DENVER & KIO GRANDE WESTERN ROUTE. 



163 



of the last bends the traveler may look down upon Poncha Pass, but 

 from a distance so great that good eyesight is needed to distinguish 

 even the telegraph poles that mark the line of the railroad. The 

 chain of high peaks which lies behind the pass and which is known 

 as the Sangre de Cristo Range here begins to loom up, and as the 

 journey continues it grows steadily in apparent magnitude until it 

 is lost to view over the summit of Marshall Pass. 



As the train continues to climb upward the traveler will observe 

 that the slopes become less and less rugged, and he soon begins to 

 realize that the mountain masses about him, which looked so formid- 

 able when seen from below, are really only the foothills of the higher 

 range and that many of these foothills have a nearly common height 

 and are relativel}' flat topped. These flat tops stand at an altitude of 

 9,300 to 9,500 feet and may correspond with the rolling plain at the 

 north foot of Pikes Peak and with the tops of the Front Range 

 as seen from Denver. Their equivalence with those features can not 

 be regarded as proved, but they suggest that at one time much of 

 the mountain region of Colorado was a rolling plain above whose 

 generally even surface only a few high knobs projected. Later this 

 surface was upraised to its present position, and the mountains as 

 we know them to-day were carved from the uplifted mass. 



As soon as the railroad reaches the top of the hills that front the 

 valley it changes its course to one directly toward Mount Ouray, 

 which is the most conspicuous feature in the landscape. The road 

 winds considerably, but from time to time the peak can be seen 

 from either side of the train, though the best views are from the 

 left. The peak is not symmetrical, but looks as if some giant had 

 taken a great bite out of the side next to the traveler, as shown in 

 Plate LXIX, B. And, indeed, a giant has taken a bite out of the 

 side of the mountain, but the giant was a glacier that once lay high 

 up on its slopes and that gradually ate out a great amphitheater or 

 cirque, as it is called by geologists.^^ This cirque looks large even 



51 The exact method by which a 

 glacier excavates an amphitheater or 

 cirque is not very well understood, as 

 all the work is done under the ice and 

 hence can not be seen. It can be 

 judged only by the form of the cirque 

 after the glacier has melted away. 



The term glacier means moving ice. 

 The snow falling on a mountain side 

 consolidates into ice under its own 

 weight and finally becomes so heavy 

 that it begins to move down the slope. 

 In doing so it takes with it some of 

 the underlying rock to which it has 

 frozen, and this action, repeated many 



times, tends to produce a hole in the 

 mountain side. As the tendency is to 

 pluck out the rock equally in all di- 

 rections from which the ice moves to 

 the point of outlet the cirque has a 

 semicircular shape and the plucking 

 tends to cut back horizontally, so that 

 the floor of the cirque is nearly level 

 or it may be slightly deepened so as 

 to form a rock basin. The walls of 

 cirques in many kinds of rocks stand 

 nearly vertical, but the walls of the 

 cirque in Ouray Peak, which are com- 

 posed of granite, take on a more gentle 

 slope, as shown in Plate LXIX, B. 



