OEEGO^ SHORT LINE OGDEK TO YELLOWSTONE. 119 



produced by outwash from the mountains. In other words, the 

 debris brought down from the surrounding mountains by the nu- 

 merous streams has spread out as a great apron, filUng the valley to 

 a considerable depth, and every year, especially at times when the 

 streams are high, a little more sand and gi-avel arc added to the 

 deposit. The valley of old Bonneville River, now occupied by 

 Marsh Creek, is cut in this fill. At Downey the flat floor is composed, 

 at least near the surface, of well-rounded sand and partly cemented 

 gravel. It is sai 



was 



hill 



farmers 



Virginia. 



ids m the vicmity. 

 here and at Arimo, 



typ 



3S 



mi 



Elevation 4,-90 feet. ^ j ^^^^ j,^ ^f Idaho. iVftcr leaving Yir- 



Opflen 100 railed. I' "-1^^*^ ^ _ ., .,-.iii.T 



ginia the train runs down below tlic level of the 

 Arimo. unnor bench and at Marsh Valley sidmg passes 



upper 



Elevation 4,736 feet. 

 Ogden 105 miles. 



m 



g the railroad 



Thecrravel shows the chai^acter of the vaUey fiUing. xVi'imo is one 



to 



numerous httle settlements on the mam 

 .^A J>^,^^i.fA^a which parallels the track for many nul 



Creek has been flooded with 



one 



of the later stages of geologic history, probably m Pleistocene 

 glacial thne. Lava of this kind, a basalt, is mdespread m south- 

 ern Idaho. It is seen first in Marsh Creek valley about H mdes 



between mHeposts 106 and 107. The edge of 



north of Arimo 



first 



the 



east side of the creek, just north of some ranch buildmgs. Marsh 

 Creek flows along the west side of the lava and theraiboad runs 

 alono- the east edge for a short distance, graduaUy gomg up on the 

 uppe^r surface, which it traverses to McCammon The surface ap- 

 pears smooth, but so much of it is bare rock partly hidden by sage- 

 bush that the land is not cultivated. Near McCammon where there 

 is more soil on the lava, crops are being raised. Just before reachmg 

 McCammon the traveler can see on the east the defile --1^-^ ^ortneuf 

 River has cut through the mountains. In the forties ^-^ ^^^^^^^^^^ 

 neers from the Mississippi Valley bound for Oregon d-erge^^ 

 the Astor route and entered the Snake River valley through h^ 



am where travelers now pass along in Pulhnans 



Packards, 



