BANKS OF THE ASSINXIBOIXE. 



141 



recommence thirty miles further up the stream by the 

 road, and although the distance from Lane's to Prairie 

 Portage is not more than forty-three miles, the course of 

 the winding Assinniboine would probably exceed ninety 

 miles. The river banks are heavily timbered, and sustain 

 trees of very large dimensions. The distance between the 

 top of the banks on either side of the river is variable, but 

 it appears to be generally between 600 and 800 feet, at 

 sharp turns it was often not more than 400, and when- 

 ever it exceeded that distance one side was steep and 

 washed by the water, the other occupied by a sand spit 

 or mud-flat at the foot of the opposite bank. 



During my stay at Prairie Portage, in September, 1857, 

 I had an excellent opportunity of examining the relation 

 of the sand and mud flats to the river banks, as well 

 as the forest which fringed it to the depth of half a 

 mile. The river is here about 180 feet broad, and with 

 a rapid current sweeps under the south bank, which forms 

 the outer arc of a very beautiful curve extending over 120 

 degrees. The cord of this arc is well defined by the old 

 north bank of the river, under which, probably, it once 

 swept, but now only touches when the channel is full dur- 

 ing spring freshets ; the length of this cord is perhaps 700 

 yards, and at each extremity the river is seen sweeping 

 between steep banks, sixteen feet high, until, a little lower 

 down or a little higher up, similar curves, with their ac- 

 companying sand and mud-flats recur. These sand and 

 mud-flats are arranged in the order of the specific gravi- 

 ties of the materials which compose them, but with such 

 singular regularity, and with such curious and interesting 

 admixtures, that I have considered it worth while to de- 

 scribe them with some degree of particularity. 



At the western extremity of the curve, a few rounded 

 boulders were seen, not exceeding eight inches in diameter ; 



