The Island of Arran has long been celebrated among geologists for the variety and extensive development of its igneous rocks. The basaltic group is well represented in its various forms of structure and modes of occurrence; the more highly silicated series by felsites and porphyrites, forming dykes and huge amorphous or columnar masses; while the glassy varieties are illustrated by dykes and veins of pitchstone. All these rocks may be readily studied in the small area comprised within the southern half of the island, the greater part of which consists of eruptive rocks, and sandstones of the Carboniferous period. It is among these sandstones that most of the igneous rocks have been intruded. Some, however, are evidently interbedded and contemporaneous, forming great sheets of melaphyre between the Carboniferous strata.

I Have had the pleasure of reading Mr. Bonney's paper, “On a Cirque at Skye,” and send you these few lines rather as an appendage to it than in the spirit of criticism. I think Mr. Bonney has made out the greater part of his case very well; but being a rather more “ardent glacialist” than he (though far less acquainted with glaciers), I do not think he has attributed quite enough to their operation in the formation of a cirque. Speaking of a Glacial period, he says, “The cliffs would still be cut back, by water in summer, by frost in winter; the talus borne away or crushed by the glacier, the rocks below somewhat worn and rounded, but still the completeness of the Cirque as a whole forbids us—unless we assign it entirely to glacial action—to suppose that it was more than slightly altered by this.”

A Discussion on the geological features of a locality between one who has never been on the spot and another who has seen so little of it as not even to know which is the bottom or top of an elaborate section which he has designed to illustrate these very features, is not likely to prove particularly instructive to the geological public, and for these reasons I would gladly have avoided it, had not Mr. Green thought proper to bring my name prominently forward in a paper entitled “Notes on the Geology of part of Co. Donegal,” in last month's GeologicalMagazine; which paper, it' may be remarked, was read and discussed on the 20th June last at the meeting of the Geological Society, although the Society subsequently declined to print it in the Quarterly Journal.

Without occupying valuable space with introductory remarks, I would begin with a description and attempted explanation of the drifts along the coast of Rhos Bay, or what is now generally called Colwyn Bay. Well-sinkings, clay and gravel pits, and coast sections, very clearly reveal a quadripartite arrangement of drifts similar to what may be seen in Cumberland. A recent well-boring at Old Colwyn went through loose gravel 9 feet; brown clay, 33 feet; and was stopped in blue clay. In Mr. Pender's brickfield, west of the Station, the pit-section and a well-boring have revealed red brick clay nearly 20 feet; sand and a little fine gravel, 16 feet; boring drill stuck fast under 60 feet of blue clay. In the ballast-pit close to the Railway Station, 30 or 40 feet of sand and gravel lie under a thin covering of red clay, the former (according to Mr. Darbishire, though this I overlooked) being underlaid by brown clay; and the sand rises up from beneath the red clay at a spot south of the road between New Colwyn and Mr. Pender's brickfield.

In the Magazine for December I gave a brief outline of certain phenomena connected with the Scottish Till, the chief aim of my paper being to insist that beds of clay, sand, and gravel frequently occur in that deposit, and that we can no longer consider these as either insignificant or accidental.