224 
Proceedings of the Royal Society 
From these data, which are fairly consistent with one another, 
we find the following value of the true compressibility of water 
per ton, the unit for pressure (p) being 1 ton-weight per square 
inch, and the temperature 12° C., 
0-0072 (1 -0-034 i9); 
showing a steady falling off from Hooke’s law. 
Sea- Water, at 12° C. 
Pressure, 
1 
2 
3 
4 
Mean, 
1 
0-00606 
611 
615 
627 
0-00615 
2 
0-00595 
607 
598 
601 
0-00600 
2-5 
0-00600 
600 
594 
590 
0-00594 
3 
0-00588 
593 
586 
586 
0-00588 
Note . — The sea-water employed was collected about l-l miles off the 
coast at Portobello. 
These give, with the same correction for glass as before, the ex- 
pression 
0-00666 (1 -0-034 p). 
Hence the relative compressibilities of sea and fresh water are 
about 
0-925 ; 
while the rate of diminution by increase of pressure is sensibly the 
same (3^ per cent, per ton weight per square inch) for both. 
With the same apparatus I examined alcohol, of sp. gr. 0-83 at 
20° C. 
Alcohol, at 12° C. 
Pressure. 
1 
2 
3 
4 
Mean. 
1 
0-01202 
1193 
* 
* 
0-01200 
2-5 
0-01040 
1052 
1050 
1056 
0-01049 
3 
0-01043 
1050 
1043 
1058 
0-01048 
These experiments were not so satisfactory as those with water. 
There are peculiar difficulties with the silver film. I therefore 
make no definite conclusion till I have an opportunity of repeating 
them . 
I intend to perform the whole of these experiments at other 
temperatures, with the identical apparatus, as soon as possible next 
winter. 
