34 



the falling off is more marked, exceeding that of the unmanured 

 crop. The figures are : — 



The existence of the third type of variation precluded the 

 possibility of obtaining true curves of exhaustion. 



The paper contains a detailed analysis of the mathematical 

 methods employed for the deduction of statistically homogenous 

 material for the further study of meteorological effects. 



RAIN. 

 VIII. K. J. Russell and E. H. Richards. '' The Amount 

 iind Composition of Rain jailing at Rothamsted." 

 (Based on analyses made by the late Norman H. J. 

 Miller.) Journal of Agricultural Science, 1919. 

 Vol. VIII. pp. 309-337. 



The ammoniacal nitrogen in the Rothamsted rain-water 

 amounts on an average to 0.405 parts per million, corresponding to 

 2.641b. per acre per annum. The yearly fluctuations in lb. per 

 acre follow the rainfall fairly closely. The monthly fluctuations 

 also move in the same direction as the rain, but the general level is 

 highest during May, June, July and August, and lowest during 

 January, February, March and April. 



The nitric nitrogen is on an average one-half the ammoniacal, 

 viz., 1.331b. per acre per annum. The amounts fluctuated vear 



