Oh the Conipresiibility of l^aler. 55 



was found that the bottle had been crushed into many thousand 

 pieces. The other bottle was very tightly corked; but not having 

 been left down a sufficient length of time, it came up whole, 

 having filled to within one inch and a half. The cork had been 

 driven in, and remained so ; but the cementation was unaltered, 

 excepting at the surface, where it had become a little concave. 



Being satisfied that the piezometer as first constructed, would 

 not show all the compression, I determined to make one difter- 

 ently modified. The object was to avoid the friction occasioned 

 by the collapsing of the leather upon the rod under such great 

 pressure. The drawing in Plate I, fig. 3, shows another modi- 

 fication of the piezometer, made since I have been in this country. 

 This proves my suspicions to have been correct ; since, under the 

 same pressure, it indicated nearly double the compression shown 

 by the former. 



This instrument is constructed as follows, fig. 3, being a sec- 

 tion of it. It is simply a small tube, A, closed at the end, B, and 

 water-tight. At the upper end, C, the water is allowed to enter 

 through a small aperture, E, closed by a very sensible valve open- 

 ing inwards., The tube is flattened at D, in ordtr that it may 

 yield to the e>q)ansi()n of the water when taken out of the press. 



The experiment with this instrument was made at Mr. Keir's 

 manufactory, in the presence of many scientific gentlemen. The 

 piezometer being ])erfectly filled with water (the weij^ht of which 

 was accurately known) was put into an hydraulic press, and sub- 

 jected to a pressure of about three hundred and twenty-six at- 

 mospheres. When it wss taken out and weighed, there was found 

 an increase of water amounting to three and a half per cent. 

 This water had been previously boiled, and cooled down to a 

 temperature of forty-eight degrees, and kej)t at the same tempe- 

 rature during the experiment. 



A machine calculated to avoid loss of pressure from destruction 

 of the materials of which it is composed, will be made with all 

 convenient speed. This machine being constructed with metallic 

 stuffings and flexible metallic pistons, will effect a much greater 

 pressure than the hydraulic press, the power of which is limited 

 by the animal stuffing now used. It is probable, a pressure of from 

 two to three thousand atmospheres may be oljtained before the 

 metallic piston is destroyed. 



It is expected that this machine will be sufficiciilly accurate to 

 give the exact ratio of the coni|)rcssibility of water with much 

 greater precision than has hitherto been obtained ; but the re- 

 Bults of further experiments must be the subject of a future com- 

 munication. 



29, Aublui rriarb, June 0, 1820. 



IX. Notices 



