S I 



547 



SO I 



and sliglitly fibrous roots, at the same ensis, gives as being the most fertile 



time that, like the spinach, it has to for the grasses : — 



afford repeated cuttings; and thus, re- " Fine sand, 115; aluminous stones, 



quiring a repeated development of 70 ; carbonate of lime, 23; decompos- 

 ing animal and vegetable matter, 34 ; 

 silica, 100; alumina, 2S ; oxide of 

 iron, 13; sulphate of lime, 2; soluble 

 vegetable and saline matter, 7 ; loss, 8 ; 

 total 400." 



I have already stated what forms a 

 fertile soil; it maybe added, that, to 



parts, it needs abundant food in its im- 

 mediate neighbourhood. A soil with a 

 just proportion of decomposing matter 

 will be capable of absorbing moisture, 

 during the droughts of summer, from 

 the atmosphere; for the most fertile 

 soils are always the most absorbent. 

 Yet it must not be too retentive of constitute it eminently sucli, its earthy 



moisture, which is the case in such 

 soils as contain too much alumina ; 

 neither must it too easily part with 

 moisture, a fault which is a character- 

 istic of those soils which contain an 

 e.tcess of silica. 



A subsoil of gravel, mixed with clay. 



particles must be in a minute state of 

 division; the more so the more fertile it 

 will be. 



In the above analysis 185 parts only 

 were separable by sifting through a fine 

 sieve; 215 parts were impalpable; 

 whereas poorer soils will ofien have 



is the best, if not abounding in oxide ! 300 parts coarse matter to every 100 of 



of iron ; for clay alone retains the moist- 

 ure, on the arable surface, in too great , 

 an excess; and sand or chalk, on the 

 contrary, carries it away too rapidly. 

 It is, however, evident, that to insure 



finely pulverized constituents. 



In affording warmth to plants the 

 earth is of considerable importance, 

 and the power of accumulating and re- 

 taining heat varies as much in soils as 



these desiderata in any soil, at all sea- the proportions of their constituents. 



sons, IS impossible; and it is manifest 

 that a soil that would do so in one cli- 

 mate would fail in another, if the mean 

 annual temperature of them should dif- 

 fer, as well as the amount in inches o 



Sir Hum[)hrey Davy found that a rich 

 black mould, containing one-fourth of 

 vegetable matter, had its temperature 

 increased in an hour, from (Jo^ to SS^ 

 by exposure to the sunshine, whilst ^ 



rain which fall during the same period- , clialk soil was heated only to 09' undef 



Thus, in the western parts of England, 

 more than twice as much rain occurs 

 as in the most eastern counties, or in 

 the proportion of forty-two to nineteen ; 

 a soil in the cast of England, for any 

 given crop, therefore, may be richer 

 and more tenacious than the soil re- 

 quired for it on the western coast. 

 Alumina, or clay, imparts tenacity to 



similar circumstances. Hut the firstj 

 when removed into the shade, cooled 

 in half an hour 15*^ ; whereas the latter 

 lost only 4°. This explains why the 

 crops on light-colored tenacious soils 

 are in general so much more backward 

 in spring, but are retained longer in 

 verdure, during autumn, than those on 

 black lisrht soils. The latter attain a 



a soil when applied; silica, or sand, genial warmth the more readily, but 



diminishes that power ; whilst chal k ami part from it with c<iual speed. Different 



lime have an intermediate effect. They plants affect different soils. Every 



render heavy soils more friable, light gardener must have observed that there 



soils more retentive. These simple is scarcely a kitchen garden but has 



facts are important; tw-o neighbouring some particular crop which it sustains 



gardens, by an interchange of soils, In luxuriance, tar superior to any other 



being often rendered fertile, which be- garden in its neighborhood, or to any 



fore were in the extremes of tenacity other crop that can be grown on it. A 



and porosity. 



garden I once cultivated would not 



From these statements it is evident , produce, without the preparation of an 

 that no universal standard or recipe can artificial soil, the coniinon garden-cress 

 be given for the formation of a fertile {Lepidium sativum), whilst the raspberry 

 soil; but a soil, the constituents of was remarkably luxuriant; and we 

 which approach in their proportions to ' have seen that the composition of a soil 

 those of the following, cannot be un- has a main influence in these peculiari- 

 productive in any climate. It is a rich ties. It is certain that a soil is often 

 alluvial soil, which Mr. Sinclair, in his considered unproductive, and the un- 

 iuvaluablc Ilortus Gramineus Wobuni- productiveness attributed to some de- 



