Temperature on the Specific Heat of Aniline. 55 



coefficient of this wire was found to be "00029. The re- 

 sistances of the different parts of the wire were, after 

 correction for the errors of individual coils, &c, merely ex- 

 pressed in terms of the mean box ohrn, the absolute value 

 being of no consequence so long as the fixed points were 

 determined in terms of the same standard. The remaining 

 two arms of the bridge were constructed of german-silver. 

 They were wound together, boiled in paraffin, placed in a 

 bottle, and I expended much care in finally adjusting them 

 until equal. Their resistance was about 5 ohms and the 

 galvanometer about 8 ohms, which, assuming the resistance of 

 the thermometers as about 20 ohms each, would give nearly the 

 maximum of sensitiveness. A single storage-cell was always 

 used, and a resistance of 40 ohms was placed in the battery 

 circuit when the thermometers were in ice. A table was 

 then calculated which gave the resistance necessary in the 

 battery circuit when the thermometers were at any tempera- 

 ture in order that C 2 R (where R is the thermometer resistance) 

 should be constant. Thus the rise in the temperature of the 

 thermometer coils due to current-heating was always the 

 same, and consequent errors were eliminated, a point to which 

 I attach considerable importance. 



The value of R 1 — R in thermometer AB was 6*88815 ; 

 therefore a difference of 1 ohm at 50° C. indicated a differ- 

 ence of 14°*5177 C, and as 



*> 



dpt_ /ig 2£-100 \* 

 dt~\ 100 2 J ' 



the degree value of any bridge-reading at other tempera- 

 tures can be deduced. 



There was no difficulty, in the arrangement above described, 

 in reading with certainty a difference of yoVo° ^-j an d> as an 

 illustration, I may mention the fact that if the thermometers 

 were placed in separate hypsometers side by side on the 

 bench and one of the hypsometers was then removed to the 

 ground (about 3 feet below) , the difference in the bridge-wire 

 reading thus caused slightly exceeded *4 millim. 



Before leaving this portion of the subject I may mention 

 that I carefully compared the thermometer AB with two 

 standards from the International Bureau of Weights and 

 Measures, which passed through my hands this summer 

 on their way to Sydney University, and further with a 

 separate standard sent me by the Bureau in February 1893. 

 As the particulars of this comparison are now in the press t, I 



* Trans. 1891, A. p. 142. 



t ' Science Progress,' September 1894. 



