 
 money rather than to afford protection from lightning; and hence, in travel- 
 ling through the country, we often find a vast amount of labor and expense 
 wasted on lightning-rods in many cases to their positive detriment. On 
 several occasions we have seen a lightning-rod earned alongside the metal 
 staff which supported the weather-vane, while at the same time it was care- 
 fully insulated from it; and it is within our personal knowledge, that, on 
 three of the new colleges devoted to the special culture of science, the light- 
 ning-rods are carefully and expensively insulated from the building by means 
 of glass insulators. The Trustees of these institutions seem to be unaware 
 of the fact that it is the opinion of our ablest electricians that the best way 
 to carry a lightning-rod to the ground is to carry it down the inside of the 
 house. The rods to which we have alluded are a standing satire on the 
 science taught within the walls which they have been erected to protect. 
 
 Almost all the lightning-rods which are sold by these itinerant vendors are 
 patented; and it may therefore be worth while to remind our readers that 
 aU the essential requisites for perfect protection may be embodied in a rod which 
 does not infringe any patent. The issue of a patent for any device is no 
 evidence whatever of the value of that device. Nine-tenths of ah" the inven- 
 tions protected by patents are perfectly worthless. Every sensible mechanic 
 knows this. Many patents are obtained simply for the sake of the opportunity 
 which it gives the patentee to talk and argue about his invention. Indeed, 
 a great many of these men feel a good deal as did a certain applicant for a 
 patent, who, upon being asked by the examiner, "Of what possible use can 
 such a device be?" replied, " Wall, I guess it is gootl for me to sell rights to 
 it." There is no doubt but that all the various devices of hollow rods, twisted 
 rods, hacked rods, and the endless variety of plans devised for attaching rods 
 to buildings, are perfectly childish. If you have a good solid rod put up with 
 the precautions which we detail, you need not be afraid. You are as sate as 
 any lightning-rod man can make you. That owners of houses may in most 
 cases find it desirable to employ competent mechanics to put up lightning- 
 rods, we do not mean to deny. But we feel certain that a slight knowledge 
 of the subject would have saved our house-owners, and especially our hard- 
 working farmers, thousands of dollars out of which they have been swindled 
 by " Lightning-Rod Men." 
 
 NEW YOKE, JUNE, 1871. 
 
LIGHTNING-RODS, 
 
 AND 
 
 HOW TO CONSTRUCT THEM. 
 
 An American Invention. Whatever differences of opinion 
 may exist in regard to the authorship of the discovery of the identity of 
 lightning and electricity, there can be none in regard to the fact that 
 Franklin, and Franklin alone, invented the lightning-rod; and, strange 
 to say, when it left his hands it was nearly as perfect as it is to-day. 
 Notwithstanding the many patents that have been issued for alleged 
 improvements in lightning-rods, we would as soon trust our property to 
 a rod constructed after the directions given by the inventor as to one 
 made according to the latest devices, covered by the broad seal of the 
 United States Patent-Office. It is true that during the last half-century 
 we have learned something about rods and their mode of action, and 
 have acquired a more perfect knowledge of the special points which de- 
 mand attention, in the effort to secure perfect safety. But it will be 
 found, on examination, that Franklin's old rod embodies all the points 
 necessary for a perfect conductor, and that, consequently, we are not at 
 the mercy of any patent-right monopoly in this matter. 
 
 Are Lightning-Rods Really a Protection! There are 
 
 many instances on record where buildings protected by rods have been 
 struck and injured. But this is not to be wondered at, when we reflect 
 that fully one-half nay, perhaps three-fourths of all the rods now 
 actually erected, violate the fundamental principles upon which their 
 efficiency depends. Besides serious errors in regard to arrangement 
 and continuity, it will in general be found that it is only by the merest 
 accident that a good ground connection is ever 'Secured. This point 
 will be more fully discussed in a subsequent paragraph. Meanwhile, 
 the following facts prove irrefragably the great value of well-constructed 
 rods. The Cathedral of St. Peter, in Geneva, although so elevated as to 
 be above all other buildings in the neighborhood, has for three centuries 
 enjoyed perfect immunity from damage by lightning; while the tower 
 of St. Gervaise, although much lower, has been frequently struck. 
 This doubtless arises from the fact, that all the towers of St. Peter are 
 accidentally furnished with very perfect conductors. The great column 
 
8 -L I<> H 5>rN-'G - E O D S. 
 
 of London known as the Monument, erected in 1677 in commemoration 
 of the great fire, although over two hundred feet in height, has never 
 been struck; while much lower buildings in the vicinity have not es- 
 caped. The Monument, however, is protected by a most perfect con- 
 ductor; the upper end terminating in a vase from which proceed 
 numerous metal plates designed to imitate the appearance of tongues 
 of flame. The vase communicates by means of stout bars of iron with 
 the metal staircase which descends through the middle of the column, 
 and terminates in the ground. A ntill more striking instance of the 
 value of lightning-rods is a church on the estate of Count Orsini, in 
 Carinthia. This building was placed upon an eminence, and had been 
 so often struck by lightning that it was deemed no longer safe to 
 celebrate divine service within its walls. In 1730, a single stroke of 
 lightning destroyed the entire steeple; after it had been rebuilt, it was 
 struck on an average four or five times a year, without counting ex- 
 traordinary storms, during which it was struck from five to ten times in 
 a single day. In 1778, the building was reconstructed and furnished 
 with a conductor; and, according to Lichtenberg, up to 1783, that is 
 to say, during the space of five years, the steeple had been struck only 
 once, and this stroke had fallen upon the metallic point without pro- 
 ducing any damage. For two or three years after its erection, the 
 church of St. Michael in Charlestown had been frequently damaged by 
 lightning; a conductor was attached to it, and during the following 
 fourteen years it had not been injured. The steeple of St. Mark's in 
 Venice has a height of 340 feet, and was frequently struck by lightning 
 until a proper lightning-rod was applied to it, since which time it has 
 not been injured. These facts leave no room for doubt in regard to 
 the great value of lightning-rods. 
 
 What the Lightning-Rod Should do. It is not our 
 
 purpose to enter into an attempted exposition of the theories of elec- 
 tricity, its phenomena and laws. For these we must refer our readers 
 to any of the ordinary works on Natural Philosophy. At present we 
 propose to deal with bare facts, and to give concise directions for prac- 
 tical guidance. The function or office of the lightning-rod is twofold. 
 In the first place, it acts as a means whereby the accumulated electricity 
 existing in the atmosphere is silently drawn off, and allowed to pass 
 into the earth, and thus prevent an explosion; and, in the second, 
 it acts as a path by which explosions, lightning flashes, or disruptive dis- 
 charges (as they are more properly called) may find their way to the 
 earth freely, and thus be carried off without any danger of their acting 
 with mechanical violence, as they are certain to do when made to pass 
 through what are called non-conductors. Experience teaches us, that, so 
 long as a discharge of electricity passes off through a wire that is large 
 enough to carry it safely, it dees not cause any damage or give rise to 
 the exhibition of mechanical violence. A spark from the prime con- 
 
LIGHTNING-RODS. 9 
 
 ductor of an electrical machine, if passed through a moderately fine wire, 
 does not injure it; if passed through a thick card, it will pierce it; and, 
 if passed through a small block of wood, it will rend it asunder. On 
 the occasion of every thunderstorm, there is a large quantity of elec- 
 tricity to be conveyed from the clouds to the earth, through the air, 
 which is, in general, a very poor conductor. This electricity always 
 tends to pass by the easiest path, or, as electricians say, the line of least 
 resistance. The resistance of any line may be lessened by various cir- 
 cumstances, such as the presence of hot vapors, as from chimneys, 
 heated haystacks in the open field, or heated haymows in the barn ; the 
 existence of a line of carbonaceous matter, such as exists in a column of 
 smoke; the presence of a tree with its leaves and sap, or of a house with 
 its chimneys; or the fact that the air has been rendered moist by the 
 passage of a shower of rain. So difficult is it, however, to detect the 
 circumstances which render any particular path more easy than others, 
 for the electricity to follow, that we are often unable to give a reason 
 for its following a particular course, and the action of this mighty force 
 seems to us like a mere freak. Such ideas are, however, entirely wrong; 
 and we may accept most implicitly the statement, that the flash will 
 always take the easiest path, and it must be our duty to determine 
 beforehand what this path shall be, and to make it so easy and so per- 
 fect that the resistance will not cause the electricity to produce the 
 slightest mechanical violence. And if we do BO, then, just as one may 
 hold in the hand a slender wire while a powerful charge of electricity is 
 sent through it, even so we might hold in our hands a good lightning- 
 rod at the instant of its being struck, and yet receive no injury. 
 
 The Proper Material for Lightning-Rods. The fore- 
 going considerations clearly show that lightning-rods should be made 
 of the very best conducting material, and of a size sufficient to carry off 
 the heaviest discharge that is ever likely to fall upon them. Of all well- 
 known substances, metals are the best conductors; but even amongst 
 metals there are great differences in this respect; some metals, accord- 
 ing to Becquerel, conducting nearly 75 times better than some others. 
 But, on examination, we find not only great differences in the conduct- 
 ing powers of the metals, but great differences in the estimates of differ- 
 ent observers. Thus it will be seen that Keiss estimates the conducting 
 power of silver at four times the value which is given to it by Ohm; 
 both estimates being referred to copper as a standard. It must be 
 noted, however, that there is a certain marked uniformity of result in 
 the determinations of all these savans. They all place gold, silver, and 
 copper very high in the scale; while the values assigned to platinum, 
 iron, tin, and lead are very low. We may perhaps note that the de- 
 terminations made by Lenz are, in general, regarded as being amongst 
 the most reliable. There are, however, but two metals whose claime 
 are worth considering, copper and iron. The others are too costly. 
 
10 
 
 LIGHTNING-KODS. 
 
 The following table gives the relative conducting powers of the different 
 metals according to the best authorities: 
 
 Table Giving the Conducting Power of Metals for Electricity. 
 
 METAL. 
 
