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♦ KNOWLEDGE <► 



[March 1, 1887. 



and most oljvious remedy for this is to cut away only a 

 portion of the coal, leaving other portions standing to sup- 

 port the roof. This is the old and primitive method of 

 working, which is still followed in many colliery districts. 

 It is variously designated " pillar-and-stall," " post-and-stall," 

 " bord-aud-pillar," and in Scotland " stoop-and-room " work- 

 ing. There are various modifications of this mode of work- 

 ing, the technical details of vrhich it would be tedious here 

 to describe. The problem is by no means a simple one, the 

 necessities of ventilation being imperative, as well as the 

 economical and safe removal of the coal itself. 



The simplest and commonest mode of ])illar-and-stall 

 working may be understood by comparing the proceedings 

 to the laying-out of the ground-plan of a new American 

 city, the coal which is first cut out corresponding, on a 

 somewhat narrower scale, to the parallel main avenues and 

 the side streets at right angles to them, the pillars of coal 

 that are left behind corresjionding to the houses between the 

 streets. A current of air, amounting in some cases to a 

 fresh breeze, is made, by means to be described hereafter, to 

 traverse all these streets, though their united length may 

 run into miles. 



It is obvious that a large amount of coal remains as 

 sujiporting pillars after all this street cutting is done. The 

 pillars may amount to as much as three-fourths of the seam, 

 and rarely if ever to less than one-third, modern progi-ess 

 tending rather to increase their dimensions as the pits are 

 deeper. In some of the deep Newcastle pits they amount to 

 as much as four-fifths : 30 to 40 yards long and 20 to 

 30 yards wide. As much as 40 yards by 40 yards are 

 reached. These, of course, have to be finally removed more 

 or less completely, and this removal or " robbing " of the 

 pillars is a dangerous part of the miner's work. In pits 

 where open candles are used in the primary workmgs, 

 safety lamps are demanded for this. This demand, in such 

 cases, is, I suspect, rather due to the coal dust than to the 

 fire-damp, which is commonly credited with it. 



The pillars are cut away one by one, and "jiids" or 

 wooden props are wedged into their places. TiiLs is continued 

 until all the pillars of one compartment of the mine called a 

 " panel " are removed. Then the juds are knocked away, the 

 roof falls in, and the iloor creeps up, forming a mass of 

 ruins called a " goaf." 



A panel is simply a space of some acres surrounded by 

 thick walls of coal, to cut off free communication with the 

 other parts of the mine. This prevents the mischief that 

 has arisen from the accumulation of gas in the midst of the 

 debris of the goaf of old workings. These panel walls are 

 the last portions of the coal to be removed before the pit is 

 finally abandoned. 



The mode of robbing the pillars is either by driving a 

 bord through them, and thus obtaining a good place for the 

 supporting juds in the middle part of the original pillar, or 

 by slicing them away from their faces. Much care and skill 

 is required in the economical and effective placing of the 

 supporting props, and of pack walls to protect the men from 

 the falling roof. 



A vast quantity of coal, the wasted pillars of older work- 

 ings, remains hopelessly buried. In the older and cruder 

 modes of working the pillars were left as small as possible, 

 and finally they were crushed, the roof coming down and 

 burying them. The greatest waste of this kind has occurred 

 in the richest of all our coal seams, the 10-yard seam of 

 South Staffordshire. The gi-eat height between the floor 

 and the roof of this seam — 2.5 to 3G feet— renders the use of 

 juds or wooden pillars inapplicable for support, and also 

 demands some peculiar modes of working generally, which 

 are thus described by Mr. Warington W. Smyth : " Main 

 workings or sides of u-ork are opened in the form of a 



square or parallelogram, 50 yards in the side or more, and 

 shut off by a rib of coal 7 or 8 yards thick, at the least, 

 from all other workings, except at the entrance a narrow 

 holl-hole. Driving out in the lower coals, and gradually 

 rising to the higher ones, the colliers open stalls of 5 to S or 

 10 yards wide, forward and across, so as to leave square 

 pillars, generally 9 or 10 yards in the side, and whenever 

 the unsoundness of the coal or roof appears to require it, 

 sparing additional supports of coal in men-of-ioar 3 or 4 

 yards square." 



Those who are so easily satisfied, as many are, concerning 

 the prospective duration of our coal supply .should ponder 

 on the fact that this wonderful seam, on which was based 

 our supremacy in iron making and most of the other 

 industries dependent on coal, is now very nearly exhausted ; 

 only a small fraction remains, and that is but the portion 

 which is the most difficult to work, and which consequently 

 must become dearer and dearer as the difficulty increases. 



It is quite true that we shall never exhaust our coal 

 supplies, for the simple reason that there will always 

 remain a great deal which cannot be worked ; but we actually 

 have exhausted, or have reached the verge of exhaustion 

 of those fields which, by their exceptional richness, gave 

 us our advantages over our neighbours, who have now 

 much more coal than we have, though none so cheaply 

 olitainable as that which we originally had, and which 

 twenty years hence we shall have no longer. We shall still 

 have plenty of coal then, but it will be quite as costly as the 

 coal of France, Germany, Belgium, &c., and much more 

 costly than that of America and China. 



In my next I will describe lonj-wall working, which is 

 moi-e economical, and when properly conducted, safer than 

 the methods above described. 



GREAT CIRCLE SAILING. 



By Richard A. Proctor. 



R. FROITDE in his " Oceana " touches from 

 time to time on great circle sailing, or, in 

 other words, on that method of dii-ecting 

 their course at sea, by which the wiser 

 seamen take the shortest course from port 

 to port. He is not always strictly accurate 

 in his remarks on this advantageous method 

 of sailing, but he is always interesting ; 

 nor do the slight errors in matters of detail detract from 

 the general accuracy of his statements. At the very outset 

 of his ocean travelling, one day only from Plymouth, we 

 find him observing that th.^ Australasia was, " owiside the 

 Bay of Biscaj', far to the westward of our course as traced 

 on a flat chart ; but the captain tells us," he proceeds, " that 

 %ve should see it to be right on a spherical one, and we 

 entirely believed him." In reality the great circle course 

 from Plymouth to Cape '\'erde passes but slightly to the 

 west of the cour.^e traced on a Mercator's chart, which we 

 assume to be what ]Mr. Froude means by a flat chart — at 

 any rate, it is the only kind of flat chart used by seamen. 

 Yet the piinciple is sound which underlies Mr. Fronde's 

 statement; and, slight though the advantage may be which 

 a great circle course has over a rhumb course (the ruled line 

 on a Mercator's chart), the difference of distance is worth 

 saving. In the case of a sailing vessel, indeed, which 

 against adverse winds may have to beat across the course 

 which a steamship or a ship under fair winds would pursue, 

 a very slight gain on the shortest course may result in a 

 very considerable gain on the whole journey. Consider, for 



