1877.] Surface Geology of Eastern Massachusetts. 579 
and polished rock surfaces — commonly ascribed to glaciation 
were produced. The comparative immobility of a large glacier 
causes it to move almost as a unit, and, ‘strong in solid single- 
ness,” it can be swerved by none but the largest reliefs, especially 
in a region of gentle slopes and low altitudes like Southeastern 
New England. So that generally, only in so far as the fashioning 
of these reliefs has been determined by their structure can the 
progress of the ice-cap be regarded as influenced by the geolog- 
ical constitution of the land over which it moves. Hence we 
are led to conclude that surface lineaments resulting from a 
wide-spread glaciation will exhibit great uniformity of trend 
over wide regions, and a general independence of the structure of 
the subjacent rocks; and such is conspicuously the fact in East- 
ern Massachusetts. 
There are perhaps no surface features which are more clearly 
the product of glaciation than the lakes and ponds found, and as 
a rule found only, in glaciated regions, and which abound in 
New England. The great extent to which regions which have 
been subjected to the action of an ice-sheet are distinguished by 
the presence of lake basins becomes more apparent when we 
reflect that, as has been pointed out by Professor N. S. Shaler, 
these basins are probably much fewer and smaller now than 
when first formed at the close of the glacial epoch; for “ there 
are in operation in the regions characterized by glacial lakes no 
forces capable of producing such depressions; on the contrary, 
all the forces at present in action tend to obliterate the existing 
basins.” Professor Shaler has called attention also to the facts 
that these lake basins seldom, “ except the smallest, present any 
approximation to a circular figure ;” and that ‘ the major axis 
as usually a north and south trend.” The following data 
(derived from approximate measurements, made on good maps, 
of the ponds and lakes of Eastern Massachusetts) show, among 
other things, how general is this elongation in a north and south 
3 rection, Two hundred and ten basins were measured, includ- 
mg all but the very smallest, in that portion of the State east 
of Worcester. The mean direction of all the major axes is 
about N. 5° W. The mean ratios of the major axes to the 
Minor axes is 2.5; that is, the ponds are, on an average, two 
and one half times as long as broad. The average trend of the 
longer diameters, it will be observed, coincides very closely with 
the mean direction of the glacial strie of this region, and the 
_ Soutses traversed by erratics. In only thirty of the two hundred 
