1903.] The Evaporation of Water in a Current of Air. 81 



A list of papers on the subject is here given for reference : 



Regnault (' Ann. Chim. Phys.' (3), 15, 129, 1845). 



Fairbairn and Tate (' Phil. Trans./ vol. 150, p. 185, 1860). 



Wiillner and Grotrian(< Wied. Ann./ vol. 11, p. 544, 1880). 



Perot ('Comptes Rendus/ vol. 102, p. 1369, 1886). 



Batelli (' Mem. dell' Accad. di Torino/ (2), vol. 41, p. 33, 1891, and 



(2), vol. 43, p. 1, 1892). 



Ramsay and Young ('Phil. Trans./ A, 1892, p. 107). 

 Bauer (' Wied. Ann./ vol. 55, p. 184, 1895). 



Griffiths* has calculated the density of saturated water-vapour from 

 latent, heat of evaporation by means of the thermo-dynamical equation 



L = j< s '-<>Jr 



The values of dp/(FF were taken from Broch's reduction of Reg- 

 nault's experimental results; the author has recalculated the den- 

 sities, replacing these values of dpjdT by numbers calculated from 

 the vapour pressures given by Luther, t Both series are given in the 

 following table : 



This method is a very indirect one, but is free from the errors 

 involved in most of the experimental methods. Since L and J have 

 been determined with great accuracy, the densities calculated from 

 them should be accurate at the higher temperatures where dp/cFT 

 is known with fair accuracy. The mean density so obtained is very 

 close to the normal density, 0'6227. 



I believe the greater number of the experiments quoted are 



rendered inaccurate by the condensation of vapour on the sides of 



the glass vessel employed, owing to the hygroscopic nature of 



lass ; this is impossible to avoid, but in my experiments it will have 



' Phil. Trans./ A, vol. 186, 1895, p. 325. 



t ' Pbysiko-chemische Messungen/ Oslwald-Luther, p. 156. 



