270 GEOLOGY AND MINING INDUSTRY OF LEADVILLB. 



600 feet given must be considered a conservative estimate. The underly- 

 ing Wliite Porphyry is shown as disappearing in the middle of this body, 

 since the latter is supposed to connect with the lower body in California, as 

 shown in Section L. A slight anticlinal structure is shown in the sedi- 

 mentary beds beneath the porphyry, as a probable connection between the 

 Great Hope anticline on the north and that under Printer Boy Hill on the 

 south. The block between Pilot and Mike faults, it is seen, is practically a 

 wedge-shaped mass which has slipped down between the two faults. In 

 this area is the intersection of the line of cross-cutting White Porphyry, 

 which is therefore indicated here as spreading out under the Blue Lime- 

 stone. On Iron Hill the line of section passes through the workings of 

 the Iron mine; and the data down to the horizon of the Blue Limestone are 

 derived from actual exploration. The transverse body of Gray Porphyry 

 developed in these workings is supposed to be an offshoot from the intrusive 

 sheet at the base of the Blue Limestone; it should not have been represented 

 as actually projecting into the White Porphyry. 



West of the Iron fault the section crosses what is probably the greatest 

 thickness of White Porphyr)^ left above the Blue Limestone, but the depth 

 of the latter immediately adjoining the fault is, as already stated, purely 

 theoretical and given as a probable maxinmm. 



Section G. — Scction G follows also a slightly broken line along the south 

 slope of Ball Mountain, through Green Mountain and the head of Califor- 

 nia gulch, and then along the northern edge of Dome Ridge. At its eastern 

 end it crosses diagonally the South Dyer fault. Between Mosquito and 

 Ball Mountain faults the development of White Porphyry in the lower 

 horizons is even more striking than in the preceding section. Between Ball 

 Mountain and Weston fault the distribution of the porphyr}^ bodies is 

 similar to that in the preceding section, but the Pyritiferous Porphyry is 

 supposed to be thinning out to the southward. 



Between Weston and Pilot faults the section shows a probable vent of 

 the lower body of Pyritiferous Porphyr}', which is known to cut across 

 the strata, and probably comes through the Archean in this vicinit}-. In 

 the wedge-shaped mass between Pilot and Mike faults a sheet of Pyritifer- 

 ous Porphyry is supposed to extend between the White and Blue Lime- 



