766 GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



quartzite and then cuts obliquely into the latter for a short distance; it, then 

 follows the bedding-plane for a few yards, and, again cutting across the 

 strata, disappears under the debris. The measurements were made with a 

 pocket level, checked by observations with an aneroid barometer, taken at 

 the base and again at the summit of the cliff; the discrepancy between the 

 two measurements amounting to only a few feet. 



Section from top of Sheep Mountain downward: 



Foct. 



White Porphyry, 300 to 400 feet. 



!Blue Limestone, brecciated at top, with abundant 

 secretions of black chert. 180 

 Lighter-colored limestone 20 

 200 



{Parting Qnartzite, line Drained, white 70 

 White Limestone, silicious at base, with white chert 

 secretions 100 

 230 



f Ued cast beds 8 



I Shales, interbedded with "sandy "limestones" .'!0 



Reddish, fine-grained sandstones, with indistinct im- 



Cambriau.. ..\ Passions 40 



Gap i 10 



Qnattzite 22 



White Porphyry, 12 feet. 



White contact quartzite .... 65 



175 



005 



Archean G neiss 



The total thickness here obtained of the lower Paleozoic series, which is 

 605 feet, is a little greater than that obtained at other points, which may possi- 

 bly be due to the swelling of the beds that would naturally succeed a com- 

 pression, if such exists, on the side of the fold next the fault. The contact 

 of the White Porphyry and underlying Blue Limestone, which was here 

 visible over a considerable distance, was carefully studied, especially on the 

 side of the fold next the fault. The upper part of the Blue Limestone is 

 particularly dark and full of black chert. The actual line of contact is 

 marked by a breccia, whose character varies much. Now it is composed 

 mainly of White Porphyry fragments, then of chert, and again of a mixt- 

 ure of both with black shale or limestone. Sometimes arms of the White 



