DENVER & RIO GRANDE WESTERN ROUTE. 133 



the warm springs which gush from the same formation at Glenwood 

 Springs and give that place its reputation. Why the water should 

 be warm at both these places is a question that can not yet be an- 

 swered, for neither spring has any apparent connection with a fault 

 that would permit the hot waters to rise from great depths, or with 

 old volcanic flows or vents in which circulating water would come 

 into contact with rocks that still retain some of the heat they had 

 when they were ejected from the earth's interior. However, there 

 maj^ be some underground connection with one or the other of these 

 features which is not apparent at the surface but which would 

 account for the temperature of the waters carried in this limestone. 



The limestone rises toward the west at an angle of about 15°, and 

 within a distance of half a mile the underlying quartzite appears 

 at the level of the track. As the river cuts deeper and deeper into 

 the rising rocks the canyon becomes more ,and more rugged, and the 

 short bends give rise to many towers and pinnacles upon the pro- 

 jecting points. As the rocks continue to rise in the direction in 

 which the train is going, lower and lower rocks come into view. 

 Next below the upper quartzite, which is about 100 feet thick, lie 

 shale and thin-bedded sandstone, about 40 feet thick, and upon these 

 lies white quartzite, about 270 feet thick. So far the section in this 

 canyon is almost identical with that seen in the deeper canyons up 

 Eagle River, but here there is still another member, which seems not 

 to be present farther east. This member is a coarse quartzite whose 

 chief characteristics are its rich pink or maroon color and the re- 

 markable regularity in the thickness of its various beds, as well as 

 the evenness of the bedding planes which separate them. These 

 characteristics are well shown in Plate LVII, B. The full thick- 

 ness of this quartzite can not be seen here, for within a short dis- 

 tance the beds dip sharply in the other direction and the quartzite 

 disappears below water level. Farther down the river, however, 

 where the quartzite rests on the granite, its thickness is about 80 

 feet. The liighest point on this arch in the rocks is reached about 

 half a mile beyond milepost 346. Beyond this point the beds dip 

 rather steeply downstream until the Leadville limestone is at track 

 level on the left, and then the whole series is broken by a great fault, 

 which, as shown on the map, crosses the railroad at milepost 347. 



Beyond the fault the land on both sides of the river is compara- 

 tively low and smooth, and then the Leadville limestone rises again 

 from track level. Where it is seen by the roadside it is much broken, 

 having evidently been greatly disturbed and crushed. The rise of 

 the formations downstream is gradual but steady, so that near mile- 

 post 349 all the sedimentary rocks are again above water level and 

 the granite makes its appearance. Plate LVIII is reproduced from 

 80697°— 22 10 



