_Description of the strata._ The character of the strata of Europe and Asia indicates the persistence of the northern gulf and southern ocean of Cretaceous times in Eocene times also, though the area of each had shrunk in the meantime, owing to the physiographical changes which occurred at the end of Cretaceous times, giving rise to more extended land areas, and producing a shallow water phase over wide extents of ocean,--the final shallow water phase of the third and last great marine period of the British area. It is difficult to ascertain the exact importance of the physical break between Cretaceous and Eocene rocks in the south-east of England, owing to the subterranean solution of the upper part of the chalk, subsequently to the deposition of the Eocene strata, but the contraction of the Cretaceous gulf is shown in several ways, one of the most significant being the distribution of Cretaceous and Eocene rocks in the south-west of England. The existence of an outlier of Cretaceous rock at Buckland Brewer in North Devon, only three miles from the Atlantic Ocean, indicates the former extension westward of the Upper Cretaceous beds, while the occurrence of an outlier of Eocene rocks at Bovey Tracey in South Devon, resting not on Cretaceous but on Palæozoic rocks, shows that there was an uplift after the deposition of the Cretaceous rocks and before the Eocene rocks were deposited there, and that during the period of uplift the Cretaceous rocks were removed. Owing to these physical changes, the Eocene rocks of Britain are mainly mechanical sediments, some, as the Oldhaven beds, being composed of coarse pebbles over a fairly wide district, while some of the earlier Eocene rocks are estuarine or fluvio-marine. The Eocene rocks of Britain occur in four areas, namely, the London Basin, the Hampshire Basin, the Bovey Tracey outlier, and the north-east of Ireland and western Isles of Scotland. The deposits of the three southern areas may be considered together, and give general indications of an approach to land when passing westward. The Lower London Tertiary strata are fluvio-marine at the east end of the London Basin; they become shallower water deposits when traced westward, and begin to disappear. The London Clay is an estuarine deposit, which is generally supposed to have been laid down at the mouth of a large river flowing from the west. It is absent in the Bovey Tracey outlier.