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of rich soils ; for the vegetable nourishment is long 

 preserved in them, unless taken up by the organs of 

 plants. Siliceous sands, on the contrary, deserve the 

 term hungry, which is commonly applied to them ; for 

 the vegetable and animal matters they contain not be- 

 ing attracted by the earthy constituent parts of the 

 soil, are more liable to be decomposed by the action of 

 the atmosphere, or carried off from them by water. 



In most of the black and brown rich vegetable 

 moulds, the earths seem to be in combination with a 

 peculiar extractive matter, afforded during the decom- 

 position of vegetables : this is slowly taken up, or at- 

 tracted from the earths by water, and appears to con- 

 stitute a prime cause of the fertility of the soil. 



The standard of fertility of soils for different 

 plants must vary with the climate ; and must be parti- 

 cularly influenced by the quantity of rain. 



The power of soils to absorb moisture ought to 

 be much greater in warm or dry counties, than in cold 

 and moist ones ; and the quantity of clay, or vegeta- 

 ble or animal matter they contain greater. Soils also 

 on declivities ought to be more absorbent than in 

 plains or in the bottom of vallies. Their productive- 

 ness likewise is influenced by the nature of the sub- 

 soil or the stratum on which they rest. 



When soils are immediately situated upon a bed 

 of rock or stone, they are much sooner rendered dry 

 by evaporation, than where the subsoil is of clay or 

 marie ; and a prime cause of the great fertility of the 

 land in the moist climate of Ireland, is the proximity 

 of the rocky strata to the soil. 



