DECEMBER. 367 



inorganic ingredients necessary for the support of plants. In general soils 

 are wanting in some or other of these ingredients, and are, tlierefure, 

 not fitted to grow perhaps any one crop witli luxuriance. 



The first step in the improvement of soils is thorough drainage where 

 it is required, and, after that, deep cultivation and the addition of those 

 ingredients of which it is most wanting. 'J he advantages of drainage 

 have so often been insisted on, that it is not necessary to state them here. 

 By deep digging we not only make a free passage for the roots, and let 

 the air and rains penetrate more easily ; but, in addition to these, we 

 bring new earth to the surface. This forms a deeper soil, and more or 

 less alters both its physical qualities and its chemical composition. A 

 subsoil may gradually become rich in those substances, of which the 

 surface soil has been robbed by the rains ; by bringing up a portion of 

 this subsoil by deep digging we restore to the surface soil a part of what 

 it has been gradually losing. We bring up what may probably render 

 it more fertile than before. By deep and frequent working of the land 

 its parts are more minutely divided, the air gets access to every particle, 

 it is rendered lighter, more durable, and more permeable to the roots. 

 The vegetable matter it contains decomposes more rapidly by a constant 

 turning of tha soil, so that wherever the fibres of the roots penetrate they 

 find organic food provided for them, and an abundant supply of the 

 oxygen of the atmosphere to aid in preparing it. The production of 

 ammonia and of nitric acid also, and the absorption of one or both from 

 the air, take place to a greater extent the finer the soil is pulverised, and 

 the more it has been exposed to the action of the atmosphere. All soils 

 likewise contain an admixture of fragments of those minerals of which 

 tne granatic and trap rock are composed, which, by their decay, yield 

 new sup[ilies of inorganic food to the growing plants. The more 

 frequently they are exposed to the air, the more rapidly do these frag- 

 ments crumble away and decompose. There are few soils so stubborn 

 as not to show themselves grateful in proportion to the amount of this 

 kind of labour that may be bestowed upon them. 



The physical properties of soil have a very great influence on its 

 average fertility. The admixture of pure sand with clay soils produces 

 an alteration which is often beneficial, and which is almost wholly 

 physical ; the sand ^opens the pores ot' the clay, and makes it more 

 permeable to the air. I have seen clayey soils which refused to grow 

 Carrots, but which, after a good portion of river sand had been mixed 

 with it, and it had been got fine by frequent working, grew as fine a 

 crop of Carrots and of as good quality as any person could desire. The 

 admixture of clay with sandy or peaty soil produces both a physical and 

 chemical change. The clay not only consolidates but gives body to the 

 sand or peat, but it also mixes with them certain earthy and saline 

 substances necessary to plants which neither the sand nor peat might 

 originally contain in sufficient abundance. It thus alters its chemical 

 composition, and fits it for nourishing new races of plants. Such is the 

 case also with admixture of marl, of shell sand, and of lime ; they 

 slightly consolidate the sand, and open the clays, and thus improve the 

 mechanical texture of both kinds of soil ; but their main operation is 

 chemical, and the almost universal benefit they produce depends mamly 



