SPECIFIC GRAVITY. 



139 



FIG. 83. 



the apparatus to a fixed point marked on the rod (as c). 

 The given body, which must weigh less than W, is placed 

 in the pan, and enough weights (= w) added to sink the 

 point c to the water line. It is evident that the weight of 

 the given body is W w. It is now taken from the pan 

 and placed in the basket, when additional weights (= x) 

 must be added to sink the point c to the water line. 



Ww 



Sp. Gr. = 



x 



(Why ? 



251. Fahrenheit's Hy- 

 drometer. Fahrenheit's Hy- 

 drometer is similar in form to 

 Nicholson's, but is made of glass 

 instead of metal, so that it may 

 be used in any liquid. The bas- 

 ket is replaced by a bulb loaded 

 with shot or mercury. The 

 weight of the instrument ( W) 

 is accurately determined. The H 

 instrument is placed in water, 



FIG. 84. 



