this specimen of the cunning skill of nature. On the northeast side of the hills, extending from their summits, are large numbers of the steam-vents, with the sulphur linings and deposits of the sulphur over the surface. These hills are entirely due to the old hot springs, and are from 50 to 150 feet in height. The rock is mostly compact silica, but there is almost every degree of purity, from a kind of basalt to the snow-white silica. Some of it is a real conglomerate, with a fine silicious cement inclosing pebbles of white silica, like those seen around the craters of some geysers. Although at the present time there are no true geysers in this group, the evidence is clear that these were, in former times, very powerful ones, that have built up mountains of silica by their overflow. The steam-vents on the side and at the foot of these hills represent the dying stages of this once most active group. Quite a dense growth of pines now covers these hills, which rise up in the midst of the plains, and from their peculiar white appearance are conspicuous for a great distance. At one point there is a steam-vent so hot that it is difficult to approach it, emitting a strong sulphurous smell, and within two feet of it there is a larger spring, boiling like a caldron. So far as I can determine, there is no underground connection of any of the springs with each other. Sometimes the rims of these craters, as well as the inner sides of their basins, have a beautiful papulose surface, the silica just covered with a thin veil of delicate creamy sulphur. At this locality are some very remarkable turbid and mud springs. One of them has a basin twenty feet in diameter, nearly circular in form, and the contents have almost the consistency of thick hasty-pudding. Indeed, there is no comparison that can bring before the mind a clearer picture of such a mud volcano than a huge caldron of thick mush. The surface is covered all over with puffs of mud, which, as they burst, give off a thudlike noise, and then fine mud-waves recede from the centre of the puffs in the most perfect rings to the side. Although there are hundreds of these mudpots, yet it is very rare that the mud is in just the condition to admit of these peculiar rings. The thud is, of course, produced by the escape of the sulphureted hydrogen gas through the mud. The mud is so fine as to have no visible or sensible grain, and is very strongly impregnated with alum. For three hundred yards in length and twenty-five yards in width, the valley of this little branch of Alum Creek is perforated with these mud-vents of all sizes, and the contents are of all degrees of consistency, from merely turbid water to a thick mortar. The entire surface is perfectly bare of vegetation, and hot, yielding in many places to a slight pressure. I attempted to walk about among these simmering vents, and broke through to my knees, covering myself with the hot mud, to my great pain and subsequent inconvenience. One of the