8 GUIDEBOOK OT THE WESTERN UNITED STATES. 



is a great incliiied block 350 miles long and SO miles wide, with a gentle 

 slope to the west and an abrupt descent on the east to the deserts of 

 Nevada. This abrupt descent marks a line of faults, east of which 

 the desert country has gone down and west of which, to some extent, 

 the Sierra Nevada has gone up. The Sierra Nevada consists of a 

 great irregular mass of granite which in early Cretaceous time was 

 intruded in a molten condition into sedimentary and older igneous 

 rocks^ both of which sets of rocks, in consequence of the heat and 

 squeezing which accompanied this intrusion, were changed in part 

 to schists and slates. After the range had been deeply worn down 

 by erosion, floods of lava were poured over the surface in Tertiary 

 time and the range was tilted up to its present general fonn. That 

 form^ however, has been much modified in detail b}^ comparatively 

 recent erosion and by the canyon cutting of the present streams. 

 South of the Dominion of Canada three rivers, the Columbia, 

 the Klamath, and the Pit, flow across the Pacific System from the 

 interior plateaus to the ocean. Other large streams, such as the 

 Willamette, in Oregon, and the Sacramento and San Joaquin, in 

 California, flow northward or southward for many miles in one 

 or another of the longitudinal depressions of the Pacific valley bolt 

 before turning westward across the western line of mountains to 



reach the Pacific. 



The valley belt is the great agricultural region of the Pacific coast, 

 and in Washington and Oregon, owing partly to its accessibility to 

 ocean-going ships by way of Puget Sound and the Columbia, it con- 

 tains most of the population. In Cahfornia, however, the broad 

 fields, orchards, and vineyards travereed by the Sacramento and 

 San Joaquin are rivaled by the many sniaUer but fertile valleys of 

 the Coast Kangcs. The superb harbor of San Francisco sufficiently 

 accounts for the situation of the metropolis; and the rapid growth 

 of Los Angeles, the second city in the State, is due to a combination 

 of shipping advantages with highly profitable kinds of agriculture 

 and extensive resources in petroleum. 



NoTR.— For the convenience of the traveler the sheets of the route map in this 

 book are so arranged that he can unfold them one by one and keep in view the one to 

 which the text he is reading relates. A reference is made in the text to each sheet 

 at the place where it should be so unfolded, and the areas covered by the sheets are 

 shown on Plate I. A list of these sheets and of the other illustrations, showing where 

 each one is placed in the book, is given on pai;*^6 137-138. A glossary of geologic 

 term*? is given on pages 133-136 and an index of stations on jiagos 13^142. 



