C 321 } 



during the night, and drop the greatest part of their 

 manure during their labour in the day-time. 



The exportation of grain from a country, unless 

 some articles capable of becoming manure are intro- 

 duced in compensation, must ultimately tend to ex- 

 haust the soil. Some of the spots now desart sands in 

 northern Africa, and Asia Minor, were anciently fer- 

 tile. Sicily was the granary of Italy : and the quan- 

 tity of corn carried off from it by the Romans, is pro- 

 bably a chief cause of its present sterility. In this Is- 

 land, our commercial system at present has the effect 

 of affording substances which in their use and decom- 

 position must enrich the land. Corn, sugar, tallow, 

 oil, skins, furs, wine, silk, cotton, &c. are imported, 

 and fish are supplied from the sea. Amongst our 

 numerous exports woollen, and linen, and leather 

 goods, are almost the only substances which contain 

 any nutritive materials derived from the soil. 



In all courses of crops it is necessary that every 

 part of the soil should be made as useful as possible 

 to the different plants ; but the depth of the furrow 

 in ploughing must depend upon the nature of the soil, 

 and of the subsoil. In rich clayey soils the furrow 

 can scarcely be too deep ; and in sands, unless the 

 subsoil contains some principles noxious to vegetables, 

 the same practice should be adopted. When the roots 

 are deep they are less liable to be injured, either by 

 excess of rain, or drought ; the layers shoot forth 

 their radicles into every part of the soil ; and the 

 space from which the nourishment is derived is more 



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