page 243 note 1 Murchison, , Siluria, p. 351Google Scholar, Quart. Geol. Soc. vii. 163; xii. 267Google Scholar. Binney, , Id., vol. xii. (1856) p. 138Google Scholar. Harkness, , Id., p. 262. It was not the objectof these observers to investigate the igneous rocks of the Ayr, and they treated them simply as intrusive masses, though the singular aspect of the “breccia” led Mr. Binney to remark that “the cementing paste has much the appearance of felspathic ash.”Google Scholar In a later paper (Quart. Journ. Geol. Soc. vol. xviii. (1862) p. 437) he expresses his doubt whether the trap seen near the breccia is interstratified or intrusive. In the course of an excursion into Ayrshire in 1862 I descended the course of the Ayr from Sorn to Stair and recognized the breccia as a true volcanic tuff; or gravelly ash, closely resembling the red trap-tuff of Dunbar. The trap at the same time was found to presentall the characters of true lava flows, and I saw it coming again to the surface on the westside of the basin. Though it was clear from these sections, that the Permian sandstones of Ayrshire contained at their base a contemporaneous volcanic series, I was unwilling to publish any paper on the subject until the whole of the ground had been examined. From the results of this excursion, however, the Permian basin was represented to be bounded by igneous rocks, on the east and west sides, on the Geological Map of the British Isles, published in 1864 in their Educational Series by Messrs. W. & A. K. Johnston, and in the Explanatory Handbook to that map (p. 67) I have referred to the true volcanic nature of the breccia and its associated trap. Since that time, the Geological Survey having been extended into Ayrshire, I have had an opportunity of mapping the Permian basin in detail. The full results will properly appear in the Official Memoirs, and I shall here, with the sanction of the Director General of the Survey, offer a brief summary of them.Google Scholar
