168 GEOLOGICAL SURVEY OF THE TEEEITORIES. 



of tlie valley like some monument, the surrounding rock having been 

 washed away. On June 16 we crossed Bear Eiver and found immedi- 

 ately a change in the rocks. Instead of limestone we came across green- 

 stone, among which I obtained specimens of aphanite and melaphyre, 

 the latter amygdaloidal in places. The specific gravity of some of these 

 specimens is as follows : three specimens of dark-green aphanite, 2.5 ; 

 and two specimens of melaphyre, 3.1. Continuing for about five miles, 

 they are intercepted by quartzites containing a small percentage of 

 lime. 



About three miles above the town of Oxford I found some men mining 

 for silver. W. J. Cooper, of Oxford, is the owner of the lode, which is 7 

 feet wide, and dips west at an angle of about 40°. The strike is north 

 and south. The wall-rock on either side is greenstone. The gangue 

 of the lode is composed of quartz, with calcite and feldspar. Some good 

 crystals of calcite were seen, and also brown spar, (rhomb spar.) The 

 ore is principally chloride, reddish and greenish. A shaft has been 

 commenced, but has reached only the depth of 30 feet. 



Six miles above Oxford we entered Marsh Creek, or Eound Yalley, 

 passing from Utah into Idaho Territory. The entrance to this valley is 

 between two high huttes, one consisting of a ferruginous sandstone of 

 a bright-red color on its weathered surfaces, the other composed of a 

 bluish siliceous limestone. Passing through this natural gateway, we 

 were in an old lake basin, the rocks being modern Pliocene sandstones 

 of a white color, all containing some lime. The road soon ascended to 

 the top of a terrace of drift formation, covered with a sparse growth of 

 sage-brush. Leaving this valley the following day, June 18th, we en- 

 tered the valley of the Port Neuf Eiver. Just before entering the valley 

 we passed over a floor-like layer of dark basaltic rock. We followed 

 the river on its right bank. All along the left bank there is a layer of 

 basaltic rock, its hexagonal columnar form reminding one of the Giant's 

 Causeway. The formation over which our road led us was drift, while 

 the hills on our right presented alternations of limestones and quartzites 

 succeeding each other at short intervals. There seems to have been 

 some point higher up the valley from which the molten mass flowed 

 during the Tertiary x3eriod, for the formation on which it rests is Tertiary. 



In crevices in the rock in many places I obtained specimens of obsi- 

 dian. As we neared the mouth of the valley it became wider and wider, 

 and the mountains receded until they spread out into the Snake Eiver 

 Valley. 



Emerging into the valley we turned to the right and crossed the bills 

 to Fort Hall, a post that has only recently been established, in Idaho 

 Territory. We arrived there on the 21st of June. The following day 

 I made a visit to some warm springs in Lincoln Valley, about three 

 miles southeast of the fort. I found five springs situated at the head of 

 a depression in the valley, whose direction was east and west. They 

 gush forth from the foot of the hills, the bases of which are limestones. 

 In spring No. 1, which was the warmest, the thermometer recorded 

 87° F. It was about a foot in diameter, nearly circular, and 9 inches in 

 depth. The next two, No. 2 and No. 3, to the southeast of No. 1, 

 had equal temperatures, each being 77° F. Only one of these was 

 defined as a spring, being 3 feet in diameter and 2 feet in depth. In the 

 other the water merely poured forth from the rocks in a narrow stream. 

 No. 4 and No. 5 were of the same character as the last mentioned, and 

 readied each the temperature of 09° F. They were still more to the 

 east. The water in all was beautifully clear, due to the presence of car- 

 bonate of lime. The specific gravity of the water was 1003, and con- 