 NAME OF OBSERVER. 
 
 BEC- 
 QTJEBEL. 
 
 OHM. 
 
 DAVY. 
 
 LENZ. 
 
 HEISS. 
 
 POOTLLET. 
 
 Copper, 
 
 100-00 
 
 100-00 
 
 100-00 
 
 100-00 
 
 100-00 
 
 100-00 
 
 Silver, 
 
 73-60 
 
 35-60 
 
 109-10 
 
 136-25 
 
 148-74 
 
 
 Gold, 
 
 93-60 
 
 57-40 
 
 72-70 
 
 79-79 
 
 88-87 
 
 103-05 
 
 Zinc, 
 
 28-50 
 
 33-30 
 
 
 
 
 
 Platinum, 
 
 16-40 
 
 17-10 
 
 18-20 
 
 14-16 
 
 15-52 
 
 22-50 
 
 Iron, 
 
 15-80 
 
 17-40 
 
 14-60 
 
 17-74 
 
 17-66 
 
 (15-60 
 1 18-20 
 
 Tin, 
 
 15-50 
 
 16-80 
 
 
 30-84 
 
 14-70 
 
 
 Lead, 
 
 8-30 
 
 9-70 
 
 69-10 
 
 14-62 
 
 10-32 
 
 
 Mercury, 
 
 3-45 
 
 
 
 
 
 2-60 
 
 Potassium, 
 
 1-33 
 
 
 
 
 
 
 Brass, 
 
 
 28-00 
 
 
 29-33 
 
 27-70 
 
 ( 15-20 
 \23-40 
 
 Palladium, 
 
 
 
 16-40 
 
 
 18-18 
 
 
 Cadmium, 
 
 
 
 
 
 38-35 
 
 
 Nickel, 
 
 
 
 
 
 13-15 
 
 
 Cast Steel, 
 
 
 
 
 
 
 ( 13-00 
 \ 20-50 
 
 Comparing the estimate of the different authorities given, we find the 
 estimated relative values of copper andiron to vary between 14. 6 and 
 18.2 for iron to 100 for copper. 
 
 It is found, however, that different samples of both copper and iron 
 vary very much in their conducting powers. Pure copper being taken 
 at 100, it will be found that the conducting power of even the best 
 selected samples of commercial copper is less than this by from five 
 to 15 per cent. ; while the ordinary commercial article falls below this 
 standard by from 30 to 60 per cent. On the whole, we are perhaps safe 
 in taking the relative conducting powers of iron and copper as one to 
 four. That is to say, that, if a rod of copper of a given size is found 
 to be sufficient, then an iron rod, to be equally safe, ought to weigh 
 four times as much per lineal foot. 
 
 Proper Size. Great differences of opinion exist in regard to the 
 size of rod necessary to insure safety. The old directions by the French 
 Academy of Sciences, named a rod of from one-half inch to one inch 
 square as a safe conductor. The following extract from the last report 
 gives their latest views upon this point: "A discharge of our electric 
 batteries is capable of melting several yards of very fine iron wire. A 
 flash of lightning is capable of volatilizing more than one hundred yards 
 of bell-wire, or of the wire that is usually employed in connection with 
 the hammers of public clocks. In 1827, upon the packet-boat New York, 
 a surveyor's chain forty yards long, made of iron wire a quarter of an 
 
LIGHTNING-RODS. 11 
 
 inch in diameter which served as a lightning-rod on the vessel, was 
 melted by a flash of lightning and dispersed in red-hot fragments. No 
 instance has ever occurred in which lightning has raised to a red heat 
 a bar of iron some yards long, and four-tenths of an inch square, or 
 having a section of one-sixth of a square inch. Hence a square rod of 
 iron, the side being four-tenths of an inch, has been adopted in the con- 
 struction of lightning-rods." This shows that the enormous conductors 
 recommended by Professor Henry and others are unnecessarily expen- 
 sive and clumsy. 
 
 The sizes usually adopted have not been determined by very careful 
 investigation, and cannot be regarded as safe guides in practice. Or- 
 dinary rods, made of iron, are about half an inch square ; and few cop- 
 per ones are more than equal to a wire a quarter of an inch in diameter. 
 We are satisfied, however, that it is not in size that ordinary rods are 
 deficient, but in continuity, arrangement, and ground connection. It is 
 of the utmost importance that lightning-rods should be equal to any 
 demand that may be made upon them ; and, after carefully examining 
 the subject, we feel satisfied that the conclusions reached by the French 
 Academy are very nearly correct. Instead of a square rod, however, 
 we would recommend a strip or bar one inch wide and three-sixteenths 
 of an inch thick, or, if it were a quarter of an inch thick, it would do 
 no harm. A rod of the first-named dimensions will weigh ten ounces 
 per lineal foot. The weight of the second will be thirteen ounces per 
 foot. If a copper rod be used instead of an iron one, it may be made 
 much thinner ; but we could hardly recommend its reduction to the 
 fifth or sixth of the size of the iron rod, as theory would indicate. A 
 copper rod, having the width of one inch, should be not less than the 
 twelfth or the tenth of an inch thick. A rod of the latter size weighs 
 six ounces (.384 Ibs.) per lineal foot. 
 
 The Best Form for the Rod. More nonsense has been 
 written in regard to this subject than in regard to any other connected 
 with lightning-rods, except perhaps that of insulation. It has been the 
 subject of several patents, and has furnished an immense amount of 
 capital to itinerant venders of rods so much so, that we deem it neces- 
 sary to present clearly the reasons which lead us to beliere that the 
 efficiency of a rod depends, other things being equal, solely upon the 
 amount of metal which it contains, and not at all upon the form that 
 may be given to it. 
 
 If we examine the rods ordinarily found in market, and puffed by 
 those who have invented them, we shall find that, instead of being 
 solid bars of a square, round, or merely flattened form, they are tubes, 
 twisted ribbons, or bars whose cross-section has the form of a star. 
 And if we ask why these complicated and expensive forms have been 
 adopted, we shall be told that it is for the purpose of obtaining the 
 greatest amount of surface with the least amount of metal, and this is 
 
12 
 
 LIGHTNING-RODS. 
 
 done because electricity always resides on the surface. Those who 
 reason in this way, however, prove clearly that they have never studied 
 the subject, else they would be aware of the fact that while static elec- 
 tricity, as it is called that is, electricity at rest always disposes itself 
 on the surface of bodies charged with it, electricity in motion pervades 
 the entire substance of the bar through which it passes, and conse- 
 quently the power of such a bar to convey electricity is measured by 
 the quantity of metal that it contains, and not by the extent of surface 
 that it presents. Pouillet showed this in a very clear and decisive man- 
 ner. He measured the conducting power of a fine wire of cylindrical 
 form the form that presents the least possible surface in proportion to 
 its cubic contents and then, having flattened and annealed it, he tested 
 it again. Its surface was enormously increased, but its power to con- 
 duct electricity was lessened rather than otherwise ; this diminution 
 being probably due to the fact that the wire was increased in length, 
 and, consequently, its cross-section was somewhat diminished. An ex- 
 periment, equally decisive, and perhaps somewhat more easily per- 
 formed, is at the command of every one who has access to a small elec- 
 trical machine and a two-quart Ley den jar. Take a fine gold wire, say the 
 one-fiftieth of an inch in diameter. This wire will present nearly the 
 same surface as a ribbon of metal l-32nd of an inch wide. The wire will 
 carry off, without being injured, any charge 
 that can be imparted to the jar. If, how- 
 ever, we pass the charge through a strip of 
 gold leaf having several times the surface 
 of the wire, it will be completely burned 
 up and dissipated. 
 
 The following very interesting experi- 
 ment shows clearly the difference between 
 the action of electricity at rest and elec- 
 tricity in motion, and exhibits also the fact 
 that surface is of no avail in carrying off a 
 charge of electricity. Take a Leyden jar 
 of large size say two gallons having the 
 usual knob and other arrangements, shown 
 in Figure 1. In the wooden cover insert a 
 glass tube carrying at its upper end a wire, 
 lying horizontally across it, this wire hav- 
 ing a ball at each end, so that the discharge 
 may take the form of a spark or an ex- 
 plosion and not pass off silently. Between 
 the horizontal wire and the knob of the 
 jar stretch a strip of gold-leaf (B), and 
 charge the jar in the usual manner. So 
 long as no discharge passes through the gold-leaf, it will remain unin- 
 jured, although it is evidently charged as intensely as the machine can 
 
 FIG. 1. 
 
LIGHTNING-RODS. 13 
 
 charge it. But if we discharge the jar by laying one ball of the dis- 
 charger on the outer coating of the jar and the other on the knob (A), 
 the gold-leaf will be destroyed. But a wire the thirtieth of an inch in 
 diameter, although presenting far less surface, would have carried off 
 the charge with impunity. In short, to end the matter, we may state 
 that while no flash of lightning has ever been known to injure a copper 
 rod half an inch in diameter, we have frequently, by artificial means, 
 dissipated an amount of gold-leaf that presented a greater amount of 
 surface. 
 
 The French Academy, although they give no specific directions as to 
 form, always speak of a square rod. The well-known authority, Sir 
 William Snow Harris, in his work on " The Nature of Thunderstorms," 
 says : " Provided the quantity of metal be present, the form under 
 which we place it is evidently of no consequence to its conducting 
 powers, since it would be absurd to suppose that a mass of metal, 
 under any form, did not conduct electricity in all its particles ; indeed, 
 we know that it does so, and that it is impossible to fuse by electricity 
 a portion only of a homogeneous metallic plate of uniform thickness." 
 For ourselves, we recommend the form of a flat ribbon, from purely 
 mechanical reasons. A bar of metal in this form is more easily bent, 
 more conveniently attached to the building, and is less conspicuous, than 
 when in any other form. Its conducting power is neither improved nor 
 impaired. 
 
