Strata in the Brook Pulcovca. 
387 
nothing of the kind seems to occur opposite x 9 which should have 
been the case, were they to be continued in a straight line ; and no 
trace of them is to be seen on the other side of the small peninsula 
formed by the river between M and Z, This is the only instance 
in which the strata appear broken through ; in all their other 
accidents, they are bent, but never dislocated. It seems as if a rent, 
which first meets the river at z, having crossed it to y, by a small 
curve, cuts off the point of the rock H 9 and re-appears at x, The 
circumstance of its being filled with diluvium and boulders proves, 
if not precisely the time of its disruption, at least that its filling up 
was not anterior to, and probably contemporaneous with the 
deposition of the diluvium of the plain above j the evenness of the 
soil above, and the perfect conformity of the line of cliff, its face, 
and height, all seem incompatible with the idea of its being a mere 
landslip of recent occurrence (of which a good example occurs lower 
down the valley) ; an earthquake seems the only remaining post- 
diluvian cause which could produce such an accident, though it may 
be thought that the undisturbed appearance of the upper bed of 
diluvium and superficial soil is as incompatible with the one as the 
other. However, from the causes by which recent landslips are 
produced, it seems hardly possible, that a mass of hard rock like this 
should be so cleanly cut through, and that it should sink perpen- 
dicularly in the same spot in which the correspondence of the strata 
with those adjoining points it out to have been.* 
*■ It will be observed that the dip of the two bodies of rock on the outside of the dykes, 
x and ?/, Opiate 24, fig. 3) is in the same direction, though at different degrees of inclination. 
Supposing, then, that in their original position the strata eg, (the coloured beds) were con- 
tinued so as to join without interruption those parts now on the outside of the two dykes, 
they would not present a greater variety of dip than is now exhibited immediately* on 
* This is only seen in the general view, (fig. 1, plate 25,) where it immediately overlies the black clay 
with pyritical nodules at L The limestone in this valley exhibits fewer traces of petrifactions than any 
where else- 
