keep his own work in line and, being proud of a fine piece of work, will urge the miners to drive the headings straight. With heavy trains and motors and the high speed required for large outputs, the importance of a straight track is apparent.

When rooms are driven on sights, usually each room is given a pair of sight plugs, but in some cases only every other room is so provided, the intermediate room being kept in line, as well as possible, by leaving a pillar of constant thickness on each side, which thickness is determined by measuring through the cross-cuts. As the direction of rooms is rarely of prime importance, sights in them are not moved up, unless it is absolutely impossible to see the face from them by reason of smoke, roof falls, etc. Room sights are commonly placed in the necks anywhere from 8 to 20 ft. from the entry line. Surveyors prefer to wait until the necks have been turned for a number of rooms before placing the sights in any of them. The instrument is then set up at any convenient station and the line of sight made to coincide with that of the entry. A series of tacks is placed in line the proper distance apart (when rooms are turned at 90°, distance width of room+width of pillar) and are driven down into the tie or into a plank laid across the rails, one tack for each room. The instrument is set up over each tack in succession and a right angle to the heading line is turned and two sight plugs are placed in the room neck as far from the entry as possible. The distance of each tack from the entry station is noted and the distance from the line of the entry to the outbye room sight plug is also measured and recorded. Room sights may be set by bisecting the eye of the spad and are commonly placed 18 in. to 2 ft. from the rib. Where rooms are inclined to the entry, the distance between their centers measured along the line of the entry is found from the formula:

If

Surveying and Note Keeping.-The laws of most states require that the mine workings be surveyed and mapped at least once every 6 mo. If the necessary measurements and side notes have been taken at the times the entry sights have been moved up and have been mapped, the mine, so far as the main roads are concerned, is always within a few weeks of being up to date. this has not been done, the procedure will depend on whether lines of sight are carried up one or both entries of a pair. If each entry has its sights, the O end of the tape should be held at the last station appearing on the map and the tape stretched out to the next station. The surveyor may then walk along the tape and, when opposite a break-through, note the distance to both sides of the opening as say +256 to +267 (the opening being 11 ft. wide). The assistant should carry the 0 end of a tape (usually a 50-ft. metallic tape) to the rib at each side of the cross-cut, and the surveyor should measure the distance to the nearest -ft. mark to these points from the entry line and note whether the break-through has been driven to the right or left from the entry. Room necks may be located in the same way.

It is advisable, where the entry is crooked, to note the places where the tape comes nearest and farthest from the rib. Many surveyors do not take offsets to the corners of the pillars made by the various openings, merely noting the plusses, or distance measured along the tape opposite which these openings come. When so mapped, the entries appear perfectly straight, which makes an attractive but inaccurate map. When the exact distance between stations as well as the necessary vertical angles have been taken at the time the stations were moved up, the use of a transit is unnecessary when making the entry surveys, but it is highly advisable to remeasure these distances as a valuable, in fact as the only possible, check on the original distance measurements until a close is made and the survey calculated.

After taking the notes between the first pair of stations, those between the next pair should be taken, and similarly until the foresight man with the tape reel is at the last station. This may be anywhere from 25 to 200 ft. from the face. To get the entry line, the foresight man, carrying the reel, should be sent ahead; and when he is at the face, the tape may be brought in line by sighting over the entry sight plugs to a lamp held on the reel. After completing the side notes on one entry, those on the parallel entry or entries are taken. These notes are entered in tabular form as taken, beginning at the bottom of the page and working toward the top. The plusses, or distances from the instrument, are in one column and in other columns are the offsets to the corners of the openings, each placed in the horizontal line of the proper plus.

