156 W. Upham—Work of Prof. H. C. Lewis. 
and its terminal moraines in the United States, and later in Ireland, 
Wales and England. The present article reviews his contributions 
to our knowledge of these drift formations and of the history of the 
Ice Age, bringing into comparison and correlation the glacial records 
of America and Europe. Comprehensive as were Professor Lewis’ 
observations and studies in this field, he was planning yet more 
thorough and extensive exploration of the drift in Britain, Germany 
and Scandinavia, when he was taken from us. In his death the 
geologists of two continents mourn the loss of a most gifted and 
faithful fellow-worker, who indeed already had achieved a grand 
life-work in the few years allotted to him. 
Professor Lewis first became specially interested in the glacial 
drift and the terminal moraine of the North American ice-sheet 
during the later part of the year 1880, when in company with Prof. 
G. F. Wright he studied the remarkable osars of Andover, Mass., 
the gravel of Trenton, N.J., containing paleeolithic implements, the 
drift deposits of the vicinity of New Haven, Conn., under the 
guidance of Professor Dana, and finally the terminal moraine in 
Eastern Pennsylvania, between the Delaware and Lehigh rivers. 
The following year Professors Lewis and Wright traversed together 
the southern border of the drift through Pennsylvania, from Belvi- 
dere on the Delaware west-north-west more than 200 miles across 
the ridges of the Alleghanies to Little Valley, near Salamanca, N.Y., 
and thence south-westerly 130 miles to the line dividing Pennsyl- 
vania and Ohio, which it crosses about fifteen miles north of the 
Ohio river. The report of this survey of the terminal moraine was 
published in 1884, forming volume Z of the Reports of Progress of 
the Second Geological Survey of Pennsylvania. With the similar 
exploration of other portions of this great moraine done a few years 
earlier by Prof. Chamberlin in Wisconsin, Profs. Cook and Smock 
in New Jersey. and the present writer in Long Island, thence east- 
ward to Nantucket and Cape Cod, and also in Minnesota, it com- 
pleted the demonstration of the formation of the North American 
drift by the agency of land-ice. 
The observations of the moraine in Pennsylvania detailed in this 
volume are summarized by Prof. Lewis as follows:—‘The line 
separating the glaciated from the non-glaciated regions is defined by 
a remarkable accumulation of unstratified drift material and boulders, 
which, heaped up into irregular hills and hollows over a strip of 
ground nearly a mile in width. forms a continuous line of drift hills 
(more or less marked) extending completely across the State. These 
hills vary in height from a few feet up to 100 or 200 feet ; and while 
in some places they are marked merely by an unusual collection of 
large transported boulders, at other places an immense accumulation 
forms a noteworthy feature of the landscape. When typically de- 
veloped this accumulation is characterized by peculiar contours of its 
own,—a series of hummocks, or low conical hills, alternate short 
straight ridges, and inclosed shallow basin-shaped depressions, which 
like inverted hummocks in shape are known as kettle holes. Large 
boulders are scattered over the surface; and the unstratified ull 
