On the Cowpressih'ility of JValer. 63 



to screw on and off at pleasure ; being also made water tight. 

 The rod or plunger, D, which was five-sixteenths of an inch in 

 diameter, was made to pass through a tight stuffing box, E. On 

 the rod immediately above the stuffing box, was fixed a flexible 

 ring, a. A cannon, fig. 2, of a sufficient size to contain the pie- 

 zometer, was fixed vertically in the earth, the muzzle being left 

 about eighteen inches above ground, and the touch-hole plugged 

 tight. At the mouth a strong cap, A, was firmly screwed on. 

 In the centre of this cap a small forcing pump, B, was tightly 

 screwed, the piston of which was five-eightlis of an inch in dia- 

 meter. There was an aperture, C, in the cap, to introduce a 

 valve for the purpose of ascertaining the degree of pressure. One 

 pound pressure on this valve indicated an atmosphere. The pie- 

 zometer 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 piezo- 

 meter 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 com- 

 pression, of about one per cent. We have seen by repeated expe- 

 riments, that to be able to produce this degree of compression, 

 three per cent murit 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 further experiments, 1 was obliged to embark for this 

 country. On my passage, however, I had frequent opportunities 

 of re|)eating 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, 

 indicating, as in the beibre-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 astrongempty porter 

 bottle to the depth of one himdred and fifty fathoms, having first 

 tightly corked and sealed it, in the following manner. Six co- 

 verings of cotton cloth, saturated with a composition of scaling 

 wax and tar, were strongly fastened over the cork, by a cord 

 wound round them, directly under the projection at the neck of 

 the bottle. After the bottle had been suffered to remain at the 

 depth mentioned a few minutes, it was drawn up. No \,atcr was 



found 



