504 THE COLLIERY GUARDIAN. March 5, 1915. the rise. Although gas was being given oh along the whole face, there was only a very slight increase in the quantity at the roof of J. T. Fisher’s gate, 21yds. from the top of the rise, where a rapid increase occurred. Apparently all the gas given off rapidly streamed to the top and accumulated there; on this point there can be little difference of opinion. The suggestions with regard to the developments of the explosion are open to criticism $ but the writer offers them as a possible explanation of the many conflicting points connected with the explosion. LETTERS TO THE EDITORS. The Editors are not responsible either for the statements made, or the opinions expressed by correspondents. All communications must be authenticated by the name and address of the sender, whether for publication or not. No notice can be taken of anonymous communications. As replies to questions are only given by way of published answers to correspondents, and not by letter, stamped addressed envelopes are not required to be sent. THE REDUCTION OF WORKING COSTS AT THE FACE. Sirs,—The interesting paper read before the South Staffordshire and Warwickshire Institute of Mining Engineers on the above subject, an abstract of which appeared in the Colliery Guardian of February 26, is of such interest to all mining men, that no apology is required for criticism. To Mr. Cashmore’s general premisses few will take exception. One or two comments on these may be made, however. Thus it is said : (1) That increased cost of production is due, amongst other things, to restricted hours; and (2) that there is a falling off in the efficiency of the underground workman. If the first is not the cause, largely, of the second, how does Mr. Cashmore account for it? Surely, not the national decadence that the Germans allege. As a matter of fact, the causes are many, and are not to be counter- acted by palliatives in the way of machines and conveyors. As for the points (3) and (4), the increasing difficulty in obtaining men, and the decreased return on capital, are not new, but old, problems, and provide their own remedies. Scarcity of men sends up the wage rates, because demand for coal exceeds supply, and increases prices. Again, decreased return on capital sooner or later sends people out of the trade, reduces supply, and tends to increase profits by enhanc- ing prices. Further, (3) and (4) cancel to some extent each other. If, through bad trade, that is, low prices, a pit is shut down, the pitmen find work elsewhere, and the difficulty of obtaining men • for other collieries is reduced. It is not, however, Mr. Cashmore’s general premisses that I wish to criticise particularly, but his comparison of hand versus machine cutting. He says that 6d. to 8d. per ton may be saved by machine cutting, “ given reasonable opportunity.” This may, or may not, be realised, and depends largely on three conditions, which, however, he has entirely missed in his analysis. (1) The rate of wages. It will be easily seen that if wages in Mr. Cashmere’s district fell to one-half of their present rate, he might, unless in the most exceptional circumstances, draw all his machines to bank. On the other hand, if wages were doubled, the makers of coal cutters would be busy. In this connection, too, he seems to be under a misapprehension as to the effect of the machine on individual efficiency. If the loss due to inefficiency is 10 per cent., and a machine or conveyor is introduced which increases the output 10 per cent., the loss due to inefficiency still exists, and is reduced only to the extent of 1 per cent, approximately. (2) If the coal is soft, it falls on the machine, and has a double effect : (a) It is more costly to cut; and (b) the percentage of round coal is decreased, in many cases even below that produced by hand cutting in the same seams. On the contrary, soft coal is easily and com- paratively cheaply cut by hand. (3) The success or failure of machine cutting depends (other considerations apart) on the height of the seam. In a seam 41 ft. high, it might, or might not, be advisable to introduce machines. In an 18 in. seam, with hard roof and floor, the question is easily decided. In the meantime, i.e., under present economic condi- tions, it must usually either be cut by machine or left in. In view of these three points, Mr. Cashmore’s hypo- thetical conditions—a 5Jft. seam, with 100 yds. of face uninterrupted by faults—are about the worst he could have chosen for the success of his argument. Take the case of band cutting in this seam; he assumes a face advance of about 3^ ft. per week of 5| days. The rate of advance in well-conducted longwall faces worked by hand and single-shifted should be not less than 2 ft. per day, or 11 ft. per week of 5| days. This brings the output up from 31| tons per day to something above 100 tons. He next supposes the seam machine cut twice a week to a depth of 4| ft. In passing, it might be asked : What are the machine and machine men doing during the other four shifts? If the face was 200 yds. long, and undercut 6 ft. deep thrice per week, or if the face 100 yds. long was undercut 3 ft. deep six times per week, success would be possible. But Mr. Cashmore can hardly think seriously of successful machine cutting where the rate of advance is only 9 ft. per week. Rapidity of advance is one of the chief elements of success. He is somewhat out of his depth in the case of the machine conveyor face. It is only in certain excep- tional cases that their working in conjunction can be made to pay. Apart from that, take the case of