Analysis of Red Ash coal from Dorrance mine, Wilkes-Barre, Pa.

AIR SAMPLES FROM BALTIMORE RETURNS.

The samples of air (Lab. Nos. 1300, 2534, 1299, and 2533) from the Baltimore workings were taken in the two outlets at the foot of the Baltimore upcast shaft. The air comprises not only the total return air from the Baltimore workings but also that of the Red Ash and Five-foot returns. The total volume of methane carried was 1,620 cubic feet a minute, but if the values for the Red Ash (1,024 cubic feet) and the Five-foot (about 250 cubic feet) be deducted, there remains only 346 cubic feet to the minute as the volume from the Baltimore workings. These workings extend under a large portion of the wide district lying between the Pettebone mine and North Market Street, Wilkes-Barre, and from the south side of the river north nearly to Rutter Street, as well as a small area southeast of the Dorrance shaft. In the north half of the area the Baltimore coal separates into two beds, the upper (7 feet thick) being known as the Cooper bed and the lower (6 feet thick) as the Bennett, which are worked separately. The area of the workings, which are shown in figure 28, was approximately 1,000 acres, of which probably about one-third was pillars and two-thirds gangways and chambers. The workings were ventilated by about 200,000 cubic feet of air a minute, which, seemingly, carried only about 0.2 per cent methane. There were large areas of old workings, but considerable coal was being mined in places.

The workings extend over the prominent anticline just north of the river, the crest of which to the west develops into a 60 to 80 foot

fault, and to the north descend 200 feet into a broad syncline traversed by a low anticline. The depth below the surface is mostly 600 to 800 feet and much of the area is covered by 50 to 100 feet of sand, gravel, and clay deposited by the Susquehanna River.

AIR SAMPLES FROM FIVE-FOOT RETURNS.

The return from the Five-foot workings could be sampled to advantage only at the head of No. 10 plane, or after it had ventilated about two-thirds of the worked area. As shown in Plate V this area, about 600,000 square feet, extends along the north side of the Susquehanna River just north of Dorrance breaker for about 2,000 feet east and west and 600 feet north and south. The beds dip gently 5° to 10° north into the main basin and are approximately 500 feet below the surface. The return sampled ventilated about 20 working faces which, with gangways and other spaces, had a length of about 15,000 feet. As the coal bed is 5 feet thick, 75,000 square feet of coal was exposed. The return air (sample 1221) carried 191 cubic feet of gas a minute, or about 2.5 cubic feet a minute for every 1,000 feet of coal surface. The amount of coal being mined was nearly 110 tons a day, including waste, so the methane was at the rate of about 14 cubic feet a minute per ton.

AIR SAMPLES FROM HILLMAN RETURNS.

It was practicable to sample the Hillman returns at only two places, one in the main return at the foot of the upcast shaft, and the other in the main return near the west boundary of the property. The area of the Hillman workings in the Dorrance mine is shown in Plate V. The workings comprise a broad belt under the river and an extensive district to the northwest, covering in all about 220 acres. They extend across the prominent anticline previously mentioned and down into the syncline to the north, and the northernmost gangway passes over the next anticline north. The depth beneath the surface is mostly from 300 to 400 feet and except near the Dorrance shaft the the entire area is covered by about 100 feet of sand, gravel, and clay deposited by the river. The return air from the Hillman workings comes to the foot of the upcast shaft through two airways. One, carrying 1,082 cubic feet of methane (see sample 1212) a minute, is from the eastern and southern parts as far as the downcast at Thompson Street, Wilkes-Barre. To the east some miners were robbing pillars in an area filled by flushing. The thickness of the bed is about 63 feet.

One split ventilated a small area of workings in the Bowkley coal bed and then passed out the upcast, but this split carried little of the Hillman gas. The second airway, sampled at the foot of the main

upcast (sample 1211) and carrying 695 cubic feet of methane a minute, received two splits: one drained new workings north of the river, where about 50 miners were employed, and a large area of old workings; the other was from workings that extended under the river and to the north as far as the west boundary.

