464 NORFOLK SOCIETY. 



by the presence of disagreeable odors, and by the liquids 

 retaining their coloring matter. The interesting details in 

 regard to these experiments will be found ill the various 

 communications of Messrs. Thompson, Way, Lawes, and 

 Gilbert, in the Journal of the Royal Agricultural Society. 



These results agree precisely with common observation, and 

 the existence of a strong affinity in clayey soils for the ele- 

 ments of manures, cannot be doubted, although the precise 

 nati\re of this affinity may not be fully known. 



There is another well known property in clays, which, when 

 properly considered, serves to explain their tendency to inert- 

 ness, and teach the great fact on which we started, that they 

 should be made lighter, and more exposed to atmospheric 

 action. The binding- nature of such soils can hardly have 

 escaped the observation of every farmer. We see, for example, 

 that if clay, while in a moist state, is cut from its bed in 

 pieces, there is a tendency in the particles which form these 

 pieces to cohere ; the particles attract each other, and as the 

 moisture evaporates they combine firmly together. The firm- 

 ness with which they thus unite, and the degree to which the 

 air is excluded, depends much on the size of the lamps or 

 pieces. If they are a foot square, they bind together and 

 remain more or less in these dimensions, and the air acts on 

 but a comparatively small part ; but if they are only an inch 

 square, the strength of cohesion is proportionately less, and the 

 exposure to the air proportionately more ; consequently the 

 finer division is more favorable to friability. 



But the question may be asked — What has this to do with 

 the point — why is this exposure to the air necessary ? It has 

 been already shown that the elements of vegetable nutrition 

 in clayey soils are latent, not sufficiently soluble. Now the 

 great dissolving or decomposing agent of nature is oxygen^ 

 one of the elements of the atmosphere. 'One object, therefore, 

 in exposing clayey soils to the air, is, that the oxygen may 

 bring the food of plants into a soluble state, available to 

 plants. 



But besides the development of soluble food, another impor- 

 tant effect is produced by the aeration of clayey soils. It is a 

 common expression that clays are " cold," and that they require 

 to be " warmed up," to bear crops. It is so in fact, and hence 



