196 REMARKS ON SANDSTONE AND 



tions may have taught him to look for above the granite. He 

 will find recent marine sandstone abounding in organised 

 remains, with its stratifications nearly perpendicular, and in 

 immediate contact with the side of a granitic mountain of 

 vast magnitude tind elevation, and of a character most ma- 

 nifestly and highly primitive. The inclination of the strata 

 of this sandstone varies within a shori distance from liori- 

 zontal to an angle of more than sixty degrees. It is some- 

 fimes difficult to determine, by the eye alone, which way it 

 varies from an exact perpendiculai-. 'I'hose laminpe or 

 strata of it, which are most distant from the primitive occu- 

 pying the eastern ridges of its first elevations, have the least 

 inclination, and may with propriety be denominated the up- 

 permost. At the level of the surface of the great plain they 

 sink beneath the alluvial, and in the immediate neighbour- 

 hood of the river Platte tney are no more seen. The up- 

 permost are of a yellowish grey colour, moderately fine, 

 compact, and hard, constantly varying however at different 

 points in colour, as well as most other characters. The 

 light coloured varieties frequently contain numerous small 

 round masses of about the size of a musket ball, whicii are 

 more friable than the rock in which they are imbedded, and 

 from which they are easily detached, leaving cavities cor- 

 responding to their own shape and diihensions. They are 

 commonly of a dark brown colour, and of a coarser sand 

 than that which enters into the composition of the rock it- 

 self. Mr. Say informed me that their appearance was not 

 unlike that of certain organic remains of the Genus Ovulite. 

 Where these are found, I could never discovei- any of those 

 numerous animal relicts which are so common in many of 

 the secondary rocks of this district. 



Crossing the edge of these strata of sandstone, the cha- 

 racter of the rock is found to change, on coming ncai-cr to 

 the primitive. The rock becomes more coarse and frial)le, 

 its colour inclining more to several shades of red and brown. 

 This variety contains numerous masses of iron ore. and does 

 not appear to abound in the remains or impressions of orga- 



