97 



1869.] -^ ' [Hayden. 



and other metamorphic rocks, and inclining from the flanks may be seen 

 the viptvirned edges of the Potsdam sandstone, Carboniferous limestones, 

 brick red sands and sandstones. Triassic, Jurassic marls, Cretaceous 

 and Tertiary rocks, all dipping at various angles, but in such a way as to 

 be easily accessible to the student. 



The Laramie range is equally systematic in its plan of development 

 but rather anore complicated, and the results of erosive action are much 

 more strongly shown and the superficial deposits or drift in many places 

 conceal the underlying rocks. Like the Black Hills the Lamarie range 

 does not give rise to any important streams of water. Myriads of little 

 streams originate in or near the dividing ridge and cut their channels 

 down the slopes and flow into the North or South forks of the Platte. 



The main branch of the North Platte rises in the range of mountain 

 which forms the north side of the Middle Park, very near Long's Peak. 

 It takes a course a little west of north, flows through the middle of the 

 north park, cutting its Avay through immense canons between the North 

 Park and the Laramie plains. It then continues \ nearly a north course 

 through tertiary as well as cretaceous rocks to its junction with the 

 Sweet Water, when it bends around to the eastward so that near the Red 

 Buttes its course is nearly south-east until it reaches the main Platte 

 near Long. 101°. 



The Sweet "Water, which is the principal branch of the North Platte, 

 rises in the southern end of the Wind river mountains, and flows nearly 

 east and iinites with the North Platte near Independence. These 

 streams flow through nearly every variety of geological formations 

 which occur in the West. From the junction of the Sweet Water to 

 Red Buttes, it flows through granite, carboniferous limestone, red beds, 

 Jurassic marls, and White river tertiary beds. From the Red Buttes, 

 through lignite-tertiary to a point about 100 miles north-west of Fort 

 Laramie. There the White river tertiary beds overlap the lignite-tertiary, 

 and then contiu.ue to the forks of the Platte. 



The Medicine Bow and the two Laramies are important branches 

 of the North Platte, and take their rise in the lofty snow capped moun- 

 tains on the south side of the Laramie plains. The region north of the 

 North Platte is mostly a vast sage plain and but few small branches flow 

 in from that direction, but a multitude of small streams cut deep chan- 

 nels through the sides of the Laramie range and flow into the North 

 Platte. 



From Red Buttes to Fort Lamarie, a distance of 150 miles, many 

 beautiful little streams rise in the Laramie and pour a good volume of 

 water into the Platte. These creeks occur every few miles, and in their 

 passage from the mountain they have not only worn a deep channel in 

 the steei) side of the mountain, sometimes 1000 feet or ]nore in depth, 

 but they have also scooped out a wide deep valley which affords the best 

 of pasture, ground for stock in summer and warm sheltered places in 

 winter. 



The main branch of the South Platte rises in the range of moun- 



