1895.] The Latent Heat of Evaporation of Water. 217 



My conclusion therefore is 



Temp. L. 



40-15 572-60 



30-00 578-70 



Section II. 



On p. 218 will be found, I think, a fairly complete table of results 

 published since the year 1843. 



The values obtained by Winkelmann (' Wied. Ann.,' 9, 1880) are 

 not included in the table, as they are not based on independent 

 experiments, but deduced from the observations of Regnault. 



In Paper L I have given reasons for my conclusion that much 

 greater weight attaches to the values of Dieterici and E-egnault than 

 to those given by the other observers. 



Dieter ici's method was to determine the mass of ice formed by the 

 evaporation of a certain mass of water at 0. Hence, his results, like 

 my own, are independent of thermometric errors, or errors in the 

 determination of the water equivalent of his apparatus. Certain of 

 his experiments were performed by placing the water to be evaporated 

 in platinum, instead of glass, tubes, and to these he attaches, I think 

 rightly, greater importance than he does to the remaining experi- 

 ments. His conclusions are as follows : 



" Die Versuche mit dem Platingefasse ergeben 



L = 596-73, 



mit eiriem wahrscheinlichen Fehler des Mittels von +0 '13."* 



He succeeded in altering the rate of evaporation very greatly, and 

 that without affecting his results. I cannot here even enumerate 

 other considerations which lead to the conclusion that the result of 

 Dieterici's platinum tube experiments carries great weight. 



As stated in the above table, Regnault performed twenty-two ex- 

 periments over the temperature range 2 to +16. There can be 

 little doubt, however, that his results over this range are of small 

 value, and he was evidently of this opinion himself, f 



Winkelmann has written a criticism of Regnault's experiments, + 

 in which he comes to the conclusion that it is necessary to reject this 

 series of experiments, and, in Paper L, I give additional reasons for 

 their rejection. The chief arguments are as follows : 



(1.) Regnault determined the temperature of the vapour in the 

 spiral by observations of the pressure in the condenser. 



* ' Wied. Ann.,' rol. 37, 1889, p. 504. 



t See ' Memoires de 1'Acad.,' rol. 21, 1847, pp. 712719. 



J ' Wied. Ann./ vol. 9, 1880. 



VOL. LVII. R 



