338 J. S. Newberry — Surface Geology of the country 



The peculiar fineness of the soil of the northern portion of this 

 belt has been supposed to have something to do with the 

 prevalence of grass and the absence of trees, since in Illinois 

 and Wisconsin, along the border line between the forest and the 

 prairie, the levels where the soil is fine are grass-covered, while 

 the swells and ridges, rocky or gravelly, carry trees ; but as I 

 have shown elsewhere, these local peculiarities of the soil, favor- 

 ing, the first grass and the second trees, have to some extent 

 caused the observed interlocking of prairie and forest. Farther 

 west, with every kind of soil and geological structure, there are 

 no trees, but every where grass, while east of the Mississippi and 

 beyond the battleground between the two forms of vegetation, 

 all kinds of topography, soil and substructure are covered with 

 forest. No one who has traversed the continent along several 

 parallels of latitude and has studied the relations of vegetation 

 to soil and geological structure will fail to find conclusive 

 evidence that the influence which has determined the kind and 

 quantity of vegetation in the varied topographic and climatic 

 districts of the west is the rainfall. 



The valley of the Little Missouri is deeply cut in a table land 

 composed of the Laramie coal-measures, of which 200 or 300 

 feet with several seams of coal are exposed in the cliffs. Thou- 

 sands of silicified tree-trunks are scattered over the surface and 

 innumerable stumps are apparently standing where they grew, 

 but no foreign material is anywhere visible. A few miles below 

 the railroad crossing the valley expands and opens into the 

 famous Mauvaises Terres, or " Bad lands of the Missouri." The 

 course of that stream being here nearly east and west and the 

 valleys of the tributaries north and south, these coalesce and 

 form in the old lake beds picturesque but dangerous labyrinths. 



As soon as one enters the valley of the Yellowstone he finds 

 himself surrounded by transported material. Gravel and bowl- 

 ders of crystalline, sedimentary and volcanic rocks form the bed 

 and bars of the river, increasing in coarseness and quantity to 

 Livingston, but in all this material I was unable to find any- 

 thing that was to me even presumably of eastern origin. 



Dr. C. A. White (this Journal, vol. xxv, 1883, p. 206) re- 

 ports finding what he considers eastern glacial drift along the 

 valley of the Missouri and that of the Yellowstone, but my 

 search for such material was vain.* 



The geology of the Yellowstone Park has been well described 

 by Dr. Hayden and his assistants, Mr. W. H. Holmes and Mr. 

 A. C. Peale, but I was surprised to find the traces of glacial 

 action so widespread and unmistakable. It is probably not too 



* As will be seen farther on, I found in the valley of the Missouri about the 

 falls great quantities of drift with bowlders of fossiliferous limestone, quartzite, 

 gneiss and granite, all remarkably like the eastern drift, but which I subsequently 

 traced to their place of origin in the Belt mountains. 



