July 28, 1916. THE COLLIERY GUARDIAN. 167 A dvertisers would like to hear of a AY. COLLIERY for DISPOSAL, already developed and showing satis- factory returns; in Yorkshire or Midlands preferred, but if situate in other locality would be considered.—Box 6482, Colliery Guardian Office, 30 & 31, Furnival-street, Holborn, London, E.C. V/VTanted for cash in advance, 2,000 tons ▼ ▼ Midland Brights and Nuts, also 1,000 tons Steam Large and Steam Nuts ; also wanted on simple hire, 100 modern Coal Wagons.— DIBBCT COALS LTD., Yeovil. The following Second-hand Plant and MACHINERY FOR SALE at the CWMTILLERY AND ROSE HEYWORTH COLLIERIES, and TENDERS are desired for same, ihcluding removal. The Plant. &c.. can he seen by appointment.—Apply, LANCASTER’S STEAM COAL COLLIERIES LTD., Cwmtillery, Mon. 1 LANCASHIRE BOILER, 7 ft. 8 in. diameter, 28 ft. long, furnace tubes 3ft. diameter, each with 5 cross tubes, insured with the British Engine, Boiler and Electrical Insurance Co. for 80 lb. pressure. 2 old LANCASHIRE BOILERS, 7ft. 3 in. diameter by 30 ft. 3 in. long, furnace tubes 2ft. 2 in. diameter, lately used as air receivers at 551b. pressure. 1 old LANCASHIRE BOILER. 8 ft. diameter by 30 ft. long, furnace tubes 3ft. 2in. diameter, each with 7 cross tubes; tubes and front end plate withdrawn: last used for 100 lb. pressure. 1 old EGG-END BOILER, 4ft. diameter by 37ft. long, lately used as air receive*- for 601b. pressure. 1 WROUGHT IRON OCTAGONAL DRUMSHAFT, 11g in. over flats by 13 ft. 4 tn long, with 2 wrought iron clanks, 2 ft. 6 in. throw. 1 WROUGHT IRON DRUMSHAFT, 9gin. diameter by 17ft. long, with 2 wrought cranks, 2 ft throw. 1 WROUGHT IRON DRUMSHAFT, login. by 12ft. 6in. long, with 2 wrought iron cranks. 2ft. throw. 1 STEEL CRANKSHAFT, 10in. diameter by 9ft. 8in. long, with swell in centre 11 in. diameter, for flywheel. 1 CAST IRON FLYWHEEL, in halves, secured by bolts and keys 14 ft. diame er, rim 8J in. wide by Kin. deep, 11 in. bore, 6 arms 3£ in. by 9in., to fit above shaft. 1 HEAVY CAST IRON FLYWHEEL, in halves, secured by bolts, 10 ft. diameter, ll^in. face, bore 9g in. 1 WROUGHT IROV CRANK SHAFT, 9g in. diameter, 6 ft. 8 in. long, with 2 cranks. 18in. thro#. 1 old lOh.p. LOCO. TYPE BOILER. 3 old WATER HEATERS. COUNTY BOROUGH OF SALFORD. ELECTRICITY DEPARTMENT. The Electricity Committee are prepared to receive TENDERS for the following PLANT, which is being removed to make room for larger units Two *• Browett-Lindley ” six cylinder Compound Engines, direct coupled to Mather and Platt d.c. generators, each set having an output of 800 kilowatts at 440/550 volts. One “ B nley-Davidson ” 8,000 gallons per hour vertical steam Feed Pump. One “ Hall ” 5,000 gallons per hour vertical compound steam Feed Pump. All the foregoing plant can be seen in actual use by appointment, and further particulars obtained from the Borough Electrical Engineer, Frederick-road, Salford. Tenders to be delivered by noon on Monday, 7th August, 1916, to the Chairman, Electricity Committee, Frederick-road, Salford. L. C. BVANS, Town Clerk, Salford. Pumps.—Wanted, complete set 4 in., 5 in. or 6 in., gunmetal, treble barrel, deep well pumps, engine frame, air vessel, suction, 200 ft. rising main.—Fullest details, price, JELLBTT, 12, Henrietta-street, Strand, London, W.C. QfY-h.p. 400/440-volt Mather & Platt W MOTOR, compound interpole pipe ventilated, 1,400/1,600 revs.; also Mining Starter Panel for sale; all as new.—DRUMMOND A CO., Commercial-street, Middlesbrough. Qplendid pair of Horizontal Engines, kjz 13 in. by 24 in., expansion valves, Soho governor, belt flywheel 10 ft 6in. by 13 in., recently overhauled and fitted with new cylinders by makers Sandycroft Ltd.; bargain for quick sale. 40 h.p. LOCO. TYPE BOILER, complete mountings, 150 lb. pressure, excellent report by Davey, Paxman & Co.; cheap before removal to stores; Apply, EDWARD RATCLIFFE, Engineer, Hawarden. LOCOMOTIVE AND OTHER STEAM CRANES. W ton Wilson Loco. Crane, 30 ft. steel jib, 100 lb. w.p., all motions; £850. 