VALLEY OF THE HAWILHAMOOK, AND THE GREAT COLORADO. 51 
30 to 45 degrees west, and the ranges appear much broken into ridges. It is most proba- 
ble that the range on the east of the stream is a prolongation of the range through which 
the Hawilhamook flows at the place called Striped Cañon. As the survey followed the valley of 
the river, the rocks composing these mountains were not very extensively examined, but the 
granite composing them was seen at several projecting spurs which reach to the river, and were 
crossed. On one of these points Mr. Marcou mentions the occurrence of red porphyry and 
gneiss, and at another place porphyry, trap-rock, gneiss and granite, and serpentinoid granite, 
or protogine, were found between Camps 129 and 130. At the base of the mountains, strata of 
red sandstone and conglomerate were found in connexion with basaltic and amygdaloidal trap. 
These are much uplifted and metamorphosed near Camp 129. Beyond Camp 131 similar strata 
were found. These strata were believed by Marcou to be Tertiary, and probably are similar to 
those found along the valley and at the mouth of the Hawilhamook. 
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BANKS OF THE HAWILHAMOOK. 
; The above sketch was taken about six miles above the mouth of the stream, and serves to 
Show the rugged and desolate appearance of its rocky banks. In engraving the sketch, the 
peculiar characteristies of the different rock formations were lost, and the whole seem formed 
alike 
II. COLORADO RIVER TO SAN PEDRO. 
In turning west from the valley of the Colorado, the ascent of the range of mountains bound- 
ing it on the west was commenced. These have a peculiarly rugged outline, and Mr. Marcou 
Observes of them that they are extremely abrupt, and have peaks as in the Alps. The same 
singularly ‘serrated outline, which has the greatest resemblance to the teeth of a saw, is seen in 
the mountains around the Colorado desert, and on the Colorado north and west of Fort Yuma. 
