SCIENCE 



Eleventh Year. 

 Vol. XXII. No. 559. 



OCTOBEE 20, 1893. 



Single Copies, Ten Cents. 

 $3.50 Per Year, in Advance 



Contents 



Indian Relics. C. M. Pleyte 



Science Teaching- in Secondary Schools'. " Geo. 



G. Groff 



Birds of Rare Occurrence in 'Northern' Colo- 

 rado. Wm. Osburn 



Can We See 1he Picture in the 'Landscape? 



Waldo Dennis 



Coral Formations. G. H.Perkins.... 

 The Protection of Our Wild Plants and Ani- 

 mals. John Gifford 



Silk Spinning Plv Larva;. H. Garman. .' .' .' .' '..'.' 

 Scars on Apple Tree Trunks. Frank Bolles.. 

 A Mistake in Teaching Botany. B. Fink 

 Fungi Versus Insects. Gerald McCarthvr 

 Letters to the Editor: 



Inductive Psychology. E. A. Kirkpatrick.. 

 The Absence of Air From the Moon. S 



Tolver Preston 



The Sounds of R. Laura Soames '.'. 



Fossils of the Bridgeport Quarries. Paul 



Van Riper 



Coon Cats. I. N. Baskett. '..'.... '. '. '. '. '. '. '. .'..'. ! 

 Damage to Cotton by Lightning. A. P. 



McKissick 



Rhytina gigas Linn, at Princet'o'ii. "John 



Eyerman 



Sugar From Corn Stalks. A. 'stevenso'ii " 

 ■'Curious Ears of Indinn Com." A.St'v'nson. 

 Evolution of Science Teaching in Primary 



Schools. C. D. McLouth.. 

 Birds That Sing in the Night, j. M. Edson,'. 

 New Fire from the Lightning Stroke. 



Walter Hough 



Notes and News '.'.'.'.'.'.'. 



Book-Reviews 



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HEW METHOD OF PROTECTING BUILDINGS FROM LIGHTNING. 



SPARE THE ROD AND SPOIL THE HOUSE! 



lightning Destroys, Shall it be Your Souse or a Pound of Copper ? 



PROTECTION FROM LIGHTNING. 

 What is the Problem? 



Ik seeking a means of protection from llgtitning-aischarges, we have In view 

 two objects,— fhe one the prevention of damage to buildings, and the other 

 the prevention of Injury to life. In order to destroy a building In wholf or In 

 part, It Is necessary that work should be done; that Is, as physicists expre-.3 

 It, energy Is required. Just before the lighluicg-dlscharge takes plaje, 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 this 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? 



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 scientific 

 men had not come to recognize the fact that the different forms of energy — 

 heat, electricity, mechanical power, etc.— were convertible one Into the other, 

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

 more. The doctrine oi 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 years ago ; and 

 among these were the attracting power of points for an electric spark, and the 

 conducting power of melals. Lightning-rods were therefore introduced with 

 the Idea that the electricity existing In the lightning-discharge could be cou- 

 veyed around the bulldlug 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 iu accordance with Franklin's principle 

 have not furnished satisfactory protection. The reason for this i^ apparent 

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

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

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

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

 that the greatest display of energy wil 1 be ou the surface of ttie very lightning- 

 rods that were meant to protect, and damage results, as so often pro^us to be 

 the case. 



It will be understood, of course, that this display of ener3:y on the surface 

 of the old lightning-rods is aided by Iheir being more or i*^ss Insulated from 

 the earth, but in any event the very existence of suc'a a mass of metal &-^ 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 be given 

 to the rod so that It shall a. ii this dissipation ? " 



As the electrical energy Involved manifests Itself on the surface of conduc- 

 tors, the Improved rod should be melalllo; 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 shall 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 be readily destroyed — will be readily dissipated —when a 

 discharge takes place; aul 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 th6 utility of such a rod is to 

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

 bodies iu 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 recorded this dissipation 

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

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



I would therefore mafee 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 conductor, 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 ColUnson read before the London Eoyal 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 floor that the bell stood upon, and through a second floor In 

 like 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 of 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 plece>- 

 by the lightning, and the parts fiung In all directions over the square in whkh 

 the church stood, so that nothing remained above the bell. The UgblrinB 

 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 tar as the 

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

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

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

 age 1. ... No part of the aforementioned long, small wire, between the clock 

 audthe hainnjtr, oouIJ be round, except about two Inches that hung to the 

 tail nffue 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 fire, ana had only left a black smutty track on the plas- 

 tei Ing, three or four Inches broad, darkest in the mlddl", and fainter towards 

 tue edges, all along the celling, under which It passed, and down the wall. ' 



t)".e hundred feet of the Hodges Patent Lightning DIspeller (made under 

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

 address, on receipt of five dollars (15). 



Correspondence toUcited. Agents wanted. 



AMERICAN LIGHTNING PROTECTION CO., 



874 Broadway, Nevr York Citv. 



