Few parts of the world present in a small compass so instructive a series of geological phaenomena as those which are displayed in the vertical cliffs of the south coast of England. An important portion of this coast, including the Isle of Wight and the Isle of Purbeck, has been well described by Mr. Webster*, and subsequently illustrated by Dr. Fitton †. In the Second Series of the Geological Transactions‡, Mr. De la Beche has published sections of the coast from Bridport Harbour to Sidmouth; and in the same volume Dr. Buckland has given drawings of the cliffs from Sidmouth to Beer Head, and from Lyme Regis to the Isle of Portland §. The geological history of the neighbourhood of Weymouth has been partially illustrated by Prof. Sedgwick in the Annals of Philosophy ||; and it will be the object of this paper to supply its full details, illustrated by a map and sections; beginning our observations at the point where Mr. Webster’s sections end, viz., at the Promontory of White Nore, about eight miles E.N.E. of the town of Weymouth, and continuing them to Weymouth and Portland, and thence westward along the Chesil Bank to the cliffs west of Lyme Regis. To our representations of the coast we shall add many inland sections of the adjacent district, including all the strata which occupy that portion of the south frontier of the county of Dorset which lies between the great south escarpment of the chalk downs and the sea. We