242 Soil anxcx 



R^:PL^■ to dr leather. 



In our paper we did not discuss Table III in any detail because as 

 we stated the dissolved utmosphere in the soil is under further investi- 

 gation. It is sufficient to say that the gas was not obtained in the 

 manner suggested in the opening lines of the above note. The dissolved 

 gas begins to come out directly the pressure is lowered by the working 

 of the pump, and no sharp line can be drawn to indicate precisely what 

 fraction of the extracted gas was free and what dissolved. For this 

 reason we refrained from making any estimate of the amount of the 

 dissolved atmosphere except to say that it is small. No comparison 

 can be instituted between the data in Table III and those on page 44 

 owing to the difference in experimental conditions, and, moreover, the 

 first and second lots of 30c.c. recorded in Table III, on the composition 

 of which Dr Leather bases part of liis argument, certainly contained 

 some of the free air. The successive extractions were not made on 

 successive days: in some cases there had been practically no interval 

 between them. 



The conclusion we drew from the experiments was that the atmo- 

 sphere dissolved in the surface films of water and other substances is 

 almost devoid of oxygen and consists mainly of carbon dioxide with 

 some nitrogen. This seems to us to be a legitimate deduction from 

 the figures, and we do not think we can go any further at present. 

 Dr Leather says that the Pusa soil behaves differently. The figures 

 he quotes, however, seem to lead to the same conclusion: in his case 

 also the amount of gas is small and it appears to be poor in oxygen. 

 Where then is the difference? 



A. APPLEYARD. 

 E. J. RUSSELL. 



rothamsted experimental station, 

 Hakpenden. 



(Received June 29th, 1915.) 



