AGRICULTURE WITH CHEMISTRY. 99 



crops, or the soil be of a nature to receive benefit by the 

 fermentation and heat produced by the application of 

 fresh dung, preference should undoubtedly be given to 

 dung in a long state, provided it is immediately ploughed 

 in, and totally covered, which is not easily accomplished 

 with dung of this description. Long dung is always to 

 be preferred in the culture of potatoes ; for dung com- 

 pletely rotted frequently causes this crop to be watery 

 and worm eaten. Many farmers only apply coarse straw 

 or litter ; whence it might be imagined, that the benefit 

 arising from such an application, must be more depen- 

 dent on the straw mechanically keeping the ground open 

 or loose, than in contributing, by any part of its own 

 substance, to the growth of the potatoes, which cannot 

 well be supposed ; as the straw, in digging up the pota- 

 toes, is generally found in an tin decayed state. It is 

 highly probable, that the atmospheric air contained in 

 the intervals of the soil, thus made by the straw, may 

 suffer a degree of separation, or decomposition in its 

 (as it were) imprisoned state, by which means the pure 

 air or oxygen may combine with the straw, and in- 

 flammable or vegetable matter, in the soil ; whilst the 

 azotic or phlogisticated air will contribute to the growth 



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