hactob.] THE GREAT PLAINS OF THE NORTH, 323 



coarse conglomerates, with intercalations of somber-colored volcanic 

 material composed of fine and course basic agglomerates, and beds of 

 fine sands and clays deposited in shallow water and derived from the 

 denudation of land surfaces. The Livingston rests unconformably upon 



the Laramie and contains pebbles of Archean schists, Paleozoic lime- 

 stones, and Cretaceous sandstones. Away from the mountains the two 

 "roups have not as yet been differentiated. 



The railway, which for the greater part of the distance (save, for 

 instance, when crossing the Bad Lands) traverses the top of the gently 



undulating surface, on reaching the Yellowstone Valley follows the river 

 between high bluffs of Laramie sandstone. At a number of localities 

 along the river, Cretaceous rocks older than the Laramie are exposed 

 in the bluff's. Near the mountains the entire series of Cretaceous strata, 

 from the base of the Dakota to the Livingston, are upturned and well 

 shown in excellent cross-section along ravines cut by streams coming 

 down from the mountains. 



On a bright clear day the first glimpses of the Rocky Mountains 

 may be had from Billings, snow-clad peaks standing out prominently 

 both to the north and south, and three or four hours before reaching 

 Livingston the Bear Tooth Mountains to the south present a grand 

 panoramic view of rugged peaks stretching along the horizon as far 

 as the eye can reach. These mountains, whose summits reach 12,000 

 feet(3,658m.), and their western extension, the Boulder plateau. 10,000 

 feet (3,048 m.), consist of Archean gneiss and granite. The slopes 

 and foothills are made up of Paleozoic strata dipping either to the 

 north or east, and passing beneath Mesozoic beds, the uppermost mem- 

 bers of the Laramie standstone extending far out upon the plain. 

 The Boulder plateau is intimately connected with the Snowy range, 

 along the northern base of which the railroad runs from Pig Timber to 

 Livingston. 



On the north side of the valley rise the Crazy Mountains, an isolated 

 group standing out boldly from the main Pocky Mountain ranges. 

 The central portion of these mountains consist in great partof igneons 

 rocks that have broken through a broad synclinal trough of sandstones 

 and shales, made up of a great thickness of sediments of the Living- 

 ston and overlying series of beds. From the central core of igneous 

 rocks innumerable dikes have penetrated the sandstone, baking and 

 hardening the sedimentary rocks, which have resisted erosion more 

 than the easily friable beds." The most southern peaks of the 

 Crazies are situated about 15 miles [24 km.) north of the river, and are 

 easily accessible to anyone desiring to study them. 

 451 gkb 21 



