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 



