1855.] ISBISTER NORTH AMERICA, ETC. 515 



American Continent, it was at one time still greater, and that the 

 existing series of lakes, from the St. Lawrence northward, were per- 

 haps anciently united in one or more vast freshwater seas, having 

 their western margins indicated, perhaps, by the peculiar elongated 

 strip occupied by the lignite-formation previously described, which 

 presents precisely the appearance which would result from a long line of 

 shelving beach, piled with masses of drift-wood accumulated through 

 long successive periods, similar to what is now found covering the 

 shores of the inland lakes and portions of the coasts of the Arctic Seas. 



It has been stated as an exemplification of the wide changes which 

 would result from a comparatively small alteration in the present 

 level, even of such mountainous districts as Canada and the North-east- 

 ern States of the Union, that " a subsidence of 400 feet would cause 

 the waters of Lake Ontario to flow through the valleys of the Mo- 

 hawk and Hudson into the Atlantic, and at the same time convert 

 Lake Champlain into a maritime strait, thereby forming islands of 

 the States of New York, New England, and Maine, and of the British 

 Colonies of New Brunswick and Nova Scotia." A subsidence of one- 

 fourth of that amount in the prairie districts of the Saskatchewan, 

 continued to Great Bear Lake, would carry the waters of the Missouri 

 and the upper portions of Churchill and Mackenzie Rivers into Lake 

 Winipeg, and convert the plain country bordering on the Rocky 

 Mountains into an inland sea. Even at the present level the Missouri 

 has, twice within the last thirty years, inundated the valley of the Red 

 River, flowing into Lake Winipeg ; while it is a common occurrence 

 for the country through which the lower part of the Saskatchewan 

 flows to be laid under water for a distance of 200 miles above its 

 outlet by an ordinary spring-flood. About forty years ago, in a sea- 

 son remembered especially for the land-floods, a gentleman in the 

 service of the Hudson's Bay Company was drowned on the Frog 

 Portage (the low watershed which separates the Saskatchewan and 

 Churchill Rivers), by his canoe upsetting against a tree in passing 

 from one stream to the other. 



The raised beaches of Lake Superior, rising in four or five succes- 

 sive terraces to the height of more than 100 feet above the present 

 surface of the water, and which have attracted the attention of Pro- 

 fessor Agassiz and the geologists of the Canadian Survey, appear to 

 point to the existence at some former period of a much greater body 

 of water in this lake, at least, than is at present contained in it, and 

 are to some extent therefore confirmatory of the view now suggested. 



The Eocene basin of the Upper Missouri, with its very marked 

 character of freshwater deposition, is stated by Marcou to extend 

 along the upper waters of the Saskatchewan as far as Mackenzie 

 River. I have no knowledge of any such formation myself, although 

 in the unexplored territory west of the Winipeg basin there is un- 

 doubtedly ample room for its development. Its existence, if esta- 

 blished, would lend additional probability to the inference deducible 

 from the circumstances previously noticed *. 



* The views here suggested are not to he considered as prejudging the question 

 so ingeniously developed hy Mr. W. Hopkins, and supported hy the late Prof. E. 



