250 OF SPECIFIC GRAVITY AND THE WEIGHING OF SOLID BODIES. 



Then the weight gained by the vessel, by reason of the immersion 

 of the solid body, is w" w f , and this expresses the weight of the 

 body in the fluid ; consequently, the weight which the body loses, is 

 w(w"w'). 



But by the 5th Proposition preceding, the weight lost, is to the 

 whole weight, as the specific gravity of the fluid is to the specific 

 gravity of the body ; therefore, because the specific gravity of water 

 is expressed by unity, we have 



w (w" w') : w : : I : s ; that is 



w 



- w _.( w _- f ,')- (197). 



298. The practical rule for reducing the above equation, may be 

 expressed in words at length in the following manner. 



RULE. Divide the weight of the body in air, by the difference 

 between that weight, and what is gained by the vessel in con- 

 sequence of the immersion, and the quotient will express the 

 specific gravity of the solid. 



299. EXAMPLE. A solid body when weighed in air, indicates a 

 weight of 16 ounces; and when put into a vessel filled with water, 

 the vessel, the solid and the water together, indicate a weight of 36 

 ounces ; whereas the vessel when filled with water alone weighs only 

 32 ounces ; required the specific gravity of the body, that of water 

 being expressed by unity ? 



Here, by following the directions of the rule, we have 

 _ 16 _ 



""16 (36 32) - 



being a measure of specific gravity, which corresponds very nearly 

 with American ebony, a very suitable material for hydrostatical expe- 

 riments. 



300. We have hitherto been considering the nature of bodies that 

 are specifically heavier than the fluids in which they are weighed, and 

 consequently, such as would sink to the bottom, if they were left to 

 the free action of their own gravity ; we have therefore, in the next 

 place, to consider such bodies as are specifically lighter than the fluids 

 on which they are placed, and consequently, such as would float on 

 the surface, if left to the free exercise of their own buoyancy. 



This is a very abstruse, but interesting and important department of 

 Hydro-Dynamical science ; for on it depends the principles by which 

 we determine the conditions of equilibrium, and the stability of floating 

 bodies. 



