1822*] in modifying the Specific Gravity of Gases. "363 



same) from 120° up to the highest temperature which it can 

 reach without boiHng (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. The reason of this equality I sup- 

 pose to be that the quantity of heat constantly flowing into the 

 water from the fire (or the difference between the temperature of 

 the fire and water) is so considerable, that the 150° or 200° of 

 heat which have been added have no sensible effect in diminish- 

 ing that difference. 2. Six ounces of steam of 212° condensed 

 into water give out as much heat as six ounces of steam of the 

 temperature 275° ; but the second six ounces come over in a 

 much shorter period than the first. 



M. Clement, whom I had the pleasure of seeing in Glasgow 

 about two months ago, informed me that he had verified this 

 last experiment of Mr. Sharpe at different temperatures ; and 

 what adds to the value of these determinations is, that he was 

 not aware of Mr. Sharpe's experiments till 'I pointed them out 

 to him in my own library. Thus the experiments of Mr. Sharpe 

 and M. Clement serve mutually to confirm each other, and 

 entitle us to draw the following conclusion from them : What^ 

 ever be the temperature of steam from 212° upymrds, if we take 

 the same weight of it, and condense it by water j the temperature 

 of the water will be always elevated the same number of degrees. 



It follows from this general law that the latent and sensible 

 heats of steam (reckoning from 32°) added together always form 

 a constant quantity, whatever be the temperature of the steam. 

 This puts it in our power to determine the latent heat of steam 

 at every other temperature, provided we be acquainted with it 

 at the temperature of 212°. Now the latent heat of steam at 

 212° I beheve to be 1016°. The sensible heat of steam at 212^ 

 (reckoning from 32°) is 180° ; consequently the sensible and 

 latent heats of steam at 212° added together make up the quan- 

 tity 1196°. And this being the amount of the latent and sensible 

 heats of steam at every temperature, the method of determining 

 the latent heat of steam at all temperatures becomes self evident. 

 The following table exhibits the sensible and latent heats of 

 steam at a variety of different temperatures : 



Temp, of the steam. • Sensible heat. Latent heat. 



32° 0° 1196° 



50 18 1178 



100 68 1128 



150 118 1078 



200 168 1028 



212 180 1016 



250 218 978 



300 268 928 



344 312 884 



600 468 728 



