348 GEOLOGY. OF THE DEBTEE BASIN. 



entrance to the slope is sonic distance south of the outcrop of the seam, 

 the angle of descent being several degrees steeper than the dip of the beds, 

 and the coal cut onl\ at a considerable depth. 1 



Several hundred feet west of this slope is another, on the coal, having 

 a southwest direction and uniting with the first at its foot. 



The strike of the coal in the No. 3 mine is between N. 45° and 50° E.; 

 flic dip is 10° SE. in the upper levels of the mine, decreasing to 3° in 

 the lower levels. In the lowest level of the mini' the southern branch 

 of the .Marshall fault svsteni was encountered. The fracture showed a 

 X. 62 E. trend, with an inclination of its plane to the horizon of 45° SE.; 

 the downthrow being on the northwest, the fault being of the reversed 

 type. The coal in No. 3 mine varies in thickness from 8 to ;> feet. It is 

 free from partings, is square-jointed, hard, bright, and contains but little 

 pyrite and resin. 



The Fox mine. (FigS. G alld 11. PI. XVIII.) This also i.S ill tllC loWCf 



bench of coal. It is opened by a slope to the north — across the stratifica- 

 tion — the entrance to which is on the north side of the valley, a half mile 

 northeast of the Marshall No. .". mine. 



The general strike of the beds in this mine is X. 30 lv, with a dip to 

 southeast about 7 . Ar the time of the examination no faults had been 

 encountered. The thickness of the seam varies hut little from !> feet The 

 coal lies very regular, is free from partings, hut is divisible both in appear- 

 ance and in quality into an upper and lower bench, '_' or -.[ feet and (U or 

 7 feet thick, respectively. The upper 2 inches of the top bench is in places 

 a little bony. Generally the top coal is more fibrous, oily, and harder than 

 the bottom coal, scaling off in slabs in working. The bottom coal, on the 

 other hand, is dicv, has a bright luster and a conchoidal fracture; l' feet 

 from its top is a 1 "_' to Is inch band much harder than the remaining 

 portion, and somewhat resembling the top bench. 'The top coal is reported 

 to be a good steam coal, the bottom being better for domestic purposes. 



The Marshall No. I mine. SolUe (lollllt exists ;|S to tile identity of this lllille, 



but it is probably that between the Marshall No. 3 and the Fox, now 

 abandoned and on tire. It was opened by a drift (slope?) and worked to 



The custom of opening :i mine by slope through barren rock instead of by shaft is an old one 

 in Colorado. It has long been abandoned. 



