TABLE MOUNTAIN": TUOLUMNE COUNTY. 



135 



ined for want of good exposures at the time the locality was visited ; neither 

 could the exact thickness of the detrital beds be made out. On the north 

 side a tunnel was run in through the rim-rock, and at a distance of 700 

 feet from the entrance the first channel was struck, the tunnel passing just 

 under it, so that by rising a little (excavating upwards) it could be drifted 

 upon, which was done and some gold obtained, but not in paying quantity. 

 From this channel, which was found to be eighty feet in width, the tunnel 

 was continued in the bed-rock for 700 feet farther, which point it had 

 reached when examined by the writer; it was then said to be 285 feet below 

 the surface. This tunnel runs S. 80° E., the silico-argillaceous slates which it 

 traverses having a dip of 70° to the northeast ; they were of a dark color, 

 containing much disseminated pyrites. On the opposite side a tunnel had 

 been run in for a distance of 300 feet, following the surface of the rim- 

 rock, which here descends with a steep pitch, or at the rate of thirty-six feet 

 in a hundred. Here the bed-rock was overlain by "cement," and a chan- 

 nel had not been reached when the place was examined by the writer. 



At the Down East Tunnel, about a third of a mile below the Buckeye, 

 a tunnel had been run in 875 feet and the main channel reached, on which 

 drifting was being done at the time of the writer's visit. At this place they 

 passed under the small channel struck by the Buckeye Company, but did 

 not rise to it. 



At the Boston Tunnel the condition of things was more as represented in 

 the section at the Eureka Tunnel. The tunnel was run on the bed-rock 

 with sandstone just over it. After striking the main channel the drift was 

 continued alongside of it, with cross-drifts, so as to take out the pay gravel 

 and leave the tunnel securely standing. The thickness of the stratum of 

 gravel at this place was from one to two and a half feet; it consisted of 

 rounded boulders mixed with smaller pebbles, exactly like the material 

 m the bed of a modern stream from which gold is now being taken out. 



At the Maine Boys' Tunnel (Plate F, Fig. 2), on the west side of Table 

 Mountain, near those already described, the excavations made at the time the 

 locality was visited permitted the relations of the rim-rock to the channel and 

 the overlying beds of sedimentary and volcanic materials to be well made out. 

 The lava capping, which is mostly of basalt, with some cement underlying it, 

 is 152 feet in thickness. The rock between the volcanic and the bed-rock 

 is sandstone, and is well exposed by an inclined shaft sunk in it, for some 

 distance, from a point just at the edge of the junction of the sedimentary 



