40 



SPECIFIC GRAVITY OF SOLIDS. 



body in kilogrammes, since l cc of water weighs l gr , and 

 1 cubic decimetre weighs 1 kilogramme. 



To determine the specific gravity of a body we must 

 find its absolute weight by means of the balance, and 

 the weight of an equal volume of water; this may be 

 done in various ways, of which the following is an 

 instance. 



Fill a vessel which has a lateral spout, fig. 40, a, 

 with water, and allow the portion above the spout to 



FIG. 40 (| real size). 



run out. Weigh an empty tumbler, 6, place it under 

 the spout, and immerse the body e, in the water in a, 

 by tying it to a silk thread and letting it slowly down 

 to the bottom. A volume of water, equal to that of 

 the body, will be displaced by it, and will run out 

 through the spout. When all the displaced water has 

 collected in the vessel &, this is again weighed, and the 

 increase in weight is the required weight of a volume 

 of water equal to that of the body. Thus, suppose we 

 require the sp. gr. of a piece of mineral. Let its weight 

 be 116^-1, the weight of the empty vessel b, 48 gr , and 

 with the displaced water 91**. The weight of the dis- 

 placed water is therefore 91 48 = 43^, and the ; 



