OEEGOX SHORT LINE OGDEN TO YELLOWSTONE. 123 



As soon as the train leaves the gap a basalt wall is seen again on 

 the north. Probably the lava was originally continuous through the 



gap, having flowed down the valley from McCammon 

 or neu (spur). ^^ ^ great molten tongue, but if so it has been com- 



Sger mtSs. Pletely remored from the gap by the river. Plainly 



there are two lava sheets here. The columnar struc- 

 ture is well developed, as shown in the vertical wall at the edge 

 of the basalt. At a few places where there were original sags 

 in the surface of the mass radiate structure can be recognized* 

 The basalt ends in the Portneuf Valley with a gentle slope about 3 

 miles east of Pocatello. Near Pocatello the mountains swing away 

 to the west and north, making room for the city. 



A low, steep-faced reddish ridge north of the track just east of the 

 city appears to be a block of Ordovician quartzite uplifted by faulting, 



Pocatello,^ another ^'gateway to the mountains/' is the junction 

 of the divisions of the Oregon Short Line running north to Butte, 



Pocatello. 



Mont., and west to Huntington, Oreg. It was named 

 for an Indian chief and began as a tent city in 1SS2, 



Population 9, uo^ whcu the railroad was completed to this point. The 

 Ogden 134 miles. early history of this locality is a wild one. In the 

 ranger mi es. j^yg -vvheu the ovcrlaud stagc made its way through 

 Portneuf Valley trouble with Indians and with highwaymen was 

 common. The city is built on a, town site of 2,000 acres sold by the 

 Indians to the United States. It is divided by the railroad into two 

 distinct parts, connected by a viaduct which crosses the numerous 

 tracks at the station. It is growing rapidly and already has many 



noteworthy institutions, such as a Federal building, a Carnegie 

 library, a hospital, a large railroad Y. M. C. A., and fine schools, 

 including the Academy of Idaho, which bridges the gap between the 

 common schools and the State university. The electric light and 

 power used in the city is generated at American Fidls, 25 miles west, 

 on Snake Kiver. The growth of the city is due largely to the rail- 

 road shops, which give employment to hundreds of men. 



Just west of the city highly tilted Cambrian quartzite is overlain 

 by rhj^olite, a light-colored siliceous volcanic rock, which flooded the 

 surface before the basalt came. As the train leaves the station and 

 passes the roundhouses and extensive railroad shops the traveler 

 sees to the west the great Snake River plain. Far out in this plain 

 a solitary mountain appears in dim outline. This is Big Butte, the 

 cone of an extinct volcano, and the westernmost of three buttes 

 which for generations have been landmarks in this part of the country. 



Farther than the eye can see the Snake River plain stretches away 

 to the west. The valley of the ancient Snake River was Hooded 



Oj:rden. 



milepoat 



