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Show 205 ferent points of view. The traveler, as he passes up the valley of the Gallatin, toward Bozeman, from the three forks, sees on Iris left hand, to the east, a high ridge, which rises up like a wall. The abrupt side is toward the valley, and au 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 obtained from below Flathead Pass at a, far south to Mount Ellis at /. North of Bridger Gallon, the strata are lifted up so that on the west side of the ridge, toward the Gallatin, the metamorphic 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, Jurassic, Cretaceous, and Liguitic beds may be seeu inclining at various angles, sloping off eastward toward Shield's Biver. The aggregate inclination of the strata in this ridge is about uortheast. Proceeding northward, we find 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 § 0°, its is so well shown by the cross- section in the Aunual Report of the Survey for 1872, page 84. These two- pictorial sections serve to show the weathered forms of these ridges as seen at a distance, rather thau 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 II, the Silurian beds extend southward for about eight miles, then the Carboniferous strata overlie them, and are clearly exposed. This section extends along the east side of the Gallatin, and forms the bluffs 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 Beport of the Survey for 1872. No Jurassic fossils were found in this immediate vicinity; but near the Yellowstone Biver, about thirty miles to the so at h west, and at Spring Cation to the southward in the same ridge, they are very abundant. In Plate III, Section 2, the passes of Bridger Canon and Spring Canon are quite important from the fact that through one of them the Northern Pacific Bailroad must run on its way from the Yellowstone Valley. These are rather narrow gorges cut by the little streams through the ridge, thus exposing an excellent though complicated section of the rocks. The foothills 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. Mounts Delano and Cowen are on the east side of the Yellowstone Valley, their summits 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 VII, we have seven sections that are counected, and represent the east side of the Gallatin 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 twenty- five miles. The four sections of Plates VIII aud IX might have been connected 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 gneis-sic rocks. The lower end of the caiion is at a. The direction is about |