STRUCTURE OF PROSPECT MOUNTAIN. 17 



090 feet from entrance Binish-black limestone, compact granular. 



1,010 feet from entrance White limestone, compact crystalline. 



1,100 feet from entrance "White limestone, compact crystalline, partly calcite. 



1,200 feet from entrance . . Gray stratified limestone, compact granular. 



1,850 feet from entrance Black limestone, compact granular. 



1.900 feet from entrance Gray stratified limestone, compact granular. 



. First west cross-cut east side, bluish-gray limestone, com- 



SiO feet from entrance } pact, brecciated. 



( Sediment from fissure. 

 1 ._'0O feet from entrance at discovery winze near ore Yellowish-gray crushed lime- 

 stone, friable, crystalline. 

 1.200 feet from entrance Calcite, stained with manganese. 



Section of Prospect Mountain through Prospect Mountain Tunnel. TllC Pl'OSpeCt Moillltaill 



Tunnel, starting at a point about 2,700 feet west of the summit, nearly oppo- 

 site the Eureka Tunnel and several hundred feet below it, has been driven 

 2,350 feet into the mountain. For the first 1,400 feet it passes through a 

 hard compact white limestone, which in places resembles marble. This 

 limestone is not often fissured, but contains some cavities washed out by 

 water. There is nothing about it to indicate that it is mineral limestone. 

 At a distance of 1,400 feet from the entrance a fissure is encountered 

 at nearly right angles, which dips 80° to the west. From this point the 

 character of the limestone changes; it is much more broken, and many of 

 the ordinary varieties of mineral limestone are found, as well as seams 

 crossing the course of the tunnel. At 1,835 feet ore was discovered, but as 

 yet the deposit has not proved valuable. At a little over 2,100 feet strati- 

 fied limestone was encountered along a fault seam, which dips to the west 

 (see Plate II.). A.t 2,2-30 feet shale makes its appearance along a similar 

 seam. The twisting of the stratification of both the stratified limestone and 

 shale indicates that the portions of country east of these two seams were 

 raised relatively to the portion on the west. Although not absolutely cer- 

 tain, it is probable that the shale and stratified limestone encountered in the 

 end of the Prospect Mountain Tunnel is the same body as that encountered 

 in the end of the Eureka Tunnel. 



General internal structure of Prospect Mountain. It will be UOticcd that the WeSt side 



of the mountain differs greatly in the formations that compose it from the 



eastern. This in some measure is owing to the fact that a larger portion of 



the overlying rocks have been eroded, and that there has not been the same 

 2654 L 2 



