MEMOIR XXIV.] THE ELECTRO-MOTIVE POWER OF HEAT. 335 



constant by uniting all the pairs intended to be worked 

 with at once. The current, therefore, whether generated 

 by one, two, three, four, or more pairs, had always to run 

 through the same length of wire, and experienced in all 

 cases a uniform resistance. 



2d. By making each individual element of consider- 

 able length, the liability of transmission from the hot to 

 the cold extremity was diminished. 



Having, therefore, taken six pairs of copper and iron 

 wires, -j^ of an inch thick and each element 38 inches 

 long, I formed them, by soldering their alternate ends, 

 into a continuous battery. Then I successively immersed 

 in boiling water one, two, three, etc., of the extremities, 

 their length allowing freedom of motion, and the other 

 extremities not differing perceptibly from the temper- 

 ature of the room. 



The following table exhibits one of this series of ex- 

 periments : 



TABLE IV. 



Hence there cannot be any doubt that the quantities 

 of electricity evolved by compound batteries at the same 

 temperature are directly proportional to the number of 

 the pairs. 



With some general remarks, arising from the forego- 

 ing subjects, I shall conclude this Memoir. 



1. It is of importance to remember that thermo-electric 

 currents traverse metallic masses only on account of dif- 

 ferences of temperature existing at different points. 



