
SOILS AND SUBSOILS 377 
than nine oradozeninches. Owing to the presence of organic 
matter, it is dark in colour. It may consist of fine-grained, 
or relatively coarse-grained materials, or of a inixture of 
both—its general character being necessarily determined by 
that of the underlying subsoil and bed-rock. Usually it is 
coarser in texture than the subsoil into which it gradually 
passes. 
(b) Swédsoz7—An earthy accumulation of quite indetermi- 
nate character and thickness, but commonly finer grained and 
lighter in colour than the vegetable soil. Fragments of 
the bed-rock are usually scattered more or less abundantly 
through the subsoil, but are most plentiful towards the bottom 
of the stratum, where they often form a kind of rough rock- 
rubble. The subsoil proper contains no organic matter. 
(c) Bed-rock.—Just as the soil passes down gradually into 
the subsoil, so it is often hard to say where subsoil ends and 
“living-rock” begins. The upper part of the latter is often 
much fissured, earthy matter filling the cracks until, as these 
are followed downwards, they close up. 
The character of the disintegrated materials constituting 
soil and subsoil naturally depends mainly upon that of the 
bed-rock. Should the latter be made up of relatively 
insoluble ingredients—say siliceous sandstone, quartzite, 
serpentine, clay-slate or other argillaceous rock—the soil-cap 
will differ but slightly in character from the bed-rock; it will 
consist simply of disaggregated rock-material which has 
undergone little or no chemical alteration. In such cases, the 
soil-cap is usually thin and meagre. On the other hand, if 
the bed-rock be granite or any other highly felspathic rock, it 
is generally more or less deeply decomposed. The rock- 
fragments and particles of the soil and subsoil are likewise 
highly altered, the subsoil sometimes attaining a thickness of 
a hundred feet or more. 
As disintegration and alteration are continually in pro- 
gress, the subsoil may be said to be always gaining on the 
bed-rock, just as the soil continues to grow at the expense of 
the subsoil. The soil itself, however, does not necessarily 
increase in thickness, for, owing to the action of rain and 
wind, its surface is gradually lowered, the finer particles 
tending to be washed down or blown away. For the same 
