National Republican., 1884-04-07
TIE SATURDAY LECTURES.
Prof Chamberltn's Discourse on the Ice
Invasion OF North America.

PrOi. Ohahneflths DlACOthTse on ttto lSo
Invasion Of North America.
Prof. r. G. Chamberln, Of tho United
States geological survey, lectured Saturday
afternoon at the national museum upon tho
subject, "Tho Great Ice Invasion of North
America"
Prof Chamberlin said that Washington
was not founded upon rock, but that in its
depths were commingled earth and gravel
aud intermediate grades of material. Ho
referred to the wearing away of hard rock
foundations through attrition and the action
of water.
This material of sand gravel and boulders
beneath the surface OF the streets of the city
Of Washington is arranged in platforms and
tiers and is supposed to haVe been formed by
the ancient Potomac and its tributaries. Tho
lecturer referred to the superficial material
from decayed underlined rock, alluvial ma
terial derived from residuary clay and earth
matter in general, the vast mantle of COM
mingled clay, largo boulders, &C., formed by
the alluvial deposits in the northern and
southern hemispheros.
The next point in the lecture was reference
to the process OF decomposition of rock, aud
in taking away insolubc and leaving soluble
material, the presence and effects of alkali
earths and the disintegration of rock matter,
more especially in regions of glacial exist
L
cial graves composed of soluble rock, and OF
gravels and bouders which arise from de-
composition and torrental agencies. The
formations of sand gravel and boulders as
exhibited through stratiication and tho
action of running water.
Prof. Chamberlin illustrated by large maps
the distribution of the material referred to
in certain sections of North America such
as along the shores OF New England, Conoy
Island, Staten Island, the northern part of
New Jersey, thence across to Pennsylvania,
to Ohio, to Illinois, and through the valley
of the Missouri to the foot Of the Rocky
mountains. In countries where glaciers exist
these sandy and stony formations are caused
by the action of floating ice.
Prof. Chamberlin referred TO what he
termed "traveling boulders" that had como
from the parent source of formation to a dis
tance of 5000 miles. As to whence they
came from it is supposed that they had their
derivation from underlying rock in the APP
palachian range. BDulders that have had
their formation in Minnesota show range
in concentric circles with Illinois, Michigan,
Canada, &c. Prof. Chambcrlin dwelt for
some time upon this part of his subject rela
tive to stones passing from their parent
source to other localities. This, he said, is
sometimes caused by large bodies of moving
ice. The copper deposits of Lake Superior
extending from the parent formation to
Minnesota was next referred TO in the matter
of tration, both of copper ore aud bouders.
In coming directly to the subject of his lee
ture, the great ice invasion of North America,
Prof. Chamberlin showed upon the maps, as
indicated by white and purple tags, the effect
of the alluvial deposits in certain portions of
North America, the result of an enormous
invasion, and when boulders and concrete
sandy substances were carried by tho ice foes
to distances of several thousands of miles.
Prof. Chamberlin had an unusually large
and attentive audience to listen to his very
interesting aud instructive lecture.
Saturday afternoon next DR.. Bunting will
lecture upon the subject, What shall we do
with the inebriate?"