January 28, 1916. THE COLLIERY GUARDIAN. 171 present custom of burning raw coal, which not only entails the loss of valuable by-products, but also involves the production of black smoke, with all its attendant evils. Of course, in certain industrial operations, as, for instance, those in which reverberatory furnaces must be used, there may be at first some difficulty in finding a satisfactory alternative to the combustion of raw coal; but in the vast majority of cases no adequate excuses can be made for the continued use of raw coal. By the carbonisation of bituminous coal, whereby the volatile matter (z.e., tar, benzols, gas, and ammonia), is expelled and a residue of coke or “ semi-coke is left behind, it is possible to recover all the valuable by-pro- ducts, and to utilise the gas for power or heating pur- poses, whilst the residual coke or “ semi-coke ” is, for many important purposes, superior as a fuel to the original coal, both on account of its higher calorific intensity and the smokelessness of its combustion. The hard coke, obtained by the carbonisation of coal in suitable chambers at high temperatures, is employed for smelting iron in blast furnaces, and for melting iron in foundry cupola furnaces; and there is no reason why the somewhat softer coke produced in gas works, or, even more so, “ the semi coke ” obtained by carbonising coal in iron retorts or chambers at a comparatively low temperature, should not displace raw coal as a domestic fuel, except, of course, where gas heated fires or ovens are preferred. The continued use of more than 30 million tons of raw coal instead of coke, semi coke, or gas, as domestic fuel, means the deliberate sacrifice of the whole of the ammonia, tar, benzol, naphtha, and other by-products, to the value of many millions of pounds per annum. The nature and proportionate yields of the by-products obtainable by the distillation of coal depend principally upon two factors, namely (1) the character of the raw coal; and (2) the temperature at which it is carbonised. At the high temperatures prevailing in coke ovens *and gas works retorts, are obtained (1) coke (carbon plus ash); (2) benzenoid and phenolic tars, together with ammonia liquor; and (3) from 10,000 to 12,000 cu. ft. of gas (per ton of coal), whose calorific value is between 500 and 550 British thermal units per cu. ft. which no beehive coke oven installation would be allowed to remain in operation, except by express sanction of the State, and then only on special circumstances being- proved. The lecturer mentioned, as a very good example of the by-product coke oven system, the Otto system recently installed in the North of England, and described the process in detail, concluding by a reference to the advan- tage of gas fires for domestic heating in rooms that are in occasional use, and a description of the Vernon Harcourt coke grate. COST OF UPKEEP OF ELECTRIC CAP LAMPS.* One of the notable features at the Crow’s Nest mine, near Greensburg, Pennsylvania, is the installation of electric cap lamps, of.which 250 are in use. In the six months covered by the present report the lamps were burned for 34,419 lamp shifts. The cost of the spare parts and acid consumed amounted to 417’45 dols., of which 85'88 dols. was for material broken while in the care of the miners, leaving 331’57 dols. as the sum chargeable against the lamp station expense, or less than 1 c. per lamp shift. fl he figures given comprise not merely what are known as spare parts and repairs, but sulphuric acid and celluloid paste also. The cost of current, amortisation, interest and labour of lampman is not included. Bulbs and Cables Chief Repair Items. The cost of electric bulbs and cable are the two principal items in the list (see table). Schedule 6a of the United Stales Bureau of Mines requires that the average life of lamp bulbs shall be not less than 300 hours for primary and acid storage batteries and not less than 200 hoars for storage batteries using an alkaline solation. Not more than 5 per cent, of• the bulbs examined shall give less than 250 hours life with acid batteries, nor less than 170 hours life with ba'teries having an alkaline electrolyte. that the operating corporation shall charge its miners with the net amount of all, material destroyed through the carelessness of these employees ; it may be assumed, therefore, that the estimates of lamps broken by miners is not in any way excessive. Cable Breakages. The cable used is marked as 5 ft. long, though it need only be 44 ft , the additional 