Hayclen.] "^^ [FebruaiT 19, 



able circumstances to produce crops to any extent, the productions of 

 Salt Lake Valley are among the finest in the woiid. 



"We can see at a glance therefore that the whole country west of the 

 Mississippi is as it were an elevated Plateau, out of which rise, as if by 

 the bursting of the crust, a vast series of ranges of mountains, trending 

 in the aggregate nearly north-west and south-east, and each of the series 

 made up of an infinite number of minor ranges trending in almost every 

 possible direction. In many instances important ranges of mountains 

 are separated from the main chain by extended plains composed of creta- 

 ceous or tertiary formations, and without a knowledge of the geological 

 structure of the country, they would seem to be entirely disconnected. 



The Black Hills of Dakota, occupy an area of 6000 square miles. If 

 we examine the map this important range seems to be entirely isolated 

 from the main range, but from the south-western side extends a low 

 anticlinal valley, just exposing the tertiary and for a portion of the dis- 

 tance the cretaceous beds, and linking the Black Hills with the Laramie 

 range near Fort Laramie. 



Again, the same may be said of the Big Horn range, from the south-east 

 end of which along the valley of Poison Spring creek extends an anticli- 

 nal valley, joining the Big Home range with the Laramie near the Red 

 Buttes. All these isolated ranges, however distant they may appear to 

 be from the main range, or however small they may be, are really 

 connected to the eye of the geologist. It is thus that- the anatomy of this 

 great mountain system can be worked out in detail. Never can it be well 

 done, so as to command the unqualified approbation of the scientific 

 world, until the minutest topography and the geology are united together. 



The northern portion of the Laramie range properly commences near 

 the Red Buttes. Here the nucleus of feldspathic granite or syenite is 

 concealed by the overlying unchanged beds, and a broad interval occurs 

 which is occupied by a great variety of formations, ranging from the 

 carboniferous to the most recent tertiary. In its southward extension 

 this range seems to flex around from an almost easterly trend to a south- 

 west direction, forming almost a half circle. It then joins on to the 

 main range in the neighborhood of Long's Peak. Thus the Laramie 

 range constitutes the east side and the greater part of the north side of 

 the Laramie plains which forms, thus enclosed, a huge park. On the 

 south side is the Medicine Bow range, the loftiest ridges covered with 

 pei'petual snow. Connected with this range also are numerous minor 

 ranges. The west side is an open rugged barren sage plain, with here 

 and there detached small mountains extending far westward toward 

 Salt Lake valley. 



The Laramie range forms the most beautiful illustration of an anticli- 

 nal ridge I have ever met with in the Rocky Mountains, with the excep- 

 tion of the Black Hills of Dakota. Either one of these ranges if 

 thoroughly studied, would form excellent monographs of the physical 

 geography and geology of the mountain region. 



The nucleus of the Black Hills is composedof red feldspathic granite 