7-ton Steam Loco. Crane, by Smith, steel lattice jib, 40 ft. long, 801b. w.p.; new in 1914. 3-ton Steam Loco. Crane, by Smith, 1001b. w.p.; £400. 2-ton Steam Loco. Crane, by Bedfc rd Engineering Co.; £210. 2 ton Loco. Crane, by Jessop & Appleby; £175. 10-ton Fixed Steam Wharf Crane, by Wilson, steel derricking jib; £450. 5-ton Steam Derrick Crane, by Isles, 45 ft. steel jib, steel mast, 801b. w.p.; £180. JOHN F. WAKE, DARLINGTON. ^7 Second-hand Wagons for Sale, side f doors only; specification and price.—Box 6481, Colliery Guardian Office, 30 & 31, Furnival-street, Holborn, London, E.C. For Sale, One Dish-end Cylindrical BOILER, 35 ft. long by 5 ft. diameter, with fittings, suitable for a working pressure of 100 lb. per sq. inch.—Apply to DONISTHOBPE COLLIERY CO. LTD., near Ashby-de-la-Zouch. 07 anted at once, Mining Type 50-h.p. ▼ ▼ MOTOR, 3-phase, 50 periods, 3,300 volts.—Reply, EAST BRISTOL COLLIERIES, Kingswood Collieries, St. George, Bristol. LOCOMOTIVES AND TRACTORS FOR SALE. 9 in. Four coupled Loco., by Manning Wardle, copper box, 140 lb. w.p.; £350. 12 n. four coupled Hunslet Loco., copper box, 120 lb. w.p.; £600. Two 12 in. six coupled Hudswell Clarke Locos., copper boxes, 140 lb. w.p.; £800 and £850 respectively. 3 ft. gauge Loco., by Hudswell Clarke, four coupled, 9 in. cylinders, new copper box and tubes, 150 lb. w.p.; £650. 3ft. gauge Loco.,by Bagnall, 6in. cylinders, 1501b. w.p.; £350. Two 2ft. 6in. Locos., by Kerr Stuart, copper boxes, 1601b. w.p; £4C0 each. 2ft. gauge Loco., by Bagnall, 1491b w.p., 8in. cylinders : £500. 5-ton Steam Tractor, bv Wallis & Stevens, 1601b. w.p.; £300. 5-ton Yorkshire Steam Wagon, 2001b. w.p.; £225. 10-ton Road Roller, by Fowler; £210. JOHN F. WAKE, DARLINGTON. VWanted, Electric Coal Cutters, Morgan ▼ ▼ Gardner or Anderson and Boyes.—Write, giving full particulars, stating machine numbers, where can be inspected, and lowest price f.o.r., to Box 6480, Colliery Guardian Office, 30 A 31, Furnival-street, Holborn, London, E.C. For Sale, Pairs of 16 in. by 36 in. and 22 in. by 42 in. horizontal WINDING ENGINES: one new horizontal PUMP, 20 in. by 8 in. by 24 in.—Apply, ARTHUR PYATT, Kidsgrove, North Staff. BLOWERS FOR SALE. NEW AND SECOND-HAND, AND EXHAUSTERS. Two Sets Horizontal Double Cylinder Blowing or Exhausting Engines, cylinders I84 in. by 16 in. stroke, suitable for electric drive; £150 each. Steam Turbo and Air or Gas Exhauster, Rateau system, capacity 15,000 ft. per min. Roots Blower, Engine driven, 10in. outlet, 3,000 ft. per minute; £60. Roots Blower, Engine driven, 11 in. outlet, 4,000 ft per minute; £75. Baker’s Pressure Blower, No. 13,12 in. outlet: £30. New “Roots” Blowers, belt driven, 2 in. outlet, £4; 2£ in. outlet, £14; 2|in. outlet, £12. JOHN F. WAKE, DARLINGTON. Indian Mines Act, 1901, with a Digest of the Act, a reprint of the Act with explanatory notes, an appendix con- taining forms, a model code of Special Rules, Ac., by W. H. Pickering, Chief Inspector of Mines in India, and W. Graham, Barrister-at-Law.