206 Mr. Prideaux's Experimental Contributions 



M. Becquerel is, I believe, the only one who has investi- 

 gated the comparative force as well as the order of arrange- 

 ment of metals when acting in pairs; and having ascertained 

 these points by a course of delicate experiments, he has been 

 led to the inference that thermo-electricity is allied to the ra- 

 diation of caloric. 



The deep interest attached to a subject in which the mutual 

 reaction of heat, electricity and magnetism is made almost 

 tangible within a very narrow compass, led me to institute 

 the following inquiries, with the hope of their suggesting other 

 methods of elucidation. 



I. Is thermo-electricity different from that derived from 

 other sources : i. e. a different principle, or a different com- 

 bination of principles? 



II. Is it produced at the expense of caloric ? 



III. Is the radiation of heat, or any property dependent 

 upon it, the proximate cause of thermo-electricity ? 



IV. Is the proximate cause connected with the conduction 

 of heat? 



V. Will not a hot bar brought into contact with a cold one 

 of the same metal set electricity in motion ; and if so, will the 

 currents so produced bear any peculiar relation to those pro- 

 duced by pairs of different metals ? 



I. Is there any, and what, difference between Thermo-electricity 

 and that derived from other sources ? 



1. The most characteristic distinction between electricity 

 and the other imponderable fluids (if such they be,) is, its 

 [sensibly] instantaneous transmission through considerable 

 length of solid conductors. The very low tension of thermo- 

 electricity renders this as close a test as any to which it can 

 be subjected. Fifty feet of iron wire (one of the worst me- 

 tallic conductors,) was cut into two lengths, through which 

 (turned at the ends, to ensure metallic contact,) two other 

 mercury boxes were connected with those of the magnetest *. 

 A thermo-electric pair, of antimony and bismuth, heated at 

 the point of contact, had their feet dipped, first into the mer- 

 cury boxes of the magnetest, which produced a deflection of 

 80° ; and were then removed to the other pair of boxes at the 

 end of the wires, by which the deviation was reduced to 1 5° ; 

 and so repeatedly ; the interposition of such a length of iron 

 wire, between the excited metals and the magnetest, withholding 

 £ths of the deviation (about ||ths of the current) : yet was the 



* I must be excused for resuming the use of this word : "galvanometer'* 

 would be hardly applicable in this instance. 



