THE EARTH. 



120 



<>' astic also. But the trials of Mr Canton have put this past 

 all doubt ; which being somewhat similar to those of the great 

 Boyle, who pressed it with weights properly applied, carry suffi 

 cient conviction.* 



* With the barometer at 2tfi, and thermometer at 50, Canton declares l!.. 

 foUowiug to be the results he obtained : 



Cteipression of spirit of wine . . . 66 parts la a million. 



Oil of olives ... 48 ditto. 



Rain-water . . . . 4<5 ditto. 



Sea-water .... 40 ditto. 



Mercury . ... 3 ditto. 



These results he obtained in the following manner : He took a glass tuoe 

 about two feet long, with a ball at one end, of an inch and a qiuirter in dia- 

 meter ; he filled the ball, and part of the tube, with water which had pre- 

 Tiously been deprived of air as much as possible ; he then placed it under tlm 

 rpceiverof an air pump, and removed fromitthe pressure of the atmosphere; 

 under this treatment he observed that the water rose a little way in the tube. 

 On the contrary, when he placed the apparatus upon a condensing engine, and 

 by condensing the air in the receiver, increased the pressure upon the water^ 

 lie observed that the water descended a little way in the tube. In this man. 

 ner he found that water expanded one part in 21,740 when the pressure of 

 the atmosphere was removed, and submitted to a compression of one part 

 in 10,870 under the weight of a double atmosphere. He also observed that 

 water possessed the remarkable property of being more compressible in 

 winter than in summer ; contrary to the effect on spirit of wine and oil of 

 olives. Lest it might be supposed that the comi)ressibility thus discovered 

 might be owing to air lodged within the fluids employed, a quantity of water 

 was caused to imbibe more air than it contained in a preceding trial ; but its 

 compressibility was not increased. These experiments, although upon th e 

 whole so apparently decisive of the questions they were instituted to deter- 

 mine, are yet not to be received without some caution ; and in particular, 

 the remark that the addition of a portion of so compressible a fluid as r.ir, did 

 not render water more compressible than before, is rather staggering, and is 

 calculated to throw the veil of doubt over all the rest. It remains therefore, 

 for future investigation to fix the judgment of philosophers <m this subject ; 

 in the mean time, even granting all the compressibility that has been contend- 

 ed for, the quantity of it is too small to be noticed in practice. 



Persons at sea frequently try an experiment which proves, in a great de. 

 gree, the incompressibility of water. Having corked a bottle containing 

 only air, and therefore called empty, they tie a rope to it, and sink it to a con. 

 siderable depth by a sufficient weight ; on pulling up the bottle, they gen. 

 eially find it either broken, or the cork forced in : but on sinking to the same 

 or even any greater depth, a bottle filled with water, they find it, when 

 ^rawn up, to be uninjured, because the water resists compression, and 

 therefore supports the bottle ; which support, under the pressure at u great 

 depth, the air cannot suuply. 



