HYDROSTATICS. 119 



water, the equilibrium will be immediately de- 

 stroyed ; then, if as much weight be put into the 

 scale from which the body hangs, as will restore 

 the equilibrium, without altering the weights in the 

 opposite scale; that weight which restores the 

 equilibrium, will be equal to the weight of a quantity 

 of water as large as the immersed body; and if the 

 weight of the body in air be divided by what it 

 loses in water, the quotient will show how much 

 that body is heavier than its bulk of water. Thus, 

 if a guinea, suspended in air, be counterbalanced by 

 129 grains in the opposite scale of the balance, 

 and then, upon its being immersed in water, it be- 

 comes so much lighter as to require 71 grains put 

 into the scale over it, to restore the equilibrium, it 

 shows that a quantity of water of equal bulk with 

 the guinea, weighs 71 grains, or 7-2.5 ; by which 

 divide 129 (the weight of the guinea in air), and 

 the quotient will be 17.793; which shows that the 

 guinea is 17-793 times as heavy as its bulk of water. 

 And thus, any piece of gold may be tried, by 

 weighing it first in air, and then in water; and if 

 upon dividing the weight in air by the loss in water, 

 the quotient comes out to be 17.793, the gold is of 

 the standard value; if the quotient be 18, or be- 

 tween 18 and 19, the gold is very fine; but if it be 

 less than 17, the gold is too much alloyed with 

 other metal. 



By this method the specific gravities of all bodies 

 that will sink in water may be found; first weighing 

 the body in air, then in water, and dividing the 

 weight in air by the loss in water. 



But as to those which are lighter than water, as 

 most sorts of wood are, the following method must 

 be taken. A sort of pincers, or tongs, must be 

 provided, to retain the substance to be examined, 



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