Proceedings of the British Association. 121 



of manure throughout the course of the trials. He stated that although, 

 as might have been anticipated, a diminution in the latter years' 

 produce took place both in the permanent and in the shifting crops, 

 and a smaller average amount was obtained in the former than in the 

 latter, yet that after the expiration of the whole period the ground 

 still continued unexhausted ; and that an analysis of it showed it still 

 to contain sufficient of the phosphates to supply materials for 19 

 crops of barley, sufficient of potash for 15, and sufficient of soda 

 for 45. The actual diminution then of produce during the latter 

 years he attributed to the circumstance of these ingredients not being 

 in a soluble condition, it being found that from the soil so long 

 drawn upon, water impregnated with carbonic acid took up much less 

 of the above ingredients, than it did from the same that had not been 

 so cropped, and but recently manured. The greater diminution in 

 the permanent than in the shifting crop he attributed to the circum- 

 stance of the latter being supplied with a larger amount of organic 

 matter, derived from the fallow crop intercalated, owing to which 

 the plants would be more fully developed through the influence of 

 the carbonic acid and ammonia, which would be imparted to it by the 

 decomposition of the humus. He pointed out, how the mere intro- 

 duction of healthy plants into a soil might aid in rendering the phos- 

 phates and alkaline salts, locked up within the latter, more speedily 

 soluble, and hence inferred that a larger amount of these substances 

 might be extracted, where the plants were stimulated into activity by 

 the presence of decomposing organic matter. He also was led to 

 inquire whether, in the event of a scantier supply of one of the 

 alkalies or of the earths than was common, a plant would substitute, 

 ad libitum, another which might be presented to it in greater abun- 

 dance. To determine this, he obtained from Mr. Way, late assistant 

 to Prof. Graham, an analysis of three samples of six different kinds 

 of crop — viz. potatoes, barley, turnips, hemp, flax, and beans ; one 

 sample being, that cultivated for ten successive years in the same ground 

 without manure ; the second, from a similar plot which had grown dif- 

 ferent crops for the same period without manure; the third, from a plot 

 in a contiguous part of the garden which had been recently manured. 

 From the results obtained, it would appear that the aggregate 

 amount of bases, in the three samples, was about the same ; but 



