214 GEOLOGICAL SURVEY OF THE TERRITORIES. 



tlie u Divide," opposite South Park, and Eaton Mountains, and lying 

 east of the dividing ridge of the Bocky Mountains. It not only embraces 

 the plains east of the base of the mountains, but also the Upper Arkansas 

 Valley or park lying within them. It contains about twenty-six thousand 

 square miles, of which about one-fourth, or six thousand square miles, 

 can be irrigated and brought under cultivation. It is being rapidly set- 

 tled up, and will ultimately prove to be the richest agricultural portion 

 of the Territory. 



The Arkansas Eiver, rising a little northwest of South Park, runs 

 southeast nearly to Poncho Pass, where, turning a little more toward 

 the east, it passes through a canon for about forty miles, emerging upon 

 the open country at Caiion City. From this point to the eastern bound- 

 ary of the Territory it runs almost directly east. 



The mountain valley has an elevation of between seven and eight 

 thousand feeb above the sea, while that of the plain country lying east 

 of the range varies from six thousand near the base of the mountains to 

 about three thousand five hundred feet at the eastern boundary of the 

 Territory. This somewhat rapid descent of the plains eastward is a very 

 important item in estimating the agricultural capacity of this country ; 

 for it was for some time a serious question in my mind whether the 

 descent on the broad open plains was sufficient, after leaving the moun- 

 tains for some distance, to carry the water of these rivers over the sandy 

 soil; but from a list of elevations along the Kansas Pacific Railroad, 

 kindly furnished Dr. Hayden by General Anderson, superintendent of 

 that road, I learn the following important facts : That from Denver to 

 Fort Hays, a distance of three hundred and forty-seven miles, the fall is 

 three thousand two hundred and seven feet, or a little over nine feet to 

 the mile, showing it possible to pour the waters of the South Platte into 

 the channel of Smoky Hill Eiver. From Cheyenne Wells, near the 

 source of the Smoky Hill Eiver, to the same place, a distance of one 

 hundred and seventy-three miles, the fall is one thousand two hundred 

 and eighty -three feet, or over seven feet to the mile, which is sufficient 

 to carry the water upon levels sixty, or even one hundred, feet above 

 the stream, where the supply is sufficient. The Arkasas Eiver, from 

 the mouth of the Apishpa to the mouth of the Pawnee, a distance of two 

 hundred and six miles, has the remarkable fall of two thousand four 

 hundred and eight feet, or more than eleven feet to the mile. This is 

 sufficient to reach the highest extensive levels, so that, east of Pue- 

 blo, the extent of the irrigable land is limited only by the supply of 

 water, which confirms an opinion expressed by Mr. Byers in a commu- 

 nication to me concerning this valley. 



The head- waters of the Arkansas are in an oval park situated directly 

 west of the South Park. The altitude of this basin is probably between 

 eight and nine thousand feet above the level of the sea; the length is 

 about fifty miles from north to south and twenty or thirty miles in width 

 at the middle or widest point. At the lower or southern end, an attempt 

 has been made to cultivate the soil, which bids fair to prove a success. 

 Around the Twin Lakes, at the extreme point, oats, wheat, barley, pota- 

 toes, and turnips have been raised, yielding very fair crops. Below this 

 basin the river, for twenty miles, passes through a narrow canon, along 

 which, with considerable difficulty, a road has been made. Emerging 

 from tMs, it enters the " Upper Arkansas Valley " proper, which is a 

 widening of the bottom lands from two to six or eight miles. This valley 

 is some forty or fifty miles in length and very fertile. Near the southern. ' 

 extremity are some large boulder deposits, evidently formed during its 

 lake period, ere the southeast barrier had broken away before the accu- 



