Douglass : A Geological Reconnaissance. 239 



eral rods in breadth. The deposits along the stream are as charac- 

 teristic as the formation through which it passes. In its bed is sand, 

 corrugated by the rushing water after tlie rains. There are reaches of 

 angular gravel, flat bars of brown pebbles, and gray sandy levels which 

 show the sweep of the temporary rushing current. In places there are 

 a few Cottonwood trees projecting from the bed of the stream above 

 the cut-banks. Suddenly, as the train moves swiftly along, the hills 

 recede to a distance, leaving a great flat, through which the stream, 

 lined with cottonwood trees, winds its way to the Yellowstone River. 

 In descending from the high prairie toward the Yellowstone River, 

 as the strata wherever seen are horizontal, it is naturally inferred that 

 we have been descending to lower geological levels, and that the dark 

 beds near Glendive underlie the light gray ones in the vicinity of the 

 Tittle Missouri River. Glendive is about six hundred and forty feet 

 lower than Sentinel Butte and about two hundred feet lower than 

 Medora, which is in the bottom of the Little Missouri valley. 



From Glendive to Columbus, Montana, 



From Glendive, Montana, to Livingstone, a distance of three hun- 

 dred and forty-one miles, the railroad is in the valley of the Yellow- 

 stone River. A little distance west of Glendive, beds of nearly white 

 sand underlie darker beds, which contain brown layers and brown con- 

 cretions. There is a sharp line of contact between the two. There 

 appears to be a slight unconformity, but this may be only apparent. 

 At Colgate the lower beds are darker in places. Soon the rocks are 

 seen dipping to the westward at an angle of twenty or thirty degrees, 

 and again they are horizontal. Then, for some distance, there is not 

 much exposure of the rocks, as the bluffs have dwindled to grassy 

 hills ; but where there are exposures they are again gray in color. 

 Evidently we have been crossing a region where there has been a con- 

 siderable disturbance of the strata, and rocks of Upper Cretaceous age 

 (Fox Hill or Fort Pierre) have come to the surface. 



It would be interesting to study these rocks in detail, as here for 

 the first time in our western journey do we see much disturbance of 

 the rocky strata, and for the first time since leaving Minnesota are 

 there any considerable exposures of rocks older than the Tertiary. 



The geology of the eastern portion of Montana is very imperfectly 

 known. The country is a high plain, drained principally by theMis- 

 souri and Yellowstone rivers and their tributaries. The rocks of the 



