154 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1902. [bull. 213. 
against this edge, we shall have a rough illustration of the geological 
structure near the town of Bisbee. The saucer represents the synclinal 
attitude of the Paleozoic beds from the Upper Carboniferous limestone 
down to and including the Cambrian quartzite. The broken edge of 
the saucer is the great fault, while the book is pre-Cambrian schist, 
against which Upper Carboniferous limestone has been dropped by 
this fault with a throw of more than 1,500 feet. 
The town of Bisbee lies on the fault line. The hills northeast of 
town are composed of pre-Cambrian schists; those just south of it 
are Upper Carboniferous limestone, with Lower Carboniferous, Devo- 
nian, and Cambrian beds coming successively to the surface along the 
fault to the northwest. 
A little less than half a mile southeast of the center of town the 
fault encounters a mass of altered granite-porphyry and as a simple 
fracture disappears. This porphyry, which forms Sacramento Hill, a 
well-known local landmark, is a very irregular mass about a mile in 
diameter. It has invaded the pre-Cambrian schists on the northeast 
and the Upper Carboniferous (probably also the deeper-lying, older 
Paleozoic beds) on the southwest. The available evidence indicates 
that the intrusion of this porphyry took place after the dislocation of 
the invaded rocks by the great fault. The latter probably continues 
to the southeast of the porphyry mass, but it is concealed in this 
direction by the younger Cretaceous beds. The Paleozoic beds form- 
ing the faulted syncline are not merely flexed, but are cut by many 
faults, some of them of considerable throw. These faults are, as far 
as seen, of the normal type. 
The ore occurs very irregularly as large masses within the lime- 
stone. The horizontal extent of these bodies is usually much greater 
than the vertical. The}^ are rudely tabular in form and lie generally 
parallel to the bedding planes of the limestone. As a rule the impor- 
tant ore bodies have been found within a distance of 1,000 feet of the 
main porphyry mass or of the great fault fissure just northwest of the 
porphyry. In the Czar workings of the Copper Queen mine, partly 
under the town of Bisbee, ore bodies have been worked from the sur- 
face down to a depth of about 400 feet, but toward the southeast the 
bulk of the ore occurs at increasing depths. In the Calumet and Ari- 
zona mine, about 3,500 feet south of the Czar, no large ore bodies were 
encountered until the shaft had penetrated about 800 feet below thej 
level at which the first ore bod}- was discovered on the Copper Queen 
claim. The ore thus occurs at increasing depths toward the center 
of the local synclinal basin. Detailed structure sections will probably; 
show, however, that the upper limit of the ore increases in depth:: 
somewhat less rapidly than would be the case did it correspond to a 
definite stratigraphic horizon. 
With the exception of the extreme western part of the Copper Queen 
mine, all of the productive and important workings in the vicinity of 
