Nature of Sorls. 571 
account of its limited area, is almost always so greatly modified 
by improvements and the addition of manures. 
Besides this primary division of soils according to their con- 
stituent parts, there is another distinction to be considered, 
namely, in regard to the nature of the upper layer, or surface 
soil, and of the stratum immediately below, termed the sub- 
soil, or subjacent rock, as the case may be. The surface of 
arable soil ranges from an inch or two to several feet in thick- 
ness, and is equally variable in the class of vegetation it will 
support. Greater importance perhaps attaches to the nature 
of the subsoil than is usually accorded to it, for on this de- 
pends the necessity or otherwise of artificial drainage, and the 
choice of trees, shrubs, and herbs that will permanently flourish 
in certain situations. Its thickness, as well as its mineral- 
ogical composition, is, of course, indeterminate. It may con- 
sist of solid rock, or beds of gravel, sand, &c., or it may also 
be composed of soi] suitable for cultivation, and will thus 
serve to enrich the surface layer when it has been more or less 
exhausted by the crops taken from it. In the case of a heavy, 
impervious clayey subsoil, artificial drainage is beneficial, or, 
as in some instances, indispensably necessary to ensure success 
to the cultivator. 
It comes within our proyince to say but little respecting the 
improvement or enriching of ground by the addition of natural 
and artificial manures. To effeet this object it is obvious that 
the nature of the soil to be manured should be considered ; for 
some manures or moulds that would improve a heavy loam or 
clay would deteriorate the quality of a light sandy loam, and 
vice versa. Another thing to take into consideration is the use 
to which the ground is to be put. Luxuriance in the growth of 
some things is undesirable, as for instance in small shrubberies, 
and where tender subjects are planted. And then different 
subjects delight in different soils. A lawn rarely requires any 
stimulating manures, as they induce the growth of coarse 
herbage. We have seen a good piece of grass spoiled by the 
injudicious application of liquid manure. Except for hot-beds 
and the purpose of mulching the surface of the soil around 
newly-planted shrubs and trees to diminish the amount of. 
evaporation in dry hot weather, little use is made of what 
is termed green dung in the pleasure-garden. Thoroughly 
rotten leaves (leaf-mould), fibrous turf, and farm-yard manure, 
wood-ashes, soot, lime, sand, &c., are employed according to 
