T. Mellard Reade—On the Lower Trias. 593 
to have been laid down on the riverine hypothesis, we are met with 
numerous difficulties, which I for one find it impossible to solve. 
The Triassic Sandstones are found on both sides of the Pennine 
Chain ; they occupy valleys in older formations such as the Vale of 
Clwyd, where they are flanked by Silurian hills, and in the Vale 
of Eden by the Carboniferous: and everywhere they appear to follow 
what seem to be the remains of the orographic contours of the 
ancient land. So far as my experience goes, there is a general 
tendency for the sandstones to thin off against these boundaries of 
more ancient rocks, even where these boundaries are represented 
by faults. No doubt the Triassic deposits formerly overlapped their 
present boundaries to a considerable extent; but there is a limit to 
this where they abut against high ground, for there is every reason 
to believe that the pre-Triassic rocks preserve in many respects their 
pre-Triassic orography. 
My study of the origin of mountain-ranges has convinced me of 
the permanence of the more pronounced orographic features of a 
country, or what may be called lateral-pressure upheavals, which, 
while modified by faulting and denudation, can only after a lengthened 
period be finally destroyed by these combined agencies. From these 
considerations it is highly probable that the Triassic rocks which 
remain represent the deeper part of the basins in which they were 
laid down, and that they never encroached extensively on the Pennine 
Chain or the high land of North or South Wales. 
In the case of more extensive and widespread deposits it is the 
thickest parts that, being upheaved into mountain ranges, have been 
most quickly destroyed by denudation. The Triassic rocks have 
not been affected in this manner, and therefore retain in a certain 
degree the basin-like form in which they were deposited. 
One of the most remarkable features of the Triassic Sandstones 
is, speaking broadly, the persistency with which their lithological 
characters hold out over extensive areas, and their apparent independ- 
ence of the bed-rock on which they lie, or that of the hills bounding 
the valleys containing them. Very few pebbles of the surrounding 
rocks are found in the Pebble-beds of the North-west of England, and 
it is mostly in the Midland Counties where any considerable pro- 
portion of local rocks occur in the conglomerate beds. On the 
other hand, the Permian beds underlying them are often largely 
made up of local rocks; instance the limestone breccia of Alberbury, 
composed almost wholly of fragments of Carboniferous Limestone, 
or the somewhat similar “ Brockram ” of the Vale of Eden. 
Could we with any certainty localize the origin of the materials 
of the sandstones, a considerable. step would be made towards 
unravelling this knotty problem; but even as regards the contained 
quartzite pebbles, one set of observers contend that they came from 
the north, another from the south, while a third considers that they 
have been derived from the destruction of rocks in Mid England." 
It would certainly seem, whatever be the direction from which 
1 See Bonney, Address to the Geological Section of British Association, 1886, 
and Grou. Mag. 1883, p. 199; 1888, p. 55.—Harrison, Proc. Birmingham Phil. 
Soc. 1882, vol. ii. p. 157.—Hull, Grou. Maa. 1883, p. 285. 
