644 THE COLLIERY GUARDIAN March 28, 1918. FIREPROOFING MINE SHAFTS.* By E. M. Norris. In the summer of 1917 it was decided to fireproof the main tramway hoisting shaft of the Anaconda Copper Mining Company, at Butte, Mont. The shaft has three hoisting compartments and one pump compartment; it is timbered with 12 by 12 in. fir timber, and is 2,475 ft. deep. Subsidence and displacement 'of the surrounding country rock had produced exceedingly heavy ground, and had carried the shaft out of line, in several places, by as much as 2 ft. displacement. Constant repairing and re-aligning of the timbers had been necessary in order to maintain clearance for the cages. The most feasible method of fireproofing, therefore, seemed to be to cover the timbers with a coat of concrete applied with the cement gun. The cement gun, which is operated by compressed air at ordinary mine pressures, feeds a mixture of sand and cement through a hose to a nozzle having a water con- nection. The mortar in fluid form is thus sprayed upon the prepared surface in thin layers, which can be built up to any desired thickness. The cement gun can be set up at any convenient point; satisfactory results have been obtained with the nozzle a distance of 500 ft. from the gun. The shaft was thoroughly overhauled and the timbers put in the best possible state of repair. Between the 1,000 and the 1,400 levels, much loose ground lay against the shaft timbers on the north side; this was breast- boarded back and a 30 in. reinforced concrete retaining wall was erected, leaving a space of 12 in. outside the shaft timbers to allow for future movements of the ground. For convenience in handling men and materials, it was arranged to concrete the auxiliary hoisting cage compartment and the pump compartment first, using the cages of the main hoist to serve the cementing crews. The auxiliary cage was then available while the remainder of the shaft was being concreted. A tight partition of 2 in. plank was erected between the auxiliary and the adjoining hoisting compartments, for better protection of men riding on the cages. The application of concrete made this partition air-tight, which should prove a valuable feature of the fireproofing measures. It was considered necessary to guard against the spreading of fire in the timbers behind the concrete covering, as once happened in a Michigan shaft. A set of shaft lagging was therefore removed just above and below each station, and a concrete casing was built back to the walls so as to form an air-tight seal at these points. Another seal was made at the rear end of each station in a similar manner. Experiments were made to determine whether reinforcing material was necessary to hold the concrete to the timber, and, if so, what kind of material was best. It was found that if the timbers were wet down thoroughly the concrete would stick without reinforce- ment, but subsequent distortion of the timbers caused the concrete coating to shell off in large slabs. Tests of chicken wire, herringbone metal lath, and diamond-mesh metal lath showed that all these materials made equally satisfactory reinforcement for the concrete coating, the only difference being the matter of cost. Chicken wire was the cheapest to buy, but the labour of nailing it to the timbers was much greater than with metal lath. After using several thousand square yards of each of these materia’s it was found that the 27 gauge diamond-mesh metal lath, 24 by 96 inch, was the most economical and satisfactory reinforcing material; it was also determined that 6-d wire nails driven two-thirds of their length into the timber, and bent over, made the best fasteners. The compartments to be concreted were covered with timber bulkheads at each level and lathing was begun. The lathing crews consisted of six men to a lift, two or more lifts being lathed at one time according to the number of men available. With the diamond mesh material the rate of lathing was 225 sq. ft. per man per eight-hour shift. Two cement guns, type N-L, were set up on mine trucks so that they could be pushed on the cages and moved from level to level as required. With an air pressure of 75 lb. per square inch it was found that 200 ft. above, and 75 ft. below, were the greatest vertical distances from the gun at which satisfactory work could be done with the nozzle. Where lifts greater than 275 ft. occurred, it was necessary to set the guns on bulkheads in the shaft. The sand was dried, when necessary, and screened through a -Jin. screen. It was then mixed with the cement on the surface, and put into old cement sacks for convenience in handling. It was found necessary to screen the cement also, as lumps blocked the discharge and caused frequent delays. Mixtures of 3, 3J and 4 parts of sand to 1 of cement were tried. Where thin coatings (J in. or less) were applied, the 3 to 1 mixture was the most satisfactory, as it went on more evenly and formed a tougher coating. Each crew consisted of four men, two feeding the gun, and two on the nozzle. The nozzlemen worked from stage planks in the shaft and were provided with rubber gloves, safety goggles and respirators. The surface to be coated was washed oft thoroughly with water sprays. Concrete was applied in two successive layers J in. thick. After the coating had become firm it was sprinkled often enough to keep it damp for several days. It was found that a gun crew could cover from 800 to 1,200 sq. ft. of surface in eight hours. Repairs on the gun were very slight, wea,r being taken by the rubber liners. Nozzle liners lasted 48 hours, discharge liners about 6 weeks, and the cement hose several months. The shaft and station timbers were repaired and concreted from surface to the 2,000 level in 94 days, 175,465 sq. ft. of surface being covered. The average number of men employed was 54, including superin- tendence and all surface labour connected with the job. * Transactions of the American Institute of Mining Engineers. Material