REVIEWS. 749 



lay at some distance back from the drift margin, and were not supposed 

 to represent the full extent of the ice advance except locally, although 

 correlated with those of the east. At the east, by virtue of the near 

 coincidence of the moraine with the border of the drift, the word 

 "■terminal" came to have a double significance, in which terminal to 

 the drift grew to be more prominent than terminal to the ice that formed 

 it. It is needless to say that the latter is the original and true sense 

 of the term, and that up to this time it had been employed almost 

 exclusively in this sense in its application to the moraines of the Alps 

 and elsewhere. Almost none of the previously recognized terminal 

 moraines were marginal to the glacial deposits. The strength and 

 definiteness of the outer terminal moraine in the Atlantic region, and 

 the inconspicuousness of the drift outside it — which was almost over- 

 looked for the time — naturally brought into great prominence the 

 marginal position of the moraine, and fostered the development of 

 the imported sense of the word "terminal." More than this, it led to 

 the conviction that such a moraine was characteristic of the outer 

 border of the glacial drift, if, indeed, it was not a necessary feature, 

 and that by seizing upon it, and following it persistently, the precise 

 limit of the ice advance might be definitely traced out and the true 

 glacial drift distinguished from outlying drift transported by other 

 agencies. It was this view, thus derived, that stimulated and directed 

 the work of Professor Lewis in Great Britain and Ireland. His 

 supreme effort was to detect and trace across the British Isles a moraine 

 marginal to the true glacial drift, and to distinguish from this the out- 

 lying deposits which he believed to be formed by means other than 

 direct glacier action. 



The book sets forth by maps and clear descriptions the course of 

 the moraine as traced by Professor Lewis, and also the nature and 

 extent of the glacial movements that gave rise to it. It also presents 

 the distribution of the marginal waters in Great Britain, by whose 

 agency, in Professor Lewis' judgment, the extra-morainic drift was 

 chiefly deposited. These were, in his opinion, mainly fresh waters, 

 ponded back into lakes by the glacial obstruction of valleys and basins 

 sloping toward the ice. He was led to very moderate views respecting 

 the marine submergence of the land. 



It must be left to British glacialists to say how far the delineations 

 of Professor Lewis are likely to stand, but without doubt the introduc- 

 tion of the morainic method, and the definite mapping which he pre- 



