When the “Alliance Francaise” did me the honour of inviting me to give an address on this interesting occasion, the choice of an appropriate subject of discourse presented at first some little difficulty. On the one hand, as a representative of science in the “Alliance Franco—Britannique,” it appeared to be incumbent upon me to choose some topic of a scientific kind, and by preference one which would in some way link our two countries together in common bonds of association. On the other hand, it was obviously inadvisable that the theme should be of a technical character which would be little suited for a general audience. After some reflection I decided to present for your consideration a brief account of two remarkable volumes, both of which, dealing with geological questions, appeared in the year 1802, the one in Paris, the other in Edinburgh. Though the political sympathies which for so many generations had linked France and Scotland in a friendly alliance had fallen somewhat into abeyance by the beginning of last century, the two nations still continued to be drawn to each other in the realms of culture by a common ardour in the prosecution of science and philosophy, and by the mutual reaction which, in these great domains of human thought, they exerted on each other.

The corries and tarns of the Comeragh Mountains have received but scanty attention at the hands of geologists. In the Memoir of the Geological Survey dealing with this portion of co. Waterford their position and height are mentioned, and reference is made to some of the glacial phenomena in their immediate neighbourhood, but no connected description of the whole group of corries is given. Kinahan, in his “Geology of Ireland” (1878), pp. 245, 310, refers briefly to them, and inclines to the view that they were cut out by the action of the sea on the flanks of the mountains, but that the rock-basins which they frequently contain were excavated by small glaciers. The position of the corries, chiefly on the north and east sides of these mountains, as elsewhere in Ireland, is attributed by him to the preservative action of the ice and snow, which would not melt in them so rapidly (owing to their colder aspect) as on the southern and western slopes, where the corries have been obliterated by denudation effected by ordinary subaerial agents. Carvill Lewis refers to the glaciation of the Comeragh Mountains in several places, remarking that they “show signs of glaciation on their north-east side as high as 1,000 feet, up to which height they are rounded off and drift occurs. Above this they are jagged and contain cwms, glacial lakes, and other evidences of small local glaciers.”

After the granites, gneisses, schists, and sediments which make up the Swaziland System had been elevated to form a continental area extending over the northern and western portions of South Africa, denudation began, and the material thus produced was carried to the sea to form the Witwatersrand Beds. The nature of these sediments—they consist of conglomerates, grits, and shales—indicates a marine period with shallow-water conditions, which continued almost uninterruptedly during their deposition. They were accumulated first on a sinking, and then on a rising sea bottom, for the lower beds are composed largely of mud and fine sand, conglomerates only becoming abundant in the upper beds, which were formed in the later portion of the period when the sea had become sufficiently shallow to allow of the accumulation of shingle and gravel. There is evidence in the Southern Transvaal that the land from which the sediments were mainly derived lay to the west, the sea to the east, for the lower Witwatersrand Beds, which consist solely of mudstones and fine sandstones in the east, gradually develop conglomerates with a decreasing amount of shale towards the west.

The abstract in the Geological Magazine of Professor Beck's paper on ore veins and pegmatites is of great interest to myself, as it deals with two points which I pressed on geologists in 1894 and earlier, viz., the crystallisation of vein-minerals out of superheated water, and the doubtful origin of that water. The special difficulty is raised by the Dartmoor veins, as the water they contain, together with the granites, is sometimes salt and sometimes fresh, and is of all degrees of original supersaturation. I wrote as follows:

‘The question as to the marine or plutonic origin of the brineinclusions referred to is of transcendent importance in connection with the question as to whether the water ejected by volcanoes is of meteoric or marine origin, of derived from the interior magma’ (Geol. Mag., 1894, p.99).

Pendleton lies on the north-west side of Manchester and within the borough of Salford, and is traversed by the well-known Pendleton or Irwell Valley fault, a fault which has been traced for more than twenty miles from the neighbourhood of Bolton to that of Poynton in Cheshire. The fault is still slowly growing, for, on February 10th, 1889, a slip near Bolton gave rise to an earthquake of intensity 6, felt over an area of about 2,500 square miles. Small superficial movements may also be taking place close to Pendleton, though here probably aided by mining operations. Within the last seven years there have been local shakes on three occasions, namely, February 27th, 1899, April 7th, 1900, and November 25th, 1905. The materials for the study of the first two of these shakes are not quite sufficient to determine the boundaries of their disturbed areas with accuracy. The areas appear, however, to have been approximately circular in form and about four or five miles in diameter. In both cases the intensity of the shock was 4, or nearly 5. In 1899 the centre of the disturbed area was about half a mile north of Pendleton and a short distance on the north-east or downthrow side of the Pendleton fault; in 1900 it lay a mile or two farther to the south or south-south-east of the former centre.

Although the volcanic rocks of the English Lake District have received notice from time to time, any systematic account of them from the petrographical side has yet to be written. The most recent contribution, by the late Mr. E. E. Walker, treated especially of the mode of occurrence of the garnet, which is so common a constituent, not only of the lavas and tuffs, but of the associated intrusive rocks, probably referable to the same Ordovician age. There can be no doubt that this mineral is sometimes a primary constituent, but very often a product of metamorphism. The object of the present note is to record the occurrence in one instance of a rarer mineral, which has not hitherto been observed in this series of rocks. Cordierite is found as a product of thermal metamorphism in the Coniston Flags near the Shap Granite, and in the Skiddaw Slates of the Skiddaw granite area. In the latter it is remarkably abundant and wide-spread. The mineral is now found to occur, as an exceptional constituent, in the volcanic series.