used was 6,102 sacks cement, 1,500 tons sand. 165,495 sq. ft. of lathing and 2,600 lb. nails and staples. Four samples were prepared for a fire test. Pine timbers, 6 in. by 10 in. by 5 ft., were covered on all sides with lathing; three pieces were covered with chicken wire and one with metal lath. These timbers were then coated with | in. of concrete put on with the cement gun. Three of the samples were sprinkled daily for three days; the fourth was not sprinkled. After six days of hardening, the samples were placed in a large bonfire, until the concrete coating was heated to a dull red. The sample that had not been sprinkled shelled off with loud explosions, but the others were not affected. After 30 minutes the samples were pulled out and allowed to cool. Inspection showed that the only apparent effect of the baking was a slight charring of the wood on the edges, where the concrete had cracked while drying. THE AMERICAN COAL TRADE. The coal business for the old coal year is about wound up (says Black Diamond, March 9), and the trade is ready to begin the new coal year. The one thing which holds back the trade and the buyers is the lack of definite instructions from Washington as to the nation’s coal programme. Some of the most important announcements have not yet been made, and, until they are, nothing decisive can be done. Nearly everywhere the demand for domestic coal has shown a sharp decline, that result being brought about by improved weather. The same influence which lessened domestic demand in lesser measure improved transporta- tion conditions. Coal receipts are heavy. This is allowing factories to return to somewhere near to normal production. The trade has instructions that all contracts are held amenable in a way to either suspension or cancellation, and it understands that a certain zoning system, which will divide the country into three major districts, has been recommended to the fuel administration. The reason for the shortage of cars is the continued congestion of railway terminals and the absence of loco- motives. The car situation on eastern railroads has apparently improved quite a great deal. Every indica- tion points toward a most elaborate storage programme for this year, if the car supply will permit. The idea that there must be either storage in summer or famine in winter is gaining a firm hold upon the public mind, and the people prefer to store. Retail hard coal men who have recently gone .over the mining regions predict that instead of there being a 10 per cent, shortage at the outset of next winter, as predicted by the fuel administration, the hard coal shortage will be at least 40 per cent. They point to the impossibility of moving the tonnage needed with the decadent rolling stock and motive power in possession of the railroads. Washington has authorised further increases in mine price of certain coals that come to tidewater piers from the Tug River district of West Virginia, covering operations on the Norfolk and Western Railway, west of Welch to Panther, now taking a price of 2 85 dols. for run-of-mine, 3-10 dols. for lump and 2 60 dols. for slack. These are net ton prices. The milder weather has increased the movement of bituminous by water, notwithstanding the fact that demurrage at Hampton Road ports is still very expen- sive. Then, too, the movement of all-rail Pennsylvania and other kinds are improved slightly, and as a result consumers are less anxious over the situation. The Mystic Wharf market is still controlled by the fuel administrators, and New River, Pocahontas and Pennsylvania for spot delivery has sold as high as 11 dols. a ton or thereabouts. Regular shippers, how- ever, are doing business on a basis of 2’45 dols. per net ton at the mines for Pocahontas, 2’60 dols. for New River, 3 05 dols. for Pennsylvania, 2 45 dols. for Fair- mont, and 2 85 dols. for Georges Creek. New' England consumers are anxious to place contracts for new season coals, but shippers, as a general thing, are not doing much in this line. Pentre Mountain Slide Case.—Evidence has been given at several sittings of the Chancery Court within the past fortnight relative to the action of the Rhondda Urban District Council v. Cory Bros, and the Bailey Estate Trustees. It was alleged that the tipping of 500,000 tons of debris caused weakness and sliding of the Pentre Moun- tain, resulting in damage to property. One of the plaintiff’s witnesses, Mr. W. Griffiths, architect, Tony- pandy, said he thought the chief factor in the slide of the tip was the weight of the tip standing upon a very steep slope overlying ground which was very much shaken and broken up by the effects of mining operations. The absence of drainage was a most important element. The hearing was adjourned. Central Technical Library for Manchester.—On Wednes- day last a deputation representing various technical societies and institutions in Manchester, including the Manchester Association of Engineers, the Engineers’ Club, the Mining and Geological Society, and the Society of Chemical Industry, waited upon the Manchester Libraries Committee for the purpose of explaining a scheme for the provision of a general technical library. It is proposed that the collections of scientific works possessed by the different societies should be housed in one building, and a general catalogue prepared. The estimated cost of such a project is £10,000, and it is suggested that the Govern- ment and neighbouring municipal authorities should be asked to make a contribution towards the expense of maintenance. The Lord. Mayor (Sir Alexander Porter) agreed that research work was of the greatest importance, and a library on the lines advocated by the technical societies would be a valuable asset to the city. The question of cost and maintenance, however, was a serious one, the Library Committee being limited in the operations to a twopenny rate. Aiderman Plummer, the chairman of the Libraries Committee, expressed himself in