362 W. H. WEED — COAL FIELDS OF MONTANA. 



Character of the Coal Seams. — Throughout the coal-bearing sandstones of 

 the Bozeman field, seams of coal occur at frequent intervals, but thus far 

 only three seams have proved to be of workable thickness. The field has 

 been quite extensively prospected, and at several localities the workings 

 afford good sections of these seams, so that their characteristics are readily 

 determined. 



The sections show that the seams are composed of benches of coal, sepa- 

 rated by partings of sandstone and of clay, the bony coals being rare, so 

 that the coals are mined quite clean. The sandstone partings are extremely 

 variable in thickness, but very persistent throughout the extent of seam de- 

 veloped. Average sections of the highest seam worked show it to consist of 

 from 4 to 7 feet of clean coal, in three to four layers, separated by sandstone 

 partings from half an inch to 6 inches thick. The varying thickness of these 

 partings is accompanied by a variation in the thickness of the adjacent layers 

 of coal. The middle and lower seams show from 5 feet to 7 feet of firm, 

 clean coal separated by similar partings of clay and sandstone. 



The clean, clear coal very often rests directly upon a sandstone floor, 

 without any intervening layer of fire-clay. A peculiarity of the floors of the 

 two upper seams, which was first observed by Mr. Eldridge in the part of 

 the Bozeman field so far developed, is the unevenuess of the surface on which 

 the coal rests and whose depressions it fills. The resulting unevenness of 

 the seam, with the frequent " rolls " and occasional total failure of the coal, 

 is a considerable detriment to economical development. 



The roof over the seams, on the other hand, is very generally quite even 

 and regular, usually a firm, compact sandstone, so that only a small amount 

 of timbering is required in mining. 



Analyses of these coals, though showing a slight variation, indicate a low 

 percentage of ash and water and entire freedom from sulphur. 



Workings. — That portion of the field lying between Livingston and the 

 Gallatin valley has been very carefully prospected. The only mines worked 

 at present are those at Cokedale, Timberline, Mountainside and Chestnut. 

 At Cokedale the output was 49,400 tons in 1889, and is much larger for 

 1890. Seventy-eight coke ovens were in operation during the summer, with 

 some eighteen more undergoing repairs. The mines are worked from an 

 incline 650 feet deep, with three levels, the longest a mile in length. As the 

 coal dips at 45° to 50°, the lowest depth at which the coal can be econom- 

 ically mined will be reached before long. At Timberline and Chestnut the 

 mines are operated by tunnels and inclines, and the methods in use present 

 no points of special interest. The output at Timberline for 1889 was 43,838 

 tons. The character of the coal varies from a good coking variety at Coke- 

 dale to a dry steam coal at Timberline and westward. 



Above the anticlinal folds already mentioned there has been more or less 



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