— Price 10s. 4d. post free from Colliery Guardian Office, 30 A 31, Furnival-st, Holborn, London, E.C. J. W. BAIRD AND COMPANY, PITWOOD IMPORTERS, WEST HARTLEPOOL, YEARLY CONTRACTS ENTERED INTO WITH COLLIERIES. OSBECK & COMPANY LIMITED, PIT-TIMBER MERCHANTS, NE WCASTLE-ON-T YNE. SUPPLY ALL KINDS OF COLLIERY TIMBER. Telegrams—“ Osbecks, Newcastle-on-Tyne.” *** For other Miscellaneous Advertisements see Last White Page. AND Journal of the Coal and Iron Trades. Joint Editors— J. V. ELSDEN, D.Sc. (Lond.), F.G.S. HUBEBT GREENWELL, F.S.S., Assoc.M.I.M.E. {At present on Active Service). LONDON, FRIDAY, JULY 28, 1916. The London coal market is still suffering from an extreme shortage of fuel. Household qualities and hard steam coal alike are very difficult to obtain. Small nuts are exceedingly scarce, but slack is somewhat easier. In the Tyne and Wear trade a good enquiry for next month’s loading is reported. Best Bly ths have fallen, and Tynes are weaker. More free coal is coming on the Lancashire market, and prices for shipment are less firm. Quotations in Yorkshire are not materially affected by export difficulties throwing a larger tonnage on the market. Apparently the demand for house coal in the Midlands is less acute. South Wales is so » strenuously occupied with Admiralty requirements that there is little in the ordinary course to report, except considerable weak- ness through shipping difficulties and the consequent upsetting of many colliery arrangements. Business in Scotland is irregular, with a tendency to easier terms. Tonnage supplies, although still irregular, have improved this week. North-east coast rates receded, but the undertone is firm at all British ports. At a meeting of the South Wales Institute of Engineers, yesterday (Thursday) evening, Mr. Arnold Lupton read a paper on “Our Coal Resources: Economy and Waste.” Another forestry battalion has been formed in Canada for the purpose of felling trees in the United Kingdom, in order to provide pit props. The Railway and Canal Commission has ruled that, when a train of loaded wagons is tendered in irregular order, the railway company may charge extra for sorting them, no matter whether that is done on a private siding or on the railway company’s siding. A meeting of the Monmouthshire Colliery Officials’ Association will be held to-morrow (Saturday) to discuss stone-dusting regulations. The Home Office has just issued a Electric further report on Electric Bell Signalling Signalling, in which attention is With given to the question of bare wires Bare Wires. and the danger of ignition of inflammable mine gases by the break-flash at the signal wires. This report has been written by Dr. Wheeler and Prof. Thornton jointly, and is in a certain degree supplementary to the report issued by Dr. Wheeler in January 1915, in which it was shown that the break-flash may be dangerous in the presence of gas, and without certain precautions such occurrences come within the definition of “ open sparking ” within the meaning of the Coal Mines Act. Fortunately, however, as the present report shows, there are several ways in which bare-wire signalling can be rendered perfectly safe. The authors are now able to confirm the conclusions arrived at in the earlier investigation with regard to the ordinary types of electric bell, all of which were found to be capable of giving a dangerous break-flash at bare signal wires. Nearly every flash that occurs when the bare wires are separated after giving a signal is capable of igniting a mixture of firedamp and air containing from 7’5 to 9*5 per cent, of methane, the only exceptions being those that occur at considerable distances along the wire, so that sufficient resistance is introduced to lower the amperage of the current below the ignition limit. One significant fact brought out in this report is the desirability of using wet Leclanche cells instead of dry cells for this purpose. Already, except in North Staffordshire, where 10 per cent, of the batteries are dry cells, wet Leclanche cells are commonly employed. The advantage of the latter is to be found in their relative battery efficiency—that is to say, a smaller resistance will be needed to produce the