ON THE ABSOLUTE EXPANSION OF MERCURY. 15 



Expansion from 20 C. to 100'278 C. in terms of volume at 20 0. 



= 0-0145838. 



Mean coefficient from 20 C. to 100-278 C. in terms of volume at 20 C. 



Q-Q145834 



80-278 



,,,,. 



The further reduction to C., involving a correction of 20 per cent., could not be 

 effected satisfactorily until the conclusion of the third series of observations, and was 

 not required for comparing the results of the first two series, which are therefore 

 reduced to 20 C. in the tables given below. 



The corresponding observation taken on the same day, with the difference of 

 temperature decreasing, was as follows : 



November 2, 1908, 3.30 p.m. Current, 7'50 amperes. Resistance box, 21 C. 

 Bridge readings corrected for calibration 



and temperature ........ 1292*436 1657'310 



Temperatures on gas scale deduced ... t\ = 20'930 C. t-j = 100"335 C. 



Lengths on hot and cold columns . . . . /i = 192755 1 2 = 192'815 



Levels of mercury in gauge (corrected for 



scale) ........... /, = 51-1552 h, = 67'G102 



Gauge thermometers: upper 21'35 C., 2170 C. ; lower 20'9 C., 21 C. 



Temperatures of cross tubes : upper 20 "7, lower 20 C. 



Corrected difference of level, h' = 16"4515 cm. 



Temperature of h, t = 21 72 C. 



Reduction to 20 C. = 0'0001805 xO'930xH a = + 0'1942 cm. 



- 0-ou.Ms. 



Q-Q145958 

 80-335 = 00181685 - 



The difference from the first observation would be explained by a lag of O'OOl cm. 

 either way in the gauge reading, but is within the limits of accuracy of observation. 



* 



7. Summary of Observations. 



The following tables contain a summary "of all the observations taken after the 

 apparatus had been got into proper working order. Observations taken with the 

 same upper limit of temperature t 3 are grouped together to facilitate comparison, and 

 the observations in each group are arranged in order of date. The first column gives 



