762 THE COLLIERY GUARDIAN. April 20, 1917. getting the most use out of a limited quantity of material. There is, however, one point to which atten- tion should be drawn, namely, that the district in ques- tion (the rise side) does not favour, and is not likely to furnish, such a success as the dip side — for the following reasons: — (1) The roof is bad and easily broken. (2) The seam is 4| ft.—that is, 1 ft. thicker than on the dip side. (3) The canch yields few large stones suitable for packing. (4) The pack is higher and is easier to squeeze out. (5) The roof will not arch. (6) Owing to the side canch frequently slipping, bar timbering at certain times and places is rendered impracticable. (7) The consumption of timber, although light in the gateway, is very heavy in the cross headings. , The last-mentioned reason, although due in great measure to the nature of the roof, is, in the author’s opinion, also due to one or both of the following causes: — (1) Falls are frequently created by the uneven pres- sure of the roof. For instance, if a fall should occur in a gateway, it seldom takes place at the back-bye portion, which is more settled, but generally not very far from the face, where the roof is just beginning to accelerate in its downward journey. The same prin- ciple applies to cross headings. The portions of roof R/GHT WAY. PACK LIKELY TO SQUEEZE 4 OUT 1 PACK LIKELY TO CAUSE FALLS. EW Figs. 5, 6, and 7.—Showing the Right and the Wrong Way of Putting in Packs. across the gateways are more or less settled on account of the packs, while the portions across the goafs are still on the move, owing to lack of substantial support in them. The cross heading thus goes through a sec- tion of strata relatively and alternately in motion and at rest; the former tends to tear away from the latter, causing the frequent falls. (2) The roof of the portion cut off by the cross head- ing is relatively more settled than that of the portion still open. The uneven rates of descent of the roof on both sides of the heading create an uneven pressure on the roof in it, and tend to disturb it, thus also causing falls. It is easily seen that if the foregoing two uneven pressures act together—one longitudinally and the other transversely—the occurrence of roof disturbance is greatly intensified, and it is not unlikely that such is the case in the cross headings concerned. More- over, the roof breaks at every cut of the face, and these breaks sometimes disturb the overlying strata to a considerable depth, owing to the nature of the roof and the length of time that the face has been standing. As the gateways and packs are at right angles to them, these breaks make themselves less manifest; but the cross heading runs at a very small angle to them, and where the strata are more disturbed than elsewhere by them, this disturbance is subse- quently more intensified by the. firing of shots in the canches, so that roof trouble is obviously inevitable. In order to prevent stoppage of work from falls thus caused, great quantities of timber are used, and once put in it is never removed until the heading is no longer required, thus creating excessive consumption on a very large scale. As a remedy, the best plan, the author thinks, would be to drive cross headings at longer intervals from the face, when the chances are that the strata are more or less settled, and to drive them through the goaf if necessary. The driving cost would, of course, be heavy, as there is a great deal of canch to be taken off, but the subsequent saving in timber and labour, and also the great yield of large stones for face packs, would neutralise largely, if not wholly counter-balance, the initial cost. This method applies, in the author’s opinion, to all longwall work- ings with a bad roof in a seam which is a little too thick for the employment of that system of working to its full advantages. The foregoing are cases where comparatively large quantities of timber can be saved, with other bene- ficial effects, and without jeopardising the object of safety. There are, however, other points which are well worthy of consideration, and it might be advis- able to appoint a special underground timber official to see to the enforcement of them. The following is a collection of the details which will serve as a guid- ance to such an official in his daily rounds: — (1) Drawing of Props.—Always use a Sylvester prop drawer in drawing timber in the goaf. Avoid letting the men use axes as much as possible, thus prevent- ing the sometime unnecessary shortening of a valuable prop. Where a plank is supported by two props, draw the goaf one first and the face one last. Where a middle prop is used—that is, three props to one plank, as at a conveyor face—some men draw the two face props first, then ease the plank by hand, and extract it, the goaf prop being the last one to be dealt with. This method is to be recommended for the reason that a plank is more valuable than a longwall prop, even if the plank be saved at the expense of the prop. In this case, if the goaf prop is to be drawn first, that end of the'plank is relieved of its support. With the pressure of the roof (which is greater in the goaf) upon it, the plank may easily be broken at the point where the middle prop is set; whereas if the roof pressure near the face is relieved first, the goaf prop may or may not break, but the plank is more likely saved. (2) Props in Gateways.—As many of these props in the back-bye portion of a gateway are no longer sup- porting the roof, but are acting to prevent the roof from settling, and in most cases do more harm than good to the roof, the pack, and themselves, the advis- ability arises of having them drawn. If the roof there is not reliable when relieved of support, a bar prop should be put in first before the drawing of the uprights commences. Some props bear little or no pressure, and readily give way when pulled or pushed by hand ; others perhaps stand with loose ends, and all these props should be regularly combed out. At times loose timbers left as the face advances are also seen in gateways and in places temporarily stopped. These must be gathered, and sent to where such timber is stocked. (3) Props Left in Packs.