460 Aiiahjses of Books. [June, 



city is twice as great, and at 307° four times as great as 212*^. 

 iS'ovv as steam is very mueh employed as a moving force, it 

 becomes a question of considerable importance to determine the 

 cause of this increased elasticity. From the experiments of Mr. 

 Watt we learn that the latent heat of steam is 940°, while 

 Count Rumford makes it 1020°. Now is the increased elasticity 

 of steam owing to an increase in the latent heat of steam, or to 

 an increase of its density? Mr. Sharpe's experiments seem 

 conclusive in favour of the last of these opinions. He ascer- 

 tained two things: 1. That water heats equably, or in the same 

 time (supposing the heating cause the ^me) from 120° up to tha 

 highest temperature that it can reach without boiling (and that 

 temperature depends upon the pressure). Suppose, for example^ 

 that it is heated 10% or from 120° to 130°, in three minutes; 

 it will be heated from 270° to 280° in the same time. This is a 

 very curious fact, and not easily explained, unless we have 

 recourse to Mr. Daiton's supposition, that the thermometer is 

 an inaccurate measure of heat, 2. That six ounces of steam 

 of 212° condensed into water give out as much heat as six 

 ounces of steam at the temperature 27-^° ; but the second six 

 ounces come over in a much shorter period than the first. This 

 1 conceive to he a demonstration that the increased elasticity of 

 steam is owing to a corresponding increase of its density. There- 

 fore the density of steam at 212^ is 150 times greater than at 

 32°; and its density at 252® is twice as great as at 212°. Hence 

 we have the specific gravity of steam ^t difi'erent temperatures^ 

 as follows 



Sp. Gravity, 



At 32° 0-004^ 



212 0-6896 



252 1-3792 



307 27584 



This explains the elasticity of steam in a satisfactory manner, 

 and brings it under the same law as common air, and all the 

 other elastic fluids. 



2. On Resphation and Animal Heat. By John Dalton.] 

 This paper was read to the Manchester Society in 1806. There 

 is an appendix to it, written in 1810; and a second appendix, 

 wiitten in 1811. It exhibits marks of all the originality and 

 ingenuity so characteristic of Mr. Dalton; and had it been pub- 

 lished when originally written, it would have produced a great 

 improvement in the opinions of physiologists relative to respira= 

 tion. But the opinions contained in this essay are nearly the 

 same as those generally embraced by physiologists; partly in 

 consequence of Mr. Daiton's own opinions, which have been 

 long known to the world, and partly on account of the accurate 



