8 FLORA OF THE YELLOWSTONE NATIONAL PARK. 



it for a few miles on the east, the adjacent slopes are onh^ par- 

 tially forest-covered. Above Cache Creek the East Fork runs 

 in a well-timbered caiion. The short streams from the Mirror 

 Lake Plateau head in beautiful little grassy parks often of a 

 hundred acres in extent. The valley's of the main sti'eam and 

 its principal tributaries, Slough and Soda Butte Creeks, are low 

 within the boundaries of the Park, ranging in altitude from 

 6800-7500 feet, but the immediate slopes in the northeastern 

 portion rise precipitously to ragged and bare peaks and ridges 

 10,000-10,800 feet in altitude. North of Slough Creek is an area 

 of high, sparsely-timbered plateau. On the Gardiner River, four 

 miles south of the northern boundary, is located the terraced 

 group of the Mammoth Hot Springs. About here, and nearly 

 around Swan Lake and Indian Creek, are large open grass- 

 covered areas. The slopes of the Gallatin Range are well clothed 

 with forest up to the timber line, which in the Park varies from 

 9400-9700 feet. The tops of the long ridges slopiug westward 

 are in some cases bare. From the Gallatin Range southward 

 along the western border of the Park extends the Madison 

 Plateau. Its southern limit is the Pitchstone Plateau (8700 ft.), 

 at the base of which on the north and east lie Shoshone and Lewis 

 Lakes. The very flat top of the plateau is more than half covered 

 with grassy parks, but the sides are densely timbered. To the 

 westward it slopes down to the low o^jen swampj^ area of the 

 Falls River Basin in the extreme southwest corner of the Park. 

 On the Madison Plateau, as elsewhere throughout the region, 

 are scattered small, open parks and meadows, but taken as a 

 whole, it is heavil}^ timbered, and is cut by numerous dr}^ rocky 

 caiions. It has an average altitude of about 8500 feet, and from 

 Shoshone Lake it is traversed in a northwesterly direction by 

 the continental divide. At the foot of the abrupt eastern slope 

 of this plateau lie the Upper and Lower Geyser Basins in a 

 wilderness of forest. The Fire-hole River draining these areas, 

 flowing northward, meets the Gibbon River from the northeast, 

 the latter draining the Norris Ge3^ser Basin, and heading on the 

 plateau northwest of the Washburne Range. These two streams 

 uniting form the Madison, which, in its course westward, has 

 cut a gorge nearly 2000 feet deep through the Madison Plateau. 



