coal. 347 



where replaced by coal of workable thickness. The heavier coal scum lies 

 a short distance below sandstone C and is from 8 to 10 feel thick; the 

 thinner seam underlies the firsl by aboul 10 feet. A third seam, -\ feet 

 thick, is often present in the district immediately over sandstone B. 



East of the outcrop affording the above section, in the gulch leading 

 down from the Marshall-Louisville divide, a portion of the series is several 

 times repeated by reason of a number of slight fracturesand displacements 

 which were formed along the immediate rim of the deeper portion of the 

 Davidson svnclinc al the time of folding. The reduplication thus effected 

 lias in the past led to overestimates of the number of beds prevailing in 

 the rcii'ioii, the number having been stated by some geologists to be from 

 !l to 14. 



The Marshall coal field is clearly defined on the north ami west l>\- 



the outcrop of its beds; on the cast the limits of economic work are 



determined by the sharp fold constituting the rim of the deeper portion of 

 the Davidson syncline ami l>v the thinning of the beds in this direction; 



while to the south, beyond the lilllff fault, although the productive 



measures may possibly extend lor a considerable distance, evidence from 

 openings well within the limits of the syncline again indicates thinning 

 beyond workable size. 



It is difficult to estimate the general depth at which the coal lies 

 in the southern extension of this field, the exact form of the syncline being 



undeterminable. It i> probably shallow, however, when compared with 

 that at which the gently dipping beds usually lie along the foothills. 



The mines of the Marshall district include the Marshall 1, •_'. .'>, and 

 T>, the Fox (present mine), the old Fox Slope northeast of the main field, 

 and a mine known as the old Marshall Slope at the western end of the 



field; besides these a number of unimportant openings, chiefly prospects, 



are scattered over the district in various directions. The mines latest 

 worked are the Marshall Nos. 3 and 5 and the Fox: the others have long 

 since been abandoned. 



The Marshall No. 3 mine. (FigS. .1 Jllld K, Fl. XVIII.) This is Opened ill 



the lower bench of coal by a slope to the south, near the center of the 

 depressed area north of the southern branch of the Marshall fault. The 



