OF THE EQUILIBRIUM OF FLOATATION. 289 



Here then we have given w' = 0.7536 of an ounce, and s = 0.5738 ; 

 consequently, by the above rule, we have 



consequently, the specific gravity of the heavier fluid, is 



s' = 0.5738 -f 0.0188 = 0.5926 ; 



and this, when reduced to the standard of one cubic foot, becomes 

 0.5926x1728 = 1024.0128, which, on being referred to a table of 

 specific gravities, will be found to correspond with sea water at a 

 medium temperature. 



In the above operation, we have taken the specific gravity as re- 

 ferred to one cubic inch of the fluid only, but the well informed reader 

 will readily perceive, that the same result would obtain if the specific 

 gravity should be estimated by the cubic foot ; for in that case, we 

 should have w 1 0.7536 of an ounce, and 5 = 991.5264, conse- 

 quently, by the rule, we have 



23 



therefore by transposition, the specific gravity of the denser fluid, is 

 s' = 991.5264 4- 32.4864 = 1024.0128, being precisely the same 

 result as that which we obtained on the former supposition. 



369. The diagram which we have employed to illustrate the general 

 principle of the aerometer, is at the best but a very rude and imper- 

 fect representation, and in its present state, it is altogether unfitted 

 for ascertaining the specific gravities of fluids with any degree of pre- 

 cision ; it is therefore requisite, in cases where extreme accuracy is 

 required, to have recourse to some other method of indicating the 

 precise measure of density, and for this purpose, the hydrometer or 

 aerometer, is very advantageously replaced by the 



HYDROSTATIC BALANCE, 



an instrument which determines the specific gravities of bodies with 

 the greatest correctness, and which, on account of its simplicity and 

 cheapness, is rendered available for almost every purpose in which 

 the specific gravity of bodies forms the subject of inquiry. 



The Hydrostatical Balance, so called, is nothing more than a 

 common balance, furnished with some additional apparatus for ena- 

 bling it to measure the specific gravities of bodies with accuracy and 

 expedition, whether the bodies be in a solid or a fluid state. The 

 description of the instrument is as follows. 



VOL. i. u 



