( 116 ) 
I have purposely given this series of observations as it appears 
from the foregoing table that there must have been a leakage on 
that day, which could however not be detected by means of soap 
solution; the observations on other days show a much smaller decrease 
of pressure; as for instance on July 11 when the pressure at 2.44 p. m. 
amounted to 36.898 atm. and at 4.35 p.m. to 36.871 atm. And 
yet it will appear that the decrease of pressure mentioned has had 
no disturbing influence on the equilibrium, since the product of 
volume and pressure, bearing in mind the degree of accuracy attained, 
may be considered as sufficiently constant. 
For the measurement of the volume I refer back to the Proceedings 
of May 25% 1901 “The calibration of piezometer-tubes”. The following 
table has been calculated in the way described there. 
August 25th. TABLE IIL. 
Mark 50.9 
Section 0.1264 
Correction for elastic expansion of glass 0.0009 
level Height) Mean | peduced| Mean corrected Specific- 
Time. ae, of | height Volume | 
kate length | section | Volume | volume. 
mark. | men.!)) men. | 
2.40 
2.48 | —0.024 | 0.057 | 0.029 | 32.213 | 0.12690 | 4.0878 | 4.0887 | 0.030944 
3.09 | — 0.006 | 0.064 | 0.033 | 32.227 y 4.0896 | 4.0905 | 0.030958 
3.28 0.008 | 0.058 | 0.030) 32.244 r 4.0918 | 4.0927 | 0.030973 
3.48 0.026 | 0.064 | 0.032) 32.260 / 4.0938 | 4.0947 | 0.030989 
4.00 
4.07 0.046 | 0.062 | 0.032 | 32.280 / 4.0963 | 4.0972 | 0.031008 
4.19 
4.26°| 0.064} 0.063 | 0.033 | 32.297 / 4.0985 | 4,0994 | 0.031024 
4.385 
1) In Comm. N°. 67 $ 7 I neglected to draw attention to the scale of reciprocals 
devised by Boys to facilitate the drawing of curves by their curvature. 
