HYDROSTATICS- 173 



is the weight of a quantity of water equal in bulk 

 to the body. 



It follows from 30., that the weight of any body di- 

 vided by the weight of an equal bulk of water, 

 measures the specific gravity of the body. The 

 specific gravity of a body weighed as above, is 

 W 



w w ' 



Hence the specific gravities of bodies are found by 

 weighing them, first in air, and then in water. 

 The instrument with which this experiment is made 

 is tailed the Hydrostatic Balance. 



254. Let it be required, by the hydrostatic ba- 

 lance to determine the specific gravity of a body 

 60 light as not to sink in water. 



Weigh the body first in air, and then by a slender 

 thread attach to it a heavier body, that the two to- 

 gether may sink ; the heavier body being previous- 

 ly weighed, first in air, and then in water. Let 

 the compound body thus formed be weighed in 

 water; then from the weight lost by it, subtract 

 the weight lost by the heavier body, when weigh- 

 ed singly ; the remainder is the weight lost by the 

 lighter body, by which if its weight be divided, its 

 specific gravity will be found. 



CAVALLO, vol. n. p. 61. The solution there is a little 

 different, but leads to the same result. See the 

 example, ibid. 



255. If 



