The beds under review. —The upper series of the lower Carboniferous limestone consists of a series of beds varying in thickness from one foot and upwards, rarely reaching above 4 feet. At Trearne, Beith, their total thickness, when all on, is about 40 feet. The beds in this section, which may be taken as a typical one, are of a lenticular character, interbedded with thin bands of shale, which partake of the same irregularity. These irregular bands of intervening shale are characteristic of the series, whereever found, and are more abundant in the lower half of the group, dying out as the upper beds are reached. The return, at lesser or greater periods, to the shale-producing conditions, has caused this fine deposit of marine limestone to be divided into a series of beds; the shale bands being often not more than half an inch in thickness, and, with few exceptions, never rising above 6 inches. It is beyond the scope of this paper to inquire into the cause of these changes in the ancient Carboniferous sea which have produced these shales, but, in passing, it may be remarked that, after much observation, I have come to the conclusion that volcanic dust has had more to do with their formation than geologists have yet given credit for. Many of them have a greenish tinge, and others, when newly split up, are strongly marked with the same colour, while their composition is calcareous to the extent of one half. Physical aspect and extent This 250-word extract was created in the absence of an abstract