Page:The Journal of geology (IA journalofgeology21894univers).pdf/408

tions of the beaches noted by Mr. Tyrrell with those determined by my surveys at the south, I am enabled to correlate very satisfactorily the two sets of shore lines. The northern continuations of the successive lake levels from the upper Norcross beach to the Niverville beaches, which mark the latest stages of the glacial lake, just before the recession of the ice-sheet from the district crossed by the Nelson river permitted it to be reduced to the Lake Winnipeg, are thus identified upon a region lying 50 to 200 miles beyond the area examined by me.

Along the base of the escarpments of Riding and Duck mountains, where Mr. Tyrrell has traced the beaches and determined their heights for a distance of fifty miles between Valley and Duck rivers, that is, between latitudes 51° 15′ and 52° N., it is found that a very important differential elevation, increasing from south to north about three feet per mile, took place after the Campbell and McCauleyville beaches were formed, since they are thus remarkably changed from their original horizontality. It is clearly shown here that the uplifting was not uniformly proportionate and regular for the whole area of Lake Agassiz. The chief movements of elevation of its southern and central part, as far to the north as Gladstone, seem not to have extended farther, at least in their full proportion. The district next to the north along an extent of 120 miles, to the north end of Duck mountain, was perhaps only so far disturbed by these movements as was necessitated to connect the rise of the country on the latitude of Gladstone with the continuing condition of maximum subsidence on the latitude of the lower part of the Saskatchewan and the north end of Lake Winnipeg. But there ensued in this district, after the date of the Campbell beach, a great differential elevation, giving to these late shore lines two or three times more northward ascent than that of the Herman beach from Lake Traverse to Gladstone; and the total change in level of the highest observed beach, probably representing the upper Norcross stage, situated at Pine river, on latitude 51° 50′ to 52° N., is approximately 400 feet, as compared with this shore line at Lake Traverse, about 420 miles distant to the south. Nearly