12 
GENERAL GEOLOGY 
brought from the scene of his earlier studies in California 
an accurate knowledge of the coastal formations of the 
Pacific slope. The remaining member of the geological 
corps had traversed the continent by various routes and 
had studied in India, Malacca, Japan, and the Sandwich 
Islands, and thus was able to appreciate the general geo¬ 
logical relations of the countries visited, and especially to 
study the volcanic rocks. 
Mr. Palache omitted part of the route of the Expedition 
in order to examine more carefully the Alaska-Treadwell 
mine, and gave up the trip across Bering Sea that he might 
make local studies in the Shumagin Islands and about 
Chichagof Cove on the Alaska Peninsula. The results of 
his studies of these localities are reported in two papers 
following the present, and he has also contributed a short 
paper on the minerals collected. His other field observa¬ 
tions were reported to me, and are incorporated in the fol¬ 
lowing pages. In the office study of our material he has 
cooperated by assuming an important share of the petro¬ 
graphic work, and many of the rock descriptions are from 
his pen. 
In our railway journeys across the continent, both out¬ 
ward and return, we saw much of value to the geologist, 
but there was peculiar interest in the side trips to the 
Dalles of Snake River and Shoshone Falls. In the one 
we steamed swiftly for half a day between steep or even 
vertical walls made up of many superposed tuff beds and 
lava flows, often with the most perfect columnar struc¬ 
ture; and in the other we drove for many miles over the 
surface of lava flows that seemed to have cooled only re¬ 
cently. The ropy lava, the small craters, the great pustules 
which had been inflated on the surface of the liquid mass 
and then congealed and collapsed, are plainly parts of an 
enormous and very recent lava flow. This is divided by 
the river canyon, in whose vertical walls we saw other lava 
