On the morning of the 9th [8th] of July[147] we resumed our journey, travelling somewhat east of south along a small tributary of the Platte. The bed of this stream lies from south to north along a narrow valley, bounded on each side by high cliffs of sandstone. The rock is similar to that already mentioned, its strata having, however, less inclination than is observed nearer the base of the mountain. It is the margin of that great formation of secondary which occupies the plain, and appears as if broken off and thrown into an inclined position by some convulsion which changed the relative elevation of {198} the stratum. It is of great thickness, its laminæ in an almost vertical position, covering a surface of two or three, and sometimes many miles in width. On the eastern declivities of the first ranges of hills in places which may be supposed to have occupied the surface of the stratum in its original position, the rock is usually of a close grain and compact texture, and of a yellowish white or light gray colour. [147] A series of erroneous dates begins here. The expedition undoubtedly left Platte Cañon July 8, of which day the text gives no account. July 9 was Sunday, instead of July 10, as the text states below. A compensating error is introduced by giving the date July 12 to accounts of the journeys of parts of two days. The Philadelphia edition also has the erroneous dating of the ninth, tenth, and eleventh, but includes the remainder of the chapter under the last date, thus failing entirely to account for the twelfth, and really including the operations of three days (tenth, eleventh, and twelfth) under date of July 11. The itinerary for these days is more accurately indicated on the map.—ED. We observed, in various parts of the valley which traverse this sandstone district, several detached columnar masses, many of them bearing a striking resemblance to colossal ruins; also some insulated hills with perpendicular sides and level summits. These seem to be the remains of an extensive portion of the sandstone stratum which formerly covered the country to the level of their highest summits. They occur at considerable distance from the base of the primitive mountain, and their summits are occupied by horizontal strata of sandstone; for a small portion of the upper part of their elevation their sides are nearly perpendicular, but their bases are surrounded by an extensive accumulation of _débris_ sometimes rising nearly to the summit. After ascending the small stream before mentioned to its source, we crossed an inconsiderable ridge which separates it from the valley of Defile Creek. This we ascended to the place where its principal branch descends from the mountains. Here we encamped with the intention of resting on the following day, which was Sunday.[148] [148] The camp of July 8 and 9 was probably near the site of Sedalia, at the confluence of the east and west forks of Plum (here called Defile) Creek.—ED.