32 Mr. Donovan on Galvanornetric Be/lections 



one of them in consequence of more ready conduction, or greater capacity, or 

 both. But if this were true, it should happen that when these two metals in 

 contact are immersed in hot water, the resulting temporary deflection (Law xi.) 

 should be on the same side of the magnetic meridian as it would have been had 

 the deflection been caused by friction without artificial heat. But on making 

 the experiment, it wiU be found that when bismuth is on the zinc side of the 

 galvanometer, and antimony on the silver side, attrition of these metals, when 

 at the temperature of the atmosphere, will cause western deflection ; but let 

 both in contact be suddenly immersed and rubbed in hot water, and a brisk 

 eastern deflection will result, which will continue until both assume the same 

 temperature. 



For my own part I think this fact is sufficient to prove that the deflections 

 produced by attrition are independent of the heat which attrition is capable of 

 developing. There are other considerations tending to the same conclusion. 

 Professor Eeman observes, that " the point of a needle rubbed against a consi- 

 derable heterogeneous mass gives immediately the deviation ; and an increase 

 of the extent of the surfaces in friction does not appear even to add materially 

 to the intensity of electrization." Are these facts compatible with the belief 

 that heat is generated lay a scratch of the point of a needle against a large mass 

 of another metal in such degree as to excite an instantaneous deflection. The 

 friction may be eflected under the surface of iccywater, or of boiling water, yet 

 the deflection ensues, it being in both cases western, provided the bismuth is 

 on the zinc side. If friction of two metals in ice-water, or boiling water (the 

 temperature of the metals and water being the same), produce deflection on 

 the same side of the magnetic meridian, how is it possible that the heat gene- 

 rated by a single rub of these metals against each other in ice-water, or boiling 

 water, could excite them by the heat of friction sufficiently to cause a deflec- 

 tion ; for there was more than suflicient cold or heat present to neutralize, or 

 overpower, any momentary inequality of temperature which friction, perhaps, 

 of the point of the needle, could occasion. 



That it is friction, and not the heat resulting from friction, which causes 

 deflections, is still further countenanced by the fact, that when the attrition of a 

 hemisphere of bismuth against one of antimony is conducted under the surface 

 of hot water, the deflection frequently takes place rather more slowly, and to a 

 less amount, than when it is conducted under the surface of cold water. 



