420 GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



whole mass for a distance of many feet. The line between the unaltered 

 and replaced limestone has been accurately followed foot by foot, and a 

 portion of the north wall of the incline is represented on a larger scale in 

 Plate XXII, Fig. 3. 



As well as can be seen through the timbers of the incline, its upper 

 portion is practically in the porphyry and the limestone does not actually 

 outcrop. Very probably this is the crest of a slight roll, and it is prac- 

 tically level at this point or may possibly have a very slight western inclina- 

 tion. The first limestone actually seen in place is about sixty feet from 

 the surface, just above a drift which crosses under the floor of the incline. 

 It is evident, however, that the limestone rises somewhat to the south, since 

 it is said to have been found at six feet from the surface under the boarding- 

 house. From this point downwards to the second level the incline is run 

 practically in contact material or in decomposed iron-stained porphyry. 



In the second level south, about fifty feet from the incline, a limestone 

 floor is found rising rapidly to the eastward. 



In the third level ore was found below the level of the incline, evi- 

 dently in a depression of the contact line, but the workings are now closed. 



The fourth level south, which is still open, runs at first in porphyry, a 

 cross-cut to the left or eastward cutting the underlying limestone at a dis- 

 tance of 16 feet. This marks the point where the limestone rises, to wards 

 the crest of the fold, shown on the incline section. While in this section 

 the crest is comparatively narrow, it apparently widens out to the south in 

 a broad, dome-shaped elevation. At aboirt forty feet from the incline the 

 fourth level cuts through a body of hard, compact iron, resting upon the 

 limestone, and then bending to the eastward passes into the solid limestone. 

 At a distance of one hundred and twenty -five or one hundred and thirty feet 

 from the incline a streak of clayey matter was cut, carrying a little ore and 

 running off to the southward, evidently a replacement body which followed a 

 cleavage or fracture plane in the limestone. The drift then passes again 

 into solid limestone, bending off to the south at its extremity, where it 

 passes into porphyry, the limestone dipping sharply to the eastward at the 

 bend. As will be seen by reference to the map, the drift at this point is 

 nearly over the extremity of the south drift on the eighth level. 



