Societies and Academies

Abstract

LONDONGeological Society, Jan. 21.—Prof. P. Martin Duncan, F.R.S., vice-president, in the chair.—“The secondary rocks of Scotland (second paper). On the ancient volcanoes of the Highlands and their relations to the Mesozoic strata,” by J. W. Judd, F. G. S. That the rocks forming the great plateaux of the Hebrides and the north of Ireland are really the vestiges of innumerable lava-streams, is a fact.which has long been recognised by geologists. That these lavas were of subaerial and not subaqueous origin is proved by the absence of all contemporaneous interbedded sedimentary rocks, by the evidently terrestrial origin of the surfaces on which they lie, and by the intercalation among them of old soils, forests, mud-streams, river-gravels, lake deposits, and masses of unstratified tuffs and ashes. From the analogy of existing volcanic districts, we can scarcely d ubt that these great accumulations of igneous products, which must originally have covered many thousands of square miles, and which still often exhibit a thickness of 2,000 ft., were ejected from great volcanic mountains; and a careful study of the district fully confirms this conclusion, enabling us, indeed, to determine the sites of these old volcanoes, to estimate their dimensions, to investigate their internal structure, and to trace the history of their formation. The following is Mr. Judd's conclusion on the subject of his paper:—It appears that during the Newer Palaeozoic and the Tertiary periods, the north-western parts of the British archipelago were the scene of displays of volcanic activity upon the grandest scale. During either of these, the eruption of felspathic lavas, &c., preceded, as a whole, that of the basaltic; and in both the volcanic action was brought to a close by the formation of “puys.” The range of Newer-Palaeozoic volcanoes arose along a line striking N.E. and S.W.; that of the Tertiary volcanoes along one striking from N. to S.; and each appears to have been connected with a great system of subterranean disturbance, It is an interesting circumstance that the epochs of maximum volcanic activity, the Old Red sandstone and the Miocene, appear to have been coincident with those which, as shown by Prof. Ramsay, were characterised by the greatest extent of continental land in the area. The Secondary strata were deposiied in the interval between the two epochs of volcanic activity, and the features which they present have been largely influenced by this circumstance. Apart from this consideration, however, the volcanic rocks of the Highlands are of the highest interest to the geologist, both from their enabling him to decipher to so great an extent the "geological records “of the district, and from the light which they throw upon some of the obscurest problems of physical geology.—Remarks on fossils from Oberburji, Styria, by A. W. Waters, F.G.S. The author noticed the limited occurrence of Jiocene deposits in Styria, and referred briefly to the researches of Prof. Reuss and Prof. Stur upon them. He then indicated certain species of fossils which he had detected in these beds, adding about nine species to Stur's list.