176 Mr Perkins on the Compressibility Water. 
ring was made to pass through a tight stuffing box E. A 
cannon D, Fig. IS. capable of containing the piezometer, was 
fixed vertically in the earth, the touch-hole being plugged tight, 
and the muzzle about 18 inches above ground. A strong cap 
A, was firmly screwed on at the mouth, and in the centre of it 
a small forcing pump.B, with a piston | ths of an inch in dia- 
meter, was tightly screwed. A valve was introduced at the 
aperture C, to ascertain the degree of pressure, one pound of 
pressure on that valve indicating an atmosphere. The piezo- 
meter being introduced into the cannon, the water was forced 
in till the cap shewed signs of leakage, the valve at the same 
time indicating a pressure of 100 atmospheres. When the 
piezometer was taken out of the cannon, the flexible ring a was 
eight inches up the rod Z), which proved that the rod had been 
forced that length into the cylinder, and that the compression 
was about 1 per cent. In order to produce this compressionj 
3 per cent, must be pumped into the gun, an effect arising from 
the expansion of the gun, or the entrance of the water into the 
pores of the cast-iron. 
On his voyage to England, Mr Perkins repeated this experi- 
ment frequently, and with the same result, by sinking the pie- 
zometer with fifty-four pounds of lead, to the depth of 5,00 fa- 
thoms, which gives nearly a pressure of 100 atmospheres. 
Being satisfied that the above piezometer would not shew all 
the compression, he made another, consisting of a small tube, 
closed at the lower end, and water-tight. At the upper end 
the water entered through a small aperture, closed by a sen-* 
sible valve opening inwards. It was then perfectly filled with 
water, (the weight of w^hich was accurately known) and sub- 
jected in a hydraulic press to a pressure of about 326 atmo- 
spheres. When taken out and weighed, there was found an in- 
crease (^upaterr, amounting to per cent. This water had been 
previously boiled, and cooled down 48°, and kept at that tem- 
perature during the experiment, which was performed before 
many scientific individuals. 
Mr Perkins made several curious experiments, by sinking 
strong empty porter bottles to different depths ; but we must 
refer for an account of these to tlie Philosophical Transactions, 
as they do not contain any very precise results. 
