GEOLOGICAL SURVEY OF THE TERRITORIES. 150 



CHAPTER Y. 



MADISOX VALLEY GEYSER-BASINS TO GALLATIX CITY, 



CHERRY CREEK MINES. 



Late iu the afternoon of August 20 we left the upper geyser-basiu 

 and proceeded to the lower, where we found Captain Stevenson's party 

 still encamped, Dr. Hayden having moved down the river. As it was 

 too late to foHow we waited until morning, when we started at daylight, 

 and joined the party just as they were about leaving camp on Gibbon's 

 Fork, a branch of the Madison, which joins it five miles below the 

 iunct ion of the east fork. The rocks between these two points are all 

 volcanic, trachyte-porphyries, resembling those we saw at the Grand 

 Cation of the Yellowstone. In one place I noticed the same round 

 geodic masses that I saw there, only liere they were much larger, 

 measuring as much as G inches iu diameter. 



Some of the trachytes are laminated, and seem to have been twisted 

 after having been deposited. On the left bank of the river there is a 

 high bluff-wall extending from below the east fork of the Fire Hole to 

 Gibbon's Fork of the Madison. About three miles alcove Gibbon's Fork, 

 in a gloomy gorge, is a very fine fall of about 40 feet iu height. On 

 reaching Gibbon's Fork I followed it up a few miles, to visit some bot 

 springs which Dr. Hayden reported to me. These springs are on the 

 right side of the river, in a valley about a mile in length and half a mile 

 in width. The springs are situated at the foot of a ridge rising about 

 1,000 feet above them. This ridge is cut by numerous ravines, the 

 divides between being rounded, thus giving to the top of the ridge the 

 appearance of a range of conical peaks. On the op[)osite side of the 

 Madison there are vertical walls of trachyte 1,500 feet in height. The 

 springs are seven in number. The largest one is in reality a small lake, 

 iu which the water has a temperature of 140° F. It is supplied 

 by two small streams, which have their origin each in two small 

 springs a few feet above. One of these is a pulsating spring, the water 

 rising about a foot above the basin. The temperatures are 135° F. 

 to 15(io F. A short distance to the east of this lake there are 

 two other spriugs, having respectively the temperatures of 100^ 

 F. and 122° F. The temperature of the air during these observa- 

 tions was 01° F. About the center of the valley there is an old 

 spring-basin composed of three terraces, rising about 18 inches one 

 above the other, in much the same manner as the terraces of the 

 Gardiner's River springs. Here the springs are extinct and the 

 terraces are overgrown with grass. There is considerable lime, and a 

 coating of iron lines all the channels of the streams, carrying away 

 the overllow of these springs. They have all doubtless passed their 

 most active period. 



Messrs. Jackson and Coulter, with some other members of the survey 

 who followed Gibbon's Fork some ten miles above its mouth, have given 

 me the following notes in regard to a fall which they discovered : 



About eight or nine miles above the month of Gibbon's Fork the valley gradually 

 narrows into a deep canou, the walls of rock rising with a steep slope on both sides 

 from near the water's edge, leaving scarcely room enough for a rough trail. After fol- 

 lowing this canon for about a mile, the slopes becoming steeper and the trail narrower, 

 the ri\er seems to issue from a perpendicular wall standing directly across the head 

 of the canon. On reaching this precipice, however, we (bund that the river makes a 

 sharp bend to the right, forming nearly a right angle with it.s former course, and just 

 at the bend makes a beautiful fall of nearly 100 feet in height. This fall is very simi- 



