AND COLLEGE, PUSA, FOR 1914-15. 17 



for it both prevents the surface soil from rising 

 to the temperature which fallow land assumes, 

 and also modifies the diurnal change. Thus 

 whilst the temperature of exposed soil at 1" 

 deep rises to about 3° C. above that of the air, 

 that of cropped land is about 2° C. below it; 

 and whilst the temperature of exposed soil at 

 the surface rises to probably some 20° C. above 

 that of the air, the corresponding figure for 

 cropped land is only some 2° or 3° C. even in 

 March, whilst in the rains it is actually lower 

 than the air. Also in respect of diurnal 

 change; at 1" deep, whilst exposed soil suffers 

 a change of some 20° C. in March, that of 

 cropped land is only about 13° C. at the same 

 depth; and during the monsoon whilst exposed 

 soil suffers a diurnal change of some 10° C. at 

 V deep, that of cropped land is only about 3° 

 to 4° C. 



Soil gases. For some time attempts have been made at 

 Pusa to devise an apparatus by the aid of which the gases 

 contained in a portion of undisturbed soil, taken from a 

 specified depth, might be extracted, measured and analysed. 

 Hitherto the gases contained in soils have been separated 

 for analysis by inserting a tube into the soil and aspirating 

 a portion of gas out of it. By this latter method 

 contamination with the outside air is possible, the real 

 situation from which the gases flow into the tube is uncer- 

 tain, and the direct measurement of the gas per unit volume 

 of soil is impossible. But if a portion of undisturbed soil 

 could be taken from the field in a tool which could be subse- 

 quently closed and provision made for attaching this to a 

 pump, the volume of gas so obtained could be compared 

 with the volume of the soil specimen taken from a specified 

 depth and contamination with atmospheric air would be 

 excluded. Although an apparatus for this purpose was 

 designed several years ago and employed on some preli- 

 minary work on soil gases, it was not free from imperfec- 



