EARTHS AND SOILS. 43 



and fitted for the sustenance of plants in general ; hence 

 arises the mutual benefit of combinins; earths with veseta- 

 ble and animal substances ; and hence, too, the bad prac- 

 tice of continuing the mineral manures until the whole of 

 the vegetable and animal matter is withdrawn from the 

 soil ; for by the increased activity of the growing vegeta- 

 ble, the soil is rapidly exhausted of its nutritious matter, 

 and it is left comparatively barren, if the agriculturist 

 ceases to supply vegetable and animal manure. There 

 remains then but one course, that of supplying directly the 

 necessary nutriment ; but it is unquestionably better to 

 maintain a sufficiency of vegetable matter always in the 

 earth, and never suffer a soil to be exhausted or worn out 

 by overtaxing its resources." 



We subscribe to the Professor's recommendations, 

 though we do not exactly agree with him in his premises, 

 that all calcareous matters tend to accelerate the exhaus- 

 tion of organic matters in the soil. We think this remark 

 will only apply to caustic or quick lime. Davy proved 

 that it did not apply to gypsum ; and it is generally con- 

 ceded, that calcareous soils are less liable to be exhausted 

 than soils that are not calcareous. 



2. Gravelly soils " differ materially from sandy," 

 says Sinclair, "both in their texture and mode of man- 

 agement. They are frequently composed of small, soft 

 stones, sometimes of flinty ones ; but they often contain 

 granite, limestone, and other rocky substances, partially, 

 but not very minutely decomposed. Gravel, being more 

 porous than even sand, is generally a poor, and what is 

 called a hungry soil, more especially when the parts of 

 which it consists are hard in substance and rounded in 

 form. Gravelly soils are easily exhausted, for the animal 

 and vegetable matters which they receive, not being at- 

 tracted by the earthy constituent parts of the soil, which 

 are seldom sufficiently abundant for that purpose, are more 

 liable to be decomposed by the action of the atmosphere, 

 and carried off from them by water. 



" Gravelly soils are improved by draining, where they 

 are troubled with springs ; — by deep ploughing ; — by mix- 

 ing with them coats of clay, chalk, marl, peat, or other 



