G R A 



GRAVITY specific. ' J'inct, Bland.) 



1. Of the specific gravities of a body and fluid, having 1 given the one, 

 to find the other. 



Case 1. When the body is heavier than the fluid. 



Let w weight lost by the body when immersed in the fluid, W its 

 whole weight in vacuo, * spec. grav. of the fluid, S .= that of the body j 

 then 



w : w : : : s. 



whence * or S may be found. 



\V 



Cor. I. If different bodies be weighed in the same fluid, S is as .from 



w 



whence we may compare the spec. grav. of two bodies. 



Cor. 2. If the same body is weighed in different fluids, s is as tc ; from 

 whence \ve can compare the spec. grav. of t\vo fluids. 



Case 2. When the body Q is lighter than the fluid in which it is weigh- 

 ed. 



Connect it with a heavier body P, so that together they may sink. 

 Find the weight lost by P -f Q, and the weight lost by P, when im- 

 mersed ; then the difference = the weight lost by Q ; and .*. its specific 

 gravity may be found by the last case. 



2. If the specific gravity of air be called m, that of water being 1, and 

 W the weight of any body in air, and W' its weight in water ; then its 

 weight in vacuo is nearly 



W + m (W -, W). 



3. If ff be the specific gravity of a body ascertained by weighing it in 

 air and water, and m the specific gravity of the air at the time when the 

 experiment was made j the correct specific gravity, or that which would 

 have been found, if the body had been weighed in vacuo, instead of air, 

 is 



ff 4. m (1 <r). 



4. If a body float on a fluid, the part immersed (Q) : the whole body 

 (p + Q) ;: sp. grav. (s} of the body : sp. grav. (S) of the fluid. 



Cor. Hence if the same body float on different fluids, Q is as ~ ; on 



which principle the Hydrometer is constructed. For let the instrument 

 be successively immersed in two fluids, and the magnitudes of the parts 

 immersed be observed. Then the magnitude of the part immersed in the 

 first : that immersed in the second :: spec. grav. of the second fluid : to 

 that of the first. 



A considerable improvement lias been made iu the hydrometer, by 

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