BETWEEN IRON-DOME AND MIKE FAULTS. 245 



broken, and passes suddenly into granite ; the plane of the fault is here 

 nearly vertical. South of this point it passes between the (P-46) shaft 

 of the Hard Cash mine in vein material on the west and the two (P-31 

 and P-35) which are in Lower Quartzite on the east. It crosses Stray 

 Horse gulch between the Argentine tunnel and the Devlin shaft, then is lost 

 sight of in an area of White Porphyry, in which it bends to the west, and 

 is next seen in the Codfish Balls (0-37). Its course beyond this through 

 the mines of Iron Hill will be described in detail in Part II, Chapter II. 



Beyond California gulch it is again lost sight of in porphyry, but its 

 line would carry it into the axis of a synclinal fold between California and 

 Iowa gulches. The actually proved continuation of its movement is along 

 the California fault up California gulch to the Dome fault, which runs south 

 across Dome Hill and in Iowa gulch passes into a probable anticlinal fold. 

 The displacement of this fault is an upthrow on the east, its maximum of 

 about one thousand feet being reached opposite the Iron mine, and decreas- 

 ing both to the north and south. 



The area between Mike and Iron-Dome faults from the southern bound- 

 ary of the map to the Adelaide cross-fault is practically a block of easterly- 

 dipping beds, the surface being principally formed by the main sheet of 

 White Porphyry, with a fringing outcrop on the west of the Blue Lime- 

 stone, and, where erosion has cut deep enough before the Iron Dome fault is 

 reached, by those of the lower formations. These are actually exposed 

 only on the south slope of Iron Hill, facing California gulch. 



Long and Derry Ridge. On Long and Deny Ridge, west of the Mike fault, 

 the underlying rocks are buried beneath the moraines of Empire and Iowa 

 gulches, and, as shown on the general map, by Lake beds, so that the indi- 

 cations afforded by shafts of the position of the outcrops of Blue Limestone 

 are compai-atively rare. As far as known, the Echo and Hoodoo, at the head 

 of Thompson gulch, are the only ones that have proved it, the one at a 

 depth of 160 feet, the other at a depth of about one hundred and ten feet. 



Josephine Porphyry. The Josephine, Pine Tree, Aurora, and other shafts 

 have developed a body of porphyry which has been called after the first- 

 named shaft, in which it has been best developed. It apparently forms a 

 sheet between the White Porphyry and underlying Blue Limestone, the 



