Note 274 — Chapter XIV · THE SILURIAN VOLCANOES OF IRELAND

Ibid. Sheets 81 and 91. These rocks are chiefly augitic andesites, a few are basalts, and some seem related to felstones. Probably many of them are intrusive sills of uncertain age. The "ashes" contain fragments of felsite and porphyrite often of considerable size (Guide to Irish Rock-Collection, p. 36).

[275] Ibid. Sheets 91 and 92 and Explanation to these Sheets (1871), p. 10; Guide to Irish Rock-Collection, p. 36. Some of these lavas are andesites, others are felsites. Mr. M'Henry has contended that certain "ashes" and "agglomerates," particularly those exposed on the coast at Portraine, opposite Lambay Island, are "crush-conglomerates" due to terrestrial disturbances, which have affected both intrusive igneous rocks and the sedimentary series into which these have been injected.