LA BONTE RIVER — LA PRELE. 69 



stones, the same as those forming the crest of the ridge, and which 

 seemed to be the result of some force from beneath. The rocks 

 were so broken that no indication could be obtained of their strati- 

 fication. About one mile from La Bont^, the ridge on the left be- 

 came lower, and the dip of the rocks was evidently less. They 

 are composed of gray and white sandstone, clayey shales and clay, 

 from which some few fossils were collected. 



The formation over which we have been travelling to-day seems 

 to have been the result of the upheaving of the underlying strata, 

 and the direction of the force would appear to have been from 

 N. N. W. to S. S. E. It is not improbable that the trap and red 

 sandstone seen on the Platte about twelve miles above Fort Lara- 

 mie is the result of the same action, as that point would be in 

 about the direction in which such a line would strike the river. 

 The formation of the high ridges seen on the north side of the 

 Platte is undoubtedly owing to the same cause. The strata ob- 

 served to the right of the road before leaving the valley of the 

 La Bont^ were not conformable with those on the ridge, but had 

 a slight dip to the south-east. They consisted of clay and coarse 

 sandstone, and were analogous to those passed in the early part of 

 the day. There can be but little doubt that they have been de- 

 posited since the elevation of the ridge. 



Tuesday, July 24. — Ther. at sunrise, 49°. Temperature of the 

 spring the same. The road to-day passes over a rolling country, 

 being spurs of the Black Hills. We crossed the dry beds of several 

 small streams, skirted, in some instances, with willows, box-elder, 

 wild-cherry bushes, and occasionally with some large cotton-woods, 

 until we reached the river La Prele. At this spot the mules were 

 watered only, it being impossible to procure a blade of grass for 

 them all the day. Consequently, we were obliged to continue on 

 some four miles farther, until we reached the Platte, where we en- 

 camped in a pretty little grove of large cotton-woods, with but a 

 very scanty supply of grass. The artemisia seemed, to-day, to have 

 taken complete possession of the country ; and what little grass 

 once grew along the road has been literally burned out by the 

 passing emigrants. 



Upon arriving at the encamping ground, it was found, to our 

 great grief, that the barometer was broken. It had been firmly 

 fixed in an upright position, in the small spring-carriage, and care- 

 fully strapped to one of the stancheons ; but in coming down a 

 steep and rough ravine, it must have received a jar that snapped 



