50 GREEN TRAILS AND UPLAND PASTURES 



line of approach. Next I must know which way the 

 water flows, and get the feel of the division ridges, the 

 contour of the country. Many a time after riding in 

 a motor car over a new region, I have been miserable 

 until I could walk a few miles, to catch from my own 

 exertions the sense of rise and dip, to explore with a quiet 

 eye the valley ramifications. Hence the long ride up 

 beside the Lewis Range was, for me, a necessary in- 

 troduction. I was getting my bearings. I was seeing 

 for myself the truth of what the literal Park folders had 

 told me. 



Both the great northwestern prairie and the area now 

 split by mountain ranges were once lake or sea bottom. 

 By some pressure on the earth's crust a great crack was 

 formed, and one edge of the crust came up over the 

 other, sliding eastward from twelve to fourteen miles. 

 In Glacier Park it is called the Lewis Overthrust. As 

 this crust was thousands of feet thick, it is easy to see 

 that a vast line of precipice was formed, exposing every 

 strata of soil and rock deposited during untold ages be- 

 fore. Behind this precipice, for many miles, was the 

 hump made by the overlapping earth crust. Untold 

 ages since this upheaval have broken down this preci- 

 pice and carved this hump. Melting snows have made 

 vast erosion valleys. Frost and storm have swept 

 down shale slides into heaps at the base, the ice masses 

 of the glacial age ground out punch bowls or cirques, and 

 excavated canons. But even to the casual eye the line 



