OEEGON SHORT LINE OGDEN TO YELLOWSTONE. 147 



At Reas Pass the train stops to test, the air brakes before descend- 

 ing the -grade to YelltnvsfoTie Park. Here the route crosses the 



Continental Divide, going from the Pacific slope 

 Reas Pass, Idaho. ^^ ^^^ ^^^^^^^ ^^ ^ g^^^^j stream that flows into 



Elevation 6,93s feet. Madison Riyer, thence to the Missouri, the Missis- 



Ogden 281 miles. ' , ' , 



sippi; and the Gulf of Mexico, Where the train enters 

 a rock cut just beyond the railroad Y on which the helper engine turns 



mar 



and 



Montana. This board says that the bomidary is 9 miles from 

 Yellowstone and 6,914 feet above the sea. The rock in the cut at 

 the divide is light-colored rhyolitic lava, but the ledges 100 feet 

 above the track on the east are obsidian or volcanic glass. This 

 black glass, which crumbles rather rapidly under the sudden and 

 great changes of temperature common at this altitude, is the source 

 of a large part of the sand that covers the broad flats below. 



to 



mountams 



moraines 



large bowlders which have evidently been transported by ice. Such 

 bowlders may be seen as the train descends the north side of the 

 mountain. The timber at Reas Pass is mostly a dense growth of 

 young lodgepole pine, through which it is difficult to travel except by 

 the opened roads and trails, because of the intricate network of fallen 

 poles killed by fire. 



The train rmis slowly down the steep grade north of the pass as it 



which 



good trout water. 



in the railroad 



cuts. DowTL a little valley the train goes, and the view reaches no 

 farther than the wooded flat-topped mountains near by. In fact, 

 there is practically nothing to see but trees from this point to Yellow- 

 stone station. At milepost 105 the foot of the grade is reached, and 

 from this pomt to Yellowstone the road bed is on the flat pine-covered 

 surface of a wnde alluvial deposit, made by Madison River when it 

 flowed over this part of its flood plain. 



The 



from the crumbhng of volcanic rocks 



onsiderable percentage of black volcanic glass. The forest here 



sometimes called 



rnin 



wiU 



to the four-horse stage coaches waituig for passen- 



YeUowstone, Mont. ^^^^ jj^ ^^^ ^^^ ^^^.^^ ^^^^ ^^^ ^^^^^ js within 



Elevation 6,669 feet. g, few Tods of a line of bhized trees at the end of the 

 ogden 291 nuies. station grounds, but those blazed trees are significant. 



They mark the boundary of Yellowstone National Park. 



