218 APPENDIX. 



Other matters, possibly of equal interest, say all that I know 

 about it. 



"It is necessary, then, in the first place, to take both a 

 geographical and geological horizon. Thus, referring to the 

 map : startins", for instance, from the Wicha-pahah, or Scalp 

 Mountain Creek, in lat. 43^ 8^ and visiting, successively, as 

 follows — the hills at the mouth of Whetstone Creek ; those 

 in the vicinity of Red Cedar, Snags, and Sailor's Islands ; the 

 Mankizitah, or White-earth River ; the American River, the 

 Great Bend (which is the Karmichigah of the Sioux), it will 

 be easy to understand all the circumstances about which I 

 shall now give an account. 



" 1st. The stratum of argillaceous limestone, observ^ed at 

 Dixon's Bluff, has disappeared, in consequence of the eleva- 

 tion of the level of the valley. 



" 2d. The calcareous marl, in horizontal stratification, 

 continues to make its appearance in escarpments, of from 

 thirty to forty feet, containing the same fossils — namely, orbi- 

 cula and fish-scales. 



" Over this bed, or rather between it and the preceding 

 one, there seems to be occasionally found a thin layer of 

 fibrous carbonate of lime, the true position of which I was a 

 long lime in determining, as I had discovered fragments of it 

 only among the rubbish at the foot of the bluff. I have since 

 observed it in place above the calcareous marl ; and it is 

 interesting that it is covered with coats of a fossil, very much 

 resembling the gryphcea Vomer, but which Mr. Conrad has 

 described under the name of ostrea congesta. 



" 3d. The bed C, composed of a foliated and selenitous 

 clay, acquires interest, as it developes itself in other localities. 

 Its thickness is variable. I have found it twenty feet thick ; 

 and its strata are divided by thin layers of a more indurated 

 white clay. In these several stages, the seleniferous clay, 



