long prop supporting this coal receives support near the middle from the collar, and the collar and leg in turn furnish some support to the roof.

This form and the following shown by Fig. 26 are applicable only under exceptional conditions; and to meet the various requirements of gangway timbering under ever-varying conditions, many other forms of timbering are and have been used, but to illustrate all of these would multiply the illustrations of this report beyond reasonable limits. It will be sufficient to indicate the fact that nearly all forms of gangway timbering in use in the anthracite region. are modifications of the regular style shown by Figs. 20 and 21, made by shortening or lengthening one or both legs, or by inclining them at different angles according to the dip of the bed, etc., etc.

Many engineers are of the opinion that the legs, as nearly as is practicable, should be set at right angles to the dip, and propping is always so set, but in gangway timbering this can seldom be done, and probably an equal number of mining engineers believe that the best form of timbering is the ordinary upright form of Fig. 21.

Gangway Driving.

In opening up new workings at a moderate depth beneath the surface or above water level, ventilation is often affected by a brattice carried along the lower side of the gangway as shown by Fig. 51, and Page plate No. 38; but the plan

usually adopted is to drive an airway parallel to the gangway, and connect them at regular intervals by cross-headings, as shown by Figs. 55 and 56.

The thickness of the pillar left between the airway and gangway is to some extent governed by the thickness of the seam. In the flat workings of the Wilkes-Barre district a pillar of from five to eight yards is usually left between the airway and gangway, and cross-headings connecting them are driven every ten or fifteen yards, or more.

When the coal bed dips at a sharp angle, the airway is commonly driven above the gangway as shown by the drawings on Atlas plates XXI, XXII, and XXIII.

When the roof is good, requiring no timbering, and the coal gives off such a small quantity of gas that separate airways are unnecessary, ventilation of the gangway heading is frequently accomplished by means of broad pipes, as described in detail in the chapter on ventilation. Board pipes and a small fan are also used to keep the heading free from gas in very gaseous mines, but for this purpose a brattice carried well up to the face is more efficient.

Single track gangways from eleven to fourteen feet spread at the base, and of sufficient height for a nine foot leg, and of a width at the top to admit a seven and a half to a nine foot collar, can be driven and timbered in hard coal at a rate of about two and a quarter feet per eight hour shift, or without timbering at a rate of nearly three feet per day. In the softer coal of the Wilkes-Barre and Schuylkill regions an average of four feet per eight hour shift can be made in driving untimbered, and about three feet for timbered gangways.

Gangway driving is usually done by contract at so much per yard, and the miner taking the contract hires and pays two laborers and bears all expense for oil, powder, tools, wick, etc.

The following table shows the range of these contract prices in the southern district of Carbon and Luzerne counties during the years 1875 to 1880 inclusive:

These contracts are made on two bases, 1st. the company owns the coal obtained in driving, or 2nd. the miner owns

the coal and the company pays the contractor so much per car for all the coal (at miner's rates); these two being known by the terms "company's coal" and "miner's coal." The above table is on the basis of "miner's coal."

The contract price of course varies widely with the character of the coal, its thickness, and the size of the gangway; thus in 1879 in the Hazleton District the variation was $1.80 per yard as given in the table, and many cases might be given in which the variation is much greater.

From six to eight pounds of powder per yard of gangway eight by twelve feet is a fair average for hard coal, but in soft coal one half of this amount will exceed the average quantity required. The contractor's incidental expenses will average about one third the cost of his powder, so that his total expenses for supplies may be placed (for hard coal) at about 90 to 92 cents per yard, pay of laborers from $2.50 to $4.00 per yard, averaging $3.60, making his total average expenses in hard coal $4.50 per yard.

The profits or net earnings of miners working on gangway contracts must always vary widely with the individuals. Where one man will clear ninety or a hundred dollars a month another will make only forty or fifty. The average compensation of men doing this class of work is probably at present from sixty to eighty dollars a month.

The method of driving is similar in many respects to breast working, but some miners prefer blowing out the top first and afterward putting in four to six shots to square up the sides and blow up the bottom. The character and position of partings of slate or bone, and the direction of dip, and of the main cleavage planes always determine the plan to be employed. In some cases it is advantageous to

to put the bearing-in shots on one side and then having a free end to blow out the other side by shots located near the top and bottom corner; sometimes to fire a group of two or three central holes, and then to blow out the top, the sides and the bottom by a series of peripheral holes.

The holes are usually drilled four feet, more or less, deep, but in loose coal, holes of a greater depth can be advantageously employed.

In thick seams the gangways are generally driven near the floor of the bed, but this location is not always adhered to in steep-pitching seams. On moderate dips this location of the gangway increases the pitch of the shute and facilitates loading, and on steep dips it allows room for the airway near the roof of the bed, but increases the pitch of the shute.

When the floor is very uneven the gangway is sometimes driven as nearly as possible in a straight line, and may then run indifferently in the top or bottom benches of the bed.

Gangway Timbering.

Very few gangways are timbered with square timber, round timber being so much stronger and cheaper that it is almost always preferred.

I find that great difficulty is experienced in obtaining timber of sufficient size for good substantial work, and that timber from twelve to fourteen inches is often used where eighteen-inch stuff is really needed.

An average of a large number of measurements of what were commonly considered fair specimens of gangway timber gave somewhat less than thirteen inches, and this may be considered to fairly represent the average size (small end) of the large timber now used.

Much larger timber is, however, obtained and is, indeed, absolutely necessary at many collieries. Timber under fif teen inches is not considered worth much for gangway work in the mines of the Lehigh Coal and Navigation company, where, as elsewhere, constant effort is made to obtain a certain amount of eighteen-inch stuff.

The method of fitting the collar upon the top of the leg is shown by several of the preceding illustrations (Figs. 20 to 26) and on a larger scale by Fig. 27.

The angle at which the collar and leg are joined varies with the style of timbering. For the ordinary upright frame it is usually three or four inches to one foot.

After the legs have been placed in position with the collar resting upon them they are wedged in place and securely fastened by flat wooden wedges as shown in Figs 20 or 21, or by round wedges or lagging as shown by Fig. 28, which also shows a different method of cutting the joint.

AC.

Fig. 28.

The lagging is then driven in behind the legs and over the collars, as shown by Figs. 20 to 26, and if the roof is very poor so that it falls at the face and needs more substantial support at certain points than is afforded by any single set of timbering, long poles from three to five inches in diameter are driven in over the collar, and these are of sufficient length to lap over two sets of timbering. This is termed