Page:Quarterly Journal of the Geological Society of London, vol. 35.djvu/856

716 '16 PROF. E. HULL ON THE DINGLE BEDS AND the throat of the old volcanic vent, from which were blown out the fragmental materials above described. These volcanic beds reappear along the southern shore of Clogher Bay, and in the adjacent islands, Beginish, Young Island, and Inish- vickillane *. The representative volcanic beds in the region of the Killarney mountains are included in the Glengariff-grit series, and therefore belong to a somewhat later stage than those laid open along the Dingle coast. These beds range through a distance of about ten miles from east to west, entering into the structure of the rugged elevations above Lough Guitane, and the slopes of Mangerton, Car- rigwadra, and Killeen, north of the river Clydagh. These volcanic products consist of felstone, felstone porphyry, and beds of ashes and agglomerate, interstratifled with the sedimentary slates and grits among which they are enclosed. One of the principal vents of eruption was situated about a mile south of Lough Guitane, and is represented by the bold and sombre mass of Benaunmore. This rock consists of columnar light green fel- stone, with crystals of felspar thinly disseminated. It is traversed by several dykes of yellowish and pale pink felstone, and on either side beds of felspathic ash interstratifled with the slate of the district. Mr. Du Noyer considers the ash-beds to bear evidence of aqueous deposition"!". As illustrating the general character of these volcanic rocks, the following section (fig. 10) made by the writer and Mr. M'Henry on the hills of the Flesk valley, will probably be useful and sufficient. It will be seen, on referring to Fig. 9, that similar vol- canic products occur among the Mweelrea beds. Fig. 10. — Section of Volcanic Beds in the Hills tvest of the River Flesk near Lough Athoonyastooha. (Length of section about 600 yards.) 1. Green grits, &c. 2. Purple felstone porphyry. 3. Purple slate. 4. Beds of fine ash, cleaved. 5. Purple slate. 6. Beds of ash, cleaved. 7. Purple slate. X Felstone porphyry, either a dyke or a volcanic neck. t " Explanation " sheet 184, p. 15. Prof. A. von Lasaulx, who, with Prof. F. Romer, visited this district in 1876, gives a graphic description of these rocks as they occur on the flanks of Mangerton, in ' Aus Irland,' p. 81 et seq.
 * See Geol. Survey Map, sheet 171, and "Explanation" thereto.