205 



ferent points of view. The traveler, as he passes up the valley of the 

 Gallatiu, toward Bozeman, from the three forks, sees on his left hand, to 

 the east, a high ridge, M'hicli rises up like a wall. The abrupt side is 

 toward the valley, and an examination of its structure shows that it is 

 a part of an anticlinal ridge. In Plate III, the right-hand end of Section 

 1 joins on to the left end of Section 2, and thus a connected view is ob- 

 tained from below Flathead Pass at «, far south to Mount Ellis at L 

 North of Bridger Canon, the strata are lilted up so that on the west side 

 of the ridge, toward the Gallatin, the metamorpliic rocks are exposed, 

 while near the summit of the ridge the Silurian and Carboniferous strata 

 are nearly vertical. From the summit of the ridge, the Triassic, Juras- 

 sic, Cretaceous, and Ligniticbeds may be seen inclining at various an- 

 gles, sloping off eastward toward Shield's Hi ver. The aggregate incli- 

 nation of the stiata in this ridge is about northeast. Proceeding north- 

 ward, we tiud near Flathead Pass that the Silurian beds lie at the base 

 of the ridge, and have been elevated so that they pitch past a vertical 

 30° to 50°, as is so well shown by the cross-section in the Annual lleport 

 of the Survey for 1872, page 84. These two pictorial sections serve to 

 show the weathert'd forms of these ridges as seen at a distance, rather 

 than the details of structure. The vertical furrows, with here and there 

 a gorge cut directly through the ridge, forming what are called passes in 

 this country, are well shown. From near Flathead Pass southward 

 for several miles, the Silurian beds are lifted up in such a way that the 

 entire series can readily be made out. From the right-hand end of the 

 lower section in Plate If, the Silurian beds extend southward for about 

 eight miles, then the (Jarbouiferous strata overlie them, and are clearly 

 exposed. This section extends along the east side of the Gallatin, and 

 forms the blufls which have been cut by its waters. The surface erosion 

 of the beds is exhibited with remarkable clearness and perfection. In 

 the Silurian and Carboniferous groups the characteristic fossils are very 

 abundant. They are described in the Annual Pteport of the Survey for 

 1872. No Jurassic fossils were found in this immediate vicinity ; but 

 near the Yellowstone Eiver, about thirty miles to the southwest, and 

 at Spring CaSon to the southward in the same ridge, they are very 

 abundant. 



In Plate III, Section 2, the passes of Bridger Cafion and Spring Cauon 

 are quite important from the fact that through one of them the Northern 

 Pacific Eailroad must run on its way from the Yellowstone Valley. These 

 are rather narrow gorges cut by the little streams through the ridge, thu& 

 exposing an excellent though complicated section of the rocks. The foot- 

 hills are composed of the Lacustrine deposits, which jut up against the 

 sides of the mountains, sometimes nearly to their summits, apparently 

 without any disturbance, unless it be of a local character. JMounts Del- 

 ano and Cowen are on the east side of the Yellowstone Yalley, their sum- 

 mits rising far above any point on the divide. Mount Ellis, 8,419 feet, is 

 capped with Carboniferous and Jurassic rocks. Bridger Peak, 9,002 feet, 

 is capped with Carboniferous limestones, and Liberty Peak is a portion 

 of the same ridge. 



In Plates IV, V, and VI, and the upper portion of Plate Vlf, we have 

 seven sections that are connected, and represent the east side of the Gal- 

 latin Canon from its opening into the valley on the Lacustrine basin to 

 a point nearly to the source of the river, a distance of about twent.\-tive 

 miles. The four sections of Plates VIII and IX might have been con- 

 nected also, as there is but a short interval between them. At the left 

 hand of Section No. 1, we see the rounded foothills underlaid with gueis- 

 sic rocks. The lower end of the canon is at a. The direction is about 



