262 GEOLOGY AI^D MINING INDUSTRY OF LEADVILLE. 



and probabilities, it is well to state somewhat in detail the grounds on which 

 the existence of a synclinal basin is rendered probable. The first argument 

 in its favor is that of analogy, drawn from the existence of a synclinal basin 

 adjoining it on the east, in Little Stray Horse Park, which evidently con- 

 tinues southward through the block of ground between the Carbonate and 

 Iron-Dome faults. The facts to support this argument, viz, the proof of an 

 actual dip towards the center of the basin from either side, are as follows : 

 Eastern rim of basin. — First, a westem dip in the overlying beds on the 

 west side of the Big Evans anticline is shown by the developments of the 

 Oolite and Sequa shafts. Secondly, the Bob Ingersoll shaft and drill-hole, 

 on the moraine ridge west of Fryer Hill, in East Ninth street, after passing 

 through moraine material and Lake beds, are said to have penetrated nearly 

 three hundred feet of White Porphyry. This shaft is southwest of the line 

 where the White Porphyry cuts down below the horizon of the Blue Lime- 

 stone. It is probable, therefore, that the porphyry cut in this shaft belongs 

 to the upper sheet above the Blue Limestone, and the fact that so great a 

 depth as 300 feet has been reached without finding contact indicates a ver}^ 

 steep dip to the westward. The owners of the American Eagle shaft, at 

 the west base of Fairview Hill, state that the limestone in their workings, 

 which the dump shows to be White Limestone, dips both eastward and 

 westward, which would show that there is an anticlinal fold here.^ Third, 

 along the west base of Carbonate Hill, the Pocahontas (T-40), Weldon 

 (T-41), Rough and Ready, and other shafts have been sunk to a consider- 

 able depth in the White Porphyry beneath the Wash, and the California 

 tunnel is also in White Porphyry until it reaches the Blue Limestone 

 beyond the fault. This White Porphyry can be no other than that which 

 overlies the Blue Limestone, since in this region no considerable body of 

 White Porphyry is known to exist below this horizon; moreover, in the 

 Niles- Augusta, AVild Cat, Washburne, and other mines, as will be explained 

 in the detailed chapter on Carbonate Hill, there are indications of a prevailing 

 western dip to the formations west of Carbonate fault. This summarizes 

 tbe evidence of westerl}^ dipping beds on the east side of the synclinal basin. 



'Since the close of field-work, Mr. R. N. Clark, superintendent of tbe Chrysolite mine, states 

 that the estreino west workings of that mine show the Lower Quartzite and White Limestone to be 

 diiiping to the westward. 



