HISTORY OF CALIFORNIA. 



237 



equal to that of the specimen, and by dividing the 

 weight of the specimen in air by this number, the 

 specific gravity is obtained. 



weight of substance in air 

 Specific gravity 



weight of equal bulk of water 



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

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

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

 stopper ; counterpoise this phial accurately in the 

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

 pletely with pure water, taking 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) 



The specific gravity ^ f P 0wder in air 

 weight of water displaced. 



It may be useful to know the specific gravity of 

 various substances at all resembling gold in weight or 



