Rocky Mountains. 11 



strata having, however, less inclination than is observed 

 nearer the base of the mouncain. It is the marcrin of that 

 great formation of secondary which occupies the plains, and 

 appears as if broken off and thrown into an inclined position, 

 by some convulsion which changed the relative elevation of 

 the stratum. It is of great thickness, its laminse in an almost 

 vertical position, occupying 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 sup- 

 posed to have been the surface of the stratum in its ori- 

 ginal position, the rock is usually of a close grain and 

 compact texture, and of a yellowish- white or light gray 

 colour. 



We saw many masses of sandstone bearing a striking re- 

 semblance 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 mountains, and their summits are 

 occupied by horizontal strata. For a small portion of the 

 upper part of their elevation their sides are nearly perpendi- 

 cular, but their bases are surrounded by an extensive accu- 

 mulation of debris, 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 mountain, 

 where we encamped. 



Several of the tributaries to Defile creek appear to dis- 

 charge as much water as is seen in the stream below their 

 junction. This appearance is common to many of the larger 

 creeks, their broad and sandy beds allowing much of the 

 water to sink and pass off through the sand. In the evening 

 a favorable opportunity, the first for several days, presented, 

 and obsesvations for latitude were taken. 