—This evil is practised by almost all stonemen. Their excuse is that they are not authorised to draw props, and the chargeman is not always there to give the necessary direction required. The pack has to be made, and therefore the prop has to be left in. It is true that, according to the Coal Mines Act, they cannot independently draw a prop, but, at the same time, these men are used to their work, and quite capable of judging whether a prop can be safely drawn or not. Indeed, where H-girders are in the way, and they dare not under- mine in the pack, they have frequently been seen to knock them out entirely on their own initiative. When they are ordinary props they, however, leave them in. Their real object in leaving them in is to keep the roof up for reasons beneficial to themselves. If the prop is drawn, and the pack put in, the roof will exert its full pressure on it; but if the pack is badly built, it will soon become dislocated, and in the very next shift they may have to re-pack it. So long as a prop is standing, it takes the pressure off the pack, and will continue to do so until it is broken, when the pack will be forced out by it, and the gate- way made untidy and obstructive (fig. 2). By this time the canch will have advanced with the face some distance, and it is then no longer their duty or con- tract to attend to the pack. This practice must be coal filled off. coal undercut COAL TO BE UNDERCUT, fc' « G“'d* 0 c a a o o s eS orna 6 0 0 o *o o a o I 0 <0 0 0 B s a 18 ig Jg HI II SO ■-Uli binR M Fig. 10.—Plan Showing Systematic Setting and Drawing of Timber on a Longwall Face, worked with a Chain Coal-cutter. (Scale, 24 ft. to 1 in.) stopped by vigorous measures, and, if all else fail, the men should be instructed to pack round the prop concerned, leaving a clear space on the gateway side so as to enable the drawer to get at it later when he comes in to draw it. (4) Break-off Timber for Canches.—For this pur- pose planks must not be used, as the old head trees are quite serviceable. When the canch is shot down, and the pack put in, the props should be drawn. Here again the stonemen leave them standing in order to prevent the side canch from falling, which would mean more stone to be put away, and no more pay for it. (5) Loose Timber on Rolleyivays.—It is not unusual to see odd props lying by the sides of rolleyways, and on being questioned the men generally give as a reason that they are left there to be handy when any of the supports in the neighbourhood require renewal. This practice should be discouraged. A suitable place should be made to store a few props for this purpose, and on no account should they be allowed to lie at irregular places, as they eventually are likely either to be lost or to become rotten. (6) Stocks.—Stocks in flats and other places should be properly stacked, and their quantities duly noted daily, so as to form a check to the amount used. (7) Unnecessary Supports in all Roadways.—Timber is often used in roadways as supports, which after- wards are found to be unnecessary. These should be removed for obvious reasons. (8) Lar Timbering.—Bar timbering is very effective and economical, as one prop saves a plank and another prop. Its use is greatly encouraged in the collieries with which the author is acquainted, and the manager has even sanctioned the men to reduce the width of places (12 ft. places reduced to 11J ft., and 7 ft. walls reduced to 6 ft.) so as to facilitate the employment of bar timbering. The props for this purpose should, like uprights, be tapered at one end, so as to make the weakest section there. The side canch should be squared off. A nick is made at one side, into which the tapered end is inserted; the bar is then slid along the other side until the end is square with the canch. If not tight enough, a wedge can be put in, and as the side pressure becomes greater, the bar becomes quite tight (fig. 3). It must be set as close to the roof as possible, in order to make it effective, otherwise loose pieces of roof may still fall down, and as the strata settle a large portion of the height would be taken up by it (fig. 4). Figs. 8 and 9.—Showing the Right and the Wrong Way of Setting Timber to Prevent a Fall. (9) Packs.—Stones should be large and flat, and not of a round shape. They should be inbond and not outbond. The pack should be as straight in line with the side canch as possible (fig. 5), particularly where the roof is friable and incohesive; otherwise, if the pack overlaps the canch (fig. 6), the roof pressure tends to squeeze the pack out; and if the canch overhangs the pack (fig. 7), the overhanging portion tends to slip down. Neither of the above conditions is conducive towards the saving of timber. (10) Lofting s.—Lof tings in gateways are not fre- quent, but where there is a goaf break or similar trouble they are sometimes necessary. When the gate- ways have advanced and the break settled, these timbers are liable to be neglected, to get buried in the sides, and eventually to be lost sight of. These are the places to extract comparatively large quantities of timber on a small scale. In one instance, such a place was found in a gateway, and out of the two holes over 40 pieces of timber were disclosed, more than half of which were still in perfect condition for further ser- vices. These cases are, however, rare, but they are nevertheless instances that should not be overlooked. (11) Timber Used, to Prevent Falls.—The author has seen men putting planks across the middle of two other planks in the shape of an “ H ” (fig. 8), in order to prevent a small fall of roof. This practice is not pro- fitable. If a fall is so small that one or two planks will stop it, it pays to let the fall occur, and to clear it away, instead of employing and running the risk of breaking three or four planks, and the fall still to take place. If the fall should be likely to be a big one, strongish timbers should be used, and put in cross- wise (fig. 9), resting on the ends of the planks so as to let the strongest part bear the weight, in order to minimise the likelihood of breakage. (12) Systematic Timbering.—Systematic timbering should be enforced on all faces. Rows of props should be parallel, and should be as exactly in line as pos- sible. This not only facilitates drawing, but also tends to make the roof pressure uniform along the face, and less breakage likely to occur., Where a prop is con- sidered necessary for safety other than these, it should be set in addition to, and not in place of, the syste- matic row. If a chain cutter is employed, the last row of props should be 3 ft. and not 4 ft. from the face, as this machine takes only, about 2} ft. in width for its own passage, and the props so set would serve