48 
W. Pengelly on the Red Sandstones, 
of the area and at all levels in the formation — at the base of the 
sea-clifif and at hundreds of feet vertically above it. Each bed was 
formed on a shore which the tide daily covered and left dry ; a fact 
to be explained only on the hypothesis that the area of sedimen- 
tation was one of subsidence also. Slowly and gradually as the 
structure was reared, at least as slowly and gradually did the 
foundation sink. And this information is afforded not only by the 
sandstones but by the conglomerates also. They are formed of 
materials which are entirely unsorted ; coarse and fine being 
thrown down together, yet not without order; for the accumulation 
is distinctly stratified, and the unequiaxed stones lie with their 
longest axes in the plane of the bedding. This portion of the 
formation is precisely such as the waves now form on an open 
beach, and this is true of each bed in the enormous pile. Like 
the sandstones, each stratum represents a new relative level of 
land and sea ; a fact not only in harmony with, but calculated 
to enhance the chronological estimate we have already formed. 
Though, as we have seen, there were no interruptions in the 
process of deposition sufficiently important to warrant the opinion 
that our Red rocks represent more than one of the divisions of 
the Triassic system, there were periods, not of intermittence 
merely, but of unbuilding ; periods which, though comparatively 
brief, must have been of considerable duration when measured by 
human standards. Thus, it not unfrequently happens that frag- 
ments of Triassic sandstone form part of the materials of which 
a bed of Triassic conglomerate is composed. The following fact 
places this curious and important point beyond the reach of doubt. 
A nodule which I found in the conglomerates of Torbay is unmis- 
takably a portion of one of the variegated beds so characteristic 
of the Torbay sandstone ; it is evidence of a suspension of depo- 
sition, of unbuilding during the pause, and that certain of the 
variegated sandstones had become so coherent as to be capable of 
furnishing fragments which could endure the rolHng action of the 
waves and yet preserve all the characteristics of the bed whence 
