A 



SCIENC 



Eleventh Year. 

 Vol. XXI. No. 533. 



APRIL 31, 1893. 



^63ur„ Single Copies, Ten CentS 



ws^n'-' 



"j,y„ 



Contents. 



Laboratory Instruction in Physics. D. W. 



Bering 211 



A New Method of Child Study. J. Mark 



Bald.cia 213 



Japanese Nursery Notes. Albert S. Ashmead. 215 

 Notes and News — 215 



Evidence of Two Pre-Mokainic Glacial Move- 

 ments. G. D. Sioezey ■ 216 



Some Notes on Lighthouse Apparatus. J. 



Kenicard 216 



A Japanese Sick with Scarlet Fever. Albert 



S. Ashmead 218 



Electrical Notes. R. A. F. 318 



Letters to the Editor. 



Low Temperatures. Fred. G. Plumvier 219 



Where is the Litre? T. C. Mendenhall 219 



On the Teaching of Biology. Francis H. 



Herrick 220 



A New Source of the So-Called Mexican 



Onyi. George P. Merrill 221 



Book Reviews. 



The Metaspermse of the Minnesota Valley. 

 Joseph F. James 221 



Eacered at the Posi-Offloe of New Yort, N.Y., as 

 Second-Class Mail Matter. 



LEADERS IN SCIENCE SERIES. 



II. LOUIS AGASSIZ. His Life and Work. 



By Charles F. Holder. 12mo, illustrated, $1.50. 



Partial Contents: The Boyhood of Agassiz— His 

 Life at Heidelberg— His Friendship with Humboldt 

 —His Career at Harvard— His Travels— His Re- 

 ligious Belief— His Works— etc. 



" Taken as a whole no more useful life of Agassiz 

 has ever been prepared, and this volume can be 

 warmly recommended to all who wish to gain fa- 

 miliarity with one whose name and fame will live 

 always. The illustrations are excellent." — Boston 



"Mr. Holder has devoted himself rather to the 

 story of Agassiz's life and accomplishment than to 

 an analysis of him as a scientist. He has made a 

 thoroughly interesting volume, wholesome, helpful 

 to all classes of readers."— Proi!JdeJice Journal. 



I. CHARLES DARWIN. His Life and Worlt. 



By Charles F. Holder. 32mo, illustrated, $1.50. 



" Mr. Holder is one of the American savants who 

 have made Darwin and his system of philosophy a 

 subject of profound study, and his book relating to 

 him is one of the best that have been produced for 

 popular use." — Philadelphia Bulletin. 



"The author has given us a capital account of 

 Darwin's voyages, adventures, and discoveries, in- 

 dicating in broad outlines his theories and scien- 

 tific opinions, and not neglecting to throw into 

 strong light the lovable personal character and in- 

 dividual traits of the great naturalist." — Christian 

 Union. 



*»* Notes on New Books, a quarterly bulletin, 

 prospectus of the Story of the Nations and Knicker- 

 bocker Nuggets sent on application. 



G. P. PUTNAM'S SONS, 



IV C'^, 



''^ Per Yeak, in Advance. 



BUSINESS ;>:.JUNITY. 



There is an opening for a 

 young man to open a New 

 York office of the American 

 Lightning Protection Co., 

 operating under my patents. 

 But little capital will be re- 

 quired. 



N. D. C. HODGES, 



874 BROADWAY, NE W YORK 



NEW YORK; 

 ■ and 29 W. 23d Street. 



LONDON: 

 24 Bedford St., Strand. 



USEFUL. HAIVD-BOOKS. 



The Ornamental Penman's Pocketbook of Alpha- 

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 ters, 135 pp., fully illustrated, 12mo, cloth. 75 cts. 

 Notes on Design of Small Dynamo, by G. Halliday, 

 79 pp., with a number of plates to scale, 12mo, cloth, 

 $1. The Phonograph and How to Construct It, by 

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 SPON & CHAMBERLAIN, PubUshers, 12 Cortlandt 

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NEW METHOD OF PROTECTING BUILDINGS FROM LIGHTNING. 

 SPARE THE ROD AND SPOIL THE HOUSE! 



Lightning Destroys. Shall it be Tour House or a Pound of Copper? 



PROTECTION FROM LIGHTNING. 



What is the Problem ? 



In seeking a means of protection from ligktning-diacharges, we have In view 

 two objects,— the cue the prevention of damage to builolngs, and the other 

 the prevention of Injury to life. In order to destroy a baildiug iu whole or in 

 part, it is necessary that work should be done ; that is, as physicists express 

 if, energy is required. Just before the lightning-discharge takes place, the 

 energy capable of doing the damage which we seek to prevent exists iu the 

 column of air extending from the cloud to the earth in some form that makes 

 it capable of appearing as what we call electricity. We will therefore call it 

 electrical energy. What this electrical energy is, it is not necessary for us to 

 consider in thla place ; but that it exists there can be no doubt, as it manifests 

 itself in the destruction of buildings. The problem that we have to deal with, 

 therefore, is the conversion of this energy into some other form, and the ac- 

 complishment of this in such a way as shall result in the least injury to prop- 

 erty and life. 



Why Have the Old Rods Failed P 



When lightning-rods were first proposed, the science of energetics was en- 

 tirely undeveloped ; that is to say, in the middle of the last century scieotlfic 

 men had not come to recogoize the fact that the different forma of energy — 

 heat, electricity, mechanical power, etc.— were convertible one iuto the omer, 

 and that each could produce just so much of each of the other forms, and no 

 more. The doctrine of the conservation and correlation of energy was first 

 clearly worked out in the early part of this century. There were, however, 

 some facts known in regard to electricity a hundred and forty yeai's ago; and 

 among these were tbe attracting power of points for an elecd-ic spark, and the 

 •conducting power of meials. Lightning-rods were therefore introduced with 

 the idea that the electriclcy existing in the lightning-discharge could be con- 

 veyed around the building which it was proposed to protect, and that the 

 building would thus be saved. 



