niYSlGAL FEATUKES OF THE GL'EAT BASIN. 313 



Canon, Utah Lake, and Salt Lake City. Work was continued at main 

 (•aiiiii until August 16tli, Avlien collections and notes were packed and our 

 field-work ended. 



niYSICAL FEATURES OF THE GREAT BASIN. 



While the region traversed by the survey after its equipment embraces 

 the entire distance from Sacramento City, California, to points in Utah 

 eastward of the Salt Lake Valley, the actual field-work began only at the 

 eastern base of the Sierra Nevada, and was thus entirely confined to the 

 intei-ior area of continental drainage known to geographers as the Great 

 Basin, and which Ave shall frequently refer to in the following pages by this 

 name, as well as by that of the "Interior," a convenient synonymous term. 

 This vast area corresponds almost strictly in its geographical boundaries 

 with the " Middle Province" of zoologists. The route of the expedition 

 was mainly across the middle portion of the Great Basin proper, so that 

 the founa encountered was that typical of the Middle Province. 



In few regions is the influence directed on the distribution of birds by 

 that of the plants so manifest to the observer as in the one under consid- 

 eration; and as vegetation is influenced so materially by configuration of 

 the surface, conditions of the soil, elevation, etc., a brief description of the 

 physical features of the country embraced within the limits of our trip is 

 necessary to the intelligent understanding of the nature of the Middle 

 Province avifauna, and the manner in which it is divided into bands of 

 restricted range, according to conditions of environment. Such an excellent 

 description of the field of our investigations has been given by Mr. Watson, 

 the botanist of the expedition, that we cannot do the subject greater justice 

 than to quote the following from "Geographical Notes," on pages xiii-xvii 

 of the Botanical Report:' — 



' Professioual Papers of the Eusiueer Department, U. S. Army, No. 18. Keport 

 of the Geological Exploration of the Fortieth Parallel, made bv order of the Secretary 

 of War according to acts of Congress of March 2, 1867, and March 3, 1SG9, under the 

 direction of Brig, and B'vt MajorGenerul A. A. Humphreys, Chief of Engineers, by 

 Clarence King, U. S. Geologist. Volume V, Botany. By Sereuo Watson, aided by 

 Prof. Daniel C. Eaton and others. Submitted to the Chief of Engineers, and published 

 by order of the Secretary of War under authority of Congress. Illustrated by a Map 

 and Forty Plates. Washington: Goverumeut Printing OfiQce, 1871. 



