Page:Quarterly Journal of the Geological Society of London, vol. 35.djvu/841

Rh 1867. Prof. Jukes, in a paper comparing the rocks of the South-west of Ireland with those of Devonshire, admits that the Dingle beds seem to be physically more connected with the Upper Silurian than with the Old Red Sandstone.

In this year also Sir Roderick Murchison, in the fourth edition of 'Siluria' (p. 178), after describing the conformable upward passage of the Dingle beds with Silurian fossils into the "Glengariff grits and schists," maintains that the latter represent "those slates and grits which in Germany, Belgium, and North Devon form the lowest portion of the Devonian system."

In the maps and explanatory Memoirs of the Geological Survey of Ireland the "Glengariff grits and slates," which are the representatives of the "Dingle beds," are coloured and described as Old Red Sandstone; but in the Dingle promontory these beds are separated from the Old Red Sandstone, and are coloured reddish brown. This is explained by Prof. Jukes to be due to the fact that while the boundary line of the "Dingle beds" is quite distinct in the Dingle promontory, it was found impossible to draw any corresponding line elsewhere. He "therefore thought it best not to prejudge the question."

Prom the above abstracts and notices of authors it will be seen that the opinions regarding the age of the Glengariff grit and slate series are various. We might almost say "quot homines tot sententiæ." All are agreed that the beds form a group intermediate between Old Red Sandstone above and Upper Silurian beds below; by some authorities they are classed with the Upper Silurian, by others with the Devonian, by others with the Lower Old Red Sandstone. Be it recollected, however, that as far back as 1839 the late Sir Richard Griffith expressed his opinion that this series, together with the subjacent fossiliferous Silurian beds, would eventually prove to be of Silurian age. This view he subsequently illustrated and enforced; and Prof. Jukes admits that "theoretically it is the better of the two" alternatives between Silurian and Old Red Sandstone. I have never been able to understand exactly why it has been departed from by other observers. For myself, I not only concur in this view upon the grounds which he has advanced, but I hope to be able to adduce in this paper evidence additional to any yet offered in its favour.

The question having been confessedly left an open one by my predecessor, and subject to further investigation, I obtained the permission of the Directer-General to reexamine the sections in Kerry and Cork likely to throw light upon it; and in company with Messrs. J. O'Kelly, Senior Geologist, and Mr. A. M'Henry, Assistant Geologist, I made a tour of the district during the month of September 1878.

We first visited the sections in the Dingle promontory, then