304 THE EARL OF BERKELEY, MESSRS. E. G. J. HARTLEY AND C. Y. BURTON: 
With Piezometer 3c. The mean relative coefficient at 29°"5 C. between 
8 and 89 atmospheres was 0 163 x 10 -5 . 
With Piezometer 7. The mean relative coefficient at 30°'4 C. between 
28 and 117 atmospheres was 0'169 x 10 -5 . 
All the piezometers, except 7 and 8 which are made of soda-glass, are of Jena 
No. 16 m glass, we may therefore mean the results for 1a and 3c at 30° C. 
If we take Amagat’s value for the coefficient compressibility of mercury at 0° C., 
namely 0'392xl0 -5 and correct it to 30° C. by means of Carnazzi’s (‘ Nuovo 
Cim.,’ 5, 1903, pp. 73-89) temperature coefficient, we get 
0‘393 x 10W 
Then the Jena-glass piezometer at 0° C. will have a coefficient of 
0'392 x 10 _ft —0"169 x HF 8 = 0’223 x 10“ 5 ; 
and at 30° C. it will be 
0'393 x 10- 8 -0'164 x Ur 5 = 0’229 x 10 -8 ; 
whilst the soda-glass piezometers, Nos. 7 and 8, may be taken to have, at 0° C. and 
30° C., the coefficients 
0'221 x 10 -8 and 0"224 x 10~ 8 respectively. 
The Compressibility of Water .—For purposes of comparison we give two observa¬ 
tions at 0° C., which have already been published; these were obtained with 
piezometer 1a, and the mean relative coefficient was, between 15 and 76 
atmospheres, 4"886 x 10~ 5 in the one case, and in the other 4"904 x 10“° for a range of 
1 to 61 atmospheres. On adding the coefficient of compressibility of the Jena-glass 
the mean coefficient for water becomes 5T09xl0~ 8 and 5T27 x 10 _o respectively. 
These numbers agree with one another remarkably well and do not differ greatly 
from Amagat’s values. The new results for water at 0° C. and 30° C. are given in 
Table II., where the columns tabulate the following : — 
(l) Gives the number of the piezometer; (2) the mean temperature to which the 
results are reduced ; (3) the pressure range—in the experiments with piezometers 
7 and 8 the range is given both for a rising pressure and a falling one ; (4) gives the 
mean relative coefficient of compressibility ; (5) the coefficient for the glass of the 
particular piezometer in use, derived from the compressibility of mercury; (6) the 
coefficient of the liquid alone, 
