56 
SCIENGE, 
Vol. XXIII. No. 573 
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SSS SSS 
NEW METHOD OF PROTECTING BUILDINGS FROM LIGHTNING. 
SPARE THE ROD AND SPOIL THE HOUSE! 
Lightning Destroys. Shali it be Your House or a Pound of Copper? 
PROTECTION FROM LIGHTNING. 
What is the Problem? 
IN seeking & means of protection from lightning-discharges, we have in view 
two objects,— the one the prevention of damage to buildings, aud the other 
the prevention of injury to life. In order to destroy a building in ahole or in 
part, It is necessary that work should be done; that Is, as physicists express 
it, energy is required. Just before the lightniug-discharge takes place, the 
energy capable of doing the damage which we seek to prevent exists in 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 thatit 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. y 
Why Have the Old Rods Failed? 
When lightning-rods were first proposed, the sclence 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 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 years ago; and 
among these were the attracting power of points for an electric spark, and the 
conducting power of metals. Lightning-rods were therefore introduced with 
the idea that the electricity 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 savede 
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 olectrical 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 lightning- 
rods that were meant to protect, and damage results, as so often 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 thelr being more or fess insulated from 
the earth, but in any event the very existence of such & mass of metal as an 
old lightning-rod can only tend to produce a disastrous dissipation of olectrical 
energy upon Jts surface,— ‘‘ to draw ths lightning,” as lt ls s0 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 
tothe rod sothatitshalls. ‘n 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 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; an1it 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 ouly 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 wilbout the rupture of the walls (the wire cannot be 
boarded over); butin every case that I have found recorded this dissipation 
takes place just as gunpowder burns when spread onaboard. 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 conductor, the conductor goes, but the 
other objects around are saved 
A Typical Case of the Action of a Small Conductor. 
Franklin, ina 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 floor that the bell stood upon, and through a second floor in 
like manner; then horizontally under and near the plastered ceiling of that 
second floor, till it came near a plastered wall; then down by the side of that 
wall to aclock, which stood about twenty feet below the bell. The wire was 
not bigger thana 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 nothing remained above the bell. The ligbtring 
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-quill. From the end of the pendu- 
lum, down quite to the ground, the bulljing 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 
tatl of tue hammer, and about as much that was fastened to the clock ; the 
rest being exploded, and its particles dissipated in smoke and alr, as gun- 
powder is by common fire, 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 ceiling, under which it passed, and down the wall.”’ 
ne aundred feet of the Hodges Patent Lightning Dispeller (made under 
patents of N. D. C. Hodges, Editor of Science) will be malled, postpaid, to any 
address, on receipt of five dollars ($5). 
Correspondence solicited. Agents wanted. 
AMERICAN LIGHTNING PROTECTION CO., 
' 874 Broadway, New York City. 
