98 United States Survey of the Territories. [February, 
Sandy, a large eastern branch of the Green, to the foot of the | 
ind River mountains; thence crossing the head of the basin, 
fording the large and rapidly rising streams which make up the 
New Fork of the Green, they reached the main Green, and trav- 
eled down its western bank, going in to Granger, Wyoming, on 
the Union Pacific Railroad, for supplies on June 23d. 
‘ The party left the field at Ogden, Utah, on September 3oth, 
having been in the field just four months. The area surveyed 
was between 12,000 and 13,000 square miles; 347 stations and 
locations were made, 53 of the stations being important ones, 
were marked with stone monuments for future reference. 
The geological work of Dr. A. C. Peale in the Green River 
district connected directly with the western edge of the Sweet- 
water district. With the exception of a small area of granite 
along the south-western side of the Wind River mountains, and 
some basaltic flows in the north-western portion of the district, 
the rocks are sedimentary, including the rocks from the Silurian 
to very late Tertiary age. 
The first month of the season was occupied mainly with the 
survey of the Green River basin. 
The next area taken up was that lying between Green river 
and the Bear, with a strip along the northern edge of the district, 
reaching westward beyond Fort Hall. 
The Blackfoot, Portneuf, and Bear all have basalt in their val- 
leys. On the Portneuf it extends almost to the Snake River 
plain, appearing as a narrow belt. Its surface slopes, but not so 
much as the present bed of the stream. In some places the vol- 
canic rock appears to have pushed the river to the western side — 
of the valley. The lower valley of the Portneuf is interesting — 
from the fact that it is the probable ancient outlet cf the great 
lake that once filled the Salt Lake basin. At the head of Marsh À 
creek, which occupies the valley, continuing directly south from a 
that of the Lower Portneuf, is the lowest pass between the Great — 
- Basin and the drainage of the Columbia. In fact, so low and flat — 
is it that a marsh directly connects the two streams, one flowing — 
to the Bear and the other to the Portneuf and Snake rivers. . 
The bend of Bear river at Soda springs is one of the most | 
remarkable features of the whole district. Rising in the Uintah 1 
_ mountains, Bear river flows northward for over two hundred — 
miles, and at Soda springs bends abruptly and flows southward 