 Arrangement of the Rod in Regard to the 
 
 Building. The arrangement of the rod deserves the most careful 
 consideration, not only because upon it depends in a large measure the 
 efficiency of the conductor, but because the amount of metal used de- 
 termines largely the expense of the rod. The arrangement usually 
 adopted consists in elevating from each chimney a tall spike, and con- 
 necting the several spikes or points by rods which either join the main 
 conductor, or descend directly to the earth. This is very well, and is in 
 accordance with the directions of the French Academy of Sciences, but 
 is not quite as perfect as it might be. 
 
 It is very obvious that the most perfect, though not the most economi- 
 cal, arrangement would be to cover the entire building with a sheet of 
 metal. Then it would be impossible for the lightning to strike any 
 point without falling upon a good conductor. But such an arrangement 
 being obviously inadmissible, we must so arrange matters that the 
 most exposed points shall be the conductor and its connections. With 
 this object in view, the French Academy recommended the use of rods 
 elevated nine to twelve feet above the building ; and, after a good deal 
 of experiment and observation, came to the conclusion that a rod was 
 capable of protecting efficiently a space covered by a radius equal to 
 twice the height of the rod, above the most elevated part of the build- 
 ing. For ourselves, a very careful examination of the conditions which. 
 
14 LIGHTNING-RODS. 
 
 arise during a thunderstorm, leads us to place no confidence whatever 
 in elevated rods, and to depend wholly upon so arranging the conduc- 
 tor that every part of the building shall be protected. 
 
 In a former paragraph we stated that the lightning stroke always 
 follows the line of least resistance, and that this line may be deter- 
 mined by the presence of vapor, smoke, moisture, etc., forming ascend- 
 ing or descending streams or horizontal layers ; and it is in this way 
 only that we can explain how it happens that a house furnished with 
 very elevated conductors, will be sometimes struck on the gable, or why 
 a mast unfurnished with a conductor, will be struck, while a taller 
 mast, distant but a few feet, and provided with a conductor, is not 
 struck, and evidently has not served to carry off the discharge. If the 
 line of least resistance were always the shortest line mathematically, 
 the rule of the Academy would hold good. But let us consider the case 
 of the building shown in the acccompanying engraving (Figure 2)> 
 
 FIGURE 2. 
 
 which represents a barn furnished with a conductor and exposed to a 
 thunderstorm. We will suppose that the barn has been newly filled with 
 hay, which is giving off the warm vapor that is pouring out of the end 
 window, and forms an invisible band of conducting matter between the 
 cloud and the barn, marked out in the engraving by dotted lines the 
 direction of the wind being shown by the arrow. In this case, the flash 
 will pursue the longer path between c and d, in preference to the shorter 
 one between a and&, and the barn may be set on fire, although furnished 
 with one of the best of rods. The same deflection of the bolt might 
 be caused by rain, by a column of smoke, or by the fact that a part of 
 the building had been moistened, while other parts had been kept dry, 
 as frequently happens when the rain is driven in particular directions 
 by a strong wind. In considering this subject, it must be borne in mind 
 that the flash does not leave the cloud and pursue a sort of experimen- 
 
LIGHTNING-RODS 
 
 15 
 
 tal path through the atmosphere, leaping from point to point like a boy 
 picking his way through a swamp now going forward, now sideways, 
 or sometimes going backward for the purpose of obtaining a new point 
 of departure. On the contrary, before the slightest disruptive action has 
 taken place, the electricity has, by the power of induction, marked out 
 for itself the precise path that it will take, and it pursues that path in- 
 flexibly. Every turn, every break,has been clearly defined ; and it would 
 be of no use to introduce into the neighborhood of this path any good 
 conductor, unless the path itself were thereby electrically shortened. 
 No additional elevation given to the conductor shown in the engraving, 
 and no spike or spikes raised from other parts of the ridge of the roof, 
 would have tended to render this path shorter. But if the conductor 
 had been simply carried along the ridge, and down the edges of the 
 roof at the gable, a way of escape would have been opened, and the 
 barn would have been saved. 
 
 In the accompanying engraving we give a figure of a small house, in 
 which the arrangement of the lightning-rods is shown by dark lines. 
 It will be seen that all spikes and points are avoided as being costly, 
 unsightly, and inefficient, as will be more fully explained in a subsequent 
 paragraph, treating of the termination of the rod in the air. Each 
 chimney is surmounted by a cast-iron cap, to which the rod is attached, 
 
 FIGURE 3. 
 
 and, after descending to the ridge, the rod is led along it in every 
 direction, and caused to descend along the edge of the roof at each 
 gable. It is of course obvious that if the building be crowned with a 
 Mansard roof, and finished with crestings, these will answer every pur- 
 pose of a lightning-rod so far as they go. But all buch crestings, as 
 
16 LIGHTNING-RODS 
 
 well as the waterspouts, tin or other metal roofs, eave-troughs, etc., must 
 be brought into metallic connection, so that the building may form, elec- 
 trically, a homogeneous mass. 
 
 A single good rod, carried to the ground and placed in perfect electri- 
 cal contact with the earth, as hereafter directed, is as good as a dozen 
 rods We often see a building provided with several rods, all descend- 
 ing into the earth. Such an arrangement shows great ignorance on the 
 part of those who directed the matter. In the first place, the extra 
 metal employed could be used to much better advantage by being dis- 
 tributed over the upper portion of the building ; and, in the second, good 
 earth connection's are too expensive to be needlessly multiplied. The 
 heaviest item of expense in the construction of most rods is, or ought 
 to be, the earth connection, if it be properly made. One good one is 
 amply sufficient ; half a dozen poor ones are of no use at aU. 
 
 It is obvious that the rod should be carried from the roof to the 
 ground by the shortest possible way. Some have even recommended 
 that it be carried down the chimney a plan in which there is nothing 
 objectionable, provided it happen to be the most convenient. 
 
 BarnS. Before leaving the subject of the arrangement of light- 
 ning-rods, it may be well to say a few words in regard to the peculiar 
 conditions found in barns, ice-houses, and similar structures, and the best 
 means of protecting them. It has long been known that barns, and 
 stacks of hay and grain, are peculiarly liable to be struck by lightning ; 
 and the reason of this is not difficult to discover. It rarely happens 
 that grain or hay is perfectly dry when put away, and the peculiar 
 character of the atmosphere that prevails during the approach of a 
 thunderstorm furnishes just the conditions necessary to produce heat- 
 ing or fermentation, and the consequent production of a stream of dense, 
 moist vapor, having comparatively high conducting power. This 
 stream of vapor forms in reality a conductor leading from the clouds to 
 the barn, or stack, but ending there the very condition that we should 
 seek to avoid ; for while a conductor that leads past any object is a sure 
 protector, a conductor that leads to an object, and ends in that object, 
 is an equally certain destroyer. Our aim must, therefore, be to cause 
 any natural conductor that may exist, to coincide with our artificial 
 conductor, and unite with it. This is best accomplished by furnishing 
 all barns designed for the storing of hay with a ventilator on the ridge, 
 and leading the lightning-rod to this ventilator. Where there are no 
 ventilators but doors, or large open windows in the gable, as in the barn 
 shown in Figure 2, the most efficient method will be to carry a stout 
 rod horizontally from the ridge, for a distance of two or three feet. 
 To carry it vertically in such circumstances will be of no use, as it will 
 then be led out of the current of conducting vapor, while if it project 
 horizontally, it will be carried into that stream, whether the vapor 
 ascecds vertically, or is carried off in the manner shown in our sketch. 
 
LIGHTNING-RODS. 17 
 
 Where ventilators are placed on a barn for the purpose just mentioned, 
 they should take the form 'of an observatory, or cupola, and the rod 
 should be carried down at least four sides or corners of this cupola. 
 
 Should Lightning-Rods be Painted? it is not 
 
 many years since one of our popular journals, whose main claim to 
 public favor is based upon its supposed reliability in scientific matters, 
 gravely informed its readers that lightning-rods should not be painted 
 because the electricity passed along the surface, and to paint the rod 
 would be to render the surface a non-conductor and of course to destroy 
 the efficiency of the rod ! And in a circular published by the well- 
 known E. Meriam, of Brooklyn Heights, a circular which was not 
 only published in our most widely circulated public journals, but was 
 distributed by the thousand by Mr. Meriam himself, this idea is advo- 
 cated. As Mr. Meriam's name has been very generally regarded as of 
 pretty good authority, it is no wonder that this idea has in many quar- 
 ters taken strong hold of the public mind, and it may not be out of place 
 to state the grounds upon which it is regarded as erroneous by all scien- 
 tific men. 
 
 In the first place, it is an erroneous idea that it is the surface alone 
 of a rod which has the power of conveying the electricity. This we 
 Lave shown very fully when discussing the proper size and shape of the 
 rod. In the second place, the surface of the metal would remain me- 
 tallic even if covered with a dozen coats of paint. The fact is, that 
 every lightning-rod is covered with a coating of non-conducting ma- 
 terial, whether we will or not ; and this material is quite as good a 
 non-conductor as paint ! We refer, of course, to the air which of ne- 
 cessity surrounds every rod, and which is well known to be a non-con- 
 ductor. Even in the case of static electricity, which resides almost 
 exclusively on the surface, it is found that to paint or what is the 
 same thing to varnish the conducting surfaces does not diminish their 
 power to receive, retain, or convey a charge of electricity. All elec- 
 trical apparatus is carefully varnished with one of the best of non-con- 
 ductors, shellac varnish. Even the prime conductor, which it is desi- 
 rable to keep in the very best condition for receiving and conveying 
 electricity, is always thoroughly varnished ; and this operation has never 
 been known to affect its efficiency. Submarine cables are always most 
 carefully insulated throughout their entire length, and yet this opera- 
 tion does not detract from their conducting power. The truth is, that 
 arguments innumerable might be advanced to show that paint does no 
 harm ; but the above will suffice. In conclusion, we would merely ask 
 the opponents of painting why they are all advocates for insulation ? 
 It seems to us, that, if a coat of paint is sufficient to destroy the conduct- 
 ing power of a rod, the insulators themselves must detract from its 
 efficiency, since it must be very difficult for the lightning to dodge 
 around them ! ! 
 