the number of tubs to be handled on the conveyor road; 240 tons require 480 10 cwt. tubs, but Mr. Cashmore says they must not be “ topped.” In this case, they will each carry, say, 8 cwt. Therefore, 600 tubs must be handled at the conveyor and filled per day. Just see what this entails. What with a legal eight hours day—lateness in arriving at the face and unavoidable detentions—the conveyor will not be delivering fully more than perhaps six, or at most, seven hours per day. At six hours per day, that means 100 tubs per hour—-or one every 36 seconds. It is possible, perhaps, but the manager will require more than three conveyor atten- dants, and the haulage organisation (which must be maintained close to the face to deal with 600 full tubs per day) must be fairly elaborate. If a loss of 15 minutes ’occurs owing to a derailed tub, the filling is detained to the extent of 25 tubs. The paper leaves the important question of the support and control of the roof very much ‘ ‘ in tl e air,” and the whole question cannot be considered without reference to this. Mr. Cashmore says debris might be taken in tubs via the top road, filled into the conveyor, discharged at suitable points, and packed into the face. Where will he get the debris? As 240 tons of coal were taken out, and as debris is heavier, at least 150 tons must be used. Some may be got by ripping the roads and repairing, but the bulk of it must come from the surface. This must cost money to fill; if the underground roads are long, a large number of haulage attendants are required. A further complication is introduced if the workings rise from the shaft; after reaching the conveyor it must be shovelled in and eventually packed by hand. How much would this cost? Would Is. 6d*. per ton, at present wage rates, cover it? How much simpler and cheaper it would be to divide the 100 yds. of face by six roads, ripped 12 ft. by 4| ft. This would, with debris from the road repairers, efficiently pack the working for about 8d. per ton, even if the ripping cost 18s. per yard. But the further con- sideration is : How is the conveyor to be kept in efficient good order? For six hours per day, it must deliver a stream of coal 2 in. wide by 4 in. deep, at the rate of 60ft. per minute; in the afternoon its work is almost equally heavy. During the night it must be shifted, during which time running repairs must be effected. These will be either perfunctory or expensive, or both. Again, with a 4^- ft. advance per day, how are the ends of the face to be kept forward, and the line of the face preserved? This may be done by double-shifted hand cutting, but this is impossible if the conveyor is work- ing double-shifted. A small auxiliary coal cutter is necessary. Mr. Cashmore’s reference to hydraulic stowing is somewhat inept. The question is simply one of cost. When mechanical engineers produce a plant that can compete with the- hand method of the present day, colliery owners will need no coaxing to adopt it, and until that time coaxing is useless. One point is worthy of notice in the paper, which shows the danger of confusing unimportant with impor- tant details. Mr. Cashmore says a modern coal cutter will cut 200 to 250 sq. yds. per shift with an oil con- sumption of one pint. Now, although the machine used 50 times that amount, that is, 6| galls., at 3s. per gallon the cost per ton of coal is only Id. on 240 tons— a negligible matter in comparison with the promised economies. In conclusion, while perhaps a great need of the mining industry at the present day is bold speculative thinking, such would be useless unless the data used would stand critical examination by practical men. Fairview, Irvine-road, John Gibson. Kilmarnock, February 27, 1915. COAL PRICES. Sirs,—There have been several articles in the daily Press recently on “ The Patriotism of Yorkshire Colliery Gwners,” with special reference to a group of collieries which Sir Arthur Markham is connected with, i.e., Brodsworth, Bullcroft, Hickleton, and Oxcroft. The articles set out that Sir Arthur Markham and his co-directors have, out of the generosity of their hearts prompted by their patriotism, passed resolutions that they will not sell any quality of coal at a higher price than 15s. per. ton at the pit mouth. It was also reported that the pits covered by the resolutions have an aggregate output of 4,000,000 tons per annum. It is only fair to Sir Arthur Markham and his co-directors that the general public should have a true and proper appreciation of this laudable combination of patriotic spirit and generosity, and I venture to suggest that the under-mentioned information should be furnished through the Press :— (1) What is the actual aggregate output of the pits covered by the resolutions? I am told it is a long way below 4,000,000 tons. (2) Out of this output how much is already sold on contract, and how much is available per week at the present time for open market sale at a maximum price of 15s. per ton after contract obligations have been carried out? (3) It would be interesting to the general body of householders, who are supposed to be hit most heavily by the advanced coal prices, and for whom Sir Arthur Markham professes such beneficent consideration, to know what proportion of open market house coal is included in the alleged 4,000,000 tons, and what is the weekly quantity at present available for disposal. ■ (4) If the maximum price for any quality is to be 15s. pit, it is to be hoped that it is not the intention of Sir Arthur Markham to put up the price of smalls (which as recently as December last only commanded a market price of 