At the Lehigh mine the thick seam is twenty feet higher than at the exposure a mile to the west. The characteristics of the seam are the same at both points, and, although there is a break in the exposure of half a mile, it may be safely affirmed that but one thick seam is exposed in this locality, and the difference in elevation is to be accounted for by the unevenness of the surface on which the coal was deposited. The seam contains no clay and only a foot or two at the top consists of the inferior "slack" coal. The dip of the seam

CLAY

is variable and slight, prevailing to the southeast.

Fig. 12, Section at the Lehigh mine.

The "butt entry" system of mining is employed, which consists of running the rooms directly from the the mine entries. Entries are twelve feet high and from ten to twenty feet wide. The coal forms a great arch for a roof and practically no timber is used in the mine. Rooms are cut twenty feet wide, separated by six-foot pillars. When an area is about to be abandoned, the roof of the rooms is dressed down so that only two or three feet of coal are left. The great thickness of the seam facilitates mining, and the miners earn large wages at 40 cents a ton for room work and 60 cents for entries. The mine is practically free from water, the small amount entering it (October, 1902) being removed by a windmill. For ventilation air shafts with burning fire pots at the base are used. All hauling is done by horses, the large entries allowing the use of large animals, and a single horse brings to the surface cars containing three or four tons at one haul. A photograph of the tipple and side track at this mine is given in plate XXVII.

Seven and one-half feet from bottom of layer:

Volatile matter

Fixed carbon

Ash .....

Total

PER CENT

42.63

49.22

8.14

100.00

PER CENT

43.57

46.50

9.93

100.00

PER CENT

39.99

51.60

8.41

100.00

PER CENT

40.70

48.24

10.89

100.00

PER CENT

44.32

48.53

7.15

100.00

PER CENT

41.50

51.80

6.61

100.00

PER CENT

40.97

51.30

7.73

100.00

Lignite at Dickinson. At two points on the outskirts of *Dickinson considerable quantities of lignite are mined. The plant of the Dickinson Pressed Brick and Fire Clay Company is situated on a terrace of the Little Heart river about thirty feet above the water. This terrace gives the following section:

Plate XXX illustrates this section. The clay is stripped from: the lignite, and considerable quantities of it are made into brick, while the lignite is used in firing the kilns, even the thin, impure layer being profitably consumed. The five-foot seam is exposed at a number of points along the river.

The Lenneville mine, one-fourth of a mile east of Dickinson, shows an eight-foot seam which bows up at both ends, so that although the surface is level, the amount of stripping necessary in the center is twelve feet, while at the ends of it is only six feet, the total length of the exposure being only 120 feet. The bank is one-third of a mile from the river, and at least twenty-five feet higher than the seam mined at the Dickinson brick yard. The lignite ordinarily sells for $1.50 at the mine. A number of hundred tons are taken out annually.

Coal on Green River.-Throughout its entire course lignite outcrops abound on Green river. Near its mouth. at Gladstone the coal, though excellent in quality, has not been found in seams more than five feet thick. At the Rust and A. B. Powers farms, in Township 140, Range 95, Sections 26 and 27, three miles from the mouth of Green river, a seam nearly five feet thick outcropping a few feet above the water of the river is mined by stripping for local use. The Laramie clays have in many places. been removed by erosion, and gravel and alluvium have been deposited on the coal, and in the flat terraces SO formed the amount of stripping necessary to secure the coal is often moderate. Two miles farther up the stream, in Township 140, Range 95, Sec