March 8, 1871.
Lieut. Lewis de Teissier Prevost, H. M. 47th Regiment, and John Haines, Esq., Vernon Lodge, Addison Road, Kensington, were elected Fellows of the Society ; and Dr. C. Nilsson, of Lund, was elected a Foreign Member of the Society.
The following communication was read : —
On the Red Rocks of England of older date than the Trias. By A. C. Ramsay, LL.D., F.R.S.
In a previous paper* I stated that the red colour which stains the New Red sandstone and marl is due to the presence of peroxide of iron, the iron probably having found its way into the water as a carbonate, which by contact with the air, afterwards became peroxidized, and encrusted the sedimentary grains as a thin pellicle. I further stated that I believed that iron could not have been deposited in this manner in an open sea, but rather in inland isolated waters, and I confirmed this opinion by other facts which tended to prove that our New Red strata were formed in a lake or lakes, which at the period of the deposition of the Keuper marls, were salt.
I now propose to examine the bearing of the red colour due to peroxide of iron in other formations of older date, as to the physical conditions under which those strata were deposited — that is to say, whether they were formed in the open sea or in inland waters. In doing this I will also take into consideration any other circumstances, physical or palaeontological, that may tend either to confirm or to throw doubt on the idea stated above. I will not treat of the pretriassic red rocks either in ascending or descending stratigraphical order, but simply in the manner that seems most convenient to illustrate the points at issue. If some of the following passages appear like a partial repetition of arguments used in my previous paper, I can only say that they are brief, and seem to me to be necessary for the proper understanding of the questions I am about to raise.
Old Red Sandstone. — Mr. Godwin-Austen long ago stated his opinion that the Old Red Sandstone, as distinct from the Devonian rocks, was of lacustrine origin. The absence of marine shells helps to this conclusion ; and there is nothing to indicate that the fossil fish found in it belonged entirely to marine genera and species. The reverse is the case ; for the Polypterus, the nearest living analogue of some of them, inhabits the rivers of Africa, and the Lepidosteus, less closely allied, is found in the fresh waters of the Worth American continent. Even though some Old-Red-Sandstone fish have been found in the Devonian rocks of Devonshire and Russia along with marine shells, this proves nothing except that some of them were fitted to live in either fresh or salt water, like various modern fishes.
The Upper Silurian rocks of Shropshire, Herefordshire, Mon-
- On the Physical Relations of the New Red Marl, Rhaetic Beds, and Lower
Lias (see p. 190).
