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; SOILS AND SUBSOILS 381 
felspar, but also to some extent from the ferro-magnesian 
constituents. Other intermediate rocks, as syenite, trachyte, 
phonolite, give subsoils that are richer in potash than lime. 
Upon the whole, then, we arrive at the conclusion that 
excellent soils may be derived from the decomposition of 
igneous rocks generally, some of them so argillaceous as to 
be properly designated clay-soils, others of a fine loamy 
character, and yet others of intermediate character— but all 
under favourable conditions, being capable of high cultiva- 
tion. The colour ‘of the soils is lighter or darker, according 
as the parent rocks are poor or rich in iron-oxides. Prob- 
ably, the most fertile soils are those yielded by the basic 
rocks (basalt, etc.), and some of the intermediate rocks 
(diorites and porphyrites), forming, as they do, dark loams, 
rich in the soluble ingredients required for the growth of 
plants. 
Soils from Metamorphic Rocks.—The weathering of 
certain metamorphic rocks results in the formation of quite 
as deep and good soils as are yielded by igneous rocks 
generally. On the other hand, many of the schists and their 
associates supply only meagre barren soils. It will suffice for 
our purpose to note one or two examples. 
Guezss.—As this rock consists of the same mineral con- 
stituents as granite, it weathers much in the same way, and 
the resulting soil is similar—a gritty clay, which, according to 
the physical conditions, may or may not be fertile. At high 
elevations the soil is either a mere rubble of grit and stones 
or a thin clay, from which the soluble constituents have 
usually been removed. Under more favourable conditions, 
as regards elevation and climate, the same rock may be 
covered with a deep and fertile soil-cap. 
Mica-schist.—This rock, composed of quartz and mica in 
variable proportions, often yields a good loamy soil, which in 
favourable positions would be highly esteemed by agriculturists. 
Unfortunately, in these islands it usually occurs at consider- 
able elevations, where climatic conditions do not favour 
cultivation. Nevertheless, the fertility of the soil is evidenced 
by the character of the trees it supports—the coniferous 
forests grown upon the mica-schists of the Scottish Highlands 
being much superior in every respect to those which struggle 
