474 REPOET UNITED STATES GEOLOGICAL SUKVEY. 



that in the spring time, when the Yellowstone range and all the high 

 country thereabouts is disgorging its winter accumulations of snow, 

 this lake does not have a broad water connection with the larger lake; 

 in other words, it may for a short time be the fore finger. 



Flat Mountain makes a most decided break in the uniformity of the 

 slope of the shore-line. The mountain rises 500 feet above the lake, 

 and all this height is represented by a precipitous, rocky slope from the 

 summit to the margin of the water. On the east, however. Flat Mount- 

 ain slopes uniformly and gently down to the shore of the south arm. 

 Flat Mountain arm has a length of 3 miles, with a mean width of 

 less than half a mile. The corresponding dimensions of the south arm 

 are 8 miles and 2^. Between the south and southeast arms is a long, 

 narrow projection known as the Promontory. From a low isthmus, but 

 little above the lake near the head of these deep bays, it rises to a height 

 of 1,000 feet above the lake, at the same time broadening from 1 mile 

 to 2. It ends abruptly in a rocky precipice facing to the north. 



The head of the southeast arm is in part limited by a steep wall, the 

 same which borders the valley of the Upper Yellowstone on the west, 

 and in part by this marshy valley. The border of the lake is here very 

 ill defined, the marsh extending inland for at least 2 miles to the east- 

 ward from the clear water of the lake. 



Proceeding down the eastern shore of the lake we find a succession of 

 valleys, opening out on the shore and mountain spurs, terminating ab- 

 ruptly at the water's edge. 



Beaverdam Creek is a large mountain stream, occupying the first of 

 these valleys, and entering the lake very near the head of the south- 

 east arm. Three miles above its mouth, just within the mountains, it 

 receives a large branch from the right, known as Eocky Creek. 



North of this stream, a heavy mountain spur, headed by the fine 

 peaks Langford, Doane, and Stevenson, and bearing many minor sum- 

 mits, reaches from the crest of the Yellowstone range to the shore of 

 the lake. Then follows a broad valley, drained mainly by Milky Creek, 

 north of which is the spur known as the Signal Hills. Then succeeds 

 a third valley, in which are three creeks of considerable size, all head- 

 ing in the mountains, besides several smaller ones heading in springs 

 and swamps in the dense forest. There follows then a third spur from 

 the mountains, terminating on the border of the lake with a round- 

 topped hill, which I have named Lake Butte. 



Next we come to the valley of Turbid Creek, on whose lower course, 

 near the lake shore, is quite a large collection of hot springs. This 

 stream heads in the mountains about Mount Chittenden, and flows 

 through Turbid Lake, a small body of water v/hich is rendered milky 

 from the numerous sulphur springs which dot its shore. 



Beyond the mouth of Turbid Creek the lake shore runs out in a 

 bluff point, named from a spring on the extreme point. Steamboat Point. 

 Passing this point we see the shore retreating in smooth, graceful curves, 

 making Mary's Bay. A mile east of this the lake receives its largest 

 afSuent, next to the Upper Yellowstone, in the form of Pelican Creek. 

 This stream heads among high timbered hills to the northeast, against 

 the East Fork of the Yellowstone. Comparatively little of its water 

 comes from the high mountains of the Yellowstone range, its drainage 

 area comprising little more than the foot-hills. It heads in three large 

 branches, two coming from the north and the third from the east, the 

 three uniting within a hundred yards of one another. A fourth large 

 branch. Lake Fork, coming from the north, joins the stream about a 

 mile below the forks. The lower course of the stream is very sluggish 



