26 
Mr. W. Pengelly on the Red Sandstones, 
Two replies have been given to the first question. According to 
one of these, the beds, when neither "blotched" or "mottled," 
received the colours the}^ possess at the time of their deposition ; 
whilst the other supposes the colour to have been produced, subse- 
quently to that period, by the chemical action of infiltered matter. 
The first reply appears to commend itself on several accounts. It 
is difficult to conceive of any infiltered matter selecting and rejecting 
successive and alternate beds of Sandstone, apparently identical in 
everything but their hue, as must certainly have been the case, on the 
second hypothesis, at the Corbons Head and elsewhere. I have in 
my collection a nodule of sandstone, having the " variegated " char- 
acter most distinctly marked, which I extracted from a bed of 
purplish red conglomerate at Roundham Head, Torbay ; that is to 
say, a fragment of variegated Triassic sandstone in a bed of Triassic 
conglomerate ; from which it seems safe to infer that some of the 
sandstone beds had been formed and coloured long before the forma- 
tion of the conglomerate in which I found the specimen ; that is, 
they were coloured at an early part of the Lower Triassic Age. 
It has been already stated that no fossils have been found in the 
red rocks of our county. Grant that the sea of deposition was 
surcharged with the red oxide of iron — a substance known to be 
inimical to animal life — and the absence of fossils is simply a con- 
sequence of the absence of animal life within the South Devon area 
during the Triassic period ; but this granted, the proposition that the 
rocks received their colour when they were deposited will be at once 
admitted ; whilst if it be, not granted, we have no reason to suppose 
that animals — which lived in great abundance in other Triassic areas 
— did not live also within seas of what is now Devonshire, and no 
reason, so far as we know, why the rocks should be everywhere en- 
tirely destitute of their exuviae, since we cannot suppose that a 
change in the colour would obliterate every trace of organic remains. 
The exceptional colours present many difficulties. The ' ' blotched " 
beds seem to indicate the discharge of the prevalent hue by chemical 
action of some kind. Mr. W. Yicary has recently called my atten- 
tion to a paper, by J. W. Dawson, Esq., on " the Colouring Matter 
of Red Sandstones, and of Greyish and White Beds associated with 
them." His observations primarily apply to certain "red" rocks 
in Nova Scotia, but have a general application. He attributes the 
red colour to the peroxide of iron, and assigns reasons for beHeving 
it to have been rather a chemical precipitate than a substance tritu- 
rated mechanically. He thinks that in many cases the grey, dark, 
and white beds, interstratified with those of a red hue, were, without 
doubt, originally uncoloured, but that "there are other instances in 
which they appear to have consisted of red sediment deprived of its 
colour by chemical agents after its deposition ;" and adds " This may 
be efi'ected by the agency of organic matter in two ways, the first of 
which applies more especially to marine, the second to freshwater 
deposits." 
