The object of this paper is to place on record the occurrence of olivine nodules in a British basalt which, though closely allied in structure to some of the Tertiary basalts of the Continent, belongs undoubtedly to the Carboniferous age. Olivine nodules frequently occur in the Continental basalts and have been considered by some writers as inclusions of peridotites, but by others as segregations from the magma.

Zoœcia generally elongated, but very variable in shape and dimensions; length of area ·68 to ·48 mm., breadth of area ·36 to ·2 mm.; no fornt wall, side walls very low, with a further depression at the head of the zoœcium, and furnished all round with slender buttresses, which are much more easily distinguished in the upper part of the zoœcium, owing to their greater size and Projection there, than in the lower Part.

Étel is situated on the west of the Megalithic district of which Carnae is the centre. It stands about 2 kilometres from the sea on the Rivière d'Étel. This so-called river is really an arm of the sea, which drains the extensive estuarine basin to the north-east, which is, in its way, almost another Morbihan (Little Sea) similar to the well-known one farther east. The tide rushes into the latter at a rate of from 7 to 11 knots per hour, at neap and spring tides respectively, and its ingress into and egress from the Rivière d'Étel cannot be much less. M. P. Le Strat, who has been much at sea in different parts of the world, considered that the incoming tide was rushing in at a rate of 7 or 8 knots an hour under the bridge of Lorrois, where the river narrows, when we passed it on October 11, 1909. The channel of the Rivière d'Étel is thus kept permanently open, and ships of from 50 to 150 tons are engaged in the tunny fishery and smaller boats in the sardine trade. Messrs. Peneau have a sardine-curing establishment at La Magoire, just opposite, across the river (Diagram, Text-fig. 1, p. 7).

The subject of ‘pleochroic halos’ has become endowed with peculiar interest since Professor Joly suggested that they are due to the radio-activity of the inclusions round which they occur. On looking into such petrographical literature as I possess, it appears that very few precise observations have been made regarding these halos, and it has occurred to me, therefore, that some of my own notes on the subject may be of general interest.

The wolfram veins in the Grainsgill greisen, near Carrock Fell, are an example of ore-bearing pegmatites, a vein-type uncommon in the British Isles, and one, moreover, the study of which is of much interest in its relation to ore-genesis. The veins have long been known, and intermittently exploited for tungsten-ore, but their economic prospects are not bright. Of previous workers, Mr. Alfred Harker has described the greisen which carries the veins, while the various mineral occurrences have been recorded by Mr. J. G. Goodchild and others.