18 LIGHTNING-RODS 
 
 To our readers we would say, paint your rods, no matter of what 
 material or of what construction. By so doing, you will protect them 
 from the influences of the atmosphere, which in the case of some 
 metals, such as iron, is very destructive. Moreover, you can thus 
 cause them to resemble, in color at least, the building to which they 
 are attached ; and, as lightning-rods can never be an ornament to any 
 edifice, you will thus be enabled to hide what would otherwise be a 
 disfigurement. In a series of directions by Professor Henry, of the 
 Smithsonian Institute of Washington, communicated to a gentleman of 
 Boston, and extensively published by the papers throughout the Union, 
 it is recommended to paint the rods with Uack paint, on the ground 
 [that such paint is a good conductor. The alleged fact is not true, and 
 i the directions are injudicious. Black paint does not conduct any 
 better than any other paint ; this we have tested by experiment. To 
 attach a black rod to a light-colored house would be outrageous. 
 
 Termination of the Rod in the Air. At an early 
 
 period in the history of the lightning-rod attention was called to the 
 rapidity with which points give off and receive electricity, and also to 
 the fact, that when a Leyden jar is discharged by means of a sharp 
 point, we no longer have that loud explosion that occurs when the ends 
 of the discharger are furnished with balls. Reasoning from these facts, 
 Franklin, with his usual sagacity, recommended the use of pointed 
 conductors, and they have been used ever since, although at first they 
 were most bitterly assailed by certain court favorites in England. This 
 famous discussion, which was known as " The War of the Knobs and 
 Points," ended in the almost universal acceptance of the form recom- 
 mended by Franklin; and wherever lightning-rods were used, they were 
 made to terminate in points. 
 
 Some persons, seeing that a single point is so efficacious, have advised 
 that several be used, upon the ground that two points would do twice 
 as much work as one. Those who adopt this view forget that the more 
 we multiply the points, the more nearly do we approach to the form of 
 a ball or blunt rod. Experiment shows very clearly that two points 
 are not as efficient as a single one, and that the more points we have, 
 the more the conductor acts like a ball. 
 
 After all, however, the term point is a comparative one. That which 
 would be a fine point when opposed to the side of a house, becomes a 
 blunt rod when used in connection with the ball of a Leyden jar. And 
 how large may that point be which will bear to a thunder-cloud, ex- 
 tending over thousands of acres, the same relation which a fine pin 
 bears to the knuckle of the human hand, or even to the conductor of an 
 ordinary electrical machine? Under such circumstances, the entire 
 railings of a Mansard roof become, virtually a point ; and a space equal 
 to that exposed by the top of a chimney, is certainly small. 
 
 Considerations such as these have led many of our best electricians to 
 
LIGHTNING-RODS. 19 
 
 discard the use of points, and to advocate the adoption of blunt conduc- 
 tors, and even balls. Thus De La Rive, in his " Traite d'Electricite," 
 (Tome III, page 161), speaking of the aerial termination of lightning- 
 rods, says : ' We even believe that a small sphere of gilt copper would 
 be preferable, for it would resist more powerfully all destructive agen- 
 cies, and its radius of activity would not be much less than that of a 
 moderately simrp point. It would also have the advantage, that its 
 influence would be exerted in all directions, an important feature in 
 the not very rare cases, in which the lightning strikes buildings later- 
 ally." The truth is, that the point is not one of very great importance; 
 though, in regard to the causes which induce lightning to strike build- 
 ings laterally, those who have studied carefully the section on the ar- 
 rangement of the conductor, will be able to appreciate the probable 
 efficiency of a gilt ball in warding off such strokes. 
 
 The ablest and clearest exposition of this subject that we have met, 
 is that given by the Committee of the French Academy, in their last 
 report upon the protection of buildings from lightning. This commit- 
 tee consisted of MM. Becquerel, Babinet, Duhamel, Fizeau, Edm. Bec- 
 querel, Regnault, le Marechal V aillant, and Pouillet, all names of men 
 standing in the front ranks of scientific Frenchmen. After describing, 
 the main features of a well-constructed lightning-rod, they go on to say : 
 " Supposing a lightning-iod to be erected in accordance with these 
 conditions, let us examine, in a general manner, the phenomena 
 which would occur during thunderstorms. The electricity developed 
 by influence in the subterranean water-bed, instead of accumulating 
 there, as we have formerly described (when no conductor was present 
 Trans.\ finds the foot of the conductor, and rushes to escape by this 
 path ; for, even in the interior of a solid metallic bar, however long it 
 may be, the electric fluid expands itself with a rapidity which may be 
 compared to the velocity of light. It is in this way that the electric 
 fluid in the subterranean water-bed is attracted by the cloud, and sud- 
 denly accumulates in the upper part of the lightning-rod. It there pro- 
 duces certain curious phenomena, which it is necessary to detail. 
 
 " If the lightning-rod ends in a very fine and sharp point of gold or 
 platinum, the fluid attracted by the cloud exerts against the air, which is 
 a bad conductor, a pressure so great that it will escape, producing at 
 the same time a luminous star, visible in darkness. The rays diverging 
 from this star diminish in brightness as they recede from the point ; 
 they are rarely visible for a greater distance than fifteen to twenty cen- 
 timetres. The air is powerfully electrified by them, and there is hardly 
 any doubt but that these particles of air, thus charged with fluid from 
 the point, that is with the attracted fluid, are carried even to the cloud 
 itself, if the air be calm, and thus neutralize a portion, more or less ap- 
 preciable, of the fluid with which the clouds are charged. It is this 
 neutralization which is called the preventive action of the rod. 
 
 "At the same time that the sharp point gives rise to the luminous star 
 
20 LIGHTNING-RODS 
 
 (aigrette), the escaping electricity often attains such a degree of inten- 
 sity that the point becomes heated even to fusion ; in this case, gold, 
 and even platinum itself, although much less fusible, fall in large drops 
 along the copper or iron to which they are attached. When a lightning- 
 rod has thus lost its sharp point, and when its upper end has become a 
 mere large, fused button of gold or platinum, we naturally inquire if it 
 has not been rendered useless ? This question may be answered in the 
 negative, provided the rod continues to fulfill two essential conditions, 
 which are : 1, that it shall be continuous, and 2, that its lower extremity 
 shall communicate largely with the subterranean water-bed. In losing 
 its point, the lightning-rod loses only its preventive action. The star is 
 now produced only under the influence of a much more powerful elec- 
 trical action ; and fusion; which depended chiefly upon the fineness and 
 sharpness of the point, is renewe 1 only with great difficulty, whilst, at 
 the same time, it leaves things precisely as they were before. The air 
 is no longer electrified by the star in a luminous form ; this part 
 of the preventive action has disappeared ; the other part, that 
 which depends upon the electrifying of the air by contact with the 
 upper part of the rod, is probably much lessened. Finally, if, as often 
 happens, the electrified air from the star, and from the rod itself, should 
 be carried by the wind away from the cloud, the preventive action is 
 often reduced to nothing, which, however, is not greatly to be regret- 
 ted. The conclusion is, that in losing its sharp point, a lightning-rod, 
 in reality, loses but a very trifling advantage. 
 
 " These considerations led the Commission of 1855 to advise that the 
 upper end of the rod be terminated by a cylinder of copper, eight-tenths 
 of an inch in diameter and eight to ten inches long, the summit being 
 tapered off into the form of a cone one and a quarter or one and a half 
 inches high. This copper cylinder is attached to the rod by means of a 
 screw, and is brazed to it so as to make metallic contact certain. 
 
 " Taking, now, for our example, a rod, of which the summitis termin- 
 ated by a cone of copper, and leaving out of consideration what is 
 known as the preventive action, let us examine the phenomena which 
 are produced during storms. 
 
 " The copper cone may still sometimes present the spectacle of a lu- 
 minous star, but less often than sharp points of gold or platinum ; even 
 then it resists fusion by reason of its form, and, above all, by reason of 
 its great conducting power. If the lightning should strike, it is by the 
 copper cone that it penetrates the rod, and it is by the rod that it passes 
 to the subterranean water-bed and is neutralized. The two points of 
 departure of the lightning reside, one upon the cloud and the other upon 
 the summit of the lightning-rod ; there is no appearance of light or of 
 electricity in any other part of the circuit. The current produced by the 
 lightning passes through the entire substance of the conductor, just as 
 the current produced by an electric or voltaic battery passes through an 
 iron wire of sufficient diameter. 
 
LIGHTNING-RODS. 
 
 21 
 
 " These are the phenomena attending an ordinary 
 stroke of lightning, only it does no damage to the 
 rod or to the edifice which the latter protects ; it re- 
 sembles the innumerable discharges which, during a 
 thunderstorm, occur in the middle of the atmos- 
 phere. 
 
 ' Figure 5 gives a section of the copper cylinder at- 
 tached to a stiff iron rod, which supports it above the 
 building." 
 
 These conclusions we consider perfectly judicious, 
 and they show us the utter inutility of those numer- 
 ous points which we find sticking up all over our best 
 houses, and which so greatly disfigure them. In re- 
 gard also to the necessity for gilding the copper cone, 
 the popular notions are equally at fault. We have 
 examined the subject carefully, by experiment, and 
 have found that a common, rough, cast iron ball draws 
 sparks almost if not quite as well as a copper ball gilt 
 and unvarnished. Even a painted metallic ball draws 
 a spark without any appreciable inferiority to a bright 
 brass ball, so that, for ourselves, we do not see the 
 necessity for either gilding or platinizing the end of 
 the rod. If our readers desire to have their rods 
 terminate in gilt points or cones, we have no objec- 
 tions to offer, except on the score of expense and un- 
 sightliness. 
 