ŏ 238

167.62

5-155-5

4-140-5 3-110-6 4-91-6

5-72-7

4-30

20-8

42

13

5-16

14-7

53

e18 237

Each surveyor will have his own set of abbreviations: Common ones are Bt for break-through (or cc for cross-cut), Rm for room, r or rb for rib. Thus +256, 5.5 Btr, means that at 256 ft. from the station and 5.5 from the line is the corner of a break-through, which is driven to the right. Sometimes these notes are amplified and illustrated by sketches as shown in Figs. 1 and 2. In most mines, particularly in the case of butt entries, only the room entry is driven on points, the air-course being kept as nearly on a parallel line as possible by maintaining a constant thickness of pillar between it and the room entry. In this case, the distance from the tape or the offset is measured not only to the edge of the cross-cut, but also to the corresponding edge of it on the air-course and to the far side of the air-course as well. These three measurements might be recorded as follows: +254, 5-26-37 and +263, 6-26-36. The plusses are at 254 and 263 ft. from the station and show that the break through is 9 ft. wide. At the first plus, the distance to the corner of the break-through is 5 ft., the distance to the corresponding corner on the aircourse is 26 ft. (the pillar being 26-5-21 ft. thick), and 37 ft. to the rib of the air-course, which is 37 -26-11 ft. wide. At the inner side of the crosscut the pillar is 26-6-20 ft. thick, and the air-course 36-26-10 ft. wide. The advantage in measuring continuously out from the tape is twofold: The surveyor does not have to leave the entry, and consequently has time to enter his notes in a concise and cleanly way as the foresight man does the running around and, above all, by standing on the entry he is able to keep the small tape with which the side notes are taken, exactly at right angles to the large tape; further, notes thus kept are easier to map, requiring but one setting of the scale, regardless of the number of offsets taken from any plus.

FIG. 1

It is usual to make sketches as the side notes are taken, in order to illustrate and make plain any points that might be obscure to the office man that plots the notes. Two forms of such notes are shown in Figs. 1 and 2; both are of the same entry, the air-course parallel to which is located by measurements through the break-throughs. Such notes are begun at the bottom of a page and sketched upwards in the order in which they are taken. The form shown in Fig. 2 is preferable as being the clearer. It will be noticed that in both cases

+8

0238 167.62

6

+157
+185 55

8 9

+140

45

+91

+ 72

7

the air-course is located not by continuous offsets, but by single measurements through the pillar, the disadvantages of which method have been explained. The ends of pillars are so rarely square that it is commonly difficult to decide at just what point a break-through begins. This is illustrated at a and b, Fig. 2. The proper way to locate such a rounded pillar is to take a plus and offset at the point where the pillar begins to round (+155, a) and a second plus and offset where a sight tangent to the end of the pillar may be had (+157, b). The distance between the stations is always noted on the sketch. In the case illustrated, the distance from the last station to the face is shown (8 ft.) beyond the figures for the length of the line.

The survey of a series of rooms in which sights have been placed is a comparatively simple matter. The sight strings are lowered (the miner generally keeps them hung up against the rib), and the helper goes to the face, unwinding the 400-ft. tape as he goes. The O end of the tape is held at the first or outer sight plug, the distance of which from the line of the entry was measured when the sights were placed. The transitman, by means of the room sights, places the man at the face in line and takes the side notes in the manner explained. If the rooms have not been driven on sights, it is customary to place a tack in a tie at the mouth of each room, the tacks all being on the entry line, but at irregular distances apart as they are placed so that the instrumentman may see the face. After the tacks are lined in, their respective distances from the instrument are measured and recorded.

FIG. 2

The instrument is set over the tack at the first room, the vernier is set at the azimuth or bearing of the entry, and a backsight is taken upon some station. The foresight man unwinds the tape on his way to the face, where he holds the reel on an X he has marked on the coal in chalk, and to which the transitman takes a sight. The 0 of the tape being at the instrument, a line is established to the face, and the side notes may be taken as before explained. In many instances a line is run up every other room only (thus, up rooms 1, 3, 5, 7, etc.) the intermediate rooms being located with sufficient accuracy by offsets through the cross-cuts.

It sometimes happens that practically all the rooms on an entry are so blocked with falls of slate that it is impossible to see to the face and thus survey each room separately. In such a case, a line is run from the entry up some room not blocked by falls and a survey made of the faces of the rooms by running a line along them through the break-throughs. If desired, stations may be established in ties in each room near the face, and sights taken down the room until stopped by the falls; or a line may be run down every other room. Usually, offsets from the line along the face will locate the pillars and face line with sufficient accuracy for all practical purposes, particularly if a good portion of the rooms have been mapped from surveys made before the fall of roof took place.

Level Notes. All level notes are kept as in outside work, with the exception that, as the rod is reversed in getting the elevation of a station in the roof, the record of the reading is prefixed with a minus sign. A record of such a reversed rod, when the target is 3.78 ft. below the station, is recorded -3.78.

A shaft is measured (if deep) by a fine steel wire running about an accurately graduated wheel (a sufficient number of turns being laid to prevent slipping) and noting the number of turns before the bottom is reached. The wire may be measured before and after the operation, to insure against stretching. An aneroid mining barometer, if in good condition, will give quite accurate results if a number of trips are made between top and bottom, to give an average. In this case the barometer must be left quiet 10 or 15 min., to be sure that it has expanded or contracted to the proper degree. For rough measurements, the length of the winding rope between top and bottom is taken.

