20 



no manure was added. The experiment, therefore, deals simply 

 with deep cultivation effect, and is not complicated by any disturbing 

 factors due to the operation of the manure. 



The effect of bastard trenching on the soil, when unaccom- 

 panied by manuring, was found to be only small. Beyond a ten- 

 dency to facilitate the drainage of water from the top spit to the 

 lower spit in the clays and heavy loams, and slightly to increase the 

 nitrates, no definite change seemed to be produced. The effect on 

 the growth of trees appeared to depend largely on the character of 

 the seasons following the trenching and planting, as was exemplified 

 by the different results obtained in the same plot of ground after 

 trenching in 1895, and after retrenching in 1910. The practical 

 conclusion may be drawn that bastard trenching by itself, done 

 without addition of manure to the bottom spit, is not likely to bring 

 about any sufficient change in the soil to justify the trouble and ex- 

 pense of the operation. Of course, if there is a pan to be broken 

 the case is different ; but where there is no pan, the main use of 

 bastard trenching seems to be that it affords an opportunity for 

 adding manure or other fertilising material to the bottom spit. 

 Unless advantage is taken of this, the real benefit of the process is 

 missed. 



X. The Composition of Rain Water collected in the Hebrides 

 and in Iceland." N. H. J. MlLLER. Journal of the 

 Scottish Meteorological Society, 1913. [iii] 16, 141—158. 



Systematic analyses have been made for a number of years of 

 the amounts of ammonia and nitrate in rain. The question was at 

 one time of great interest in connection with nutrition of crops, 

 Liebig having maintained that plants derived a considerable pro- 

 portion of their nitrogen from this source. The analyses have long 

 disproved this view and interest has now shifted to another problem : 

 the source of the ammonia invariably found in the rain water. Sam- 

 ples of rain have been collected systematically from various stations 

 in the Hebrides and in Iceland, remote from atmospheric pollution, 

 in order to ascertain how the amounts of ammonia and nitrate com- 

 pare with those found at Rothamsted. The results were as follows : — 



