Upham.] 
228 
[ Feb. 18 * 
General Meeting, February 4, 1891. 
Prof. W. H. Niles in the chair. 
Mr. G. H. Barton read a paper on the Hawaiian Islands. 
General Meeting, February 18, 1891. 
President F. W. Putnam, in the chair. 
The following paper was read to the Society : — 
WALDEN, COCHITUATE, AND OTHER LAKES EN- 
CLOSED BY MODIFIED DRIFT. 
BY WARREN UPHAM. 
The lakes and ponds here considered are bounded wholly or in 
large part by modified drift, that is, beds of gravel and sand, or 
rarely of fine silt or clay, which were supplied directly from the 
melting and receding ice-sheet, in which these materials had been 
held and from which they were brought and deposited in their 
present position by streams flowing down from the ice-surface. 
After a brief description of lakes Walden and Cochituate, which 
are examples of these gravel-enclosed basins near Boston, others 
are noticed in Maine, New Hampshire, and Massachusetts, and 
near Providence. For the more distant portion of the drift-cov- 
ered area within the United States, my examination of the greater 
part of Minnesota during six years of work on the geological 
survey of that state furnishes further details of these lake basins, 
with citation of typical examples. They are frequent, often 
abundant, in all glaciated countries, being found by scores, hun- 
dreds, and thousands, throughout Canada, in our northern states 
from Maine to Minnesota, in the British Isles, and over north- 
western Europe, so far as the ice-sheet extended. 
But they do not include all, probably not so large a proportion 
as a third, of the vast number of lakes and lakelets on the areas 
of glacial drift. Many of these lakes and ponds lie in basins 
which are enclosed wholly or in large part by the unmodified gla- 
cial drift or till, which is spread in smoothly undulating sheets 
