1902.] 



On the Measurement of Temperature. 



485 



distance of one metre from the apparatus. By this means it was 

 possible to obtain readings concordant to 0*01 mm. 



In calculating the pressure, corrections were made for capillarity, 

 taking into consideration the height of each meniscus, which was 

 measured at each observation, and for the temperature of the column. 

 The volume of the dead space, which varied with the distance of the 

 mercury in it from the point, and with the height of the meniscus, 

 and the expansion of the bulb with the change of temperature and 

 pressure between 0° and 100° C, were taken into consideration in 

 making the final calculations. 



In determining the value of the coefficients, the pressures P and 

 Pioo, which the gas would exert, supposing the whole of it was at the 

 temperature of melting ice or of saturated steam under normal pres- 

 sure, were first calculated. Each of the values of P or of Pi o given 

 in the following table, is the result of four consecutive measurements 

 of the pressure, temperature, etc. 



Pressure Coefficient of Hydrogen. 



Series I. (a) P 694-458, 694-452 



Pioo 948-789, 948-824, 941-809 



a 0-00366261 



(b) P 696-103, 666-102 

 P 100 951-059, 951-044 

 a 0-00366252 



(c) P 706-528 

 P 100 965-291 



a 0-00366246 



Series II. P 520-326, 520-311 



Pioo 710-897, 710-882, 710-907 



a 0-00366268 



Pressure Coefficient for Helium. 



Series I. (a) P 690-232, 690-238 



Pioo 743-044, 943-044, 942-992 



cc 0-00366241 



(b) P 671-422, 671-418 



Pioo 917-322, 917-328, 917-352 



cc 0-00366270 



Series II (a) P 522-984, 522-984 



Pioo 714-576, 714-529, 714-577 



cc 0-00366313 



(b) P 523-016, 523-020 



P 100 714-568, 714-583 



a 0-00366255 



