tr R A 



placing a small brass cup on the top of the stem, into which small weights 

 may be put, so as to sink it in different fluids to the same point of the 

 stem. Let W = weight necessary to make it sink in one fluid, and W 

 4. w the weight necessary to make it sink to the same point in another; 

 then if one of them is water, the spec. grav. of the other = 1 000 x 



5. If a lighter fluid rest upon a heavier, and their spec. grav. be as a : b, 

 and a body, whose spec. grav. is c, rest with one part P in the upper 

 fluid, and the other part Q in the lower, then 



p : Q : ; i _ c : c a . 



6. If a and b be the spec. grav. of two fluids or solids to be mixed to- 

 gether, P and O, their magnitudes, and c the spec. grav. of the compound, 



P I Q I; b c I c a, and 



weight of P : weight of Q ; : a. ( c) : b (c a). 

 Cor. Hence from the first proportion, 



P + Q ' 



And from the second, if W and w =. weights of P and Q, 



_ (W 



' 



7. Of the magnitude and weight of a body, having given the one to 

 find the other. 



Let M magnitude in cubic feet, S = its spec. grav. that of water 

 being 1000, W = weight in avoirdupois ounces, then 



W = M X S. 



Or let W = its weight in grains, and S its spec. grav. that of water 

 being 1, B its bulk in cubic inches, then 



B= 



252,576 S' 



Cor. If the weight is expressed in pounds Troy, it must be multiplied 

 (to reduce it to grains) by 5760 ; if in pounds avoirdupois, by 7002. 



We may thus find the magnitude of bodies which are too irregular to 

 *dmit of the application of the common rules of mensuration; or we may, 

 ty knowing 1 the spec. grav. and magnitude, find the weight of bodies 

 v hi<'h. are ro ponderous to be submitted to the action of the balance or 

 steel y:mi, 

 131 



