3f)8 GEOLOGICAL EXCURSION TO THE ROCKY MOUNTAINS. 



Of the largest bill and close to the roadside lies Chrome spring, a 

 constantly boiling pool of the most delicate sulphur-yellow tint. Two 

 miles beyond Crater hills. Alum creek is again crossed just before it 

 empties into the Yellowstone, and a short distance northward the road 

 leaves Ilayden valley and follows the west bank of the Yellowstone 

 tor three miles along picturesque rapids inclosed between walls of 

 rhyolite. 



YELLOWSTONE CANYON AND FALLS. 



The Grand Canyon hotel, on the west side of the river, is situated on a 

 glacial bench about one-quarter of a mile back from the canyon and the 

 Lower falls of the Yellowstone. The Yellowstone canyon trends to the 

 north and northeast, curving around an east spur of Mount VVash- 

 burne, its length from the upper falls to Junction Butte being about 18 

 miles. At the Lower falls the walls of the canyon measure 700 feet, 

 and live miles beyond, 1,000 feet, the width of the canyon varying from 

 one-quarter to three-quarters of a mile. Rhyolite forms the canyon 

 walls which are more or less decomposed by hydrothermal action, their 

 color being due to various conditions of oxidation of the iron. Where 

 the greatest decomposition has taken place the iron has been leached 

 out, leaving a white kaolin-like material. A few hot springs may be 

 seen steaming in different parts of the canyon, showing that thermal 

 action is not yet extinct. The gaily colored walls extend about li venules 

 beyond the Lower falls, but below this the rock is dark colored, still 

 fresh and unaltered. The Lower falls are 310 feet in height, and may 

 be seen to the greatest advantage from inspiration Point, one of the 

 cliffs which overlook the canyon below the Falls. Lookout Point fur- 

 nishes another excellent point of view. 



In following the bridle path along the brink of the canyon one should 

 see the massive glacial granite boulder (Fig. L5), near where the side 

 path leaves for Inspiration Point. 



One-half mile above the Lower falls are the Upper falls, 110 feet in 

 height. Here the rhyolite is undecomposed, mostly glassy, and more 

 or less spherulitic, and is well exposed on Cascade creek. 



From the hotel an expedition may be made to the summit of Mount 

 Washburne which on a clear day commands a view over the Park and 

 the Absaroka range. 



YELLOWSTONE FALLS TO MAMMOTH HOT SPRINGS. 



Leaving the hotel at the Falls the road climbs up a steep ascent to 

 the top of Solfatara plateau, an extension northward of Central plateau, 

 which was crossed when going from the head of Xez Perce Creek to 

 Ilayden Valley. The thermal action seen on Solfatara plateau is in 

 every way similar to that observed at Highland springs, but is by no 



