Sentence:  It is there seen that at a distance from the valleys of streams, the old glacial <WSD>drift</WSD> usually comes to the surface, and often rises into considerable eminences. 
Meaning of the word marked with <WSD> tags:  A collection of loose earth and rocks, or boulders, which have been distributed over large portions of the earth's surface, especially in latitudes north of forty degrees, by the retreat of continental glaciers, such as that which buries former river valleys and creates young river valleys.