The Portland daily press. [volume] (Portland, Me.) 1862-1921, 1885-04-07
Society of Natural History.

Vice President Thompson announced the re-
ceipt of large number Of government publ
cations obtained through the influence of Con-
gresham Reed, and a valuable election of
plants from the department of agriculture.
Also OF nineteen skins of birds, mostly from
Maine, given by A. S. ellison. Nevada fossils
by G. W. Verrill. Chameleon and lion fish, by
Capt j. f. Mountfort. Gorgonia, Casco Bay,
by Arthur S. Harding.
Mr.. Manning read paper upon the rock ex-
cavations at Georgetown and Sawyer's Islands.
After referring to well known localities where
pot-holes are found, as the Albany Basins,
Dians's Baths at North Conway, the Basin at
Franconia, N. H., the large number at Bel
lows Falls, VT, at Lewiston Falls, Brunswick,
and other places along the Maine rivers, which
are the unquestioned result of fuvial erosion,
he gave description of the excavations at
Georgetown and Sawyer's Islands, whose orr
gin is somewhat mysterious, and upon which
all writers do not agree.
On Georgetown Island there are four perfect
ones, besides remains of several others. The
two largest are situated upon the side OF q
rocky hill, from 40 to 80 feet above tide water
and short distance from the steamboat land
ing at Riggsville. The largest is from feet
inches to feet in its several diameters, the
longest being from east to west; depth nearly
nine feet, with sides bullying q little near the
centre; the bottom is uneven, having a Range
upon one side two feet or more in width, which
narrows as it extends around until lost in the
opposite wall. The smaller one is perfect
circle at the margin, 3 feet 10 inches in diam
ter, with depth Of feet. They are always
filled with water from the surface drainage,
which Mr.. Manning and his friends siphoned
out to make the examination. They were
cleaned out by Mr. Riggs nearly So years ago,
who took out about two cart loads of rounded
boulders, gravel and sand, also from the bot
tom OF the largest one q boulder weighing five
or six hundred pounds. The stone was irreg
ular in shape, but well rounded and polishe
upon one side, the other being more fattened'
The two other pot-holes mentioned are
smaller, one situated just above, the other juet
below tidewater. On Sawyer's Island only one
retains its shape, which was originally about
three feet in depth and thirty inches in dame
ter, the sides rounded in graceful curves much
like the smaller end of an egg. In close prox-
unity are the remains of several others, de-
stroyed by the crumbling Of the ledge. The
formation OF these pot-holes has been ascribed
by different writers to human handiwork, the
action of the sea, during a subside nee of the
land, huvial erosion, or erosion by the sub
glacial stream.
At Cohoes, N. Y, two series of pot-holes are
found; one, along the bed and valley of the
Mohawk river; the other, on higher level, in
a general line north and south, crossing the
valley diagonslly instead of following its di-
rection.
These latter were described by Prof. Agasslz
in discussion before the American Associa-
ton of Science at Hartford, in 1857, as the
work of cascades pouring down through Gre
vases formed in the glacier by the physical
features of the underlying surface. The rea-
discussed, that of glacial erosion either by the
action Iof the "pouring cascade or the SUBJ
glacial stream offering the only satisfactory
explanation. The march of the glacier over
Georgetown Island is shown by the ploughing
upon the farm of Mr.. Campbell near the pot
holes, and by line of boulders running north
and south for some distance across the Knub-
BILE, as the promontory which forms one side of
the cove. is called.