IMPROVEMENT OF THE SOIL. Ill 



sufficient to add to them some fat marl, or, for want of 

 that, calcined clay. These soils, being naturally warm, 

 require the fresh dung of neat cattle ; the unctuous ma- 

 nures are best adapted to them. 



Sand incorporated with finely divided calcareous earth, 

 forms an excellent means of amendment, especially if it 

 be combined with clay or fat marl. I have likewise seen 

 the rich mud drawn from rivers, used with great success 

 in improving calcareous soils. 



There is a great resemblance in many respects between 

 sandy and siliceous soils : both are formed, generally, by 

 the alluvion of rivers ; both of them are nearly barren 

 when they contain no other principles ; and both of them 

 form the base of very good soils, if they are suitably 

 amended. 



When these soils are formed by the inundations of rivers, 

 or by streams that have taken new channels, they are for 

 some time destitute of fertility ; but the successive swell- 

 ings of the rivers deposit a rich mud, which becomes at 

 length incorporated with the first layer; and when the 

 whole is well- united, an excellent soil is formed. This 

 mud is very fertilizing, from its containing the remains of 

 all those animal and vegetable substances, which muddy 

 waters carry with them in their overflowings. When these 

 soils are left to themselves, we see plants springing up on 

 them spontaneously, from the seeds deposited by the waters 

 •which conveyed them there. 



Soils of this kind rarely require manuring : successive 

 inundations constantly renew their fertility : their level is 

 raised by the accumulation of deposits, till at length they 

 are not subject to being overflowed, excepting when the 

 rivers rise unusually high ; and in those cases the large 

 pebbles, which never float upon the surface of water, can- 

 not be deposited upon them. These lands, so valuable for 

 agriculture, do not offer much resistance to the rapid 

 current of great inundations, which often carry them off*; 

 nor to the masses of ice, which at the breaking up of the 

 frosts gully and furrow them. I believe I ought here to 

 devote a few lines to pointing out some methods for pre- 

 serving these valuable lands from such accidents : it is of 

 more consequence to preserve property than to improve it. 



In order to prevent the evils of which I have just spoken, 

 it is customary to surround lands of this kind with planta- 

 tions of trees; but trees of a large size cannot take wot 



