at diftrent Degrees of IJeat. 271 



fame piece of iron be weighed in water of the temperature of 

 75°, it will lofe but 13,313 grains; for the lofies of weight 

 will be as the weights of equal volumes of water at thofe tem- 

 peratures, which, as we have feen, are as 253, 1 8 to 252,8 ; there- 

 fore, its fpecific gravity in water of the temperature of 62° 

 •will be 7,49; and in water of the temperature of 75°. 7,51 1 ; 

 but we may corredl this by the above analogy, for 

 ^ 253,8 . 252,18 :: 7,51 I . 7,49. 



By this means we obtain the advantage of difcovering the 

 true weight of a cubic foot of any fubftance whole fpecific gra- 

 vity is known, which it is now plain cannot be know^n when 

 bodies are hydroftatically weighed at any temperature a few 

 degrees above or below 62% without fuch redudion, or fub-^ 

 trading the quantities in the fourth column. 



This method is equally applicable, and with equal neceffity, 

 to other means of finding fpecific gravities, as areometers, the 

 comparifon of the weights of equal meafures of liquids, the 

 different lofles of weight of the fame folid, when weighed in 

 different liquids, &c. In all which cafes the weight of water 

 at 62°, or the lofs of weight of a folid in water at 62% (hould 

 be found by the above analogy. 



Dr. Hales and fome others have eftimated the weight of a 

 cubic inch of water at 254 grains, which is an evident miftake, 

 as it is true in no degree of temperature, and produces an error 

 of more than three ounces in the cubic foot. 





