240 GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



mass of silicious vein material containing pockets of carbonate, at a depth 

 of 230 feet. Inasmuch as this sliaft starts at an elevation of about two hun- 

 dred and fifty feet above the Great Hope, the absolute level of the contact 

 is here even higher than at the Great Hope, as shown in Section L, Atlas 

 Sheet XXI. 



A number of shafts near this — the Galesburg (K-33), the Wliite 

 Prince (K-36), and Nettie Morgan (K-38) — have also reached the 

 contact after passing through Gray and White Porphyry. The Big Six, 

 at a depth of 300 feet, and the Tiger bore-hole, at 500 feet, as already men- 

 tioned, were still in White Porphyry, showing that in a southwest direction 

 it thickens very rapidly. Between Evans giilch and Little Evans the moraine 

 ridge buries the rock surface to such a depth that except at its western end 

 it has not been reached. 



On the slope of Prospect Mountain, as will be shown later, the Gray 

 Porphyry is overlaid by the Weber Shales. The underlying White Por- 

 phyry is thinning out to the northeast, while still farther north the Mount 

 Zion Porphyry comes in between the Gray Porphyry and the Weber Shales. 



Yankee Hill anticline. — Across the west slope of Yankee Hill, just below 

 its crest, runs the axis of an anticlinal fold, which in Evans gulch prob- 

 ably bends to the southwest to connect with the anticline shown at the 

 forks of Little Evans, at the south base of Canterbury Hill. The rock 

 surface in the crest of the fold on Yankee Hill is formed of White Por- 

 phyry, belonging to the sheet which comes between the White and Blue 

 Limestones, this region being northeast of the imaginary line alread}^ men- 

 tioned as running southeast from Fryer Hill, along which the main sheet 

 of White Porphyry splits in two, one portion remaining above the Blue 

 Limestone and the other being found below it. 



North slope of Yankee Hill. — The regular succcssioii of bcds on either side 

 of the axis of this anticlinal fold is best shown in the shafts on the north 

 side of the hill. In Johnson gulch the Andy Johnson (P-1) shaft reaches 

 the contact after passing through both the main sheet of Gray Porphyry 

 and the underlying White Porphyry, the latter being here 84 feet thick. 

 The Bevis No. 3 (P-5), Bevis Discovery (P-6), and the Boulder Nest 

 (P-8) shafts have started in Wliite Porphyry and readied the contact 



