124 NATURE OF SOILS. 



which has long been cultivated, often constitute a very large pro- 

 portion. The two together, or either singly, will form a soil ; 

 the first use of which is to afford to the plant the power of affix- 

 ing itself, so as to raise its stem, leaves, and flowers, into the 

 most direct influence of the air and light. The next object 

 which it should fulfil, is to supply the roots with a sufficient and 

 regular amount of water ; and this will be effected, according as 

 it is capable of imbibing water readily, from the atmosphere, and 

 from the neighbouring springs, ponds, or streams. 



177. Soils maybe divided into the clayey, the calcareous 

 (those containing much carbonate of lime), and the sandy. A 

 stiff soil opposes the ramification of the roots, whilst a sandy one 

 does not afford them sufficient hold ; it follows, therefore, that 

 no plants will grow advantageously in the former, but those 

 whose roots do not naturally extend far, and whose vegetation 

 is slow ; whilst those are most suited to a sandy soil whose roots 

 spread extensively. It is by means of the Arundo arenaria or 

 Sea-reed, that the Dutch attempt to check the progress of the 

 drifting sand-hills, which threaten desolation to large tracts of 

 country ; and when the soil is once fixed by it, and improved by 

 the decay of the individuals first produced, it affords support to 

 vegetation of more value. 



178. Again, every one knows that a stiff clay will retaiji its 

 moisture for a long time ; and that it parts with it, or receives 

 more, with much difficulty ; whilst, on the other hand, a sandy 

 soil absorbs much water, but soon loses it again. In climates 

 where rain occurs pretty often, a calcareous soil is usually pre- 

 ferred, as retaining its moisture sufficiently long, and yielding it 

 with facility ; if, however, the temperature of a country be high, 

 and rain fall but rarely, a stiff soil is preferable, as it will not 

 become dry in the intervals ; whilst., on the other hand, a sandy 

 soil answers better in a region where showers frequently descend. 

 The defects of one soil, in regard to its power of supplying vege- 

 tation with moisture, may be in some degree remedied by ad- 

 mixture with another ; this process is called in agriculture the 

 tempering of soils. Thus, a stiff clayey soil may be tempered by 

 mixing with it chalk, ashes, or sand, by which it is rendered 