By one of these methods a bench mark should be located below, connected with the outside work, and referred to tide water. The rod must be reversed to get the elevation of all stations in the roof, and all such readings are noted with the minus sign, as -4.32' (read 4.32 ft. below station). Roof stations are almost certain to settle, from the pressure of the superincumbent rocks. To check such settling, the distance from roof to floor must be accurately measured. Some measure from floor to rail of track; this is inaccurate, as the track may be shifted or the grade changed in making repairs, or to take out a sag. Whenever a level survey is begun the distance between roof and floor should be measured to see if it agrees with the notes. If it differs, the fact should be stated under the original notes, as a check for future work.

PITCHING WORK

The survey of workings in highly inclined coal seams does not differ in methods from those employed in surveying mines in flat seams, but there are sundry minor modifications in detail varying from mine to mine, as peculiar or local difficulties have to be overcome.

Stations.-The seams are usually folded along the line of strike so that the entries, or gangways, that are driven approximately upon a water-level, are curved and crooked to the same extent as the seam. For this reason, gangways cannot be driven upon sights, and stations are established as needed as the survey proceeds. As these stations are placed solely with a view to obtaining as long or as many sights from one point as possible and as the spads used do not have to be set exactly on line, much smaller drills and plugs may be used in pitching than in flat work. In some cases, the holes are only to in. in diameter and but in. to 1 in. long as a maximum. Various devices for quickly establishing these more or less temporary stations have been adopted in the anthracite regions of Pennsylvania, some of which are here given.

1. The simplest top station is a shallow conical hole, made with the point of the foresight man's hatchet, which is dug into the top rock and rotated, and is called by some a jigger station. Corps using these entirely have a jigger consisting of a steel-pointed extension rod, with an offset holding a paint brush. The rod is long enough to allow the point to be driven into the roof at any height, and its rotation marks a circle with the brush, which is also used to mark the number beside it. Centers are set under such

stations and sights are given by another tool-also called a jigger. This is an extension rod, beyond the upper end of which projects a piece of sheet iron shaped like an isoceles triangle, with the upper and smaller angle cut off so as to form an end in. broad, and in this end is cut a U-shaped groove.

The sights are given and the centers set by putting the plummet cord in this groove, and placing the end in the jigger hole in the roof. The cord must be more than twice the length of the section of the place, as it must be held in the hand, run over the jigger notch, and hung vertically to the plummet, which must come to the floor when the stations are set. The rod and cord are held in the left hand, and the right is free to steady the bob, give sight, or set the center. The advantages are the quickness with which the centers are set and the sights given, and the ease with which the highest stations are reached. The disadvantages are the impossibility of making the jigger hole perfectly conical, so that the jigger can be set in the same place on two successive sights, and the plummet cord will hang exactly in the same place. 2. A twist drillin. in diameter is used to make a hole in the roof; a piece of cord or, better, a copper wire is placed across this, and a hardwood shoe peg is driven into the hole and binds the cord tight. The plummet is tied to the lower end. A cord will soon rot, and, if in the gangway, is pulled out by the drivers for whip lashes, while the wire is more permanent; but even this will be pulled out by catching in the topping of a car in a low place. 3. The use of spads is dispensed with, and all the stations put in rock roof where possible. A-in. twist drill makes a vertical hole 1 in. deep. Into this, when a sight is to be taken, the foresight man puts a steel clip with serrated edges. This is made by bending upon itself a thin piece of steel in. wide. When the ends are pressed together it will go into the hole, and the spring of the sides and the serrated edges hold the clip in the hole so that it is hard to pull out. The cord passes through a hole in the center of the bend and is, therefore, in the center of the hole-no matter how the clip is inserted. It is removed by pressing together the ends of the clip. This is the easiest and quickest way of working, as there is no eyehole to be freed from dirt and no knot to be tied and untied. The hanging of the plummet takes a fraction of a second, and the station will remain as long as the roof keeps up. disadvantages are the putting of the holes inclined to the vertical by a careless man, and the many roofs that are unfit for piercing with a twist drill.

The

Stations are generally marked upon some regular system, as in flat work, although in some mines the objectionable practice of numbering stations at random as they happen to be placed still prevails. In the case of leased properties two surveys will commonly be made, one by the operator and another by the land owner. When this happens, each corps will have its distinctive mark as, for example, the one a circle and the other a cross (+), with possibly a distinguishing letter selected from the name of the corps as a further means of identification. If both corps use the same station each will place about it its distinguishing sign and number, and the notes will state" Sta. 617= Sta. 432 of ( ) Corps."

