72 G. H. Kinahan — The Silurian Rocks of Ireland. 



Let it be clearly understood that, in no place in the above-discussed 

 rocks — of Cork, Dingle, Toormakeady, Louisburgh, Croaghmoyle, 

 Curlew Mountains, or the Fintona districts, have fossils been found 

 to prove distinctly that they are of Silurian age. The only indirect 

 evidence of that kind which can be produced being the fossils in the 

 Mweelrea beds ; which may perhaps be on the same geological horizon 

 as the unfossiliferous rocks of Toormakeady, Louisburgh, Croagh- 

 moyle, and the Curlew and Fintona districts ; while on the other 

 hand there are plants of Carboniferous types found in the Dingle and 

 Glengariff beds. Therefore it is no doubt possible, that (if there is 

 such a distinct formation as the Old Red Sandstone) these rocks may 

 belong to it. It is evident, however, that they all are of one and 

 the same age, 1 and it is the height of absurdity to class the Dingle 

 beds, 2 with plants of a Carboniferous type, among the Silurians, 

 while the Curlew and Fintona rocks are put in a separate formation 

 and called Old Red Sandstone. That the Old Red Sandstone forma- 

 tion is the Sick Man of Geology seems proved ; as its supporters are 

 reduced to suggesting the existence of extraordinary unconform- 

 abilities to allow of its existence ; or to distorting the different rock 

 sections and representing the rocks, not as they really are, but as 

 they ought to be in the opinion of these different observers. The 

 title of Old Red Sandstone to be ranked as a distinct formation 

 seems to depend on the meaning given to the expression a Geological 

 Formation. The generally accepted meaning seems to be — a series 

 of strata with a more or less well-defined beginning and ending, its 

 distinctness being marked palaeontologically and (almost always) 

 stratigraphically ; — these characteristics the Old Red Sandstone does 

 not seem to possess. 



In South-west Ireland, indeed, there is a vast continuous unbroken 

 series of reddish, purplish, and greenish arenaceous and argillaceous 

 rocks, over 20,000 feet thick, that extend upward from the typical 

 marine Silurians of Dingle to the typical marine Carboniferous of 

 Cork. These must represent the time during which the Old Red 

 Sandstone accumulated, in Ireland or elsewhere. In this series, 

 except in the upper 1000 or 2000 feet, (Yellow Sandstone) fossils 

 occur at rare intervals, and are principally plants allied to Carbon- 

 iferous types. In the Yellow Sandstone terrestrial fossils ai*e 

 much more common ; while in the lower beds of the overlying 

 Carboniferous Slate, strata containing terrestrial and marine fossils 

 alternate with each other. 3 In South-west Ireland the rocks, 



1 In the Dingle Silurians, in the Toormakeady conglomerates, in the Mweelrea 

 beds, in the Curlew rocks, and in the Fintona rocks, there are peculiar and 

 characteristic felstones and traps that seem to he of the same age. 



2 As the Continental and American geologists have found plants like Carboniferous 

 in the Silurians, this evidence against the Silurian age of the Dingle and Glengariff 

 beds may be considered in part at least as done away with. 



3 It has been suggested that there is an unconformable overlap of the Carbon- 

 iferous Slate on the Yellow Sandstone. This, however, is perfectly impossible, for 

 such an overlap could not exist without, in places, adding rapidly to the thickness of 

 the Carboniferous Slate, which nowhere happens ; furthermore, the Carboniferous 

 Slate everywhere graduates downwards into the Yellow Sandstone, and the latter 

 into the Old Red of the Cork type. 



