
SOILS AND SUBSOILS 379 
referred to, and we have learned that of its three constituents 
quartz is practically insoluble, while the felspar and its ferro- 
magnesian associate (mica or hornblende) are more or less 
readily broken up and resolved into kaolin and certain 
alkalies and alkaline earths which tend to be washed away 
as bi-carbonates in solution. Under favourable conditions, 
therefore, the subsoil overlying granite consists of an 
aggregate of larger and smaller roughly rounded or sub- 
angular fragments, in all of which the felspar is more or less 
strongly kaolinised. These fragments are set in a gritty clay- 
like earth, usually reddish, brownish, or yellowish in colour, 
through which non-elastic scales of bleached mica may be 
plentifully scattered. Although the soluble carbonates tend 
to be leached out, yet a larger or smaller proportion is left 
behind, for the gradual decay of the rock-fragments and 
particles is continually setting free fresh supplies. The 
vegetable soil does not differ essentially from the subsoil ; 
it is a gritty clay, often stonier than the latter, but more 
deficient, as a rule, in soluble ingredients, and showing few 
or no scales of mica. 
Since granites vary in character, their soil-caps are not 
uniformly alike. Very coarse varieties necessarily yield 
stonier soils than the finer grained kinds; while the resulting 
clays often differ much in the proportion of soluble materials. 
The soil derived from granites containing hornblende and a 
notable quantity of apatite, may be expected to be charged 
to some extent, not only with potash and lime, but phosphoric 
acid. Much, however, depends upon the position occupied by 
the bed-rock. Inthe low grounds of non-glaciated regions, 
granite is often decomposed to a very great depth, and may 
give a soil capable of high cultivation. But, in our own 
country, the rock usually occurs at mountainous elevations, 
where the conditions for the formation of a persistent soil-cap 
are not favourable. Wind, rain, and melting snow, and the 
steep gradients of the surface, all conspire to prevent the 
accumulation of disintegrated rock-materials. The hill-slopes 
are covered with sheets of grit and rough gravel (=quartz) ; 
over the low grounds the clay may here and there accumulate, 
but the soluble materials are, for the most part, removed. 
Granite may be taken as the type of the acidic felspathic 
