218 PROPERTIES OF AI& 



bottle, are together rarer, and consequently 

 lighter, than the density of the water which 

 they have displaced ; or, in other words, the 

 bottle swims by the levity of air ; it sinks by 

 the excess of weight in the bottle ; instead, 

 therefore, of proving the gravity of water in 

 water, it only goes to prove, that water is den- 

 ser, and consequently heavier, than air ; and 

 more especially than of the rarified medium 

 which remains after the denser parts have 

 been exhausted out of the bottle. 



If the parts of water retained their gravity in 

 water, the different propositions on which hy- 

 drostatics are founded, would be altogether 

 violated; instead of the different parts of a 

 fluid mass, being as much pressed as they are 

 pressing, equally in every direction, the dif- 

 ferent parts of that fluid would press in a par- 

 ticular one ; instead of the whole mass of a 

 fluid being at rest, when the surface of it is 

 level. Instead of this state of equilibrium of 

 equality of pressure on every direction, the 

 pressure of fluids would in that case be as their 

 quantities of matter, the pressure which they 

 produced would be the pressure of weight of 

 weight perpendicularly downwards, not side- 

 ways, or upwards. If the weight of water in- 

 creased in proportion to its quantity, whether 

 of length or of breadth, or of both together, the 

 pressure of weight which it would occasion, 