 The terminations which we recommend are these : 
 The rod itself, painted, for the ridge and gables, and 
 cast-iron caps on the chimneys. Such caps maybe 
 made highly ornamental instead of being a disfigure- 
 ment, as are the ordinary points with which most houses bristle, while, 
 at the same time, they serve a most useful purpose in the preservation 
 of the chimneys and the prevention of all loosening of the bricks a most 
 disagreeable, unsightly and dangerous, though a most common occur- 
 rence. All we have to say, however, is that if you desire a number of gilt 
 points sticking up all over your house there is no objection to your 
 putting them up. Our opinion is, that they do little or no good, though 
 they certainly do no harm, further than to disfigure the building. Where 
 the roof is finished off with railings, crestings, finials, &c., no better 
 termination than these can be desired. 
 
 The Best Method of Attaching Lightning- 
 Rods tO Buildings. It is a very prevalent opinion that light- 
 ning-rods should be carefully insulated from the buildings to which they 
 are attached, and hence most rods are made to pass through glass tubes 
 or insulators, the avowed object being to prevent the electricity from 
 
 FIG. 5. 
 
22 LIGHTNING-RODS. 
 
 passing into the building. The extreme worthlessness of such arrange- 
 ments ought to be obvious to any person that ever observed a flash of 
 lightning, and the positively dangerous character of the insulators will 
 be apparent to every one that carefully studies the principles which 
 govern conduction and induction. That a flash of lightning which will 
 pass through a hundred feet of air should be unable to pass from the 
 lightning-rod to any other object, merely because an inch or two of glass 
 is in the way, is a proposition too absurd to find favor with any sensible 
 man. When, moreover, we find that during a thunderstorm this in- 
 sulator is in general deluged with rain, it does not require much acumen 
 to see that the little efficiency that it ever had will, under such circum- 
 stances, be totally destroyed. We may, therefore, set it down as toler- 
 ably certain that none of the insulators in ordinary use answer the 
 purpose for which they are intended; or, in other words, that no insula- 
 tor can be invented which will prevent the lightning from leaving the 
 rod if there is any inducement for it to do so. The latter statement 
 will not appear extravagant when we remember that the discharge from 
 a powerful Rhumkorf coil will pierce through five inches of solid glass, 
 so that, if a lightning-rod were entirely cased in a glass tube, an arti- 
 ficial flash of lightning can be produced which will pass through it as 
 easily as a spark from one of the old machines would pierce a card ! 
 And if such a result can with safety be produced by artificial means, in 
 a room filled with people, what would be the limit to the effects pro- 
 duced by natural means where thousands of acres of cloud-surface are 
 engaged? Insulators do very well to talk about, but as a security 
 against Heaven's artillery they are powerless. 
 
 But not only are insulators worthless they are positively dangerous, 
 if the principle upon which they are adopted is fully carried out, which, 
 however, is but rarely done. A very little consideration will show this. 
 Thus if a house be furnished with a carefully insulated lightning-rod, 
 and should also have any large surface of metal, such as a tin roof, an 
 extensive system of gutters, or such like, connected with it, it is easy to 
 see that the house must resemble a large Ley den jar, of which the tin 
 roof, or other mass of metal, constitutes one coating, and the lightning- 
 rod and the earth constitute the other, while the insulators and the dry 
 material of the house represent the glass of the jar. If both the outside 
 and inside of this jar (the tin roof and the earth) had been connected to- 
 gether, it would have been impossible to have brought one coating into a 
 condition opposite to that of the other. But the rod being carefully insul- 
 ated from the roof, it is obvious that the inductive action of the cloud 
 will bring the roof and the earth into opposite conditions ; and if a man 
 were to form the path of least resistance between them, the discharge 
 would take place through his body, and he would probably be destroyed. 
 It is obvious, then, in the first place, that lightning-rods should be con- 
 nected with all large masses of metal which may exist in or upon the 
 house, such as metallic roofs, tin or iron gutters, or pipes, iron railings, 
 
LIGHTNING-RODS. 23 
 
 etc. In the second place, the rod should be attached to the house in the 
 neatest and least obtrusive method possible. If the rod be flat, it may 
 be pierced with small holes and tacked directly to the building ; but a 
 better way, both for round, square, and flat rods, is to employ properly 
 shaped staples of stout wire. These staples may be driven into the 
 studding of wooden houses or into the joints of brick walls, and, when 
 properly painted, will not present an unsightly appearance. 
 
 Where something better than mere staples is desired, 
 the device shown in the annexed engraving may be em- 
 ployed. It consists of a strap of metal of the same kind 
 as that of which the rod is made, bent as shown in the 
 engraving, Figure 4, and pierced with two holes, whereby 
 it may be attached to any structure by means of a couple 
 of screws as shown. The advantages of this device are, 
 that it does not weaken the rod, is not unsightly, permits 
 the rod to slide on the building as it expands and con- 
 tracts by heat and cold, and permits it to be easily ap- 
 FIG. 4. plied or removed without injury to the building. Staples, 
 however, are nearly as good and much cheaper. 
 
 Termination in the Ground. Upon the perfection of 
 
 the ground termination mainly depends the value of the lightning-rod. 
 If this be defective, no other good features can possibly make up for it. 
 And yet, so little is it understood, that a careful examination of a very 
 large number of rods leads us to believe that fully one-half the light- 
 ning-rods in existence are defective in this respect, and, consequently, 
 furnish but an insufficient protection. 
 
 In discussing the proper size of the rod, we stated that a rod of cop- 
 per need not be as large as a rod of iron, for the simple reason that 
 copper is a better conductor than iron. Now, it is well known that the 
 terms conductors and non-conductors are only comparative ; all conduc- 
 tors resist the passage of electricity to a certain degree, and all non- 
 conductors allow it to pass, though with difficulty. Iron conducts 
 many thousands of times better than water, but water conducts many 
 thousands of times better than dry earth. And just as we are able, by 
 increasing its size, to make an iron rod conduct as freely as a copper 
 one, so, by increasing the volume of water or soil employed to carry off 
 the electricity, we can make it almost as efficient as the metallic con- 
 ductor. These facts lead us to the following conclusions : 1. The end of 
 the rod ought to be made to terminate in a layer of soil that is perma- 
 nently wet; and 2. The end of the rod ought to expose to this soil as 
 large a surface as possible. 
 
 Permanently moist earth is to be attained only at considerable depths, 
 say at the level of the water in the wells in the vicinity. Unless we 
 reach this point, we can never be sure that our rod does not terminate 
 in dry or but slightly moist soil ; consequently, no effort should be spared 
 
24 LIGHTNING-RODS. 
 
 in sinking the rod to a sufficient depth. This is most easily accom- 
 plished at the time when the foundations are laid ; and we would advise 
 all builders to sink the lightning-rod termination when they sink the 
 foundation. A short portion of the stem may be allowed to rise above 
 the ground, and the conductor may be arranged and attached at a subse- 
 quent period. 
 
 In advising that the termination of the rod should expose as large an 
 extent of surface to the soil as possible, we might, at first sight, seem 
 to be departing from the principles laid down when we discussed the 
 proper form of the rod ; but the necessity for exposing a large surface 
 of rod to the soil to which the electricity is to pass will be obvious when 
 we consider that this surface is the measure of the section of solid soil 
 employed to carry off the electricity. Surface, in this part of the rod, per- 
 forms a function very different from anything performed by that part 
 of the surface of the rod that is in contact with the air. The advice 
 generally given is to bury a considerable length of the rod in coke (not 
 charcoal), and the plan is a very good one. Whether iron or copper is 
 employed, it will be well to sprinkle the coke copiously with a strong 
 solution of washing soda, for the purpose of neutralizing any acids that 
 might corrode the metals. If a trench ten feet long be sunk to the 
 depth of permanent moisture and filled to a depth of twelve inches 
 with coke, it will be ready to receive the end of the rod, and will furnish 
 a path for all the electricity that will ever tend to escape from tne clouds 
 to the earth. 
 
 As great mistakes have been often committed in this matter, we will 
 point out a few of them. The general rule being to let the rod end in 
 water, rods have been carried into cement cisterns, and cisterns hollowed 
 by human means out of the solid rock. In all such cases the end of the 
 rod was virtually insulated by the walls of the cistern, and such rods 
 would be worthless. It is a common practice amongst lightning-rod 
 men to form the earth termination by simply driving a crow-bar into 
 the earth, and inserting the end of the rod in the hole thus formed. No 
 reliance can be placed on an earth connection made in this manner. 
 The crow-bar may have been driven into perfectly dry sand ; and, in any 
 event, the amount of surface exposed by the rod, and the consequent 
 section of earth brought into action, is altogether too small. Neither 
 should rods be inserted into open wells of water, and especially should 
 we avoid doing this in the case of wells that supply drinking-water. 
 If the rod be made of copper, the well may be poisoned ; and, in any 
 event, the combined action of the air and water cannot fail to corrode and 
 injure the rod. 
 
 The accompanying engraving shows a new attachment which formed 
 the subject of a recent commendatory report from the Committee on 
 Science and Arts of the Franklin Institute, and is called though precisely 
 why, it puzzles us to tell an Equilibrium Disk. The usual size of the 
 disk is two feet in diameter. Its weight, including the seventy -two 
 
LIGHTNING-ROD IS. 25 
 
 horizontal and perpendicular discharging-points, is about forty pounds- 
 It is made of one of the common metals, though copper is preferred. 
 Iron, however, being cheapest, is generally used. Regarding the mode 
 of using it, it is stated that it should be sunk into the ground deep 
 enough to be surrounded by perpetual moisture, rarely less than six 
 feet. By exact adjustment, the rod passes through its centre, and is 
 firmly solidified to the disk by copper surrounding. The fact that this 
 device has been endorsed by a Committee of the Franklin Institute 
 gives it a certain claim to public attention, and will doubtless cause it 
 
 FIG. 5. 
 
 to be extensively adopted ; but the inventor of this attachment must 
 have very confused ideas in regard to the action of electricity and its 
 relation to points. That points serve to discharge electricity into the 
 air by imparting it to the molecules of the air, which are then repelled 
 and fly off, giving place to others, we can very well understand. But, 
 when a point is embedded in a solid mass whose particles are immov- 
 able, we cannot see how a point can act more efficiently than any other 
 surface. In so far as this new attachment presents a great extent of 
 surface, it is to be commended ; but we must remember that the same 
 extent of surface might be obtained in a far more, efficient form, and at 
 a greatly diminished cost. Moreover, while a single point, exposed to 
 the air, acts in the manner which the inventor of this device assumes 
 that his points will act, a multiplicity of points will, as we have else- 
 where stated, act pretty much like a ball. We refer to the device only 
 for the purpose of condemning it. 
 
