136 
results of correlation of the north and south 
regions weresummed up. Twenty thousand 
feet of the Arkansas Coal Measures are 
found to have been deposited during the pe- 
riod represented by the great stratigraphic 
break in the north. No discussion. 
Marine and Fresh-water Beaches in Ontario. 
A. P. Coteman, Toronto, Canada. 
Marine deposits, often rich in shells and 
other fossils, are widely distributed east of 
Brockville and Smith’s Falls, in the valleys 
of the Ottawa and St. Lawrence. They 
occur at higher levels toward the northeast 
and east than towards Brockville; they in- 
clude trees and other forms indicating a 
climate like that of to-day, and are all evi- 
dently postglacial. The shells occur in 
clay, sand and also coarse gravel. 
High beaches, such as the Iroquois, War- 
ren, etc., contain only fresh-water shells, if 
any. Still higher beaches, such as those 
reaching 1,400 to 1,600 feet above sea level 
in the highlands between Georgian Bay 
and Lake Huron, and the beaches found 
above 1,400 feet between Lake Superior and 
Missanabie, and at the same level on the 
Hudson Bay watershed northwest of Sud- 
bury, have not yet been found to contain 
shells, although if marine there must have 
been complete and widely opened connec- 
tion with the sea. The wide gravel ter- 
races on the watershed mentioned contain 
numerous and large, kettle-shaped, lake 
basins, sometimes without outlets, suggest- 
ing that they were formed by the burial of 
large blocks of ice at the border of the 
Labradorian ice sheet, and hence in ice 
dammed waters. 
In discussion Robert Bell explained the 
presence of fresh-water shells amid marine 
conditions because of the forcing back of 
salt water by an inflowing stream of fresh. 
On the north side of Lake Superior he cited 
the occurrence of marine shells up to 500 
feet, but their absence in the high gravels. 
SCIENCE. 
[N. S. Vou. XIII, No. 317. 
He argued against the existence of ice dams 
in the past. G. K. Gilbert described the 
phenomena along the St. Lawrence east of 
Lake Ontario. He cited the occurrence of 
marine shells as far as Ogdensburg. C. H. 
Hitchcock referred to the sea-shore plants 
that are found around Lake Superior, ap- 
parently left by the withdrawal of the salt 
water. He also suggested that the basin of 
Lake Ontario might be due to the re- 
moval of limestone in solution. F. B. Tay- 
lor discussed the shell-beds, beaches and 
ice-dams. H. P. Cushing instanced the 
high gravels and general physiography of 
the Adirondacks as bearing on the ques- 
tions. The Adirondacks embrace the high 
mountains, the western peneplain plateau 
and the depressed lakes. Kettle-holes 
occur on the north side but not on the 
south. Ice dams are proved by the kames 
left by subglacial streams which flowed 
against the slope of the country. 
The Geology of Rigaud Mountain, Province of 
Quebec, Canada: Osmond EpcGar Lrroy, 
Montreal, Can. Introduced by F. D. 
ADAMS. 
The chief topographic feature of the Pa- 
leozoic plain of Central Canada is a series 
of hills, which occur in the district about 
Montreal. These are of igneous origin, 
and follow a line of disturbance which is 
almost at right angles to the trend of the 
Notre Dame Mountains. Rigaud is the 
most western of the series. It consists of 
an area of hornblende syenite, which is 
pierced on its northern flank by a quartz 
syenite porphyry. The field relations of 
all the hills with the exception of Rigaud, 
show them to be of post-Silurian age. In 
the case of the latter, the contact with the 
Paleozoic is wholly concealed by drift. The 
object of the research was to ascertain if a 
genetic connection could be established be- 
tween Rigaud and the other hills to the east. 
Investigation shows that it is probably 
