APPENDIX E. — GEOLOGY. 403 



poslte of older date tlian the tertiary \Yere observed. Of the 

 specimens collected there is but a single individual indicating the 

 character of a marine formation. From the condition of the bones 

 it may even be questioned whether the deposite containing them is 

 not of post tertiary age. 



The specimens from the vicinity of Fort Laramie are all from 

 limestone of the carboniferous period. Some of the fossils are 

 identical with species- collected between the Missouri and the Big 

 Blue, and we can only suppose, from the great similarity of the 

 specimens, that it is a continuation of the same formation. From 

 the dates marked upon the specimens, it is evident that this lime- 

 stone extends to some distance on the east and west of Fort 

 Laramie. 



The specimens bearing date of July 19th, two days' march 

 northwest of Fort Laramie, are a feldspathic granite with little 

 quartz or mica. The rocks in this locality are doubtless of me- 

 tamorphic origin, probably rocks of silurian age. The specimens 

 collected three days' march in advance of this place, on the North 

 Fork of the Platte River, are shaly sandstone and thinly laminated 

 sandstones containing fossils. The fo&sils are some brachiopods, 

 with others similar to Monotis, and we may presume from the 

 described position of the beds, and from the character of the fos- 

 sils, that these beds are of devonian age. In the journal these 

 beds are recorded as dipping at the rate of 15° to the north-east. 



The specimens bearing the mark of July 24th, are precisely like 

 those collected at Fort Laramie, and contain the same species of 

 fossils. On the same date were seen (according to the journal) 

 gray and red sandstones. On the following day is recorded a bed 

 of coral, three or four feet thick, with Sigillaria and Calamites. 

 The specimens of this date sent to me are those of bituminous coal 

 and others of soft shale, but I have been unable to distinguish any 

 well-marked vegetable remains. 



From the proximity of limestone of the age of the coal, and the 

 record of sigillaria and calamites occurring in the same connec- 

 tion, it may be presumed that this coal belongs to the true coal 

 measures ; and this locality is probably an exposure indicating the 

 existence of a great basin. This point itself and the surrounding 

 country are well worthy of a more extended examination, since 

 the discovery of workable beds of coal in this region would be a 

 matter of national importance. 



The record of July 27th shows the occurrence of red shales and 



