208 Cincinnati Society of Natural History. 
tain corresponds with the Big ridge, and beyond it forms the limit of 
a former extension of Lake Winnipeg. On the east side of Red river 
the Big ridge is traced nearly due south from the Middle settlement 
to where it crosses the Roseau, 46 miles from the mouth of that stream, 
and on or near the 49th parallel. It is next met with at Pine creek, 
in the State of Minnesota, and from this point it may be said to form ~ 
a continuous level gravel road, beautifully arched and about 100 feet 
broad, tothe shores of Lake Winnipeg, 120 miles. On the west side of 
Red river, north of the 49th parallel, and north of the Assiniboine, from 
a point near Stony mountain, it extends to near Prairie Portage, where 
it has been removed by the Prairie Portage river and the waters of 
the Assiniboine. It may be seen again on White Mud river, about 
20 miles west of Lake Manitobah. 
In the rear of Dauphin lake, the next ridge in ascending order 
occurs; it forms an excellent pitching track for Indians on the east 
flank of the Riding mountain. At Pembina mountain four distinct 
steps or beaches occur, the summit of which is 210 feet above the 
prairie. 
The lower prairies enclosed by the Big Ridge are everywhere inter- 
sected by small subordinate ridges which often die out, and are evi- 
dently the remains of shoals formed in the shallow bed of Lake Winni- 
peg, when its waters were limited by the Big ridge. The long lines of 
bowlders exposed in two parallel, horizontal rows, about 20 feet apart, 
in the drift of the south branch of the Saskatchewan above mentioned, 
are the records of former shallow lakes or seas in that region. 
They may represent a coast line, but more probably low ridges 
formed under water, upon which bowlders were stranded. The fine — 
layers of stratified mud, easily split into thin leaves, which lie just 
above them, show conclusively that they were deposited in quiet water; 
their horizontality proves that they occupied an ancient coast or ridge 
below the comparatively tranquil water of a lake of limited extent; the 
vast accumulations ofsand and clay above them establish the antiquity 
of the arrangement; and the occurrence of two such layers, parallel to 
one another, and separated by a considerable accumulation of clay and 
sand, leads to the inference that the conditions which established the 
existence of one layer also prevailed during the arrangement of the 
other. It may be that these are bowlders distributed over the level 
floor of a former lake or sea, and they may cover a vast area. ) 
The Pembina mountain is par excellence the ancient beach in the 
valley of Lake Winnipeg. Itis not a mountain, nor yet a hill. Itis ' 
