BEAVER CANALS, MEADOWS, AND TRAILS. 207 



Its "bluffs" testify to the long series of centuries 

 durinsf which this river has flowed from the mountains 

 to the sea, and measure the enormous amount of sohd 

 materials which it has transported to the Mississippi 

 and thence to the Gulf. For the first thousand miles 

 these bluffs are, upon an average, upwards of four 

 miles apart; for the second thousand, upwards of 

 three miles; and for the remainder of the distance to 

 the falls, upwards of one. They bound the valley ex- 

 cavated by the river, and mark the limital range of 

 its flow. The tops of the bluffs, which are on a level 

 with the prairies, are from fifty to one hundred and 

 fifty feet above the level of the river, from its mouth 

 to the confluence of the Yellowstone; while above the 

 latter point they rise three hundred feet high and 

 upwards for miles together. 



The lands between the bluffs are level, rising but 

 a few feet above the river, and are called "Bottom 



less above, being at Fort Benton only about six feet. Ice dams 

 in the spring sometimes occasion great local rises. 



" Its high water width, for so long a river, is remarkably uni- 

 form. In the vicinity of Fort Benton it varies from five hundred 

 to one thousand feet. Near the mouth of Milk River it has in- 

 creased to fifteen hundred feet. Below the Yellowstone it is 

 about two thousand feet. From this vicinity the river gradually 

 attains an average width of about three thousand feet, which it 

 holds for some six hundred miles to its mouth. 



" Its annual discharge is about four trillions of cubic feet, or 

 about one-Qfth of that of the Mississippi. 



"At Fort Benton it is two thousand eight hundred and forty- 

 five feet above the Gulf, and at its mouth, three hundred and 

 eighty-one feet." — Pliyncs and Hydraulics of the Mississippi 

 River. Published by the War Department, 1861, p. 61. 



The June rise of the Yellowstone is about ten days in reaching 

 St. Louis, or in moving a little over two thousand miles. 



