FebriuuT 1-', lSu9-] "^ [Ilaydeii. 



NOTES OX THE GEOLOGY OF WYOMING AND COLORADO TERRITORIES. 



No. 2. 

 By F. V. Hayden. 



Before describing the geological character of the Laramie Plains and the 

 country to the west of it, I Avill attempt to present a resume of the physical 

 geography of that very interesting region. If we look at the profile of 

 the route constructed by the Union Pacific Railroad for their road from 

 Omaha to Fort Bridger, we shall find that at Omaha, the initial point, the 

 altitude is 968 feet above tide level. At the mouth of Lodge Pole creek, 

 a distance of 377 miles, we have an elevation of 3528 or a gradual rise 

 in that distance of 2560' or a grade of about 7 feet to the mile. From 

 the mouth of Pole creek to Crow creek crossing near Cheyenne 513.76 

 miles west of Omaha we have reached an elevation of 6019 feet, or an 

 average grade of over 9 feet to the mile for the entire distance. 



At Evans' Pass on the summit of the Laramie range, we have reached 

 the highest point in the Rocky Mountains,, 8248', a distance of 545.62 

 miles west of Omaha. The average grade is over 13 feet to the mile. 

 But for 100 miles west of Omaha the average grade of ascent increases 

 as we approach the mountains. 



If we take the distance from Crow Creek Crossing at the foot of the 

 mountains to Evans' Pass, "the Summit," a distance of 31.86 miles, we 

 have an average grade of ascent of nearly 70 feet to the mile. We can 

 see clearly by these figures the plan of growth of that portion of our 

 continent west of the Mississippi. A number of these profiles have been 

 constructed across the continent from the Mississippi to the Pacific ocean, 

 from the north line to the south, all pointing to the same result, and all 

 agreeing substantially in the aggregate results. 



Passing over this first range of mountains to the Laramie plains, from 

 Crow Creek Crossing to Laramie river 57.53 miles, and 571.39 miles west 

 of Omaha, the elevation is 7175 feet above tide Avater. Showing that 

 even in the i^lain country on the west side of the first range the elevation 

 is over 1000 feet higher than at the base of the mountains on the east side. 



From the latter point westward there is a continued line of ascent and 

 descent produced by the same forces that elevated the whole Rocky 

 Mountain Chain. Passing the Humbolt mountains we then descend by 

 a moderate grade to the Pacific ocean. The intermediate portions are 

 occupied by a continued series of more or less elevated mountain ranges 

 with intervening valleys which are always at a considerable height above 

 the sea, but vary at different points from east to west. For example 

 the elevation of the Laramie plains near Fort Sanders is 7175 feet, at 

 Salt Lake Valley 4285, making a difference of 2990 feet. We shall en- 

 deavor to show hereafter that this difference in the elevation of the two 

 localities of nearly 3000 feet operates most favorably upon the agricul- 

 tural resources of Salt Lake Valley. While the summers in the Laramie 

 plains are very brief, and it will always l)e difficult under the most favor- 

 A. P. S. — VOL. XT— D 



