312 Miss N. Thomas and Dr. A. Ferguson on 



If the whole o£ his results be plotted logarithmically, it 

 can be seen that they may be represented with moderate 

 accuracy over the whole range of the experiments by 



M = Ka 15 



in fair agreement with our experimental results, which we 

 shall presently proceed to discuss. 



In a later paper * Renner gives the results of experiments 

 made on the evaporation from moistened pieces of bibulous 

 paper and, inter alia, gives a qualitative confirmation of the 

 relation established by Stefan between the evaporation 

 capacity of a circular surface and that of an ellipse of 

 equal area. 



The discussion of previous work might 



" in judicious bauds 

 Extend from here to Mesopotamy." 



but thereris no need to particularize further. Mrs. Livingston's 

 bibliography provides full references up to 1909, and the 

 courtesy of the Director of the Meteorological Office has 

 enabled us to give one or two later titles, which are appended 

 below f . 



We turn now to the discussion of several errors which, 

 it appears to us, have somewhat obscured the treatment of 

 this part of the subject. They have probably arisen from 

 the fact that we can employ either of two differential 

 equations in defining k. Thus, if we employ the equation 



we obtain, following Maxwell J, a definition of k as u the 

 volume of gas, reduced to the unit of pressure, which passes 

 in unit of time through the unit of area when the pressure 

 is uniform and equal to jt?, and the 'pressure of either gas 

 increases or diminishes by unity in unit distance/ 5 



* Ber. Deutsch. Bot. GeseUsch. xxix. p. 125 (1911). 

 t F. H. Bigelow, ' The Laws of Evaporation, &c.' Buenos Aires, 

 1911. 

 B. F. E. Keeling, ' Evaporation in Egypt and the Sudan.' Survey 



Dept., paper 15 : Cairo, 1909. 

 R. Strachan, ' Basis of Evaporation.'' London, 1910. 

 J. R. Sutton, ' Evaporation in a Current of Air.' Trans. Roy. Soc. 

 Africa, i. p. 417 (1910). 

 X Phil. Mag. xxxv. p. 201 (1868). 