The length of coal surface exposed in all chambers and gangways, as measured on the mine map, was approximately 160,333 feet, and as the average thickness of the bed is slightly over 6 feet, about 1,000,000 square feet of coal was exposed without deducting for certain areas that had been filled by flushing. As the total volume of gas in the two airways at the main upcast was 1,777 cubic feet a minute, 1.78 cubic feet of methane a minute was given off for every 1,000 square feet of coal exposed. Much more of this gas undoubtedly came from new workings than from old pillars and abandoned chambers.

The return air from the Hillman workings along the west boundary of the area was in two airways and these are represented by samples 1220 and 1210. One carried 203 and the other 142 cubic feet of methane a minute, a total of 345 cubic feet. This air finally joined other splits and was included in the air from which sample 1211 was taken. The extent of the area represented by this return air was large but was not ascertained.

RÉSUMÉ OF CONDITIONS IN DORRANCE MINE.

The amount of gas emanating from the different coal beds in the Dorrance mine varies widely and as the structural conditions are closely similar throughout, these variations are not related to the structure.

The Hillman workings, which present structural conditions similar to those of the Baltimore workings, but occupy a much smaller area (220 acres), were yielding 1,777 cubic feet of methane, equivalent to 1.78 cubic feet a minute to every 1,000 square feet of coal exposed. The Baltimore and Cooper-Bennett workings, having an area of nearly 1,000 acres and coal twice as thick, have a rate only about one-fiftieth as great, although certain places in these extensive workings are very gaseous. The Red Ash workings with only 84 acres mined but very thick coal gave slightly more than 1 cubic foot of methane a minute for every 1,000 square feet of coal exposed, or nearly 2 cubic feet a minute per ton mined. The Five-foot workings, 24 acres, were producing 2.5 cubic feet of methane a minute. to every 1,000 feet of coal exposed, or slightly more than 1 cubic feet a minute per ton mined. These figures, however, do not give as close a comparison as could be desired for the amount of gas given off per square foot in working faces is greater than in most old workings. The Five-foot and Red Ash workings contained

a large proportion of fresh-coal exposures, whereas the extensive Hillman and Baltimore workings were in large part old, although in places they had many fresh working faces. The most notable features are the strong, general and local emanation of methane from the Hillman and Five-foot beds, the more moderate amount from the Red Ash bed and the very small general emanation from the extensive Baltimore workings.

HOYT MINE.

The Hoyt mine, which is one of the newer collieries of the Pennsylvania Coal Co., is in the center of the main basin 2 miles southwest of Pittston. Beds from the Pittston to the Red Ash, inclusive, are mined extensively. The workings are under the south side of the Susquehanna River for some distance and the northwest part of the mine extends under the river. North of the shaft there is a broad low anticline showing a number of crenulations to the northeastward. South of the shaft the measures slope into a shallow basin, in which the Red Ash bed is a few feet below sea level, and then rise very rapidly in a narrow steep-sided anticline, the crest of which is 238 feet higher than the bottom of the basin. This upturn is the southern margin of most of the workings, but the Red Ash bed has been followed up the rise by a gangway known as the south slope.

The mine is reported to be gaseous, especially in the workings under the river where the cover is thick and there is a sheet of clay in the valley filling. The sharp uplift south of the shaft was not as gaseous as was expected, but one heavy blower came from it in the workings in the Pittston bed. There have been several vigorous blowers in the mine. One, which continued to give off gas for many months, was from a crevice more than 16 feet deep. Another was in the roof at the end of the main gangway.

AIR SAMPLES FROM RED ASH RETURNS.

In investigating conditions in the Hoyt mine the Red Ash bed was selected because the amount of gas in its different returns varied considerably and the air currents were advantageously arranged for being sampled separately. The following table gives the results of analyses of five samples of return air, and the volume and velocity of the air at the points of sampling on November 18, 1910. The returns were also measured and sampled April 29, 1912, after mining had been suspended nearly a month. The results of the later work are given on page 145. In figure 29 are shown the extent of the workings in the Red Ash bed up to the end of 1910, the points at which air was sampled, the direction of the air currents, and the location of working faces.