ransom k] COPPER DEPOSITS OF BISBEE, ARIZ. 157 
Cambrian limestones beneath the masses that have been so profitably 
worked in the overlying Carboniferous beds. 
But more than this, it may be pointed out that less than half of the 
semicircular mineralized zone about the porphyry mass of Sacramento 
Hill has been explored at all. Ore was first discovered at the surface 
on Queen Hill, at the northwest end of the zone. From this discover} 7 
'developments have been pushed by underground exploration, often 
with little or no surface showing, to the south. There still remains, 
however, an extensive area of unknown but promising ground, lying 
just south of Sacramento Hill and extending eastward toward the south- 
eastern continuation of the great fault, which is here concealed by the 
ibasal conglomerate of the Cretaceous series. This is the eastern half of 
jthe semicircular mineralized girdle about the intrusive mass of por- 
phyry. Its exploration calls for no greater outlay or boldness than is 
already displayed in other parts of the district with less assured hope 
3f reward. 
In conclusion, it ma} 7 be said that Bisbee is less likely to suffer from 
■a lack of ore than from too rapid exhaustion of the high-grade oxidized 
ores which are necessary for the economic smelting by present pro- 
issses of low-grade sulphides. 
