552 T. Mellard Reade—On the Lower Trias. 
If we add to these characteristics the occurrence of well-rounded 
pebbles of liver-coloured and of clear translucent quartzite, white 
vein quartz, and other hard rocks, from the size of walnuts to an 
occasional specimen having a longer diameter of four or five inches, 
we shall have exhausted our lithological description. 
It is, however, to be specially noted that these pebbles occur often 
sparsely distributed through the rock, sometimes in nests, and in 
other cases in such numbers as to deserve the name of “conglomerate 
beds” given to them by Professor Hull. 
So far as my experience goes, the liver-coloured quartzite pebbles 
are confined to the Bunter Sandstones; but I have not been able to 
satisfy myself so far that these pebbles occur at a definite horizon 
in the Bunter, except locally speaking. Indeed, I am much inclined 
to believe that in some cases the theory of the pebbles being confined 
to a central subdivision has led to a misinterpretation of these rocks. 
Speaking broadly, there is a distinct lithological difference be- 
tween the Keuper and the Bunter; for although in most cases it 
would not be possible to distinguish the rocks in local specimens, we 
cannot point to any rocks in the Bunter which would be mistaken 
by a practical man for Storeton or Grinshill building-stone. The 
transition from the Bunter to the Keuper is also more marked than 
between beds of the Bunter, nor is there in the Bunter any equiva- 
lent of the Waterstones of the New Red Marl. 
The Bunter is evidently a sandstone deposit, while the Keuper, often 
beginning with a conglomerate bed, shades off into a lithologically 
distinct stone succeeded by thin-bedded sandstones, and finally by the 
great deposit of saliferous marls. These physical peculiarities are 
well known to geologists who have worked these rocks; but it is 
necessary for my argument to restate them in this connected form. 
Theory of the Origin of the Triassic Rocks. 
Hitherto I have said nothing of the topographical relations of the 
Triassic rocks ; but as the distribution of the sandstones specially 
bears upon their origin, this cannot be neglected. Unfortunately of 
the arid sandy region of Central Asia, which it is suggested best 
explains the mode in which these Triassic Sandstones have accumu- 
lated, not much is known.! 
If, however, the Bunter Sandstone is a riverine deposit, we would 
expect it to follow well-marked topographical features. Although 
there have been great orographic changes, some folding, and much 
faulting since the Triassic age, certain great features, such as the 
Pennine Chain, still remain in a modified form. 
If we try in imagination to reconstruct a river, valley or valleys, 
or even a sandy plain, representing the deposits as they are conceived 
1 The following papers bearing upon the subject are well worthy of study: “ On 
the Nature and Probable Origin of the Superficial Deposits in the Valleys and 
Deserts of Central Persia,” W.T. Blanford, Q.J.G.S. 1873, pp. 493-502. “ Alluvial 
and Lacustrine Deposits and Glacial Records of the Upper Indus Basin,” F. Drew, 
Ibid, pp. 441-71.—‘‘ Journal Across Central Asia,’? by Lieut. Younghusband, 
describing Gravels from the Altai Mountains and Sandhills, 900 feet high, 
“‘Nature,” 1888, May 17, pp. 65-6. 
