Hayden.] ^^ [Februarj^ 19, 



even far distant from the monntains, the rocks are more or less disturbed, 

 but generally not exposing older beds than the cretaceous. 



We find also that there is an irregular series of anticlinals and syncli- 

 nals resembling somewhat, but on a gigantic scale, the furrows in a 

 ploughed field. Not unfrequently we meet with a high synclinal 

 ridge, formed of rocks inclining toward each other ; and then following 

 the same beds along and across the ridges we shall find them dip]3ing 

 away from each other making a synclinal valley. 



I have given my observations along this route somewhat in detail from 

 the fact that no accurate information concerning the geology of this 

 region has ever been published ; and because we have had no definite 

 data for coloring a geological map. Our course was along the Overland 

 Stage Road just at the base of the mountains, on the south side of the 

 Laramie plains, from 5 to 20 miles south of the Union Pacific Railroad 

 line ; and by comparing my observations of the geology along the stage 

 road with those along the line of the railroad it will be seen that there 

 are many points of diff"erence. As I have before remarked, the^Laramie 

 range of mountains forms one of the most complete and beautiful anti- 

 clinal systems in the West. 



The Laramie plains, as the area enclosed by these mountains is called, 

 exhibits a broad, undulating almost treeless, surface about 60 miles long 

 from East to West, and 50 miles broad from North to South. From Fort 

 Sanders along the stage route to Little Laramie river, the distance is 

 about 18 miles. The surface is quite undulating, but all the slopes are 

 moderate in their inclination. All the basis rocks belong to the creta- 

 ceous period. At the crossing of the Big Laramie may be seen a small 

 thickness of the black clays of No. 2, and here and there are isolated 

 hills which show the yellow chalky layers of No. 3. Some of the higher 

 ridges which extend down into the plains from the foot of the mountains 

 reveal here and there the rusty yellowish arenaceous marls of No. 5. 



From Little Laramie Station to Cooper's creek the distance is 15 miles. 

 Over this interval the cretaceous rocks prevail and belong mostly to the 

 upper portion of that period. There are probably isolated patches of 

 tertiary overlapping the cretaceous beds. 0)ie of these isolated areas of 

 tertiary occurs about two miles north of Cooper's Creek Station on the 

 west bank of the creek where an excellent coal bed has been opened 

 nine feet thick. The coal is quite pure, compact, but rather light, and 

 burns well. I do not think it will be continuous over a very large area, 

 but it will yield a large amount of fuel before it is exhausted. 



From this point westward nearly to Fort Bridger, and perhaps beyond, 

 the tertiary beds may be said to prevail in the plain country. Rocks of 

 older date with comparatively few exceptions are not seen except in 

 close proximity to the mountains. In some instances the mountains 

 abut abruptly on the plains, the tertiary or cretaceous beds jutting 

 against the granite or igneous nucleus, and concealing for long distances 

 all the older rocks. Again, intervening between the i^lain country and 

 the principal mountain ranges are 50 to 100 miles of what- may be called 



