The Obsidian Creek runs slowly through this valley. Obsidian Cliff is the next object of special interest which is witnessed. It is half a mile long and from 150 to 200 feet high. The southern end is formed of volcanic glass, or obsidian, as true a glass as any artificially produced. The roadway at its base is constructed across the talus, and is emphatically a glass road. Huge fragments of obsidian, black and shining, some of it streaked with white seams, line the road. Small pieces are also plentiful. This flow of glass came from a high plateau to the east-northeast. Numerous vent pits, or apparent craters, have been discovered on this plateau. Mr. J. P. Iddings, of the Unites States Geological Survey, who has made a special study of Obsidian Cliff, contributes to the survey report for 1885-86 a paper that has in it much that is of interest to the unscientific mind. The Lower Geyser Basin is in some respects more pleasing than the Norris, although the desolation is perhaps even more apparent. People who have seen districts in which salt is made out of brine extracted from wells, state that the appearance in the Lower Geyser Basin is very similar to what is seen around manufacturing districts of that character. This basin is in the valley of the Firehole River, a strangely named stream, of a very beautiful character. In the basin itself the branches of the Firehole unite, and with the Gibbon River form one of the three sources of the Missouri, called the Madison, after the President of that name. The Fountain Geyser is the largest in the neighborhood, and is one of the best in the park. It is very regular in its eruptions, and seldom fails to perform on time for the benefit of the onlooker. It sends an immense volume of water into the air, and resembles a fountain very closely. Its basin is very interesting, and gives a good example of the singular deposits left by a geyser. When the fountain is busy throwing out its volumes of water, the appearance is very peculiar. Little notice is given of an eruption, which takes place suddenly, although at stated intervals. All at once the watcher is rewarded for his patience by having the stillness changed into activity of the most boisterous character. The water is hurled upwards in a mass of frothing, boiling and foaming crystals. The actual height varies, but frequently goes as far as thirty feet. In a moment the wall of water becomes compact, oblong and irregular. Crystal effects are produced, varying according to the time of day and the amount of light, but always delightful and peculiar.