1822.] Causes of Calorific Capacity j Latent Heat, S^c. 



ANNALS, VOL. II. (New Series.) 



Ph-(Enomejva 



Developed. 



90. P. 449 Theoretical calculations 



of water frozen by agitation in two experi- 

 ments of Thomson. 



91. P. 431. — Baromerin of vapour to 

 that of water as U to 6. 



27 



Confirmed hy 



Differ in one instance ^d part, and in 

 thp other a ^^gth. 



453. — Theoretical determination 

 capacity " of aqueous vapour 



92. P. 



of the ' 



1*83, that of water being 1. 



93. P. 454. — Formula for determina- 

 tion of baromerins of homogeneous gases 

 compared to that of water, and nearly of 

 sM gases. 



94. Ibid. — Specific heats of the lighter 

 airs exceed those of the heavier. 



95. P. 450.— Theoretical calculation of 

 vapour lost by suddenly opening water 

 heated to 400° Fahr. 



96. P. 'too. — Mean capacity of water 

 between 32° and 1 22° Fahr. to ditto be- 

 tween 122° and 212°, as 151 to 14. 



9T. Ibid. — Capacities of water and 

 .mercury decrease with ascent of tempera- 

 ture, and vice versa. 



98. Ibid.— The greater the ratio of 

 water to vapour in the experiment, the 

 less, cceteris paribus^ will be the numeri- 

 cal value of latent heat. 



99. P. 461.— The higher also either or 

 both the temperatures, the greater, under 

 equal circumstances, will be tlie value of 

 latent heat. 



100. Ibid. — Combining the notion of 

 caloric with our formula, the temperature 

 has less influence. A calculation gives 

 1 1® under certain circumstances. 



Mean diff. from four experiments by 

 Thomson, Ure, and Rumford, ^'gth of a 

 degree Fahr. 



Crawford's experiments give 1 -55. 



Has been verified in aqueous vapour by 

 Crawford's experiments. 



Crawford, De Laroche, and Berard. 

 Agrees with Watt's experiment to a 



-— th part of the whole water. 



De Luc's and my experiments as 15 to 



17 



14. 



De Luc, Dalton, Ure, and myself. 

 Experiments of Ure and Rumford. 



Have no experiments to confirm or dis- 

 prove it. 



Southern's experiments under similar 

 circumstances give an increase of 8°. The 

 nature of the thing is such that this may 

 be looked on as a coincidence. 



These are the leading facts I have deemed it needful to select. Several others I have, 

 for the sake of brevity, particularly in the latter part, it will be seen, omitted. I intend 

 to make no comment on the number, extent, and variety, of these testimonies, or of the 

 subjects to which they relate, but shall leave philosophers to form their own opinion of 

 the merits of a theory which can in so great a number of instances, and on such subjects, 

 be the faithful representative of phaenomena. 



Cranford, Dec. 12, 1831. J. HerAPATH. 



P. S. Since finishing the preceding paper, I have computed from Dr. Ure's theorem, 

 which it seems accurately coincides with experiment at 210° and 220° Fahr. the tension 

 of steam at 212°, and I find it 30- 141 3, instead of 30, the compression due to ebulli- 

 tion at 212°. This, therefore, confirms what I have said, p. 441 and 442, respecting 

 the temperatures of tension and ebullition, and respecting Dr. WoUaston's thermometer. 

 The neglect of the distinction I have alluded to will commonly make the Doctor's instru- 

 ment err nearly 75 feet, or 25 yards, in the heights determined. 



Dr. Ure's theorem will, in general, be much more commodious for practice in 

 the following forms than in the one he has given; namely, t = 28-9 x (1*34 — 



^— ^'^ F-910 



•0005 F) '<» or log. t = log. 28-9 + ^ . log. (1-34- -0005 F) where t is the 



tension, and F the Fahr. temperature in degrees. 



