206 THE FORESTS AND DESERTS OF ARIZONA 



Arizona, with an area of about 114,000 square miles, equaling 

 the combined areas of New York and the New England states, 

 or of Ohio, Indiana, and Illinois, is in the main a plateau rising 

 from the southwestern corner toward the north and east. From 

 an altitude of not more than 40 feet above sea-level, at or near 

 Yuma, the plateau level rises to 7,000 feet or more, and, with the 

 many mountain ranges that overtop the plateau, every altitude is 

 found up to 12,800 feet in the rude stone monument erected by 

 Mr Gilbert on the highest peak of San Francisco mountains. 

 There is, however, a convenient and significant altitudinal sub- 

 division of the plateau to be noted, by which the northeastern 

 section, with about one-third of the territory, is segregated as 

 the Colorado plateau — a part of the great plateau which extends 

 northward, with an average elevation of over 4,000 feet, the south- 

 western two-thirds forming a lower plateau, with an average ele- 

 vation of probably over 1,000 feet, studded with rugged sierras 

 which sometimes reach up nearly 10,000 feet. The division be- 

 tween these sections is sharp and sudden ] in most parts it is a 

 line of cliffs and steep slopes, varying from 600 to 1,200 feet 

 and more in height, which form a rim to the higher plateau, popu- 

 larly known among the Mexicans as the Mogollon and among 

 Americans as " the rim." This great escarpment forms so abrupt 

 a boundary line that a stone may be hurled from one region into 

 the other. Immediately below this rim there is a climatically and 

 botanically intermediary region or transition zone which only 

 accentuates the two main divisions. 



The convenience of this subdivision extends beyond topo- 

 graphic distinction, for the two sections differentiate climatically 

 almost as abrui3tly as the surface, giving rise, from the standpoint 

 of the visitor, to a summer section and a winter section, with cor- 

 responding differences in flora, fauna, and economic conditions. 

 Thus the range of summer and winter climate which a latitudinal 

 difference of a thousand miles effects from Maine to Florida is 

 here effected approximately by altitudinal differences within a 

 hundred miles. 



Furthermore, the two sections are best reached, and until a 

 few years ago could only be approached, by rail on two inde- 

 pendent railroad systems — the Southern Pacific affording pas- 

 sage through the southern section and the Atlantic and Pacific 

 (now part of the Santa Fe system) traversing the northern sec- 

 tion. At present there is a connection between the two trunk 

 lines by way of Phoenix and Prescott, giving access to the central 



