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THE SCIENTIFIC PAPERS OF 



cooling as the whole exhaustion from 760 millims. to 1 millira. 

 Hence to eliminate the effect of convection a very high exhaustion 

 must be obtained. 



It still remains to describe the experiments by which the con- 

 stants a, )3, y of the empirical formula connecting the resistance of 

 the wire with its absolute temperature were determined. The 

 wire was enclosed in a glass tube, stopped at either end with a 

 plug, through which the wire passed centrally. The tube was 

 fixed in a metallic trough, with an aperture in its cover sufficiently 

 large to admit a mercurial thermometer placed in contact with the 

 tube. In the first instance, the trough was filled with melting 

 ice, and the resistance of the wire measured by a Wheatstone 

 bridge. The ice was then removed, and two Bunsen burners were 

 placed below the trough, and the temperature gradually raised by 

 increasing the pressure of the gas in the burners. 



In this way a series of simultaneous observations were made of 

 the temperature of the wire and its corresponding resistance up to 

 100 C. The results are given in the subjoined table. Care was 

 taken at each reading that the thermometer had become stationary, 

 and really represented the temperature of the wire. A second series 

 of observations were taken as the wire cooled from 100 to zero ; 

 and the results are likewise given in the table. 



