34 EEPORT UNITED STATES GEOLOGICAL SURVEY. 



formations on the other side. Th^re are no outcrops of the rocks of the 

 summit sufficiently near to establish their superposition. 



In ascending the northern face of Washburn I passed up a gulch 

 that heads against the summit. At an elevation of 9,000 feet I encoun- 

 tered the trail that crosses the range by way of the first saddle north 

 of the peak. A short distance above this trail the steep cliffs of the 

 mountain begin. At the base of these, in the deeper gulches, there are 

 outcrops of a series of bedded basalts and hornblendic trachytes that 

 resemble those observed on the south side of the pass. The basalt is 

 mostly reddish and brownish, as if considerably decomposed. It is full 

 of cells which contain greenish grains, and often small concretions of 

 chalcedony. Eesting upon the upturned edges of these rocks are mas- 

 sive layers of horizontal breccias and conglomerates, composed greatly 

 of dark, compact fragments of varied sizes, that appear to be basalts. 

 There is also a large amount of finer ejectamenta. These rocks form 

 steep, crumbling, and almost inaccessible cliffs. They do not seem 

 to constitute the main body of the mountain, as the upturned horn- 

 blendic rocks project through them in places, but are filled into the 

 irregularities of the pre-existing slopes and have had unknown horizon- 

 tal extent. About the summit of the mountain we have a series of 

 hornblendic trachyte, conglomerates, mixed conglomerates, and com- 

 pact hornblendic rocks, that have great diversity of dip and strike. 

 They appear to be the stratified ejectementa formed about the cones of 

 ancient volcanoes. There are occasionally beds of basalt interbedded 

 Avith the hornblendic rocks, but in no case are the rhyolites observed. 

 The eastern si)ur of the range, which extends down to and overlooks 

 the canon of the Yellowstone, is also composed of the same series of 

 rocks that constitute the peak, while the flanks and lower slopes show 

 great deposits of the coarse conglomerates and breccias. 



I was very desirous of getting a complete panoramic view from the 

 summit of Mount Washburn, and spent all the time at my disposal in 

 sketching, so that the geology was neglected. Ail visitors to this region 

 agree in pronouncing the view from this point unequaled, and I may, 

 with the knowledge of experience, add that it is one which is unusually 

 ditficult to place upon paper. The broad expanses of the great plateau, 

 with its lakes, canons, and poorly defined forest-hidden drainage, is an 

 almost unintelligible maze which has no strong lines to tempt the pen- 

 cil. The distant ranges of the south and west, and the very compli- 

 cated tangle of mountains to the north, consume hours in their analysis, 

 and days ought to be allowed for theu' proper delineation. This is the 

 point from which the great problems of the Park should be studied. 

 No other point gives such a comprehensive view of the extraordinary 

 formations of the volcanic Tertiary i^riod. 



There are still a number of points tliat must be examined before all 

 the difficulties can be overcome. The most important are the upper 

 part of the valley of Tower Creek and the canon of the Yellowstone 

 beneath the east base of Mount Washburn. The latter point I was es- 

 peciaFy desirous of visiting, as the section is cut to such a depth below 

 the plateau level that the relation of the plateau rhyolites to the rocks 

 which constitute the core of the mountain will in all probability be 

 shown. While in the region, however, I did not realize fully that this 

 relation would be so hard to establish, or an extra day might have been 

 spent in investigation. 



The triangular spur that extends down between Tower Greek and the 

 caiion is formed in the lower flatfish part of the rhyolitic rocks. Ex- 

 tending down upon the fiat portion from the summit of Mount Wash- 



