MEMOIR XXIV.] THE ELECTRO-MOTIVE POWER OF HEAT. 327 



soapstone, the neck of the retort is inclined upwards, so 

 that the vapor as it rises may condense and drop back 

 again without incommoding the operator,. As in the 

 former case, it is here also necessary to continue each 

 experiment for a few minutes, to bring the thermometer 

 and thermal pair to the same condition. There is not 

 much difficulty in obtaining any required temperature, 

 by raising or lowering the wick of the lamp. 



The metals I have tried were in the form of wires. 

 They were in the state found in commerce, and therefore 

 not pure ; they were obtained in the shops of Philadel- 

 phia. 



TABLE I. 



Ill this table I have estimated the temperature of 

 boiling mercury at 662 Fahr. The quantities of elec- 

 tricity evolved, as estimated by the torsion of a glass 

 thread, are ranged in columns under their corresponding 

 temperatures. Each series of numbers is the mean of 

 four trials, the differences of which were often impercep- 

 tible, and hardly ever 

 amounted to more than 

 one degree. 



Now if this table be 

 constructed, the tem- 

 peratures being ranged 

 along the axis of abscis- 

 sas, and the quantities 

 of electricity being rep- 

 resented by correspond- Fig. 53. 



