GANNETT.] TOPOGRAPHY YELLOWSTONE RIVER. 475 



and marshy; the forests which are almost omnipresent in the Park are 

 here wanting, the broad valley being open and almost entirely devoid 

 of timber. At its mouth the swamps develop at times of high water 

 into a small lake or lagoon. , Between the lower course of this stream 

 and the head of the Yellowstone proper, a low ridge runs out from the 

 high hills to the northward to the lake. 



Besides the streams above mentioned, the lake receives no large afflu- 

 ents, though a number of small streams empty into it on the west and 

 south. Bridge Creek, so named from a natural bridge which spans it, 

 is a small stream which comes in from the west, some four miles south 

 of the outlet. Besides this a stream about the same size comes in about 

 a mile farther north. On the northern shore of the west arm a good- 

 sized creek comes in, and on the western shore the lake receives four 

 or five small streams. A small creek comes into the head of Flat 

 Mountain arm, and the south arm also receives several small streams. 

 The southeast arm receives, besides the Upper Yellowstone and Elk 

 Trail Creek, a small stream which flows along the west edge of the 

 valley of the Upper Yellowstone, draining the hills on the western side 

 for a distance of 6 or 7 miles from the lake; also a second stream from 

 these hills, which has its course west of the latter. 



THE YELLOWSTONE EIVEE. 



This river, the largest and most important branch of the Missouri, is- 

 sues from the lake at its northern end, and for 105 mUes holds a generally 

 northern course. At the mouth of Shields' River, near the site of the 

 old Crow Agency, it turns east, and after holding this course for several 

 hundred miles, it again turns to the northeast and continues in this 

 direction to its junction with the Missouri at Fort Union. 



From its point of exit from the lake nearly down to the Upper Falls, 

 the river is broad and sluggish, full of aquatic plants, and frequented 

 by large flocks of ducks, geese, and other aquatic birds. The gentle, 

 easy current is broken only in a few places by slight rapids which afford 

 easy and safe fords. The immediate valley varies much in width, but 

 is for the most part narrow. On the right (east) the country rises quite 

 rapidly at first, to a mass of flat-topped hills, in which head Sour 

 Creek, a branch of the Yellowstone, and several branches of Pelican 

 Creek. On the left the topography is more decided. A hea\'y, broad, 

 l)lateau-like ridge, known as Elephant's Back, abuts against the river 

 just below its exit from the lake. This ridge at first trends w^estward 

 for 6 or 7 miles, with an elevation of 8,800 feet, separating the drainage 

 of the lake from that of the river. Then it gradually sweeps around to 

 the north, and becomes the watershed between the East Fork of the Fire- 

 hole and Alum Creek, an important branch of the Yellowstone. This 

 ridge finally fades out in the high plateau region about the heads of the 

 latter stream and Gibbon Eiver, after sending a long spur down to the 

 Yellowstone Eiver, forming the northern watershed of Alum Creek. The 

 space inclosed by the semicircular ridge just described and the river, 

 drained by Alum Creek and other smaller branches of the Yellowstone, 

 is elevated but little above the level of the lake, and was formerly 

 occupied by it. It is an oasis of open countrj^, covered with grasses and 

 artemesia, amid a wilderness of forest. 



At the head of Alum Creek, on the summit of the divide, is a large 

 collection of hot sulphur springs, the waters of which have collected 

 at the foot of the springs into a i)ond, which feeds the creek. Another 

 extensive group of si)riugs occurs on a small branch of this creek, at 



