46 Mr. Ivory's Remarks on Sir J. W. Lubbock's 



1 have tried similar experiments with water placed in the 

 rays of the sun, and on all occasions the evaporation has been 

 greatest from the non-insulated vessel. There is a difficulty 

 in obtaining correct calculations from the above experiments, 

 as it is scarcely possible to keep up complete insulation from 

 electricity ; and the vessel of water must have its proportion 

 of electricity when placed in an insulating situation, which 

 will assist the evaporation for some time; but I believe if 

 complete insulation could be obtained, and a vessel left with- 

 out any electricity, that no evaporation would go on at mo- 

 derate temperatui'es, and that evaporation at low temperature 

 is owing to the extreme lightness, or rather no weight of elec- 

 tricity, buoying up the particles of water when expanded by 

 heat. 



I am, Gentlemen, yours, &c. 



Oxford, Oct. 8, 1841. G. A. RoWELL. 



X. Remarks on Sir J. W. Lubbock's " Theory of Heat and 

 Vapours" By James Ivory, K.H., M.A., Hon. M.R.I.A., 

 Instit. Reg. !Sc. Paris, et Reg. Sc. Gotting. Corresp., and 

 late a Fellow of the Royal Society of London*. 



nPHE Theory of Heat and Vapours, published some time 

 -*■ ago by Sir J. W. Lubbock, and reprinted in this Journal, 

 f S. 3. vols. xvi. xvii.], requires some observations from me. It 

 is not intended to examine minutely the whole tract, but only 

 to make some brief remarks on the two last sections which treat 

 of the atmosphere and the atmospheric refractions. The tem- 

 perature, the density, and the pressure of a mass of air being 

 represented by 5, p, p, the author assumes this equation, 



V = C + D(1 +uS), 



in which V stands for the absolute heat, that is, for the sum 

 of the sensible and latent heats, and C and D are constants. 

 The author next adopts another equation, first given by I^a- 

 place, viz. 



2 



V=A + /3^, 

 P 

 A, /3 and y being constants. By equating the two values of 

 V, we obtain 



1_ 



C + D(l +«fl) = A + ^^, 

 P 

 which is the fundamental equation of the Theory of Heat 



* Communicated by the Author. 



