METHODS OF FINDING SPECIFIC GRAVITY. 69 



performed with water at any temperature ; but the temper- 

 ature must be noted aud a correction applied for it which 

 depends upon the density of water at the experimental 

 temperature.* 



The weight of a cubic foot of distilled water at the stand- 

 ard temperature is 1000 ozs. = 62 Ibs. ; hence we find the 

 weight of a cubic foot of any substance in ounces or pounds 

 by multiplying its specific gravity by 1000 or 62|. 



It appears, therefore, that by means of the specific gravi- 

 ties of homogeneous bodies, their weights may be deter- 

 mined without actually weighing them, provided their 

 volumes are known ; and conversely, however irregular the 

 shape of bodies may be, if their weights and specific gravi- 

 ties are known, their volumes may be determined, viz., by 

 dividing the weight by the specific gravity. 



The specific gravities of gases and vapors are usually 

 determined by referring them to atmospheric air at the same 

 temperature and under the same pressure as the gases them- 

 selves. 



31. Methods of Finding Specific Gravity. The 



law of the buoyant effort, or upward pressure, of water can 

 be made use of to determine the specific gravities of bodies; 

 for, if a body be immersed in a fluid, it loses as much of its 

 weight as is equal to the weight of the fluid it displaces 

 (Art. 24) ; i. e., if it be wholly immersed, its loss of weight 

 is equal to the weight of its volume of the fluid. 



Thus, if a sphere of lead, whose weight is 11 Ibs., were 

 found to weigh but 10 Ibs. when immersed in water, we 

 should conclude that the weight of an equal volume of 

 water would be one pound, and therefore that the lead 

 weighed 11 times as much as its volume of water, and hence 

 that the specific gravity of lead was 11 ; and so for any other 

 substance. 



Renwick's Mechs., p. 334. 



