ash anthracites are hard and well adapted for use in blast-furnaces and other fires which require intense heat and great resisting power in the fuel. They all contain a high percentage of carbon, with but little ash, and neither crumble nor cake in the hottest fire. The red-ash coals, on the other hand, are softer, crumble easily, and have a tendency to melt in a hot fire; and the shade of color in the ash is a pretty good indication of the character of the coal in this respect.

(See fig. 4.) The color is due to the presence of ferric oxide; and this, in turn, is supposed to have been diffused through the air by volcanic action, to be deposited by rain in the forming coal-beds. Prof. Greene (Coal, its History and Uses, p. 63) traces the coloring of the red sandstones to the same source. The well-known intermittent character of volcanic discharges will perhaps account for the coloring of the lowest coals, the absence of color in the middle series, and the deep tint of the ashes of the upper beds; es- Extent of the Deposits.-It is probable that the prespecially when it is considered that the upper beds are ent anthracite fields of Pennsylvania are but the remthousands of years younger than the lowest ones, and nants of a great body of coal which once included them that, as Prof. Greene points out, volcanic action is all and filled up the spaces between them, the missing apt to be most intense when the volcano is about ex- portions having disappeared through denudation. The piring. The commercial importance of the coloring- writer's observations of the geology of the district show matter in coal-ashes is due, not so much to its presence that this ancient coal-field must have had an area of or absence as to its furnishing an (apparently acci- about 2000 square miles, and, supposing that all the dental) indication of the grade of the coal. All white-present beds were coextensive with it, contained about

92,840,960,000 tons. The amount of coal available | ton district, to 20 in the Wyoming, and from 20 to 40 in

at the beginning of the historic period was about 26,721,093,817 tons, of which 409,597,748 tons were mined and sent to market in the sixty years from 1820 to 1880, inclusive, as shown in Plate X.

the Mahanoy district, and to much more in local enlargements, but its average thickness is 25 feet. It is the bed sought after by all miners, and other beds are opened only when the section of the Mammoth within the operator's territory is being exhausted. It yields a hard, white-ash coal of great purity, which is in demand for furnace use and for other purposes requiring a clear, hot fire. The Holmes bed (F) lies about 100 feet above the Mammoth. It contains from 4 to 6 feet of hard, compact, short-grained, white-ash coal, well adapted for furnace use. The Primrose (or G) bed is 10 feet thick, and produces a gray-ash coal, softer than that of the Mammoth, but excellent for housekeepers' use. Farther west this bed becomes the famous Pittsburg bed (or H) of the bituminous coal-field.

The white-ash series of anthracite beds has four members-the Buck Mountain, Skidmore, Mammoth, and Holmes, or B, D, E, and F. (See fig. 4.) Another bed, 5 feet in thickness, called the Ross bed, has been traced in some places, and named "C" by some writers, but it is scarcely extensive or distinct enough to have a separate designation. (See figs. 6, 7, 8, 9, 10.) An outlying branch of the Mammoth bed is also counted separately sometimes, and called the "Seven-foot," from its usual thickness, but it is more properly credited to the great bed with which it is immediately connected. The first in the group, B, or the The measures of the Southern coal-field are shown Buck Mountain bed, has received little attention as in the accompanying cross-section of the Philadelphia yet in the First coal-field, where it averages 8 feet and Reading Coal and Iron Co.'s shaft near Pottsville, in thickness, though its coal is of good quality. In Pa. (Plate XII.). This shaft, near the south foot of the Lehigh region and the western end of the Third the great anticlinal axis of Mine Hill, is the deepest cut field it becomes very important, being 16 feet in in the anthracite coal-measures of the United States, thickness at the Buck Mountain mines, at the ex- developing a greater thickness of coal-strata and coaltreme eastern end of the Second field, and increasing beds than any other shaft in the world. It is located to a thickness of sometimes 25 to 30 feet in the cen- on the east branch of Norwegian Creek, on a lateral tral portion. In the vicinity of Scranton, in the Third branch of the Philadelphia and Reading Railroad, field, it is only 4 feet thick. On the other hand, its 96 miles by rail from tide-water at Philadelphia. Its neighbor, the Skidmore, Wharton (or D) bed, is 8 feet mouth is 729 feet above tide-level. The shaft was sunk thick at Scranton, and contains excellent coal; in the 108 feet to the Peach Mountain bed, 10 feet thick, one Mahanoy field it is usually 10 feet thick, while in the of the Upper red-ash coal series; thence down 431 feet, Schuylkill region it is but 6 feet thick, and its coal is where the Little Tracy was found, 45 feet thick, much often so rough and slaty as to be unmarketable. The beyond its usual size; at 1100 feet the Diamond bed was Mammoth bed (E) is the great bed of the anthracite re-cut, 16 feet thick, also much enlarged; at 1559 feet the gions, and produces much more of the coal sent to mar ket than all the other beds combined. (See fig. 5.) Its thickness varies from 14 feet or less in the Scran

shaft had passed through all the red-ash coal-beds to the Primrose or gray-ash bed, 17 feet thick, five feet more than its ordinary size; at 1600 feet, the bottom

MAMMOTH VEIN, UPPER
MEMBER,

SEVEN-FOOT VEIN.

INTERVENING ROCK AND SLATE, Increasing in thickness to 30 yards.

MAMMOTH VEIN, LOWER

MEMBER.

....................

5' 8"

0' 8"

1' 0"

0' 4"

3' 0"

.................11' 8"

.13' 2"

.24'10"

0' 5"

2' 9"

0' 3"

2'6"

0' 6"

0' 6"

FIG. 5.-Section showing Mammoth Vein at Shenandoah Colliery [Heber S. Thompson, Eng. Girard Estate].

VOL. II.-L