20 THE PLAINS. 



with the second plain, which at the time of its upheaval 

 was undoubtedly much more extensive than at present. 

 The line of demarkation between the second and third 

 plain is most distinctly indicated in the country south 

 and west of Fort Lyon, the second plain rising by a 

 sudden jump of from 500 to 1,000 feet from a 

 general level of the third. For from twenty to thirty 

 miles from this present line the surface of the third plain 

 is broken by large masses of the second plain, some still 

 almost perpendicular, other almost rounded into hills, but 

 all having the general level of the second plain. 



Standing, therefore, on either of the lower plains, any- 

 where in the comparative vicinity of its junction with the 

 plain above it, our horizon will be bounded more or less 

 by hills all referable to the next plain above. 



Away from the vicinity of the junction of the plains 

 we appear to be surrounded on all sides by a boundless 

 expanse of dead level. This appearance is due to the 

 fact that in looking at it the eye catches only the higher 

 lines of the upper surface of a plain which was originally 

 almost a dead level. I have already said that the inclina- 

 tion of all the plains is from the mountains. How decided 

 this inclination must have been at first is proved by the 

 peculiarity of the streams. The larger rivers, the Platte, 

 the Arkansas, and the Canadian, taking their rise in the 

 mountains, were already pouring their waters towards the 

 ocean in tortuous channels scarcely yet worn through the 

 new upheaval. They kept a general course down the 

 inclination ; the Arkansas alone swerved from its direct 

 course by a mass of hilly country (which will, I think, be 

 found to be referable to the second plain). The first rains 

 which fell upon the newly-raised lands had to make 

 channels for themselves. They naturally sought the 

 greatest inclination. It was from the mountain. An 

 examination of a good map will show how completely 

 the streams appear to ignore each other, and how each 

 independently takes its own course towards the sea. 



