1873..
JtTDD THE SECONDARY ROCKS OP SCOTLAND.
133
"3 ^o-S
a 2 SP^-Mfq
Since my return to England, my
obscurely, in the gorges cut
through the drifts by the
Easter and Wester Garty
Burns and the Lothbeg
river *.
Here then we have proof
that the great fault which
has brought about the juxta-
position of the Primary and
Secondary strata in Suther-
land has, through about five
miles of its course, become
double, the strata on the
south-east having been let
down by two steps instead
of one ; and thus a strip of
an intermediate formation
has been preserved. Similar
phenomena, on a smaller
scale, are familiar to all
field-geologists who have
mapped greatly faulted dis-
tricts.
We have thus shown that
the preservation of the in-
teresting patches of Secon-
dary strata in the north-east
of Scotland is entirely due to
the concurrence of a series of
favourable accidents. First
among these (both in order of
time and in importance) we
must rank those great dislo-
cations which have brought
the strata in question into
apposition with rocks of so
much greater hardness and
capability of resisting de-
nuding forces. The general
strike of these great faults
is from N.E. to S.W. ; and
they doubtless constitute a
portion of the results of that
great and long-continued
series of disturbances which
have so largely contributed
to the production of the phy-
sical features of this island.
The influence of this great