26 LIGHTNING RODS. 
 
 Hints to Persons Exposed to Thunderstorms. 
 
 Little that is really of value can be said upon this subject. The old 
 directions about avoiding the shelter of trees are sound ; though the ad- 
 vice which goes to an opposite extreme, and recommends us to go to 
 the middle of an open field, is decidedly bad. A tall tree will, in general, 
 protect a space of considerable diameter the accepted rule giving a 
 circle whose diameter is four times its height ; though, as elsewhere 
 noted, we do not place implicit confidence in this. Now, it is a curious 
 law of electrical action, that, if two bodies combine to form the medium 
 of conduction, one being a good conductor and the other a poor one, 
 the good conductor does not carry off att the charge ; it merely divides 
 it with the poor conductor, which gets a share that is precisely equal to 
 its capacity. When a man stands beside a tree that is struck by light- 
 ning, the charge divides, and the man is apt to receive such a proportion 
 as is sufficient to kill him. But, if he had stood at a distance a little 
 greater than the height of the tree, the latter would have attracted the 
 bolt, which in that case would not have been divided. When standing 
 in the middle of an open field, there is nothing to attract, the lightning 
 from us, and we run great risk of being struck. 
 
 The old directions about feather beds, glass windows, etc., are all 
 nonsense. One of the safest of all places is a house well protected by 
 good lightning-rods ; one of the most dangerous is a barn filled with 
 new hay and without a rod. In a house unfurnished with lightning- 
 rods, the most dangerous places are near the fireplace or chimney, or 
 near those corners down which the water-spouts descend. Referring to 
 our remarks about the division of a lightning-stroke when two parallel 
 paths are presented to it, it must be noted that the quantity of the 
 charge that passes down each conductor will be in proportion to its 
 conducting power. A good lightning-rod has a power of conduction so 
 much in excess of the body of a man, that there would be very little 
 left to pass through him. On the other hand, the conducting power of 
 trees, the soot of chimneys, tin water-pipes, bell-wires, etc., is so low, 
 that a human body might have assigned to it a greater proportion of 
 the charge than it could bear. A few years ago some wise-acre invent- 
 ed a portable lightning-rod consisting of an umbrella having a metal 
 stem, to the lower part of which was attached a chain that was allowed 
 to drag along the ground. Such a contrivance is not only useless, but 
 dangerous. It would be utterly impossible to give such a portable rod 
 a good ground connection ; and without this a lightning-rod is worse 
 than useless. 
 
 The carrying of metal rods or bars is, of course, dangerous, because 
 every mass of metal tends to open up a line of least resistance of which 
 it will form a part ; though metal cannot be said to attract lightning in 
 the sense that a magnet attracts a bar of iron. 
 
 It has been said that a lightning-rod no more attracts the lightning 
 than a water-spout on a house attracts the rain. This is but partially 
 
LIGHTNING-RODS. 27 
 
 true. The rod attracts the lightning to about the same extent that an 
 open sluice may be said to attract the escaping waters of a pond. 
 
 Lightning-Rod Swindles, Next to the substitution of 
 saw-dust packages for counterfeit money, and the sale of brass jewelry, 
 the business of putting up lightning-rods is a favorite field for the op- 
 erations of the swindling fraternity. Indeed, to such an extent is it 
 carried, that at the West there are large companies formed whose gains 
 are derived chiefly from the swindling part of their schemes, and not 
 from the legitimate business of honestly putting up good rods. These 
 scoundrels operate in a manner somewhat like this : Approaching a 
 house in the absence of the men, they so terrify the ladies by means of 
 horrible stories of persons killed and houses destroyed by lightning that 
 when the proprietor returns he gets no peace until a rod is ordered. 
 Then these fellows get an order for a rod at so much per foot, they 
 giving a verbal estimate of the amount required, which estimate is not 
 embodied in the contract, and forms no part thereof. They then go to 
 work ; and being, by the terms of the contract, the sole judges of the 
 amount required, they contrive to put on three or four times the num- 
 ber of feet originally mentioned. Of course, when the bill is presented, 
 the victim sees no way of escape from the terms of his written contract, 
 and he pays the amount ; and, when we remember that for a rod which 
 costs them ten cents per foot, these fellows frequently charge 50 or 70 
 cents, it will be readily seen that the transaction is a profitable one for 
 them. There is no doubt but that many of these suits might be suc- 
 cessfully resisted, though of course the best way is to avoid falling into 
 the trap ; and, to enable our readers to escape it, we offer the following 
 hints : 
 
 If you make a bargain with a professional lightning-rod man to put 
 up a rod for you, see that the contract specifies the number of feet as 
 well as the price per foot. In your selection of the kind of rod, you 
 will probably be guided by what we have previously said on this sub- 
 ject. If so, then remember that the best copper rod need not cost, for 
 materials alone, over fifteen to twenty cents per foot ; and, if you 
 have read attentively our paragraph on the arrangement of the rod, 
 you will find no difficulty in determining where it should be carried, 
 and, consequently, the number of feet that will be required. 
 
 The point in which you will be most apt to be cheated will be the 
 ground connection. We have already given abundant directions in re- 
 gard to this matter. Your only chance for safety lies in giving this 
 part of the work your personal supervision during its progress ; after it 
 is finished, no man can tell whether or not it is efficient, without such 
 an examination as would cost as much as it would to do the work 
 over again. 
 
 Surveying Lightning-Rods for Insurance Pur- 
 poses. Insurance companies cannot, with safety, ignore the value 
 
28 LIGHTNING-RODS, 
 
 of the lightning-rod. We therefore give a few hints, which may prove 
 of value to insurance agents who wish to determine whether a house 
 or barn is efficiently protected. 
 
 The general principles governing the subject have been already dis- 
 cussed ; but it must be borne in mind that a rod may be efficient, and yet 
 neither economical nor neat. Moreover, while, for purposes of fire insu- 
 rance, insulators are of no benefit, they are not a source of danger as 
 they unquestionably are in regard to life. Points, etc., are not of much 
 consequence if the rod has been properly arranged ; in regard to this 
 we would refer to the paragraph on tnat subject. So far as that por- 
 tion of the rod that is above ground is concerned, the chief conditions 
 to be observed are, that it shall be large enough, that it shall be contin- 
 uous, and that it shall be well arranged. It is in regard to the ground 
 connection that the great difficulty arises. To examine a ground con- 
 nection would be a work of great labor and expense ; and therefore we 
 must rely upon other sources of information. We see no safe mode of 
 obtaining the required information except by the written affidavit of 
 the parties concerned. We lay great stress upon the importance of 
 obtaining a written affidavit ; mere verbal communications, and state- 
 ments made in writing without the solemnity of an affidavit, are in 
 general too vague to be depended upon. 
 
 The points of inquiry should be in regard to the depth to which the 
 rod is carried, the mode in which it is arranged, and the extent of sur- 
 face that it presents to the soil. After these points have been testified 
 to, the surveyor should determine, by examining the wells in the 
 vicinity, and by other indications, the probable depth at which per- 
 manent moisture is to be found ; and from these data the efficiency of 
 the ground connection can be determined. Any falsification in the 
 statement made by the insured ought to void the policy ; and. if an ac- 
 cident should occur from lightning, no time ought to be lost in making 
 a thorough examination. 
 
APPENDIX. 
 
 HOME-MADE LIGHTNING-RODS. 
 
 Since the issue of this little volume, we have received numerous 
 inquiries in regard to the best material, etc., for the construction of 
 Lightning-Rods, by those who do not make a regular business of put- 
 ting them up. It frequently happens that farmers, builders, carpenters* 
 and mechanics in general, have occasion to put up Lightning-Rods, 
 and find a difficulty in procuring the necessary material and fixtures 
 for the purpose. To such persons the following hints may prove 
 useful. 
 
 In very out-of-the-way places, the rod may be made of round or 
 square iron rod, five eighths of an inch in diameter. The lengths may 
 be welded together in a blacksmith's shop, and drawn to the building 
 for which it is intended. A single rod, leading by the shortest path 
 from the highest chimney to the ground, is all that need be made in 
 one piece. Those parts of the rod that lie along the ridge and the gable, 
 may be connected to the main rod simply by a hook, which should, 
 however, be closed as tightly as possible upon the rod which it clasps ; 
 and if such joints occur over straw, shingles, or boards, it will be well 
 to slip a piece of sheet-iron, tin, or zinc, under the joint, and secure it 
 in its place by a few tacks. , No fear need be entertained that the elec- 
 tricity will not follow the rod across such joints. The electricity pro- 
 duced by rubbing a common glass bottle with a piece of flannel will 
 jump across a break half an inch wide; and it is therefore ridiculous 
 to suppose that a break of a hundredth of an inch would impede the 
 progress of a thunderbolt. But wherever such a break exists, a spark 
 may be produced, and it is to prevent the possibility of such a spark 
 setting fire to light combustibles that we recommend the use of thin 
 sheet-metal laid under the joint. 
 
 But where good copper wire can be readily procured, it forms very 
 much better material for the construction of home-made Lightning- 
 Rods. The most suitable size is No. or 00, which gives a solid section 
 that is several times that of the tubular copper-rods in common use, 
 most of which, by the way, are so light that they can not afford efficient 
 protection against a heavy stroke. But notwithstanding the increased 
 weight and efficiency of the plain wire, it will be found to cost much 
 less per foot than the fancy rods usually sold by itinerant venders. 
 Such wire can be obtained of an} 7 respectable hardware merchant, or 
 it may be procured direct from the manufacturers, of whom there 
 
30 APPENDIX. 
 
 are several, amongst others the Waterbury Brass Company, whose 
 agency is at 52 Beekman Street, New York. The wire comes in rolls 
 measuring thirty to lorty feet in length. The following gives the 
 diameters and weights per hundred feet of the sizes suitable for Light- 
 ning-Rods: 
 
 Number on Weight of 
 
 wire-guage. Diameter. 100 feet. 
 
