Observations extending over several years upon glacial phenomena on both sides of the Atlantic had convinced the author of the essential identity of these phenomena; and the object of this paper was to show that the glacial deposits of Great Britain and Ireland, like those of America, may be interpreted most satisfactorily by considering them with reference to a series of great terminal moraines which both define confluent lobes of ice and also often mark the line separating the glaciated from the non-glaciated areas.