T. Mellard Reade—On the Lower Trias. 557 
Then again, as before stated, although Carboniferous Sandstone 
boulders are scarce in the Trias of the North-west of England, we 
cannot reasonably ignore the fact that massive sandstones and grits 
exist in the Pennine Chain, which have been subjected to vast denu- _ 
dation. Considering that the strong current bedding indicative of 
turbulent water action is one of the characteristics of the Triassic 
Sandstones, and one of its difficulties, may we not reasonably assume 
that Sandstone boulders would soon get ground to sand? ‘There is 
very little of the marginal boundary of the Trias left in the North- 
west of England, and it is in this fringe that Sandstone boulders 
would most likely occur. Marginal deposits of local rocks seem to 
have been preserved in Somerset and Devon." 
Given these materials, tidal action, as I have proved in the papers 
referred to, is quite capable of selecting, distributing, and accumu- 
lating them in the form in which they appear in the Triassic deposits. 
On this theory we are not limited to depth, as the tidal wave 
produces currents acting through the full depth of the water from the 
surface to the bottom, and current-bedded sandstone might be laid 
down by this agent at a depth of many hundred feet and over very 
extensive areas. 
These ideas relating to the physiography of the Triassic period 
have been placed before the Geological Section of the British Asso- 
ciation simply as suggestions for their consideration. The subject 
is beset with difficulties, but in solving such a problem all 
possible agencies must be tried and discussed. 
A new hypothesis also has this merit, that it guides men’s thoughts 
into fresh channels, and it is only by observations renewed again 
and again on various theoretical lines that the truth can be at last 
reached. There is, doubtless, one objection that will be urged 
against the theory here set forth, namely, that it does not account 
for the entire absence of fossils in the Bunter Sandstone, while the 
subaerial river-delta theory does. 
This, doubtless, is one of the many difficulties of the question ; 
but on the other hand if marine fossils had been found, the difficulty 
of interpretation would not have existed, nor would it had the 
sandstone contained fresh-water remains. This argument, although 
possessing considerable force, is only one of negative evidence -pro- 
verbially unsafe. Also, if we admit marine action, it does not 
exclude that of the winds. Molian deposits would be certain to be 
extensively developed on the margin of such sand-laden waters, and 
thus sandstones, which do not contain pebbles, have much rounded 
grains and are irregularly current-bedded may be due to wind-action. 
As regards the Keuper Marls, the dessicated lake theory fits in 
well with their characteristics, and it may be that the Keuper Sand- 
stones show the gradual passage from marine to fresh-water con- 
ditions. The upper beds of the Keuper Sandstones show well- 
developed ripple-marks which are not common, but are not abso- 
lutely absent in the Bunter. The replacement of massive by thin 
sandstone beds, and the intercalation of shales, together with the 
1 See papers already quoted. 
