ASCERTAINING SPECIFIC GRAVITIES. 497 



these parts are again subdivided into 10, by a Ver- 

 neer scale on the slider, which divides the whole 

 length of the arm into 5000 parts. Near to the 

 extremity of the short arm, there is an additional cen- 

 tre and steel-hook, which convert the lever into the 

 common steelyard. To the hook a small weight is 

 suspended, to balance the beam when the index of 

 the verneer is at 0, the beginning of the scale ; and 

 the slider is so regulated, that when it is moved to 

 the outer end of the scale marked 1000 grains, it 

 exactly balances 1000 grains weight, hung at the 

 hook of the short arm. From this arrangement, it 

 is evident, that the value of every division of the 

 verneer, will be equal to two-tenths of a grain ; and 

 each division of the scale itself, will be equal to 

 two grains. The substance of which the specific 

 gravity is to be found, must not exceed 1000 grains 

 in weight. It is to be suspended by a hair from 

 the hook at the short arm/and balanced by moving 

 the slider along the beam. Note the number on 

 the scale, as shown by the verneer : suppose it to be 

 475, which is its weight in grains ; the body is now 

 to be immersed in water in the usual way ; move the 

 slider towards the center, until it again equiponde- 

 rate : suppose the weight now indicated by the ver- 

 neer to be 290.8 grains, the first weight divided by 

 the difference of the two weights already found, 

 gives the S. G. being in this case 2.578. This 

 differs in nothing from the common method of 

 VOL. III. i i 



