GEOLOGICAL SURVEY OF THE TEREITORIES. 79 



As the water flowed over tlie broken groniitl it l3ecame muddy, and at 

 its entrance into the Gallatin looked like the water of a miuiug-gulcb, 

 A few days previously there was a terrific thunder-storm, accompanied 

 by strong wind. 



About twenty miles up the canon the granitic rocks .cease, and a re- 

 markable ridge of limestones extends across the river with a trend about 

 southeast and northwest. On the east side of the river the sharp ridges 

 rise up to a height of 1,500 to 2,000 feet, with an inclination of 50° south- 

 west. The sides as well as the summits of these ridges are remarkably 

 rugged and jagged. A little stream comes into the Gallatin from the 

 Sphynx, a high peak on the divide between the Gallatin and the Madi- 

 son. This stream has worn its rather wide grassy valley out of the soft 

 materials of the Jurassic beds, leaving the harder Carboniferous and 

 Silurian lying against the sides of the mountain-range like a huge wall, 

 extending from Cinnabar Mountain -northwest across the Gallatin and 

 Madison Elvers. The Gallatin Eiver cuts this ridge nearly at right 

 angles. In the bed of a little stream on the west side several of the 

 outcropping edges of the limestone-strata are seen which have been 

 worn down to the level of the valley. This group of sedimentary strata 

 forms the southwest portion of the anticlinal of which the group of lime- 

 stones described a short distance above the entrance of the caiion is the 

 northeast portion. We see, therefore, that all these rivers, the Madison, 

 Gallatin, and Yellowstone, have cut their channels directly through the 

 range. Just above this range the valley expands to a mile in width, 

 and the hills on either side are much broken and are so covered with the 

 sedimentary beds that the granitic rocks are seldom seen. In the bot- 

 tom is a group of springs flowing from beneath the limestones that are 

 full of rank, algous vegetation. The temperature of the water is re- 

 spectively 540, 5Q°, 55°, 540, 43°, 44°. These springs may once have 

 been very hot, like those about the sources of the Madison. Warm 

 springs are not uncommon at various points far down the valley of the 

 Yellowstone as low as the mouth of Big Horn. Eiver. The Silurian and 

 Carboniferous strata are the same as those noticed on the opposite side 

 of the range. Conforming to the Carboniferous limestones, so far as can 

 be detected by the eye, is a group of sandstones, arenaceous limestones, 

 clays, &c., which are undoubtedly of Jurassic age. High up on the range 

 on the east side of the Gallatin are patches of the Cretaceous and Coal 

 groups, as seen on the Yellowstone near Cinnabar Mountain. Above the 

 granitic portion of the caiion there is a marked depression on both sides of 

 the Gallatin, and small streams flow into the river over the softer Jnrassic 

 beds. These beds incline at so great an angle for a distance of only about 

 half a mile, when they abruptly become horizontal. In the elevation of 

 the mountain-range in which the granitic nucleus bursts through the sedi- 

 mentary mass, tipping off on either side the strata, the whole country 

 was elevated to a greater or less extent. The central or granitic mass 

 was raised up in the form of peaks from 9,500 to 10,500 leet above tide- 

 water, and the sedimentary beds were broken off and lie on the sides of 

 the granitic nucleus in a nearly vertical position ; while, a short distance 

 above them, the crust was not so much affected by the force, the same 

 beds, though they may have been elevated to a greater or less height in 

 mass, still retain their horizontal position nearly. So we find a group 

 of brown sandstones, conglomerates or pudding-stones, and quartzites 

 passing down into clays, sandstones, and arenaceous limestones. Some 

 of the limestone-strata are made up of an aggregate of shells which ap- 

 pear to be of the Jurassic age. We pass up the open valley of the 

 Gallatin a distance of about four miles, with high walls of Jurassic 



