84 GUIDEBOOK OF THE WESTERN UNITED STATES. 



in the character of the canyon of the Arkansas is not yet understood, 

 but it could probably be satisfactorily explained if the history of 

 the river were thoroughly known. 



Above the mouth of Oak Creek the canyon of the Arkansas for 

 some distance is irregular in width and the sides are low, indicating 

 considerable age. though it is generally narrow, and farther on it 

 becomes more precipitous, until in the vicinity of Cotopaxi it is a 

 veritable canyon, though it is wider than the part of the canyon below 

 Texas Creek. 



Cotopaxi is a small settlement, hemmed m on all sides by high 

 granite walls, but fairly good roads lead from it southwestward to 

 a rich agricultural region at the foot of the Sangre de Cristo Range. 

 Small quantities of the precious metals as well as 

 Cotopaxi. some copper have been found near the town, but 



Elevation 6,385 feet, none of the mines are now in operation. Limestone 



Population 252.* ■ -, ■, ■ ■, • , • ,. 



Denver 192 miles, ^^^ oncc quamed here m large quantities for use as 

 flux in iron furnaces, but most of the limestone now 

 so used at Pueblo is quarried near Howard, farther up the valley. 

 The quarries near Cotopaxi were about 3 miles north of the rail- 

 road, at the southern end of the belt of Carboniferous rocks. (See 

 sheet 3, p. 100.) The limestone has been preserved here by being 

 downfolded into the granite, and on the east side of the downfold 

 the rock has been broken by a fault and replaced by the granite. 



For some distance west of Cotopaxi the sides of the canyon are 

 composed of massive granite, which in places stands up in nearly 

 vertical walls (see PI. XL, A), but the valley bottom is generally 

 wide enough to afford ample accommodation for the railroad and 

 for the Eainbow Highway. The canyon maintains this width for 

 some distance, but beyond milepost 194 the river passes through the 

 narrowest and most rugged part of the canyon west of Parkdale. 



About three-quarters of a mile beyond milepost 191 the railroad 

 emerges suddenly from the granite canyon into a broad valley at the 

 foot of the Sangre de Cristo Range. The course of the railroad, 

 which for a long distance has been nearly southwest, here veers to 

 the northwest along this valley. The change from seemingly end- 

 less vistas of rocky canyon walls to a broad valley in which there are 

 farms and green trees is striking and exceedingly restful and is one 

 of the surprises that are constantly awaiting the traveler in this 

 mountainous region. 



The change in scenery and in the general character of the country 

 is due to a difference in the underlying rocks, but for some distance 

 this fact is not apparent, as the rocks are not visible from the train, 

 the land near the river being composed of sand and gravel washed 