minimum' current required for ringing the bell. It is considered questionable whether it would be wise to reduce the maximum permissible battery power from the 25 volts now fixed by the Goal Mines Act; because even such low voltages as 3 or 4 with some types of bells are unsafe, while 25 volts can be made safe with proper anti-sparking devices. In the case of relays the battery efficiencies were found to be greatly superior to those of most bells, but they have higher inductances owing to the large number of coils with which the magnets are wound. Thus, although relays can be worked with a smaller battery than most bells, they generally have also a lower igniting current at which the break-flash on the signal wires becomes dangerous. It is held that the ordinary types of relays are dangerous when used with a battery of more than four wet Leclanche cells, whereas in practice it is rare to find less than six cells used. Relays, however, can be made safe by the same methods as are recommended for bells. In order to define the conditions of safety combined with efficiency, the problem is to obtain the maximum ringing power of the bell with the minimum igniting power of the break-flash. The authors of this report arrive at the conclusion that a bell with many turns of wire gives the greatest ringing power per igniting- current ampere, and is the u safest-efficient ” bell on a given circuit. That is to say, for every bell there is a definite number of windings at which the factor representing sounding power divided by igniting current is a maximum. From the point of view of inductance it is concluded that the iron magnet cores of mining bells, as well as relays, are too small, and become too easily saturated. For maximum efficiency the diameter of the core should be between 0-4 and 0-5 time that of the bobbin, which should be wound with from 25 to 30 coils of fine wire. The importance of minimising the effect of self-induction is obvious, for the effect of this factor is to produce a sudden abnormal voltage when the circuit is broken. But it is quite possible to construct efficient bells and relays without having recourse to special devices for overcoming self-induction. It is only necessary to arrange that the resistance is so proportioned that “ the maximum current obtainable on short-circuit does not exceed the uminimum” igniting-current for the system. This may be accomplished in several ways, amongst which the use of brass wire instead of copper wire for the magnet coils is perhaps the simplest and most effective, since the resistance of brass is about six times that of copper. The effects of self-induction can be overcome in several ways. The inductance voltage is propor- tional to the rate of change in the number of magnetic lines of force in the windings when the circuit is broken. Any device, therefore, which prolongs the time during which this change of magnetism takes place will lessen the rate of change. This is the object achieved by such devices as parallel-winding, copper sleeves, shunt - resistances and tin-foil layers, the mode of action of each of which is described at some length in the report. It is highly satisfactory that Dr. Wheeler and Prof. Thornton are able to show so conclusively that the bare-wire system of electric signalling, as commonly employed underground, may be made absolutely safe from the dangers of ignition of inflammable gas. That the required precautions are extremely simple in their application will render it easy for the Home Secretary" to issue safety regula- tions without imposing any undue hardship upon manufacturers or colliery managers. In the few cases where dry cells or alternating current generators are now employed for bell signalling, these can