It is a fact well worthy of note that, while the basalt-formation of Iceland bears, geologically, a very close resemblance to the basalt-plateaux of the British Isles, the Tertiary volcanic phenomena of this latter region present nothing strictly analogous to the great tuff- and breccia- or so-called ‘palagonite-formation’ of Iceland. For it is obvious that the fragmental materials of the British volcanic region, which are intercalated with the basaltic lavas and only of ‘trifling thickness,’ cannot have their geological equivalent in the great palagonite-formation of Iceland, which covers thousands of square miles, and in isolated patches is met with over a greater part of the total area of the island.The palagonite-formation has been in several respects a puzzle to the geologists who have visited Iceland: some have been of the opinion that the tuffs and breccias are contemporaneous with the plateau-basalts or even older; but the more systematic investigations of Prof. Th. Thoroddsen have shown that in reality the fragmental masses are younger than the basalt-formation. Prof. Thoroddsen thinks that towards the close of Tertiary time the central parts of Iceland were buried under a continuous covering of fragmental volcanic materials 3000 to 4000 feet thick, which formation was broken up into single mountain-masses and isolated fells before and during the Glacial Period. In the summer of 1899 it was observed that very considerable masses of ground-moraine are intercalated with the breccias which constitute hills rising out of, or bordering, the southern lowlands of Iceland; and in subsequent years observations