the Effect of Magnetic and Electric InflueJice, S^x. 267 



Magnetism, like electricity, may be rendered active on every 

 part of the surface of a body (the centre excepted), though 

 the stimulating power be applied to one of its sides only. 

 But they differ very materially in other respects : If we com- 

 municate the electric fluid to a Leyden jar, and a second be 

 connected with it by a conducting medium, they both will be- 

 come equally electrical, and that instantaneously. But in mag- 

 netism this rapid transmission of the fluid from one bar to 

 another, does not take place : if two unmagnetized bars of 

 steel be placed longitudinally in contact, or even one upon the 

 other, and a set of bars be carried over the uppermost, it will 

 become strongly magnetical ; but the lower bar, if removed 

 immediately, will not have received power sufficient to attract 

 the finest needle. 



While repeating several of my experiments on the simi- 

 larity in some respects, and the dissimilarity in others, be- 

 tween the electric and the magnetic fluids, I was led to be- 

 lieve that a more perfect conductor for securing buildings 

 from the effects of atmospherical electricity might be pro- 

 duced than any hitherto used. For the performance of the 

 experiment I procured two cast-steel rods properly hardened 

 and tempered, each three feet in length, and half an inch in 

 diameter ; one end of each bar must be hammered to a fine 

 point. 



In order to prove the superiority of a point over a knob, 

 and a pointed magnetic conductor over one nonmagnetic, I 

 conducted the experiment in the following manner : — 



I placed a brass ball two inches in diameter upon a stand, 

 at the distance of one inch from the prime conductor of the 

 electrical machine ; which in this experiment represents a 

 positively electrified cloud. When the machine was put in 

 motion, a stream of the electric fluid passed from the prime 

 conductor to the brass ball ; which may represent a building 

 or other object (if not in a negative state of electricity) in a 

 minus state compared with the prime conductor. Upon pi'e- 

 senting the unmagnetized rod to the pi'ime conductor when the 

 machine was excited, it was robbed of the electric fluid as 

 rapidly as it was produced, at the distance of nine inches, so 

 as to deprive it of the power of passing a spark to the brass 

 ball. The magnetic rod produced the same effect at the di- 

 stance of 12 inches from the prime conductor; consequently 

 we may fairly ])resume that a steel rod rendered powerfully 

 magnetic, will secure a building, in every direction, to a much 

 greater extent than one that is not magnetical. 



M. Gay-I-'H''sac (in a paper in the Ann. dc Cliiinu\ vol. xxix, 



p. 105, " On tin- length of the electric flush producing light- 



2 M 2 iiing,") 



