548 



PROCEEDINGS OP THE AMERICAN ACADEMY. 



Detailed Account of the Work. 



Couples A 2 , B 2 , C 2 > an d -^2- 

 Four new copper and german-silver couples, which will be called 

 A 2 , B 2 , C 2 , and D 2 , were made July 5, 1905, from the same pieces of 

 copper and german-silver which had furnished the materials for the 

 couples previously mentioned. Each wire was about 0.02 cm. in 

 diameter. Each german-silver wire, about 160 cm. long, was annealed 

 as the wires for previous couples had been, by carrying for a few seconds 

 a current of about 3.5 amperes, which heated it to incandescence except 

 at the ends, which were afterward cut off, leaving the wire about 150 cm. 



long. Each annealed wire was made 

 to extend through two glass tubes, 

 each about 50 cm. long and 0.3 cm. 

 in diameter of bore, and each end 

 of the wire, after being cleaned with 

 emery paper, was then tightly twisted 

 with a copper wire for a distance of 

 about 0.5 cm. The junctions thus 

 made were heated in an alcohol flame 

 and flowed with a silver solder, the 

 borax used in this operation being 

 afterward removed, so far as was 

 practicable, from the wires. 



The small glass tubes were next 

 placed in glass tubes about 54 cm. 

 long and 1 cm. in diameter, as in Fig- 

 ure 1, where C and C represent the 

 copper wires and G represents the german-silver wire. One of these 

 larger glass tubes, with its contents, was now placed in a vessel of 

 peculiar construction, due to Professor Crafts, where it could be raised 

 to the temperature of the vapor given off from distilled water boiling at 

 any required pressure, but without coming into direct contact with this 

 vapor. The other large glass tube, with its contents, was similarly 

 placed in a similar vessel containing the saturated vapor of naphthalin, 

 the purest that Eimer and Amend could furnish, at any required tem- 

 perature. The steam temperatures were found from the steam pressures, 

 measured by a mercury gauge, by means of Peabody's Tables, which 

 are based, of course, on Regnault's observations. The naphthalin 

 temperatures were calculated from the naphthalin vapor pressures by 



Figure 1. 



