1821.] Causes of Calorific Capacity, Latent Heat, $c. 459 

 mass w + 1 would remain at F 3 . whereas it is found at F 

 Hence (F s — F 3 ) . (w + 1) expresses the Fahrenheit degrees 

 of latent heat contained in a unity of vapour at F,. 



(11 >. 2 



and F 3 = (iHY ' T0H50O " 448 > therefore ( F > - SS <» + 1) 

 _ tc + -ri ^ -0008 £', which is a general expression for the 



latent heat agreeable to the usual ideas. If to satisfy the pro- 

 poser we wish to have the expression for the detached boiler in 

 terms of the elasticity E, let us put t the lower temperature equals 

 to 1000, and the elasticity of the vapour supposed to follow the 

 ordinary laws of gases at that temperature also equal to the same 



quantity 1000. Then t' = 10 x V 10 E, and the latent heat ig 



ioo to + H ; v 10 E 



equal to " " T ' , x -08 V 10 E. 



*■ to + 1 



In the case of the attached boiler we have t f = <p -1 E and, 

 t = <p _1 e ; and, therefore, the latent heat = ^-^ — - + " ' ^ . 



T ' to + 1 



x -0008 ?-' E. 



From both of these expressions, we perceive the proportion of 

 water to steam has an influence in the determination of the 

 quantity of latent heat which may be one cause of the discor- 

 dancies in the experimental results of different authors. 



Case 3. — To determine the densities in terms of the elastici- 

 ties. One of the densities, that of the attached boiler, as the 

 proposer observes, will remain the same ; we have, therefore, 

 only to determine tlie other. Putting a for the arithmeridone, 

 we have, by the theorem, p. 56, Annals for July, 1816, E cc 



P a* 



a t" m, because v is constant, and a a w ; therefore, w a 



v to ' ' ' 



% and . = -4545 x « x j|E™ =20831-26 x^vvhich 



expresses the value of the specific gravity or density of vapour 

 in terms of the elasticity E as the proposer requires, the elasti- 

 city at 212° Fahr. being 30, and specific gravity *4545. 



Scholium. 



If in the leading theorem of the first case we put F = 32°, 

 F, = 122°, and n = 90° = F, - F or 212° - F,, we get 



made the calculations. My design in pointing out these, and other things I have had' 

 occasion to allude to, is not, I assure the Doctor, to depreciate the merits of Ilia paper, 

 to which he must perceive I have been much indebted, but merely to call his attention 

 to-arrecomputatien of the results he has given ; for from no person, it appears to me, cm) 

 the rectification .of oversights come with so good a grace as from their author. 



