GENERAL GEOGRAPHY. 11 
lava flows in the region of Williams Canyon. Again, in 1858, he 
makes brief mention of the region in his " Geology of North America. " a 
The first account of any considerable value is found in Lieutenant 
Ives's report on lower Colorado River, published in 1861. Part 3 
of this report, by J. S. Newberry, describes the geology along the 
route traversed by the Ives expedition. Newberry ascended Colo- 
rado River to the mouth of the Virgin, and crossed the northern 
part of the region from Fort Mohave eastward to the Colorado 
Plateau. Later, Major Powell, in the course of his exploration of 
Colorado River, skirted the northern border as far as the mouth of 
the Virgin, and in the early seventies Gilbert and Marvine described 
its northern part in the final Wheeler reports. 6 
A few scattered references to the geology of the region are found 
also in various mining reports. In 1866 c Silliman visited certain 
mines near Fort Mohave, and described in a general way the volcanic 
rocks of Black Mesa. In 1863 Blake observed a deposit of iron ore 
near Planet, in Williams Canyon, and described the metamorphic 
strata with which it is associated/ This deposit, together with the 
copper deposits of the Planet district, have recently been described 
by McCarn e in a brief sketch of the geology of that locality, and 
Pratt f has described the occurrence of ore in the Socorro mine, near 
Harrisburg, Ariz. 
GENERAL GEOGRAPHY. 
RELATION TO SURROUNDING REGIONS. 
Arizona is divided into three general geographic provinces,^ known 
as the Plateau, the Mountain, and the Desert regions. The first 
province is well known through the writings of Powell, Gilbert, Dut- 
ton, Walcott, and others, as the Colorado Plateau; its western limit 
is very definitely marked in western Arizona by the Grand Wash 
Cliffs. Between the Plateau and the Desert regions is a mountainous 
belt comprising the second, or Mountain, region, which includes the 
greater part of the area described in this bulletin. The third, or 
Desert, region is mainly one of low-lying plains with more or less 
isolated mountain groups; it occupies the southwestern part of the 
Territory. 
a Marcou, Jules, Geology of North America, 1858, p. 23. 
b U. S. Geog. Surv. W. 100th Mer., vol. 3, pts. 1, 2, and 5, 1875. 
cSilliman, Benjamin, jr., On sonic of the mining districts of Arizona: Am. .Tour. Sci., 2d ser.,vol. 41, 
1866, pp. 289-308. 
d Blake, W. P., Iron regions of Arizona: Idem, vol. 40, 1865, p. 388. 
«McCarn, II. L., The Planet copper mines (Arizona): Eng. and Min. .lour., vol. 78, 1904, p. 26. 
/Pratt, J. II., Gold deposits of Arizona: Idem, vol. 73, 1902, p. 795. 
pRansome, F. L., Description of Globe district: Geologic Atlas I". S., folio 1 11, U. S. Geol. survey, 
1904, p. 1. 
