174 OUTLINES OF NATURAL PHILOSOPHY. 



255. If the same body be weighed in two diffe- 

 rent fluids, the weights lost will be to one another 

 as the specific gravities of the fluids. 



By help of this proposition, the specific gravities of 

 different fluids may be compared together. The 

 specific gravities of different fluids may also be 

 found, by weighing equal bulks of them. 



If a body float on different fluids, the bulks of the 

 part immersed will be inversely as the specific gra- 

 vities of the fluids. It is on this principle that the 

 hydrometer, aerometer, &c. are constructed. 



See Description of a Hydrometer, CAVALLO, vol. n. 

 p. 66. 

 ' 



256. If the specific gravity of air be called m, 

 that of water being 1, if W be the weight of any 

 body in air, and W its weight in water, then 

 W + m (W W) is its weight in vacuo very 

 nearly. 



In the mean state of the atmosphere, m .00122 

 nearly. 



257. If s be the specific gravity of a body, as- 

 certained by weighing it in air and water, and 

 m be the specific gravity of the air at the time 

 when the experiment was made ; the correct spe- 

 cific gravity, or that which would have been 

 found if the body had been weighed in a vacuum 

 instead of air, is s + m (1 s). 



When 



