GEOLOGICAL SURVEY OF THE TERRITORIES. 



93 



more than ten gallons an liour pass out of it in the little channel that 

 leads from it. On either side of the cavern, where the steam strikes, 

 there is a thin coating of vegetation of a deep, vivid green. In the 

 vicinity of these springs, various kinds of grasses, rushes, mosses, and 

 other i)lants grow with a surprising luxuriance. Over the '"grotto" 

 there is a thickness of about 30 feet of stratified clay, with a fine texture. 

 Located higher up on the side of the hili, not far from the grotto, is the 

 most remarkable mud-spring we have ever seen in the West. The rim 

 of the basin is formed by the loose mud or clay thown out of the orifice. 

 It is about 40 feet in diameter at the top, but tapering down to half the 

 size, and is about 30 feet deep. It F i g . 2 9 . 



may not improperly be called the 

 Giant's Caldron. (Fig. 29.) It does 

 not boil with an impulse like most of 

 the mud-springs, but with a con- 

 stant roar which shakes the ground 

 for a considerable distance, and may 

 be heard for half a mile. A dense 

 column of steam is ever rising, fill- 

 ing the crater, but now and then a 

 passing breeze will remove it for a 

 moment, revealing one of the most ^, 

 terrific sights one could well imagine. 

 The contents are composed of thin ' 

 mud in a continual state of the most 

 violent agitation, like an immense 

 caldron of mush submitted to a con- 

 stant, uniform, but most intense heat. 

 That it must have had its spasms of 

 ejection is plain from the mud on the trees for a radius of a hundred 

 feet or more in every direction from the crater, and it would seem that 

 the mud might have been thrown np to the height of 75 or 100 feet. 

 This ejection of the mud must have occurred within a year or two, from 

 the fact that small pines near the crater are still green, though covered 

 with mud. Small pines 4 inches in diameter and 20 to 30 feet in height 

 have been permitted to grow within 10 and 20 feet of the rim, and, 

 therefore, the throwing of the mud to any distance from the crater must 

 occur very seldom. A few of the trees near the crater, w^hich were 

 covered with the mud, were killed by the heat, but others that are lit- 

 erally festooned with it, have only the small branches and leaves de- 

 stroyed. All the indications around this most remarkable caldron 

 show that it has broken out at a recent period ; that the caving in of 

 the sides so choked up the orifice that it relieved itself, hurling the 

 muddy contents over the living pines in the vicinity. The steam which 

 arises from this caldron may be seen for many miles in every direction. 

 There are a large number of springs all around, some boiling and others 

 quiet, some of which are of great size and quite worthy of attention, 

 but we' will describe only one more in this group. At the south side 

 there is a large basin, 200 by 300 feet, containing within the rim three 

 boiling springs. The two smaller ones on the south side of the rim 

 are separated from each other by a partition of abont 4 feet, and 

 are mud-springs, and boil u^) in the centers at this time or 8 inches. 

 Their basins are 10 and 20 feet in diameter. The third basin is the 

 largest, with a rim 30 by 50 feet, and is a true geyser ; when not in oper- 

 ation, the fine mud settles to the bottom and the water bei;omes clear. 

 This is constantly but moderately agitated, not sufficiently to stir up the 



GIANT S CALDRON, YELLOWSTONE RIVER. 



