544 PROCEEDINGS OP THE AMERICAN ACADEMY. 



Furthermore, following the advice of Professor J. M. Crafts, who gave 

 us every facility to copy the apparatus which he has used in his com- 

 parative study of the behavior of boiling water and boiling naphthalin 

 under various pressures, we determined to employ for calibration pur- 

 poses all the way from 100° C. to 218° C. the saturated vapors of water 

 and naphthalin, respectively, using the water at high pressure and the 

 naphthalin at low pressure for the temperatures intermediate between 

 the limits. 



General Summary. 



1. All of the german-silver wires used in the experiments of this 

 paper, with the exception of those taken for a certain experiment to be 

 described below, were cut from one continuous strand described by the 

 dealer from whom it was procured as containing 18 per cent of nickel. 

 Special chemical analysis of a specimen of this wire, taken unannealed, 

 gave as the composition : 



Copper, 58.76 per cent. 



Zinc, 22.54 " " 



Nickel, 17.44 " " 

 Iron, 1.29 " " 



Analysis of the annealed wire resulted as follows : 



Copper, 63.19 per cent. 



Zinc, 18.48 " " 



Nickel, 17.59 " " 

 Iron, 0.71 " " 



The diameter of this wire was about 0.02 cm. 



2. Pieces of this wire were annealed by heating to incandescence by 

 an electric current and keeping them in this state for some seconds in 

 free air, the ends of each piece during the annealing being kept at the 

 same level, so that the heated wire had approximately a catenary shape. 

 After cooling, the wires were found to have suffered very little, if any, 

 permanent extension. The strength of current used was usually about 

 3.5 amperes, but it was not very carefully measured. The state of 

 incandescence probably lasted two or three times as long in some cases 

 as in others. 



3. Couples made from copper, also 0.02 cm. in diameter, and pieces 

 of german-silver annealed as in (2), appeared to differ from each other 

 in sensitiveness, when new, rather less than 0.5 per cent; but after 



