HYDRAULICS AND HYDROSTATICS. 



227 



Nicholson's Portable Balance. Fig. 241. Fig. 242. 

 (Fig. 241.) This consists of a hollow 

 cylinder of metal terminated at each 

 end by a cone ; from the top of the 

 upper cone rises a small stem of brass, 

 terminated by a cnp, a, which may be 

 slipped off ; from the end of the lower 

 cone is suspended a cup, e, that is 

 loaded with a weight, sufficient to sink 

 the instrument in water nearly to the 

 base of the upper cone ; by placing 

 weights in the cup, a, at the top, it is 

 immersed to the mark on the stem ; 

 if the weights be removed and a solid 

 body, whose weight is less than theirs, 

 placed in the cup, it may be immersed 

 again to the same mark, by placing weights along 

 with the solid in the cup, and thus the weight of 

 the solid obtained ; now place the solid in the cup 

 attached to the weight and weigh it in water; 

 having now the weight of the body in air, and its 

 loss of weight in water, its specific gravity may be 

 ascertained by dividing the weight in air by the 

 loss of weight in water, the quotient is the specific 

 gravity. Price, $3.50. 



Nicholson's Hydrostatic Balance. (Fig. 242, as above.) 

 This instrument is made of brass, highly finished, and having 

 a cage over the counterpoise for confining any solid body 

 that is lighter than water. Price, $6.00. 



Frye's Lactometer. (Fig. 243, next page.) For testing 

 the quality of milk ; made under the direction of the Board 

 of Agriculture of the American Institute, in the city of 

 New York, who have strongly recommended it to the 

 public patronage. 



This instrument was invented for the purpose of ascer- 

 taining the density, and fixing the standard weight, of pure 

 unadulterated milk, as it is produced in the best grazing 

 districts in the country, and with a view of detecting the 

 frauds practised by adulterating milk with water, so often 

 complained of by the consumer, in large towns and cities 

 throughout the Union. 



