418 GEOLOGY AND MINING INDUSTEY OF LEADVILLE. 



Tiae north drift, on the second level, follows in its curves approximately 

 the line of contact between limestone and porphyry, bending back to the 

 westward nearly under the end of the drift on the first level, showing that 

 a limestone ridge crosses the incline in a diagonal or southeast direction 

 between the first and second levels Below the second level the incline- 

 follows along the edge of the northern side of this limestone ridge for 25- 

 feet, the north face of the incline being partially in limestone and clayey 

 contact material, dijjping sharply to the north, and the south face in solid 

 limestone. Beyond, the limestone dips down to the east, and the rest of the 

 incline is in porphyry, which is more or less iron-stained. At the end of the 

 incline is a winze sunk 40 feet to the surface of the limestone, showing a 

 rapid descent of the limestone to the northeast of the ridge, which has just 

 been passed through, which is further evidenced by the appearance of bed- 

 ding planes in the porphyry itself, which incline at an angle of 45° to the 

 northeast. The drift running westward from the mouth of the Combination 

 incline, which is said to have followed the contact on its slope to the west- 

 ward, was not accessible at time of visit. 



The Carbonate Old incline runs in 170 feet at an angle of 19° and pre- 

 sumably follows the contact, but it is now closed. Solid limestone is found, 

 eight feet from its mouth, covered by iron-stained vein material and broken, 

 porphyry. Between this and the mouth of the Main incline, under where, 

 the boarding-house now stands, was the ore body from which ore was first 

 taken on this ground. The drifts are now filled up and abandoned, but it 

 is evident that the body was of considerable size and very near the surface, 

 lying in an approximately horizontal position, that is, near the crest of the 

 fold already mentioned. 



Carbonate incline. — The priucijDal workiugs of the Carbonate mine are 

 opened by the Main or Carbonate incline, which descends into the hill fora. 

 distance of 620 feet at an angle of 21° 30' and in a direction E. 2.o° S. 

 It is one of the comparatively few inclines in the distinct which have been 

 driven straight, instead of following the irregularities of the limestone sur- 

 face, the only true system for an incline from which it is expected to extract 

 any considerable quantity of ore, and one which is probably more econom- 

 ical in the long run, since, in spite of the irregularity of the limestone sur- 

 face in limited distances, the average dip is tolerably constant. 



