~ < nee ‘ 4 : bn al aa SMe 
~~ : = : si % 7 
ae = : * ai et ge? ; 
96 Erratic Phenomena aout Lake Superior.“ + 
_ tween them adheres to all the little roughnesses of the pe 
_ fills them gut, and has the peculiar adhesive:character of the m 
‘ground under the glaciers, and differing entirely in that respe 
els and pebbles and sands washed by water currents, 
which leave each pebble ‘clean, and never form adhering masses, 
unless penetrated by an infiltration of limestone. ' . 
Another important fact respecting this glacial drift consists im 
the universal absence of marine as well as freshwater fossils in i 
interior, a fact which strengthens the view that they have bee 
accumulated by the agency of strictly terrestrial glaciers ; such is, js 
at least, the case everywhere far from the sea-shore. But we- 
may conclu 
points, the se 
as they do at 
that therefor 
of marine fossil remains, and afso the influence of the tidal moye- 
ments upon them. And now swWch is really the case. Nearer the 
sea-shores we observe distinctly, in some accumulations of the 
drift, faint indications of the action of the tide reaching the lower 
surface of glaciers, and the remodeling, to some extent, of the ° 
materials which there poured into the sea. A beautiful example 
of the kind may be observed near Cambridge, along Charles 
River, not far from Mount Auburn, where the unstratified glacial 
oe 
ty, 
<a 
5 
“Sports 
drift (a) presents in its upper masses strictly the characters of true 
terrestrial glacial accumulation, but shows underneath faint indi- 
cations (b) of the action of tides. Above, regular tidal strata (¢) 
are observed, formed probably after the masses below had su 
id The surface of this accumulation is covered with soil (d). 
The period at which these phenomena took place cannot be 
fully determined, nor is it easy to ascertain whether all glacial 
drift is contemporaneous. It would seem, however, as if the ex- 
tensive accumulation of drift all around the northern pole in Eu- 
* 
a . 
at. these ancient glaciers reached, upon various 
+ 
‘e 
bia Salone 
