194 Geological Survey of the Territories in 1872. 
at from 80 to 300 feet below the level of the latter. The forma- 
tion of the Thracian peninsula cut off the Black Sea from 
the Mediterranean, and it had to seek some outlet. Before this 
time the succession of local eruptions mentioned above had 
line. The only thing which makes the problem a difficult one 
Seana at the northern 
extremity of the straits. The channel of the Bosphorus passes 
through this a distance of more than four miles. How was 
this part of the channel formed? If we knew the age to which 
this domain belongs, we might answer this question. As it is, 
Art. XXIL—Ezplorations of 1872: U. S. Geological Survey of 
the Territories, under Dr. F. V. Hayden ; Snake River Division.* 
the main front ridge of the Wahsatch range consisting of an 
face by subordinate folds, which would be apt to confuse one 
who passed hastily over them. Except where portions of 
1. Gray and drab limestones, largely siliceous 3000 ft. Carboniferous: 
2. inous quartzites to 2500 “ Devonian? 
; i gray magnesian limestones, part pebbly 1900 to 2000 “ ) Upper? and 
4, Gray calcareous shales “1000 to 1200 “ t Lower Silurian. 
5. White and ferruginous quartzite, base pebbly 1500 “ Potsdam. 
From discoveries made farther north, it became evident that 
at least the lower part of the limestones of No. 3, together with 
* This notice has been prepared for this place by Prof. Frank H. Bradley, 
Geologist of the Expedition in the Snake River Division. 
