Above the granite, clay-slate, quartzite, and Silurian formations of Nova Scotia, there occur, in the northern part of the peninsula, as stated in the last chapter, strata referable to the carboniferous group, occupying very extensive tracts, and resting unconformably on the rocks of the older series. They may be divided into three formations; the middle one3 comprising the productive coal-measures, agreeing precisely with those of Europe in their lithological characters and organic remains; an upper one, composed of sandstone and shale with fossil plants, but without coal; and a lower carboniferous group, chiefly made up of red sandstone and red marl, with subordinate beds of gypsum and marine limestone. In this lower series there are also occasionally some beds of shale with plants, and some coal-grits, and thin seams of impure coal. A variety of opinions have been entertained respecting the true age and position of the last-mentioned or gypsiferous formation, which has been generally presumed to be newer than the coal,—by some referred to the New Red sandstone, and even thought to overlie the coal-measures unconformably. Immediately after my return to England, I communicated to the Geological Society my opinion; 1st, that the gypsiferous formation, with its accompanying fossiliferous limestones, is a true member of the Carboniferous group; 2dly, that its position is below the productive coal-measures.

I shall now give some account of these middle or productive coal-measures, which contain valuable seams of bituminous coal, at various places, especially near Pictou.