construction. Out glacial Lake Agassiz ex- 

 plains it all, and we learn that the Car 

 berry sand dunes are the old delta of the 

 Assiniboine river (Fig 2 A) as it poured forth 

 from Lake Souris and emptied near the site 

 of the present city of Brandon into the waters 

 of the great lake. This delta is of much 

 greater size than that of the Pembina river 

 and was rather later in formation. 



ITS LIMITS. 



The sand and gravel of this great delta 

 extend seventy-five miles east from the old 

 shore of Lake Agassiz to where now stands 

 Portage la Prairie, northeastward fifty miles 

 to Gladstone, and southeastward, for eighty 

 miles reaching to within nine miles of Car- 

 man. When this wide extent of delta 

 material was carried down by the Assiniboine 

 it was aeposited on the lake bottom and rose 

 in many places in shoals and low islands 

 above the surface of the lake. The appearance 

 of the sand hills near Glenboro and Cypress 

 is very striking. This delta represents a 



vast amount of erosive power on the part of 

 the glacial streams and it has been calculated 

 thai ihe amount of material thus brought 

 down is equal to twenty cubic miles. 



THE ASSINIBOINE VALLEY. 



The present valley of the Assiniboine is a 

 deep cut through its own old delta, and made 

 after the waters of Lake Agassiz had receded 

 towards their present limits. The force with 

 which the river fell into Lake Agassiz seems 

 to have prevented the deposition of sand and 

 gra/ei until the station of Douglas, on the 0. 

 P. R is reached, a distance of twelve miles or 

 more from the shore line, where the soil consists 

 of boulder clay ; or it is possible that part of 

 the overlying sand of the delta may have here 

 been cleared away by the river as it cut out 

 its later channel. That it has gone on sinking 

 its channel deeper and deeper, until the river 

 runs in a valley 200 to 300 feet in depth is a 

 very noticeable fact. The sands of the old 

 delta have become the plaything of the ele- 

 ments. The fine sand driven about by every 



Fig. L 



