the Weight ascribed to Heat. 9 



To determine whether this is actually the case or not, 

 I made the following experiment. 



Having provided two bottles, as nearly alike as pos- 

 sible, and in all respects similar to those made use of in 

 the experiments above mentioned, into one of them I 

 put 4012.46 grains of water, and into the other an equal 

 weight of mercury ; and, sealing them hermetically, and 

 suspending them to the arms of the balance, I suffered 

 them to acquire the temperature of my room, 61; 

 then, bringing them into a perfect equilibrium with each 

 other, I removed them into a room in which the air was 

 at the temperature of 34, where they remained twenty- 

 four hours. But there was not the least appearance of 

 either of them acquiring or losing any weight. 



Here it is very certain that the quantity of heat lost 

 by the water must have been very considerably greater 

 than that lost by the mercury, the specific quantities 

 of latent heat in water and in mercury having been 

 determined to be to each other as 1000 to 33 ; but 

 this difference in the quantities of heat lost produced 

 no sensible difference on the weights of the fluids in 

 question. 



Had any difference of weight really existed, had it 

 been no more than one millionth part of the weight of 

 either of the fluids, I should certainly have discovered 

 it; and had it amounted to so much as 7^-5^7 ff P art ? 

 that weight, I should have been able to have measured 

 it, so sensible and so very accurate is the balance 

 which I used in these experiments. 



I was now much confirmed in my suspicions that the 

 apparent augmentation of the weight of the water upon 

 its being frozen, in the experiments before related, arose 

 from some accidental cause ; but I was not able to con- 