 000 . . .409 inches. . . 50 Ibs. 
 
 00 . . .364 " 40 " 
 
 . . .324 " 32 " 
 
 1 . . .289 " . . 25 " 
 
 2 . . .257 " 20 " 
 
 Joints are easily made by flattening the ends of the pieces to be 
 united, binding them together with fine copper wire, and soldering the 
 whole, binding-wire and all, into a solid mass, a very simple and easy 
 job. For attaching such a rod to a house, nothing is better than small 
 wire staples. A flat strip may be made to look much better than a 
 wire, but is not in any respect more efficient. 
 
 From the fact that it is much more pliable than copper wire, and 
 can be obtained in pieces of almost any length, the copper wire-rope 
 that is now so extensively used for many purposes, is an excellent 
 material for lightning-rods . It can be put up with less trouble than 
 any other kind of material, and it is the most convenient for forming 
 a ground connection; for, by untwisting the ends for a length of sev- 
 eral feet, it is easy to spread the rope over a large surface of earth. 
 
 Rods carefully constructed of any of these materials will prove 
 far superior to those in common use, besides being far cheaper. Of 
 course all the precautions detailed in the body of this work in regard 
 to arrangement, ground connection, etc., must be fully carried out, if 
 we would secure perfect protection. In general, most of the details 
 are sufficiently well attended to, with the exception of the ground 
 connection. At this point, almost all the lightning-rods ordinarily 
 put up, fail. In our first edition we dwelt upon this point very fully, 
 and further observation not only fully confirms the remarks made on 
 page 23, but leads us to believe that our statements were not half 
 strong enough. Mr. Brooks, the well-known inventor of the Paraffin 
 Insulator, a man whose practical acquaintance with the science of 
 electricity is perhaps as extensive as that of any man in the country, 
 writes me as follows: " There were three disasters in this city (Phila- 
 delphia) last season, involving a loss of over two hundred and fifty 
 thousand dollars, by lightning Solm's Woollen Factory, Morris Iron 
 Foundry, and the Point Breeze Refining Co., every one of which had 
 a lightning-rod; and the cases of general interest in the country are 
 of such common occurrence that I have, as a matter of interest, meas- 
 ured the resistance of these joints to earth, and find the average to be 
 above the resistance of a hundred miles of telegraph-wire." That is 
 to say, a flash of lightning would rather travel one hundred miles 
 along a telegraph-wire than pass from these lightning-rods to the 
 ground ! Can we wonder that buildings furnished with lightning-rods 
 are so often injured when struck? 
 
APPEMMX, ;:"> I ''. I * i i />% 31 
 
 Mr. Brooks advises that in cities the lightning-rods should be con- 
 nected with the gas or water pipes. So far as the latter are concerned, 
 there can not be much objection, but in regard to a connection with 
 the gas-pipes, we hold different views. We must remember that there 
 are two sides to this question, and two parties to be consulted, the 
 owner of the lightning-rod and the gas company. Looking wholly to 
 the interest of the former, we would advise him by all means to con- 
 nect his rod to the gas or water pipes, or both, but to be sure that the 
 connection is made outside of his own premises, as instances have 
 occurred where the pipes connected with the metre have been dislo- 
 cated, and the gas set on fire by a lightning stroke. If, however, the 
 rod be carefully connected with the pipes outside of the house, no 
 danger can accrue to the house from this source. But how is it with 
 the pipes themselves ? Those who are familiar with the character of 
 our streets, at the depth at which ordinary gas-pipes are laid, know- 
 that the soil is generally about as dry as soil can be, and it is kept in 
 this condition by the pavement above, which shields it from the rain, 
 and by the drains below, which carry oft' any little moisture that may 
 find its way below the surface. These pipes, therefore, are embedded 
 in an almost perfect non-conductor, and any electricity that enters 
 them must flow along to a considerable distance before it can find an 
 efficient outlet. In the mean time, it meets with an obstacle at every 
 joint, for these joints are always made in such a way as to be virtually 
 non-conductors. At each joint of the pipes, therefore, an electric ex- 
 plosion will occur; and, if the electricity be in sufficient quantity, the 
 joint may be entirely ruptured, and instances are on record where gas- 
 pipes have been disjointed, and the gas allowed to escape. While, 
 therefore, a connection with the gas-mains must prove very advan- 
 tageous to the individual whose house is to be protected, it may prove 
 very disastrous to the public at large. We hold, therefore, that no 
 man has a right to connect his lightning-rod with the gas-pipes of our 
 cities. Let each one find a ground connection for himself, unless in- 
 deed two or more neighboring householders should decide to combine 
 for the formation of a thoroughly efficient ground termination. Where 
 four parties combine for this purpose, the advantages would be quad- 
 rupled, and, at the same time, there are fortunately no counterbalancing 
 disadvantages. 
 
 In the instructions issued by the Inspector-General of Fortifications, 
 British army, which instructions have been adopted in the Ordnance 
 Manual published by the authority of the United States Government, 
 and are substantially the same as those contained in our own little 
 work, the following passage occurs: " If it be possible, in regulating 
 the surface-drainage, to lead a flow of water, during the rain which 
 generally accompanies thunder-storms, over the sites of the trenches 
 in which the ground terminations are laid, it will be an additional 
 precaution." The advice deserves attention. 
 
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 HOW TO USE THE MICROSCOPE. 
 
 A Simple and Practical Book, intended for beginners. 
 BY JOHN PHIN, 
 
 Editor of " The American Journal of Microscopy." 
 
 Second Edition. Greatly Enlarged, with 50 illustrations in the text, 
 
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 PRESERVATION OF OBJECTS. General Principles. Recipes for Preserv- 
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 FINISHING THE SLIDES. 
 
 Hay be obtained from any Bookseller or News Agent, or will be sent by 
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THE AMERICAN 
 
 JOURNAL OF MICROSCOPY, 
 
 -A.3STZD 
 
 POPULAR SCIENCE. 
 
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 The object of the JOTJRXAL OF MICROSCOPY ia to diffuse a knowledge of the 
 best methods of using the Microscope; of all valuable improvements in the in- 
 strument and its accessories; of all new methods of microscopical investigation, 
 aud of the most recent results of microscopical research. The JOURNAL does 
 not address itself to those who have long pursuer! certain special lines of re- 
 search, and whose wants can be supplied only by elaborate papers, which, from 
 their thoroughness, are entitled to be called monographs rather than mere arti- 
 cles. It is intended rather to meet the wants of those who use the microscope 
 for purposes of general study, medical work, class insructiou, a; d even amuse- 
 ment, aud who desire, in addition to the information afforded by text-books, 
 such a knowledge of what others are doing as can be derived only from a peri- 
 odical. With this object in view, therefore, the publishers propose to make the 
 JOUBNAL BO simple, practical and trustworthy, that it will prove to the advantage 
 of every one who uses the microscope at all to take it. 
 
 ILLUSTRATIONS The JOURNAL will bo freely illustrated by engravings 
 representing either objects of natural history or apparatus connected with the 
 microscope. 
 
 TRANSACTIONS OF SOCIETIES. THE AMERICAN JOURNAL OF MICROSCOPY 
 is not the organ of any Society, but it gives the proceedings of all Societies 
 whose officers send us a report. As the JOURNAL is devoted wholly to Micro- 
 scopy, and is in good form aud size for binding, no better medium can be had 
 for preserving the scientific records of any society. Matters of mere business 
 routine we are frequently obliged to omit for want of room. 
 
 EXCHANGES. An important feature of the JOURNAL is the exchange column, 
 by means of which workers in different parts of the country are enabled, with- 
 out expense, except for postage, to exchange slides and materials with each other. 
 
 During the first two years of its existence, the subscription to the AMERICAN 
 JOURNAL OF MICROSCOPY was only fifty cents per year, but at the request of 
 more than two-thirds ol the subscribers, the size of the JOURNAL has been 
 doubled, and the price raised to 
 
 OXE DOLLAR PER YEAR. 
 
 Four copies for three dollars. Those who wish to economize in the direction 
 of periodicals, would do well to examine our clubbing list. 
 
 FOREIGN SUBSCRIBERS. The JOURNAL will be sent, postage paid, to any 
 country in the Postal Union for $1.24, or 6 shillings sterling per year. English 
 postage stamps, American currency or American postage stamps taken in pay- 
 ment. In return for a postal order or draft for 1 5s., five copies of the JOURNAL 
 will be furnished and mailed to different addresses. Make all drafts and postal 
 orders payable to John Phin. 
 
 BACK VOLUMES. We have on hand a few copies of Vols. I and II, bound in 
 ha dsome cloth cases, which we offer for $1 25 each. Vols. I and II, bound, and 
 the numbers of Vol. Ill, as issued, we offer for $2.50. We can no longer supp y 
 complete sets of 1876-7 in sheets. To those who wish to examine the journal, we 
 will send ten odd numbeis for 25 cents. 
 
 The JOURNAL or MICROSCOPY, from its very nature, is a visitor to the very 
 best families, and its value as an advertising medium has therefore proved to be 
 much above that of average periodicals. A few select advertisements will be 
 inserted at the rate of 30 cents per line, nonpariel measure, of which twelve 
 lines make au inch. Addi ess 
 
 AMERICAN JOURNAL OF MICROSCOPY, 
 
 P. O. Box 2852, New York. 
 
NEW BOOKS IN PRESS, 
 
 Supplements to this Catalogue will be issued from time to 
 time, and will be sent free to any one desiring them. Since 
 our removal to the larger and more commodious premises at 
 14 Dey Street, we have made arrangements to greatly extend 
 our publishing business. 
 
