Page:Quarterly Journal of the Geological Society of London, vol. 35.djvu/852

712 712 PROP. E. HULL ON THE DINGLE BEDS AND of Cork, Tipperary, and Waterford attains to important vertical dimensions, is entirely absent ; consequently there can be no passage from the Glengariff grits and slates into the Carboniferous beds. Unconformable overlap upon the Glengariff Beds. A detailed examination of the working maps of the S.W. of Ireland, carried out with the assistance of Mr. A. M'Henry, has developed the following remarkable results bearing upon the past and present relations of the Glengariff series to the Old Red Sandstone and Car- boniferous beds, proving beyond question their unconformity here as well as in the Dingle promontory. If we take a series of trans- verse sections along a line drawn from the extreme S.W. of Cork or Kerry to the K.E. near the border of Cork and Waterford, the fol- lowing will be found to be the relative positions of these beds, as illustrated by the diagrams (figs. 5-8). Fig. 5 shows these relations diagrammatically and in plan. It will be observed that at the extreme left, or S.W. direction, in the district of Dunmanus, Bantry, and Glengariff Bays, the Lower Car- boniferous slate (1) rests directly upon, or against, the Glengariff beds (5). In the centre the overlap is not so great, as the Yellow Sandstone (2) rests directly upon, or against, the Glengariff beds (5) ; and at the extreme right or N.E. direction, in the district between Cork and Mallow, the overlap is still less, for the Old Red Sandstone and Conglomerate (3, 4) rests directly upon or against the Glengariff beds. These relations are still further illus- trated in the three transverse sections (figs. 6, 7, and 8). Hence it will be observed that while the formations 1, 2, 3, and 4 are every- where conformable to each other, they are everywhere unconformable to No. 5. There has, therefore, been a deeper depression towards the south-west of the old land-surface formed by the Glengariff beds, or a subsequent greater elevation and denudation towards the north-east after the Carboniferous period. The case of the S.W. of Ireland is somewhat comparable to that of the overlap of the Upper Silurian upon the Cambrian beds from Herefordshire towards the Longmynds*. Note. — The view of the relations of the beds above given has since been abundantly confirmed by the detailed re-survey of the Cork district by Mr. M'Henry during the past summer (1879). III. Comparison with Sections in Galway and Mayo. If any further evidence regarding the age of the Dingle beds than that already adduced were required, it would be found in a comparison with the Upper Silurian rocks on the banks of Killary Harbour in West Galway and Mayo. Here we find precisely similar beds, sufficiently lieve this region to have been a land -surface or shoal water during the deposition of the marine Devonian beds of Devonshire and the Rhine ; nor was it resub- raerged till towards the uppermost Devonian period. In this view, I am happy to say, Mr. A. Champernowne concurs (Greol. Mag., March 1879). To this sub- ject I purpose on another occasion to return.
 * As I have endeavoured to show elsewhere (Greol. Mag., Dec. 1878), I be-