Surveying Methods.-The method of surveying gangways and keeping notes does not differ from that employed in flat seams, except from the fact that three consecutive stations not being in line, a deflection angle and bearing or azimuth must be read at each set up. As the grade between stations may be, in fact commonly is, pronounced, particular attention must be paid to reading the vertical angle. Parallel entries (room entry and its air-course) are commonly at such a distance above or below one another that it is not usually possible to locate the one by measurements made through the crosscuts from the other and a separate line must be run in each. In case it is possible to locate the air-course by means of offsets from the main gangway, a clinometer, frequently a brass protractor with a plummet attached, must be hung from the stretched tape to give its angle of inclination. All such inclined offset sights must be reduced to the horizontal before being mapped.

If the seam pitches more than 30°, the rooms are worked with batteries; the heavy timbers forming these usually preclude the possibility of sighting from the gangway to the face. Work of this kind is surveyed by lines out the gangway and back through the faces of the rooms, which are generally clear of timber. The line along the face should be tied into the gangway line as soon as opportunity offers.

If the seam makes much gas, sights must be taken to safety lamps unless the portable battery hat lamps are used. The latter afford a very satisfactory light and, being absolutely clean, are preferable not only to the ordinary safety lamp in gaseous mines, but to the oil lamp in any mine.

The angle of dip of the seam should be taken at each station and at intermediate points if it changes radically. The thickness and quality of the coal should be observed frequently and changes of importance noted on the map. Locating Pillars for Surface Support.-It is customary to leave unmined pillars of coal to support important buildings, reservoirs, etc., on the surface. The usual method of locating these pillars is to extend vertical planes through the boundary lines of such objects, and leave untouched all parts of the superincumbent beds embraced by those planes. This is accurate only when the strata are horizontal or vertical, as beds settle normally to the planes of the strata and not in a vertical line in case the open spaces are stowed. If the spaces are left open, they are first filled by falls, and then the settling goes on according to the above rule. No cut is necessary to show the method of settling, and the place where the bed is to be left untouched may be found as follows: Draw a vertical section through the point to be supported, and also the underlying bed on the line of the dip of the bed-the section being accurately drawn to any scale. Draw through the extremities of the object to be supported, lines to the bed, which will make right angles with it. The space included will give the dimension of the pillar measured along the dip of the bed, and the dimensions of the object taken at right angles to the first plane will give the other dimension of the pillar.

MINE CORPS

The number of men required in making a mine survey and the nature of their duties depend on the nature of the work to be performed. If sights are to be moved up two men, the transitman and foresight man, can do the work; but if distances are to be measured, a third man is advisable to assist with the tape if time is an object. The third man is essential if stations are to be set at exact distances from the instrument. In all ordinary survey work where offsets are to be taken, four men are essential and five are advisable. There must be two men to hold the long tape between stations on the entry, and two to hold the tape with which the offsets are taken, one of whom may be the transitman, but it is better to have a special crew for taking offsets, leaving the surveyor free to record the notes, determine the position of the stations, etc. Much time will be saved if one of the four men can set up the transit and read the angles.

When making a complete survey of an extensive property, particularly in pitching work where short sights are the rule and branch gangways on divers grades are common, it is a material help to place the survey stations before an attempt is made to measure the angles or distances. To do this,

473

the transitman will require two assistants and the services of a mine foreman or other official familiar with the workings and who will, in emergencies, hold a lamp where needed. The backsight man remains at the station from which the survey is to start and the party goes ahead to the most distant point therefrom that the lamp is visible. At this point, a station is established in the roof with the drill, plug, and spad, and its proper number painted on the rib or roof. The backsight man comes up to the new station and the party goes ahead locating a second and succeeding station or stations as may be needed. Very frequently several sights must be taken from one station, a common case being that shown in the accompanying figure, where the road forks. Here a helper is sent up each branch, the mine foreman holding his lamp at the backsight, and the transitman shifts his position until he finds a point from which the three lamps are visible and there establishes a station. For this work the transit is not necessary, only a bucket holding the brace, and drills, plugs, spads, and a hatchet, and possibly a 100-ft. tape, being taken into the mine.

CARE OF INSTRUMENTS

The transit should be removed from the tripod and placed in the instrument box with its plates unclamped when not in use. When going to and from work, the transit should not be carried on the transit head, or the spindle will become sprung. Nor should it be carried with the arm crooked under the telescope, as the weight comes on the axis, and that soon gets sprung so that all the adjusting in the world will not make it work right. When carried in the hand, it should be reversed and the hand slipped under the compass plate and brought over so as to clamp both plates. In this way there will be no strain on any part. The person carrying the transit should be the first to