CARBONATE WORKINGS. 417 



phyry or clay material are found traversing the limestone, and half-inch 

 seams of iron-stained clay on the cleavage planes. A shaft has been sunk 

 on the hill above, which would connect it with the end of the incline, 

 had both been continued a short distance farther. As an exploration for 

 ore, therefore, the work done here is imperfect, inasmuch as, although no 

 pay ore has been discovered, it does not definitely prove that it does not' 

 exist in the neighborhood. The occurrence of these bodies of black chert, 

 which are rarely found on the northern portion of the hill, are not uncom- 

 mon along the southern slopes. While by the miners in many parts of the 

 district they are considered good indications of ore, this empirical test is 

 by no means infallible, although an evidence of passage of silicious waters. 

 One hundred and fifty feet below and west of the mouth of West Shamrock 

 incline a perpendicular shaft (T-35) has been sunk to a very considerable 

 depth on the Irish Giant claim, through Gray Porphyry into Blue and then 

 into White Limestone, without developing any important ore bodies, though 

 an impregnation of the limestone along the lower surface of the porphyry 

 might not unreasonably be expected. 



The next opening to the north is the Combination incline, just north of 

 the mine offices. This incline has an average angle of 21, flattening out a 

 little in the upper ten feet. The limestone comes practically to the surface 

 at the mouth of the incline, being covered with about nine feet of broken 

 material or slide. The workings of the incline were abandoned at the time 

 of visit, and apparently no considerable amount of ore had been extracted 

 from them. Down to the first level, the section afforded by the incline 

 itself, which cuts the contact between the limestone and the porphyry, shows 

 a wavy outline of the latter. In the first drift north, the porphyry is con- 

 siderably iron-stained and decomposed above the limestone, immediately 

 adjoining which is the usual parting of Chinese talc. At 24 feet from the 

 incline are old stopes, now filled up, in which the formation dips down- 

 ward to the north. The first drift south cuts through the crest of short 

 waves in the limestone and a body of iron from six to eight feet in thickness, 

 while in the face the porphyry goes down with a steep dip to the east and 

 south. Of the south drift, on the second level, the first 20 feet are in lime- 

 stone, more or less replaced by iron oxide, which is succeeded by porphyry. 



MON XII 27 



