Mr. Jacob Perkins on the compressibility of water. 325 
an atmosphere. The piezometer was introduced into the 
cannon, and the water forced in until the cap showed signs 
of leakage ; the valve at the same time indicating a pressure 
of one hundred atmospheres. The piezometer was then 
taken out of the cannon, and the flexible ring found to be 
eight inches up the rod, evidently proving the rod to have 
been forced into the cylinder that distance, showing also a 
compression of about one per cent. We have seen by re- 
peated experiments, that to be able to produce this degree of 
compression, three per cent must be pumped into the gun. 
This fact proves, either that the gun expands, or that the 
water enters the pores of the cast iron ; it is probable both, 
these circumstances contribute to produce this effect. 
This experiment was made in America in the year 1819, 
and before I had time to strengthen my apparatus for the 
purpose of making farther experiments, I was obliged to 
embark for this country. On my passage, however, I had 
frequent opportunities of repeating those I had already made, 
and of making others by a natural pressure. They were as 
follows. The piezometer, by the assistance of fifty-four 
pounds of lead attached to it, was sunk in the ocean to the 
depth of five hundred fathoms, which is about equal to the 
pressure of one hundred atmospheres. When drawn in, the 
gauge or ring was found removed eight inches up the rod, indi- 
cating, as in the before-mentioned experiment, a compression 
of one per cent. This experiment was several times repeated 
and with the same result. 
The next experiment was that of sinking a strong empty 
porter bottle to the depth of one hundred and fifty fathoms, 
having first tightly corked and sealed it, in the following 
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