488 J. E. TODD THE CHAXXEL OF THE MISSOURI RIVER . 



for the anomalous relation of the Missouri to the general slope of the 

 country, namely, that the general course is nearly parallel with the strike 

 of the slope of the surface instead of with the dip. This argument will 

 stand, and the burden of proof lies on the other side. 



The presence of stratified drift in the higher portions of the valley, 

 together with the absence of till at lower levels of same, is strong evidence 

 that the valley is glacial or postglacial in. formation. If streams flowed 

 at higher levels, they show the altitude of the plane of drainage at that 

 time, and the absence of till at lower levels proves that the lower portion 

 of the valley was not excavated ; for we can not conceive of the lower por- 

 tion being filled with drift, especially till, and later have it all removed. 

 The very nature of the case forbids it. 



An analogy with the cases studied in South Dakota and Montana 

 strongly argues for the Glacial or Pleistocene origin of the valle}^ of the 

 Missouri in I^orth Dakota also. 



Provisioxal History of the Origix of the Missouri ix North axd 



South Dakota 



general statement 



In this portion of the course of the Missouri it is crowded by the edge 

 of the Wisconsin ice-sheet on the left from near its origin in Montana to 

 the southeast corner of South Dakota. On its right side there lies an 

 area over which the Wisconsin ice-sheet never passed. From Niobrara 

 eastward, where the river forms the boundary of the State, there is a till- 

 sheet formed by an older ice-sheet which extends over many square miles 

 southward into northeastern Kansas. This is known as the Kansan ice- 

 sheet, which is judged to be much older than the Wisconsin. 



In South Dakota no boulder-clay or till has been found west of the 

 Missouri, although it is not unlikely that closer search may show con- 

 siderable of the Wisconsin till outside the Altamont moraine. In North 

 Dakota there are a few small patches of till lying 40 or 50 miles to the 

 west or south of the river. In northeastern McKenzie County a portion 

 shows not only patches of till of moderate thickness, but also distinct 

 moraines. In the western part of .Montana, near the High wood Moun- 

 tains, there is a moraine 50 to 100 miles in length and so continuous as 

 to change the course of streams in the vicinity. 



The general course of the moraines, both older and newer, is northwest. 

 Dr. Dawson, of the Canada Survey, considers the older drift deposits and 

 moraines next west of the Wisconsin stage in Canada to be lowan. 

 Tyrell, of the same Survey, considers them Kansan. Calhoun considers 