The question as to dissipation of the energy involved was entirely Ignored, 

 naturally; and from that time to this. In spite of the best endeavors of those 

 interested, lightning-rods constructed in accordance with Franklin's principle 

 have not furnished satisfactory protection. The reason for this is apparent 

 when it is considered that the electrical energy existing in the atmosphere 

 before the discharge, or, more exactly, in the column of dielectric from the 

 cloud to the earth, above referred to, reaches its maximum value on the sur- 

 face of the conductors that chance to be within the column of dielectric; so 

 that the greatest display of energy will be on the surface of the very lightuing- 

 rods that were meant to protect, and damage results, as so ofien proves to be 

 the case. 



It will be understood, of course, that this display of energy on the surface 

 of the old lightning-rods Is aided by their being more or less Insulated from 

 the earth, but in any event the very existence of such a mass of metal as an 

 old lightning-rod can only tend to produce a disastrous dissipation of electrical 

 energy upon its surface,— '* to draw the lightning," as It is so commonly put. 



Is there a Better Means of Protection? 



Having cleared our minds, therefore, of any idea of conducting electricity, 

 and keeping clearly in view the fact that in providing protection against light- 

 ning we must furnish some means by which the electrical energy may be 

 harmlessly dissipated, the question arises, *' Can an Improved form ba given 

 to the rod, so that it shall aid in this dissipation ? " 



As the electrical energy involved manifests itself on the surface of conduc- 

 tors, the improved rod should be metallic ; but, instead of making a large rod, 

 suppose that we make it comparatively small in size, so that the total amount 

 of metal running from the top of the house to some point a little below the 

 foundations shill not exceed one pound. Suppose, again, that we introduce 

 numerous insulating joints in this rod. We shall then have a rod that experi- 

 ence shows will b« readily destroyed — will be readily dissipated —when a 

 discharge takes place; and it will be evident, that, so far as the electrical en- 

 ergy is consumed in doing this, there will be the less to do other damage. 



The only point that remains to be proved as to the utility of such a rod is to 

 show that the dissipation of such a conductor does not tend to injure other 

 bodies In its immediate vicinity. On this point I can only say that I have 

 found no case where such a conductor (for Instance, a bell wire) has been dis- 

 sipated, even if resting against a plastered wall, where there has been any 

 material damage done to surrounding objects. 



Of course, it is readily understood that such an explosion cannot take place 

 in a confined space without the rupture of the walls (the wire cannot be 

 boarded over); but in every case that I have found rt corded this dissipation 

 takes place just as gunpowder burns when spread on a board. The objects 

 against which the conductor rests may be stained, but they are not shattered, 



I would therefore make clear this distinction between the action of electri- 

 cal energy when dissipated on the surface of a large conductor and when dis- 

 sipated on the surface of a comparatively small or easily dissipated conductor. 

 When dissipated on the surface of a large conductor, — a conductor so strong 

 as to resist the explosive effect, — damage results to objects around. When 

 dissipated on the surface of a small oondiictor, the conductor goes, but the 

 other objects around are saved 



A Typical Case of the Action of a Small Conductor. 



Franklin, in a letter to Collinson read before the London Royal Society, 

 Dec. 18, 1755, describing the partial destruction by lightning of a church-tower 

 at Newbury, Mass , wrote, " Near the bell was fixed an Iron hammer to strike 

 the hours ; and from the tail of the hammer a wire went down through a small 

 gimlet-hole in the fl.oor that the bell stood upon, and through a second floor in 

 Tike manner; then horizontally under and near the plastered celling of that 

 second floor, till it came near a plastered wall ; then down by the side or that 

 wall to a clock, which stood about twenty feet below the bell. The wire was 

 not bigger than a common knitting needle. The spire was split all to pieces 

 by the lightning, and the parts flung in all directions over the square in which 

 the church stood, so that uotbing remained above the bell. The lightning 

 passed between the hammer and the clock in the above-mentioned wire, 

 without hurting either of the floors, or having any effect upon them (except 

 making the gimlet-holes, through which the wire passed, a little bigger), and 

 without hurting the plastered wall, or any part of the building, so far as the 

 aforesaid wire and the pendulum-wire of the clock extended; which latter 

 wire was about the thickness of a goose-qulU. From the end of the pendu- 

 lum, down quite to the ground, the buillln? was exceedingly rent and dam- 

 aged. . . . No part of the aforementioned long, small wire, between the clock 

 and the hammer, could be found, except about two inches that hung to the 

 tail of the hammer, and about as much that was fastened to the clock; the 

 rest being exploded, and Its particles dissipated In smoke and air, as gun- 

 powder is by common flre, and had only left a black smutty track on the plas- 

 tering, three or four inches broad, darkest in the middle, and fainter towards 

 the edges, all along the celling, under which it passed, and down the wall."' 



One hundred feet of the Hodges Patent Lightning Dlspeller (made under 

 patents of N. D. C. Hodges, Editor of Science) will be mailed, postpaid, to any 

 address, on receipt of five dollars (?5). 



Correspondence solicited. Agents icanted. 



AMERICAN LIGHTNING PROTECTION CO., 



874r Broadway, New York City. 



