No. 2.] 



HOFFMAN ON THE BIRDS OF NEVADA. 



205 



be of no special interest in this connection. In addition to tlie fact that 

 the timber-line increases in elevation as the latitude decreases, every 

 other succeeding zone of vegetation follows in regular sequence. 



The following table, representing a series of prominent localities 

 arranged according to latitude from the extreme northern portion of^ 

 Nevada southward and slightly eastward to a point in Arizona, will 

 serve to illustrate this fact more distinctly : 



Locality. 



Camp McDermitt 



Bull llun Mountain 



Prospect nill 



Belmont Peak , 



Moimt Nagle 



Mount Magruder 



San Pranciaco Mountain (Arizona) 



Latitude. 



42 58 

 41 40 

 39 30 

 38 40 

 37 46 

 37 40 



35 13 



Altitude -c'i„„„*;^ ^e iElevation of 



above sea- ^J^'Xe.' -^T"^- 

 mg plain. 



level. 



Feet. 

 4,700 

 8,450 

 9,050 



12, 000 

 11, 000 

 11, 500 



13, 500 



Feet. 



Feet. 



* The summit of Mount Xagle does not reach the altitude of the timber-line. 



t San Francisco Mountain is referred to as illustrating the elevation of the timber-line in its southward 

 course, Ihere being no peak in Nevada, south of Mount Magruder, of sufficient height to do so. 



I Camp McDermitt is located near the month of a canon formed by a break in the Santa Rosa Mount- 

 ains, through which runs a very clear and pure stream, known as the East Branch of QuLnn's Kiver. 

 (Report of the Hygiene of the United States Army, &c., Circular No. 8, War Department, Surgeon- 

 General's Office, Washington, 1875, p. 514.) 



If we take, for example, the zone of Coniferce at any given point in 

 the northern portion of the State, as at Bull Run, we find the timber- 

 line at an elevation of about 5,800 feet, while the lower range of the 

 trees composing this belt terminates irregularly where the mountain 

 mahogany — Cercocarpus ledifolius — begins, presenting a thickness in 

 altitude of perhaps 2,000 feet. When this zone is again examined at 

 one of the southernmost peaks, we find the timber-line to have risen to 

 more that 11,000 feet above sea-level, or more than 5,200 feet above the 

 altitude of the same line at Bull Run. In the mean time, the mountain 

 mahogany — which had existed at Bull Eun as but a narrow zone and 

 rested upon one composed chiefly of Salicacioe — has been replaced by 

 the coniferous trees above and the salicaceous below, but the latter has 

 also risen with the preceding, as do the zones succeeding the latter, e. g., 

 Compositce, Artemisice, &c. The Artemisia at Mount Magruder, instead 

 of occupying the plains as at Bull Eun, covers the foot-hills, while the 

 lower slopes show numerous examples of Yucca brevifoUa, Cactacece, &c., 

 these zones having risen in elevation with their predecessors, so that 

 the plains present species not found north of this latitude, while south- 

 ward this new zone again rises in elevation, again presenting a still 

 newer form beneath it, and so on. 



The regular and successive elevation of vegetation is more fully repre- 

 sented in the accompanying illustrations, sections I to V. 



The lines of demarcation, indicating the termination of one zone and 

 the beginning of another, are often abrupt and so remarkably distinct 



