These horizontal strata are traversed
in places with small veins of whin-stone, as well as greater masses
forming rocks and hills of that material; but, except it be these, (of
which there are some curious examples), I thought there could be nothing
more of an interesting nature to observe. Chance, however, discovered to
me what I could not have expected or foreseen.
The river Tweed, below Melrose, discovers in its bed the vertical strata
of the schistus mountains, and though here these indurated bodies are
not veined with quartz as in many places of the mountains, I did not
hesitate to consider them as the same species, that is to say, the marly
materials indurated and consolidated in those operations by which they
had been so much changed in their place and natural position. Afterwards
in travelling south, and seeing the horizontal softer strata, I concluded
that I had got out of the alpine country, and supposed that no more of
the vertical strata were to be observed.
The river Tiviot has made a wide valley as might have been expected, in
running over thole horizontal strata of marly or decaying substances;
and the banks of this river declining gradually are covered with gravel
and soil, and show little of the solid strata of the country.
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