OF SPECIFIC GRAVITY AND THE WEIGHING OF SOLID BODIES. 249 



. 



and for the specific gravity of the second fluid, it is 

 ,. = *(M- 3 ) = 1.062 nearly. 



Hence, the absolute specific gravities of the fluids, are respectively 

 equal to 0.844 and 1.062, that of water being unity ; and if we refer 

 to a table of the specific gravities of known fluids, we will find these 

 numbers to correspond with alcohol and acetic acid, the two fluids in 

 which the brick is weighed. 



It is manifest, that what has been done above in respect of two 

 fluids, may be extended to any number of fluids whatever, the law, 

 and the method of determining the specific gravity, being the same 

 in all. 



PROBLEM XLIII. 



297. If a body be weighed in air, and again in a vessel filled 

 with water, the weight of the vessel and water being known : 



It is required from thence, to determine the specific gravity 

 of the body. 



The principle upon which the solution of this problem depends is 

 not so evident; it may, nevertheless, be briefly expounded in the 

 following manner. 



The body is first weighed in air ; then being put into a vessel filled 

 with water, the weight of which is known, it will expel a quantity of 

 the fluid equal to its own bulk, and because the specific gravity of the 

 body is supposed to be greater than that of water, it is obvious, that 

 the vessel and its contents will now be heavier than it was before the 

 body was put into it, by a quantity, which is equal to the difference 

 between the weight of the body, and that of an equal bulk of the 

 water ; but the body loses as much of its own weight in the fluid, as 

 is equal to that of the water displaced ; hence, the determination of 

 its specific gravity becomes easy, for which purpose, 



Put w zz the weight of the body when weighed in air, 



w' zz .the weight of the vessel and the water before the body 



is put into it, 



w" zz the weight of the vessel, the water, and the solid, and 

 5 zz the specific gravity of the solid. 



