1871.] eamsay peeibiassic red rocks. 241 



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 E.ED 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 perox- 

 idized, and encrusted the sedimentary grains as a thin pelUele. I 

 further stated that I believed that iron could not have been depo- 

 sited 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 wiU also take into consideration any other circumstances, 

 physical or palseontological, that may tend either to confirm or to 

 throw doubt on the idea stated above. I will not treat of the pre- 

 triassic red rocks either in ascending or descending stratigraphical 

 order, but simplj'^ in the manner that seems most convenient to illus- 

 trate 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 North 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, Uke various modern fishes. 



The Upper Silurian rocks of Shropshire, Herefordshire, Mon- 



* On the Physical Eelations of the New Eed Marl, Rhsetic Beds, and Lower 

 Lias (see p. 190). 