favour of the scheme. THE GERMAN COAL AND IRON TRADES. We give below further extracts from foreigu periodicals that have reached us, showing the course of the coal and iron trades in Germany:— The Iron Market in Rhenish-Westphalia. .During February the difficulties arising from the shortage of labour and rolling stock continued to impede the production of iron and steel, though, in respect of the supply of wagons some improvement was apparent. Enquiries for non-military products improved from neutral countries and the East. The general situation, however, required readjustment, the cost of production having increased considerably since the last rise in ore prices, whilst the selling prices were still controlled and unchanged, with small prospect of any alteration for the better. The official reply to protests was that sellers must try to recoup themselves for the lack of profit on some products by the sale of those giving better results, and that the large dividends paid by many concerns rendered any increase of prices undesirable. The ore output remained about the same, though the advance in prices in January will probably lead to an increased production of Siegerland ore in the current half year. The better supply of wagons has enabled mine stocks to be despatched more promptly. The same applies to minette. Siegerland mine owners, however, complain that the new price list came in too late, and that it has been largely discounted by the further increase in the cost of production. Nevertheless, the situation was on the whole more favourable than during the previous half year. The demand for pig iron continues pressing, especially for the high-grade qualities made in Siegerland. Pro- vision has been made to keep the works supplied with coke, and thus enable the output to be maintained at a high level. In other iron districts the coke supply has been less ample, partly in consequence of the wagon shortage, and partly on account of the preference given to other branches. With regard to prices, ironmasters contend that the last rise in Siegerland ores has not been taken into consideration, and that the existing rates for different grades of pig iron means a considerable loss. The supply of scrap is abundant, but it cannot be brought to the consumers in sufficient quantity when wanted owing to traffic difficulties, and some of the open-hearth plants have had to go short. Measures have, however, been taken to improve the collection of the scrap lying about everywhere and forward it to the works. Prices are unchanged and, in the opinion of holders, too low. Semi-manufactured iron is scarce, but the demand for delivery is less pressing. Deliveries remain on about the previous level, preference being given to the home trade, so that little is available for neutral markets. Moreover, the export trade is under control. Prices are unchanged, and are said by the works to be unremu- nerative, though it is pointed out from other sides that, in view of the low price of scrap, the customary addition for open-hearth grades is not justifiable. In other products the demand for munition purposes predominates. Business is quieter in sections and bars, owing to the protracted suspension of private building enterprise, and the slowing down in the extensions of war manufacturing premises. The cessation of opera- tions on the Eastern Front has lessened the demand for bridge and other constructional material. Prices for sections, joists and bars are unchanged. Welding iron, which has hitherto been uncontrolled, will probably come under the maximum price rule, for certain grades at least. Wire is in active request, and new depart- ments are being formed to facilitate the supervision of the output of winding ropes, ships’ cables and needle wire. The heavy demand for both heavy and fine plate is being fully satisfied, though less so in the case of the very thin sorts. The covenanted supplies to neutrals are being despatched ; but the quantity is insignificant in comparison with home sales, and no export is allowed except under licence. Prices have remained unchanged since August. The deliveries of rails and super- structural iron have been improved, and attempts are being made to increase them further. Gelsenkirchener Bergwerks A.G —According to the balance sheet, for 1917, the gross profits amount to 55,573,500 mk. (53,003,031 mk. in 1916;. Of this sum, 22,425,705 mk. (22,024,680 mk.) are to be devoted to writing off 2i million mk. (as last year) placed to depreciation and renewals fund, 600,000 mk. (600,000 mk.) placed to special reserve and 1J million mk. (1| million mk.) to the staff assistance fund. The dividend will again be 12 per cent, and 3,196.216 mk. (3,025,771 mk.) are to be carried forward. Additional Maximum Prices for Iron and Steel. It is reported that the War Raw Materials Depart- ment proposes to fix maximum prices for semi-manu- factured iron with a, tensile strength of 60 to 70 kilos, and 70 to 80 kilos.; bar iron (strength 60 to 90 kilos,); soft basic and open-hearth steel, for drawing ; soft iron, for drawing; drawn soft iron; drawn high-grade material; drawn or turned mild steel other than for any specified use. Merchants’ additions are also to be fixed in respect of bar steel (strength 60 kilos, and over); rolling iron of all grades; soft iron and wrought iron and steel, all grades ; drawn high-grade material; high-grade steel of all kinds for tool steel, silver steel, etc. The prices of these materials have not hitherto been controlled. Dr. J. Divine, St. Mungo’s, Holderness Road, Hull, has been appointed medical referee under the Workmen’s Compensation Act, 1906, in connection with the Hull, Hedon, Beverley, Great Driffield, Bridlington, Gorle and Howden County Courts. Dr. E. F .W. Buckell has been appointed certifying surgeon under the Factory and Work- shop Acts for Newport (I.O.W.). Dr. J. H. Murray has been similarly appointed for Stirling, and Dr. C. K. Crowther for Biggleswade.