IGO GEOLOGICAL SURVEY OF THE TERRITORIES. 



Itiv to the nppev f;ill of the Yollowstonc. The stream does not leap shorr over the 

 precipice iu one luibroken fall, but after a few feet of perpeiulicnlar desi'cut strikes 

 iijiou a sloping ledge of rock and is shot out at an angle of about 45°. The scene is the 

 more impressive from the fact that it bursts upon the view so unexpectedly, and with- 

 out the least warning, the noise of the fall being shut oif both by the iutervi-ning wall 

 of rock and the rapids, into which tbo river is broken below. Above the fall tbe river 

 runs with a smooth, slow current, no rapids breaking up its course until it reaches the 

 very brink of the precipice, over which it plunges into the narrow gorge below. 



Loaving Gibbon's Fork we find ourselves almost immediately in the 

 upper caiion of the Madison, which averages about half a mile in width 

 and is eight miles in length. The hills on either side rise from 1,200 to 

 1,500 feet above the river, those on the left side being almost vertical. 

 The valley is i^artially timbered, and the hills also, wherever the trees 

 can find a foot -hold. Near the lower end of the caiion there is a fine 

 exposure of columns high up on the right-hand side. The rock is mostly 

 a rough, puqdish trachyte, with sanitline crystals. Emerging from the 

 caiion we find ourselves in a wide valley, through which the east fork 

 of the Madison flows to join the main river. Both cut their channels in 

 serpentine manner through the modern beds, which are nmde up of 

 Pliocene sands, containing a considerable amount of obsidian, which 

 gives them a dark color. The valley is partially timbered, and must be 

 nearlj^ fifty miles in width. On the 22d we encamped near the junction 

 of the east for]c,jus't above the middle caiion, where we spent two days 

 waiting for Dr. Hayden to join us from a side-trip through Taghee 

 Pass to Henry's Lake. I made a trip up the valley of the east fork 

 and ascended one of the hills bordering it on the north. The view from 

 this point was one of the fiiirest that I have ever gazed upon. It seemed 

 to unite all the elements of beauty — hill, grassy plains, and winding 

 streams. Both forks of the Madison wind through the valley in a series 

 of graceful curves. The rocks were not well exposed on this hill, but as 

 far as I could judge the dip seems to be northeast at an angle of about 

 75° to 80°. Proceeding toward the river I came across limestones, the 

 upper layers of which 1 take to be Carboniferous, although I could find 

 no fossils to prove it. The lower layers are probably Silurian, and rest 

 on chlorite-schists, which pass into mica-schists and gneisses. The angle 

 of the dip of these limestones is still very great. At the head of the 

 valley of the east fork there is a range of mountains that ai)pear to be 

 volcanic, and is probably part of the same range that I noticed from 

 near the hot springs on Gardiner's Eiver, which I referred to iu a pre- 

 vious chapter. On one of the branches of the east fork 1 found ou 

 top of the modern beds layers of trachyte, which seem to have had 

 their origin in these mountains. 



On the 25th we moved camp down the river and camped in the midst 

 of the middle canon. In one of the gullies at the upper end of the 

 caiion I found grains of glauconite in a quartzite-rock. The western 

 side of the caiion seems to be composed entirely of metamorphic rocks, 

 while the eastern side has outcrops of Silurian and Carboniferous lime- 

 stones, which at the iti^per end incline northeast at a high angle. 



On the 2r>th I visited a small side canon on the eastern side of the 

 river, through which a small creek flows to join the Madison, 

 a short distance above camp. It was so narrow and rocky that we were 

 obliged to leave our horses .at the mouth. The first rocks we encoun- 

 tered were quartz-schists, followed by chlorite-schists, the strike seem- 

 ingly at right angles to the course of the stream, the dip being south- 

 west. The next rocks were very compact limestones, dipping under- 

 neath the chlorite-schists. The lines of junction could not be seen, but 

 they seemed to be conformable. The angle of inclination was about 00°. 



