EQUILIBRIUM OF FLOATING BODIES, 



195 



1 = 15 CC , and 12 gr of the solution a volume of 

 V8 



12 

 1-2 



= 10 CC . It follows that in alcohol 15 CC , and in the 



I 



FIG. 138 (| real size). FIG. 139 ( real size}. 



solution 10 CC will be the volumes displaced by the floating 

 tube. Now 15 CC : 12 CC :: 1 : 0'8, and l2 cc : 10 CC :: 1'2 : 1, 

 hence : The volumes displaced by the same body when 

 floating in different liquids are inversely proportional to 

 the -specific gravities of the liquids. 



This is the principle on which Hydrometers are con- 

 structed. They are instruments, usually of glass, having 

 one of the forms shown in fig. 139. They are weighted 

 at their lowest part by mercury or shot, which makes 

 them float upright in the liquid. A graduated 

 scale is placed in the interior of the upper part, and 

 that division of the scale which is on a level with the 



o 2 



