HISTORY OF CALIFOEXIA. 237 



equal to that of the specimen, and by dividing the 

 weight of the specimen in air hy this number, the 

 Fpecific gravity is obtained. 



r, .f, . 'wei;iht of substan *o in air 



Specific gravity . , ^ ^ - , , y. — 7; : 



^ o ./ weigtit ui equal bulk 01 water 



If, however, the substance is in the foim of fine 

 sand, or very small lumps, it Ls better, after weighing 

 it carefully, to take a small dry phial furnislied with a 

 stopper ; counterpoise this phial accurately in the 

 weight-scale by shot or strips of lead, then fill it com- 

 pletely with pure wat m-, tnkino: care that no bubbles 

 of air are left in, and weigh the quantity of water it 

 contains : afterwards empty the bottle and dry it 

 inside. 



Next fill the bottle about two-thirds full of the 

 powder to be examined, weigh this and record the 

 weight. Then fill the bottle once more with water, 

 taking care, as before, that all bubbles are expelled 

 and none of the powder washed out. Once more 

 weigh it. 



We have then to make the following calculation : 



Weight of powder and water in grains = 

 Deduct weight of powder alone = 



Difference (weight of water left in bottle) = 



"Weight of bottle full of water in grains = 

 Weight of water left in bottle = 



Difference (weight of water displaced | 



by, and equal in bulk to, powder) j 



_, .„ . weight of powder in air 



The specific gravity= — r °. ^ , ' ^ — y- — ^ i 



weigiit 01 water displaced. 



It may be useful to know the specific gravity of 

 various substances at all resemblino: fjold in wciirht or 



00 o 



