440 GEOLOGY AND MINING INDUSTRY OF LEADVILLB. 



essentially accurate, that given in the intermediate sections has a certain ele- 

 ment of tentativeness and uncertainty. That in the ^Etna-'Pendery ground, 

 1 epi'esented by the two latter, has already been described. 



Lower Henriett and Waterloo. — Section B sliows the structure below the Car- 

 bonate fault on a line drawn between these two claims, whose lower work- 

 ings are connected with each other. It is that of an anticlinal fold, whose 

 axis corresponds very closely with the prolongation of the Carbonate fault 

 line and whose crest has been planed off, with a sharp synclinal basin 

 adjoining it on the west, along one side of which the lower sheet of Gray 

 Porphj'ry cuts across the Blue Limestone up into the overlj-ing White Por- 

 phyry, which has escaped erosion in the hollow of the basin. On the under 

 side of this sheet of Gray Porphyry, at its contact with the limestone, the 

 latter is mineralized, and a most valuable body of carbonate ore has been 

 developed, extending into the hill at a rather steeper angle than the aver- 

 age dip of the formation. The existence of this lower ore sheet was sup- 

 posed at first to indicate merely a faulted-down portion of the regular ore 

 horizon, as it does in the ^tna-Pendery ground, the difi"erence of level 

 between the outcrops of vein material on the surface and that of the lower 

 body, prolonged in dip into the hill, being quite what would be expected 

 if the movement of the fault was normal, with a slight decrease in amount 

 toward the north. It was observed, however, that the Half Way House 

 and Henriett Lower shafts had passed through normal White Porphyry 

 over limestone, whereas a short distance east of the latter shaft the White 

 Porphyry gave way to Gray Porphyry, which thereafter continued to 

 form the hanging wall of the ore body, limestone being in all cases its 

 foot-wall. The White Porphyry contact, for reasons which the general 

 geological description must have made apparent, is necessarily the top of 

 the Blue Limestone; but the continuation of the Gray Porphyry con- 

 tact soon came directly beneath the regular outcrop of iron vein mate- 

 rial, which here has more than double the width that it has farther south. 

 Therefore it was evident that the Gray Porphyry, although itself having 

 the regular eastern dip, was in reality cutting across the Blue Limestone. 

 No direct evidence of the fold in curving stratification lines has as yet been 

 obtained, since where these would occur in mine workings the limestone 



