The Cornstone formation is more extensively developed in Forfarshire than in any other district in Scotland; and from this circumstance the result of the writer's observations regarding it, during the course of a recent visit, may be of some little interest to the reader. About two thirds the entire area of this county is composed of Old Red Sandstone. It forms a portion of that great belt of the system which, extending across the island from the German Ocean to the Frith of Clyde, represents the southern bar of the huge sandstone frame in which the Highlands of Scotland is set. The Grampians run along its inner edge--composing part of the primary nucleus which the frame encloses: the Sidlaw Hills run through its centre in a line nearly parallel to these, and separated from them by Strathmore, the great valley of Angus. The valley and the hills thus form, if I may so express myself, the mouldings of the frame--mouldings somewhat resembling the semi-recta of the architect. There is first, reckoning from the mountains downwards, an immense concave curve--the valley; then an immense convex one--the hills; and then a half curve bounded by the sea. The illustration may further serve to show the present condition of the formation: it is a frame much worn by denudation, and--just as in a _bona fide_ frame--it is the higher mouldings that have suffered most. Layer after layer has been worn down on the ridges, exactly as on a raised moulding we may see the gold leaf, the red pigment, and the whiting, all ground down to the wood; while in the hollow moulding beside it, on the contrary, the gilt is still fresh and entire. We find in the hollows the superior layers of the frame still overlying the inferior ones, and on the heights the inferior ones laid bare. To descend in the system, therefore, we have to climb a hill--to rise in it, we have to descend into a valley. We find the lowest beds of the system any where yet discovered in the county on the moory heights of Carmylie; its newer deposits may be found on the sea-shore, beside the limeworks of Hedderwick, and in the central hollows of Strathmore.