328 THE ELECTRO-MOTIVE POWER OF HEAT. [MEMOIR XXIV. 



ing ordinates, we shall have results similar to those given 

 in Fig. 53, in which it is to be observed that the curves 

 given by the systems of silver and iron, copper and iron, 

 and palladium and iron are concave to the axis of ab- 

 scissas ; but those given by platinum and copper, silver 

 and palladium, and platinum and iron are convex. 



Let us now apply the numbers obtained by these sev- 

 eral pairs for the calculation of temperatures, which will 

 set their action in a more striking point of view. The 

 following table contains such a calculation, on the sup- 

 position that for the 90 degrees from 32 Fahr. to 122 

 Fahr. the increments of electricity are proportional to the 

 temperatures. 



We are therefore led to the general conclusion that in 

 these six different systems of metals the developments of 

 electricity do not increase proportionally with the temper- 

 atures, but in some with greater rapidity and in others 

 with less. 



The results here given I have corroborated in a vari- 

 ety of w r ays and with a variety of wires. A pair con- 

 sisting of copper and platinum gave for the temperature 

 of tin when in the act of congealing 452 Fahr. instead 

 of 442 Fahr., the point usually taken. For the melting- 

 point of lead it gave 942^ Fahr. instead of 612 Fahr. 

 The melting-points of tin, lead, zinc, and occasionally of 

 antimony and bismuth, were in this manner employed, 

 for they allow time for the working of the torsion bal- 

 ance, and with the exception of bismuth, their tempera- 