 The following books are in a forward state of preparation, 
 and will be issued at an early day : 
 
 The Aquarium. 
 
 A Practical Treatise. With nearly one hundred illus- 
 trations. By. A. W. Boberts, formerly of Barnum's 
 Museum Aquaria, Collector for the New York Aquarium, 
 and Superintendent of Sea Side Aquarium. , 
 
 Mr. Roberts having had over thirty years experience, has therefore 
 been able to produce a thoroughly practical book. The accuracy of 
 the illustrations are guaranteed, by the fact that they are carefully 
 drawn and engraved by the author from life. 
 
 Taxidermy; or, The Art of Preserving and Stuffing Beasts, 
 Birds and Fishes. 
 
 This work is by a practical Taxidermist, who is perhaps 
 better known than any other of the profession in this 
 country. It will be simple, thorough and practical. 
 
 Fret and Scroll Saws: Their Construction and Use. 
 
 ' Notwithstanding the many works on this subject now before the 
 public, we think that there is room for one more. The volume which 
 we propose to bring out is by a gentleman whose profession (that of 
 an architect) has given him special qualifications for producing a 
 really good book, and one free from the errors of taste and instruc- 
 tion in practical workmanship, which have disfigured so many at- 
 tempts in this direction. It will be very copiously illustrated. 
 
 We shall also issue a portfolio of twelve designs, full working size, 
 for Fret and Scroll Saw Work. The set will be sold at a very moder- 
 ate price. 
 
Young Scientist Companion. 
 
 This is a small pocket book intended for the practical 
 man, as well as the young scientist. It will contain 
 rules and data for calculations ; tables of physical and 
 chemical data ; recipes ; processes, and in fact just that 
 practical information which every man has so often oc- 
 casion to refer to. 
 
 Cage Birds, and How to Care for Them. 
 
 With a full account of the best methods of training, etc. 
 This work is by a lady who has long been known as a successful 
 authoress, and who is noted for her skill in the care of household pets- 
 It will be splendidly illustrated with nearly one hundred engravings, 
 and cannot fail to find its way into every home where a canary or 
 other song bird is kept. 
 
 Manual of Urinary Examination,. Chemical and Microscopical. 
 
 For the Use of Physicians, Medical Students and Clinical 
 Assistants. By Frank M. Deems, M. D., Laboratory In- 
 structor in the University Medical College, New York ; 
 Member of the Medical Society of the County of New 
 York ; Member of the New York Microscopical Society 
 etc., etc. 
 
 How to Learn to Draw. 
 
 By an old Teacher of Drawing. 
 
 This is the first of a series of small practical books to be called 
 " The Young Scientist Manuals." It does not profess to teach the 
 science or art of Drawing; it is intended rather to point out to the 
 beginner the best methods of going to work. It is intended for self- 
 taught students, and contains a great deal that is not to be found in 
 the books, but is generally imparted to the pupil directly by the 
 teacher. 
 
 The price of this series has been fixed at 20 cents each, neatly and 
 strongly bound in boards. 
 
 CATALOGUE OF MICHOSCOPES.-We are preparing a CATA- 
 LOGUE OF MICEOSCOPES, with hints in regard to the selection of a 
 microscope, especially as regards its suitability for the various purposes 
 for which microscopes are used. A copy of this catalogue will'- be sent 
 free to any one applying for it. Applications received before the 
 Catalogue is published will be carefully registered, and filled as soon as 
 possible. 
 
SEW WORKING MICROSCOPE, 
 
 Manufactured by Geo. Wale. 
 
 Price With two Eye-Pieces, 2-3 and 1-5 Objectives, Iris 
 
 Diaphragm, and Black Walnut Case, - - - $35. 
 
 INDUSTRIAL PUBLICATION COMPANY, 
 
 14 Dey Street, New York, Sole Agents. 
 
THE NEW WORKING MICROSCOPE, 
 
 This Microscope has just been brought out by Mr. Geo. Wale, whose 
 reputation as a maker of fine stands is so well known. It embodies 
 several new and important features, foremost amongt which is the 
 method of hanging the body, so that it may be made to incline at 
 any angle. The method now in general use for this purpose changes 
 the position of the centre of gravity of the instrument, and renders 
 the microscope more or less unsteady. The new method avoids this 
 difficulty, and at the same time furnishes a secure and convenient 
 means of clamping the body at any position a point of considerable 
 importance, when the instrument is used for some purposes. 
 
 The stage is of a new construction, very thin, so as to admit the 
 greatest obliquity in the illumination of objects, and with clips which 
 move round it, thus giving many of the advantages of a rotary stage. 
 The clips may be easily and quickly removed, so as to leave a clear 
 stage, and they may also be so applied as to hold the slide against the 
 under side of the stage, when very oblique light is required for re- 
 solving difficult test objects. 
 
 There are two means of adjusting for focus, a coarse movement by 
 means of a well-made rack and pinion, and a fine movement, in. which 
 the entire body is moved by what is generally called a "micrometer'' 
 screw, acting on a lever. The latter movement has this great advan- 
 tage, that it does not change the distance between the eye-piece and the 
 objective (as is the case with most of the English fine movements), and 
 consequently does not vary 'the magnifying power of the instrument 
 an important point in making delicate micrometric measurements. 
 
 The diaphragm is of the Iris pattern, a form which is generally 
 acknowledged to be the best, but which has hitherto been very costly, 
 those usually supplied being sold for $16. This Iris diaphragm is a new 
 form, which, with several other features of this stand, has been patented 
 by Mr. "Wale. It may be easily and quickly applied or removed. 
 
 The New Working Microscope is of substantial make, elegant design, 
 and thoroughly good workmanship. It has the Society screw; draw- 
 tube, with Society screw at lower end for receiving long focus objectives, 
 analyzing prism, etc.; plane and concave mirrors, the distance of 
 which from the object may be varied ; two Eye-pieces ; 2-3 and 1-5 
 Objectives of .Wale's Histological Series. The 1-5 easily and clearly 
 resolves the P. Angulatumytitln light of a very slight degree of obliquity. 
 
 This Microscope, with draw-tube pulled out, and the body inclined, 
 as shown in the figure, stands 13>2 inches high ; the draw-tube pulls out 
 so as to give the standard length of body. 10 inches. When placed in a 
 vertical position, with the draw-tube pushed in, the instrument stands 
 only 10)3 inches high, so that it can be used comfortably on an ordinary 
 table. This is a great convenience in the rapid examination of liquids. 
 It is very complete in all its appointments, is capable of receiving and 
 doing justice to any accessories, and is contained in a handsome black 
 walnut box, with brass handle, lock and key. It is equal to all the 
 ordinary requirements of any physician, student or naturalist. 
 
 PRICE With Accessories, as above described - $35.00. 
 
THE YOUNG SCIENTIST, 
 
 A Practical Journal for Amateurs. 
 
 ISSUED MONTHLY. Price 5O Cents per year. 
 
 It is characteristic of young Americans that they want to be DOING something. 
 They are not content with merely knowing how things are done, or even with 
 seeing them done; they want to do them themselves. In other words, they want 
 to experiment. Hence the wonderful demand that has sprung up for email tool 
 chests, turning lathes, scroll saws, wood carving tools, telegraphs, model steam 
 engines, microscopes and all kinds of apparatus. In nine cases out of ten, how- 
 ever, the young workman finds it difficult to learn how to use his tools or ap- 
 paratus after he has got them. It is true that we have a large number of very 
 excellent text-books, but these are not just the thing. What is wanted is a liv- 
 ing teacher. Where a living teacher cannot be found, the next best thing is a 
 live journal, and this we propose to furnish. And in attempting this it is not 
 our intention to confine ourselves to mere practical directions. In these days 
 of knowledge and scientific culture, the "Why" becomes ag necessary as th 
 "How." The object of the YOUNG SCIENTIST is to give clear and easily followed 
 directions for performing chemical, mechanical and other operations, as well as 
 simple and accurate explanations of the principles involved in the various 
 mechanical asd chemical processes which we shall undertake to describe. 
 
 The scope and character of the journal will be better understood from an in- 
 spection of a few numbers, or from the list of contents found on a subsequent 
 page, than from any labored description. There are, however, three features to 
 which we would call special attention: 
 
 CORRESPONDENCE. In this department we intend to place our readers in com- 
 munication with each other, and in this way we hope to secure for every one 
 just such aid as may be required for any special work on hand. 
 
 EXCHANGES. An exchange column, like that which has been such a marked 
 success in the Journul of Microscopy, will be opened in the YOUNG SCIENTIST. 
 Yearly subscribers who may wish to exchange tools, apparatus, books, or the 
 products of their skill, can state what they have to offer and what they want, 
 without charge. Buying and soiling must, of course, be carried on in the adver- 
 tising columns. 
 
 ILLUSTBATIONS. The journal will make no claims to the character of a "pic- 
 ture book," but wherever engravings are needed to make the descriptions clear 
 they will be furnished. Some of the engravings which have already appeared in 
 our pages are as fine as anything to be found in the most expensive journals. 
 
 Sipooi^vl IXTotioo. 
 
 As our journal is too small and too low-priced to claim the attention of news 
 dealers, we are compelled to rely almost wholly upon subscriptions sentdirectly 
 to this office. As many persons would no doubt like to examine a few numbers 
 before becoming regular subsoribtrs, we will send four current numbers as a 
 trial trip fcr 
 
 FIFTEEN CENTS, 
 
 Where three or more subscribe together for the journal, we offer the following 
 liberal terms: 
 
 3 copies for $1.25 
 
 5 " 2.00 
 
 7 " " 2.75 
 
 10 " " 3.50 
 
 Advertisements, 30 cents per line. 
 
 As postal currency has nearly disappeared from circulation, we receive post- 
 age stamps oi the lower denominations (ones, twos and threes) attheir full value. 
 Postal orders are, however, much safer and more convenient. To avoid delay 
 and mistakes address all communications to " THE YOUNG SCIENTIST, Box 285?, 
 New York," and make all checks and orders payable to John Plain. 
 

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