5s. per ton at pit) to this figure, otherwise the industrial community who deal with his pits are likely to be more heavily hit than the poor unfortunate house- holder. (5) Is it a fact that immediately the Press articles above referred to were issued, orders were wired to the pits covered by the resolutions for screened coal at the maximum price of 15s. pit, and that these orders were refused with the explanation that the particular pits were fully sold? (6) How much best screened coal has been actually sold from the group at 15s. pit or less since the resolu- tions fixing the maximum price were passed? With replies to these queries before them, the general public will be better able to gauge the full measure of “the patriotic spirit and generosity ” of Sir Arthur Markham and his co-directors. It is due to other Yorkshire colliery owners to point out to the general public that at the pits under reference the seams worked are generally speaking thick seams, with a cost of production substantially less than the productive cost at the large number of thin seam pits worked in Yorkshire. There are, for instance, many colliery companies, who, if they fixed a price resolution (on the same lines as Sir Arthur Markham and his co-directors) and made the price 16s. 6d. pit, would not secure a margin of profit equal to what will be obtained at Sir Arthur Markham’s pits on a 15s. per ton maximum. In considering the reasons for the high prices now ruling for coal, it should be borne in mind that the men who have enlisted are the youngest men and the most physically fit. Those that are left have consequently a lesser productive capacity per man. The majority of collieries have large commitments on account of contracts entered into before there was any advance in prices; this in conjunction with reduced outputs leaves very little tonnage available for the open market. It should also be remembered that from the commence- ment of the war until towards the end of December 1914 coal prices were depressed, so much so that the railway companies who fixed their contracts in December 1914 to run over the whole of 1915 bought at a reduction on their 1914 contract prices. The majority of colliery owners are by no means in a happy position. Reduced outputs and increased costs of materials have necessarily resulted in substantially increased costs of production. In spite of this, it is within my personal knowledge that, with few excep- tions, Yorkshire colliery owners are loyally carrying out contracts which they entered into prior to any knowledge of these heavy burdens which circumstances have since compelled them to shoulder. It is also well known that they have shouldered these burdens most loyally. The number of miners that they have encouraged to enlist, and the assistance they are generously giving to their wives, children, and dependants is substantial proof of this. If a census could be taken of the production of coal at Yorkshire collieries, the tonnage sold on contract and the tonnage available for open market sale, the latter would be found to be comparatively so infinite- simal in quantity, that up to the present it has had practically no appreciating effect on the average pit prices. If the Government Committee appointed to investi- gate the position as regards coal prices will first turn their attention to the large coal factors who have bought coal on contract from the collieries, and who retail it to householders, they will find it is these gentlemen who are obtaining the benefit of the high prices which have recently obtained, and not the colliery owners. Barnsley, Carbonicus. March 2, 1915. VISUAL INDICATORS. Sirs,—I notice in your leading article in your issue of the 26th ult. you refer to the paper I gave before the North of England Institute of Mining and Mechanical Engineers on February 13, and to the subsequent remarks thereon, to which I have fully replied to the institute, and which will be published shortly. In reference to the method of cancelling the cautionary or advance signal “ Men,” on reading the official explanation given by Sir R. A. S. Redmayne, it certainly appeared that it was necessary that this signal should be obliterated either by the person giving the signal or automatically by the giving of the action signal. As this ruling could be considered to be in contradiction to the manner in which the “ non- cumulative ” signals manufactured by my company— John Davis and Son (Derby) Limited — are released, they corresponded on the matter with the Home Office, who replied as follows :— Referring to your letter of the 16th inst., there is no objection to the cautionary signal being shown separately, as is done in your apparatus, or to its remaining during the change of decks, so long as it is removed automatically either by the giving of the action signal, or by the engine when it starts.— February 24, 1915. With regard also to the obliteration of the cautionary or advance signal “ Men ” in the single plunger type of indicator, I understand that “ obliteration ” does not necessarily mean the setting back of the hand or pointer to zero, but it is equally met by the hand moving to “ 4 ” or “5.” This is fully borne out by clause 5 in Sir R. A. S. Redmayne’s official explanation. With reference to the information given to Mr. Arthur Andrews by the Home Office that “ 4 ” and “ 5 ” —“ Raise steadily ” and “ Lower steadily ”—were advance signals, it appears that this was a clerical error, and should have read “Action ” signals, as there is no such advance signals in the code. All Saints Works, Derby, Wilfrid H. Davis. March 2, 1915.