Mr. Perkins had never heard of the experiments of Canton, 
(made some fifty years before) which had established the com- 
pressibility of water. Although by Mr. Perkins’ experiments 
its discovery was not strictly new yet they were of high 
scientific value, because of the widely different compressing 
forces employed by him and by Canton, the latter having 
applied the pressure from half an atmosphere to two atmo- 
spheres, say from seven and a half to thirty pounds a square 
inch, whilst that employed by Perkins was from fifty to four 
hundred atmospheres, or from 750 lbs. to 6,000 lbs. per inch. 
The same rate of compression appeared in all his experiments, 
which corresponded with that shown by Canton’s experi- 
ments, and in all of which the water was compressed in 
volume directly as the compressing forces. 
The apparatus employed by Perkins was first a cast iron 
cylinder, about three inches thick, with a movable top of 
equal strength ; this, filled with water, had a force pump (as 
in the hydraulic press) to measure the pressure within by the 
leverage and size of the induction pipe. 2nd. A small 
brass cylinder, with a piston to slide in it, water tight, 
about three quarters of an inch diameter, and to have a 
column of water ten inches long under the piston. The 
piston rod, graduated to divisions of a hundred to the inch, 
had a sliding ring on it, to be pressed upon the rod as it was 
forced down upon the enclosed water, thus marking in the 
hundreths of an inch the descent of the rod ; the brass cylinder, 
being under the same pressure inside and out, was not sub- 
ject to any strain to alter its capacity. 3rd. When the 
external pressure was removed, the water in the brass cylinder 
expanding to its original length and raising the piston rod, 
would of course mark the greatest compression effected. In 
each experiment the diminished bulk of water was directly 
as the pressure applied, and under the pressure of 100 atmo- 
spheres the bulk of the water was reduced one part in a 
hundred, and, as before mentioned, this rate proved to bo the 
