OEEGON SHOTtT LINE OGDEX TO YELLOWSTONE, 117 



skittering away through the weeds. The railroad grade, which has 

 been gradually rising to Swan Lake station, now begins to descend. 

 By the overflow^ of Lake Bonneville the drainage divide was moved 

 from Red Rock Pass, where it stood before Bonneville time, back 

 to this point, nearly 7 miles farther south. Sand and gravel 

 dumped by small creeks coming out from the hills have dammed this 

 part of the valley, making a mareh which extends most of the way 

 from Swan Lake to the pass. The hills on the east are compos.vd of 

 Tertiary sediments, mostly shale, and show the Bonneville shore line 

 about 340 feet above the marsh. At Red Rock Pass red limestone 



chffs appear on both sides (PL XXXI, p. 113). From 



coming 



small valley 

 sh Creek, 



Bonneville 



River, but which, by the shift of the divide just mentioned, now 



turns 



drainage svstem. Through this valley went the magnificent 



Bonneville 



most of the wrater of Marsh 



o 



ass 



,nnel 



dry in summer. The knobs of limestone 



^^^^^- feet high, wl 



o denS^mS ^^^^ ^^^^^ ^^^^^ ^ maximum ^\ddth of 600 feet for the river 



that drained Lake Bonneville just before it was drawTi 



down to the Provo stage. 

 ville first started to overflo^ 



(See PL XXXI.) When Lake Bonne- 



r ih(> Inkp Ipvel stood hip^her than the 



The 



tops of these limestone rocks, which had been buried beneath 

 mountain waste. Gravel deposited by the stream that drained 

 the lake at its highest stage is' found on top of the red butte 

 along the base of which the train passes. The Hunt ranch, men- 

 tioned by Gilbert in his description of this old outlet of Lake Bonue- 

 ville published in 1890, was at the foot of this rocky citadel 

 limestone crags bordermg Red Rock Pass are conspicuous features of 

 the landscape and were w^ell kno^ra to the early travelers in this 

 region and to the freighters who hauled supplies for the western 

 Montana mining camps over the road that follows the course now 

 taken by the railroad. The traveler going north from the pass may 

 notice that although the steep-sided valley is a quarter of a mile or 

 more wide, its stream is only a ri\nJet meandering tlirough the 

 meadow. (See PL XXXI.) The iU-matched stream and valley afford 

 evidence tliat a great river once flowed where now there is only a 

 brook. (See pp. 97-9S.) Here, then, at or just north of the red cliffs, 



r^T-^vflnw*.^ ifc Vim fin(] he^ixn the discharore which 



Bonneville 



inflow 



