at
the best slates are invariably found in the oldest beds--that is, in
the beds which have had most time to endure the changes, whether
mechanical or chemical, which have made the earth's surface what we
see it now.

Another startling fact the section of Snowdonia, and I believe of
most mountain chains in these islands, would prove--namely, that the
contour of the earth's surface, as we see it now, depends very
little, certainly in mountains composed of these elder rocks upon the
lie of the strata, or beds, but has been carved out by great forces,
long after those beds were not only laid down and hardened, but
faulted and tilted on end. Snowdon itself is so remarkable an
instance of this fact that, as it is a mountain which every one in
these happy days of excursion-trains and steamers either has seen or
can see, I must say a few more words about it.

Any one who saw that noble peak leaping high into the air, dominating
all the country round, at least upon three sides, and was told that
its summit consisted of beds much newer, not much older, than the
slate-beds fifteen hundred feet down on its north-western flank--any
one, I say, would have the right at first sight, on hearing of
earthquake faults and upheavals, to say--The peak of Snowdon has been
upheaved to its present height above and out of the lower lands
around. But when he came to examine sections, he would find his
reasonable guess utterly wrong. Snowdon is no swelling up of the
earth's crust. The beds do not, as they would in that case, slope up
to it. They slope up from it, to the north-west in one direction,
and the south-south-west in the other; and Snowdon is a mere
insignificant boss, left hanging on one slope of what was once an
enormous trough, or valley, of strata far older than itself. By
restoring these strata, in the direction of the angles, in which they
crop out, and vanish at the surface, it is found that to the north-
west--the direction of the Menai Straits--they must once have risen
to a height of at least six or seven thousand feet; and more, by
restoring them, specially the ash-bed of Snowdon, towards the south-
east--which can be done by the guidance of certain patches of it left
on other hills--it is found that south of Ffestiniog, where the
Cambrian rocks rise again to the surface, the south side of the
trough must have sloped upwards to a height of from fifteen to twenty
thousand feet, whether