This is because the one resists the powers which have been
employed in leveling what has been raised from the bottom of the sea,
more than the other; consequently, we find more of the one remaining
above the level of the sea than of the other.
Let us now take the map of Scotland, in order to observe the mixture of
those two different species of countries, whereof the one is generally
low and flat, the other high and mountainous; the one more or less
provided with fossil coal, the other not.
From St Abb's Head, on the east of Scotland, to the Mull of Galloway,
on the west, there runs a ridge of mountains of granite, quartz, and
schistus strata, which contain not coal. On each side of this ridge we
find coal countries; Northumberland, on the one side, and, on the other,
the shires of Ayr, Lanark, and the Lothians; the one is a mountainous
country, the others are comparatively low or flat countries. Let us now
draw another alpine line from Buchan and Caithness, upon the east, to
the island of Jura, on the west; this traverses a mountainous country
destitute of coal, and, so far as I know, of any marks of marine bodies.
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