352 GEOLOGICAL EXCURSION TO THE KOCKY MOUNTAINS. 



geyser basins, although seldom on so extensive a scale. Encircling 

 the Meadows, at the base ol* the hills, are a number of local (tenters of 

 thermal activity from which large quantities of hot siliceous waters 

 drain into the basin. 



A short distance off the road, on the east side of the Gibbon meadows, 

 and easily reached by wagon, lie the Artists' Paint Pots. They con- 

 sist of a number of small springs of hot water reaching the surface 

 through brilliantly colored clays. These excessively tine clays are tin; 

 products of rock decomposition by slow and long-continued processes, 

 and the mineral matter held in suspension is the cause of the varied 

 colors in the different pots. In the white pots the coloring matter has 

 been leached out, leaving a pure white kaolin impalpable to the touch. 

 The deep indian-red pots carry finely comminuted iron oxide, which, 

 under favorable conditions, collects in certain springs. The hillsides 

 are brilliant with decomposition products derived from rhyolite in vari- 

 ous stages of alteration. 



From the Meadows the road follows the Gibbon river through Gib- 

 bon canyon, the imposing Avails of which rise in sheer cliffs 1,000 feet 

 above the stream. It is a grand exposure of rhyolite walls, exhibiting 

 remarkable forms of rock erosion. The river makes a rapid descent, and 

 at Gibbon falls, so i'wt high, flows over a line example of obsidian worn 

 smooth by the rushing waters. Along the, base of the canyon walls, in 

 close proximity to the river, steam vents and hot springs mark the 

 course of thermal action. Beryl spring, on the west bank near the 

 northern end of the canyon, is worthy of attention from the exquisite 

 coloring of the constantly agitated water which has built up a delicate 

 rim of sinter encircling the pool. 



At Canyon creek the road leaves the Gibbon river and follows the 

 ridge of rhyolite on the east side. A short distance below here, the Gib- 

 bon and Firehole unite to form the .Madison, the latter stream beingone 

 of the main tributaries of the Missouri. From a commanding point on 

 the road a distant view may be had of the Madison canyon, extending 

 in an east and west line directly across the plateau. The precipitous 

 walls on the north side of the canyon rise for L,500 feet above the river. 

 Madison plateau stretches as tar as the eye can reach, without a break, 

 beyond which both rhyolite and basaltic lavas extend westward over 

 the great plains of Snake river. 



From the same point of view, on a clear day, Mount Nayden, winch 

 is not only the culminating point in the Teton range, but the highest 

 peak in this part of the Rocky Mountains, may be distinctly seen (JO 

 miles to the south. Descending a steep ridge over rhyolitic gravels 

 the road comes out on the Firehole river, and after following the bank 

 for two or three miles enters the Lower Geyser basin, 