6 in. being added for con- servative estimation. The cable is the weak point in electric cap lamps ; but the cable attachment in use at Crow’s Nest seems to remove this trouble, and about 50 per cent, less breakage has been experienced with the new cable equipment than with that on which the figures quoted are based. According to observations made, a lamp cable is bent on the miner’s back about 7,000 times during the length of a single shift. It is easy to understand, therefore, to what a severe service it is subjected. It is not so much the kind and quality of the cable which is in question. The important matter is the manner in which the cable is attached to the lamp and battery casing. Tests are being made f om this point of view. Low Lamp Tending Charge. It is necessary to consider not only cost of material but the labour and amortisation charges. Experience shows that one man can handle at least 150 electric safety cap lamps and give perfect satisfaction. Thus 300 lamps could be tended by one lamp master and his assistant. If these men are paid 3 dols. and 2 dols. a day respectively, and 25 days are figured to a month, the monthly pay roll will be 125 dols. If they work to capacity—that is, charge and clean 300 lamps for each of the 25 shifts—each lamp-shift labour charge will be 1’66 c , or about If c. Costs per Lamp Shift. In figuring the ba’tery maintenance charges no con- sideration h s been given to battery renewals because, in the six months during which the lamps have been installed, the batte’ies have not needed any repairs. But to provide for that contingency it is well to double the repair bill arbitrarily, making that item 2 c. Adding Material used in Maintaining an Installation of 250 Lamps at Crow’s Nest Mine from March 22 to September 18, 1915. Spare parts used. March 22 to April 30. During May. During June. During July. During August. Sept. 1 to Sept. 18. Pieces. List price. Total. Pieces. List price. Total. P eces. List price. To al. Pieces. List price. Total. Pieces. List price. Total. Pieces. List price. Total. Dols. Dols. Dols. Dols. Dols. Dols. Dols. Dols. Dols. Dols. Dols. Dols. 1. Lamp bodies 3 0’70 2’10 5 0’70 3’50 2 0’70 1’40 — 7 0’70 4’90 ~ 2 0 70 l’4o 2. Lenses 8 0’20 1’60 3 0’20 0’60 1 0’20 0 20 2 0’20 0’40 8 0’20 1 60 2 0'20 0 40 3. Rubber rings for lenses 1 0’10 OTO 1 0 10 0’10 — — — — — — 105 OTO 10’50 — — 4. Bulbs 97 0’45 43’65 105 0’45 47 25 99 0’45 44’55 83 0'45 37’35 45 0’45 20’25 16 0’45 7 20 5. Bulb springs 1 0’05 0’05 1 0 05 0’05 — — — — — — — — — — — — 6. Safety devices 6 u-25 1’50 5 0’25 1’25 — — — ■— — — — — — 1 O’.5 0’25 7. Connection pieces 5 0’20 1’00 — .... 8. Rubber Avashers 1 002 0’02 9. Lamp holders 1 0’15 0’15 2 0’15 030 — — — — — — 5 0’15 0’75 3 015 0’45 10. 5 ft. cable lengths : 7 0’25 1’75 221 0’25 55’25 233 0’25 58’25 309 0’25 77 25 169 0’25 42’25 84 0 25 21’00 11. Leather sleeves — — 4 0’35 1’40 12. Aluminium shields 2 OTO 0’20 2 OTO 0’20 4 OTO 0’40 13. Casings Avith belt hook — — — 15 0’51 j 7'75 — — — 14. Hooks for locks 2 0’25 0’50 3 0’25 0’75 15. Rubber corks with pipe 3 0’07 0’21 — — — — — — - — 16. Rubber corks Avithout pipe 4 0’05 0’20 ■ . __ 17. Celluloid covers of casings — — — — 3 0’30 0’90 — — — — — 18. Celluloid covers for gas chamber — — — — — — I 0’05 0’05 — — — — — — — — — 19. Celluloid vessels — — — — — — — — — 4 1’05 4’20 — — — — — — 20. Pints of celluloid paste — — — — .—- — — — — 1 1’75 1’75 — — — 1’75 1’75 21. Carboys of acid 1 2’20 2’20 — — — 1 2’20 2’20 1 2’20 2’20 1 2’20 2’20 i 2’20 2’20 Total — — 54’71 — 108’52 — 108’05 124’95 90’95 — 34’65 Delivered lam p shifts — — 6,434 — — 5,813 ■ — — 6,561 . — — 6,0*47 ■— 1 ~ 5,905 — — 3,659 . Low temperature carbonisation is still only in the early stages of its technical development, but, helped by the Avar demands for high yields of light oils, it is now being energetically pushed forward, and has an assured future as an adjunct of the older systems of high temperature carbonisation, especially in view of the growing demands for light oils as motor fuels. Low temperature distillation (say at 400 to 500 degs. Cent.) decomposes the smoke-producing “ resinous constituents of the coal, leaving a porous semi-coke, which is easily burnt in an open fire place, and is smoke- less in its combustion. The tars obtained at Ioav temperatures are richer in light oils than ordinary gas- Avorks tar; moreover, they contain paraffins, naphthenes, as Avell as benzenes, and phenols, and from the point of view of motor fuel they are very interesting. The gas obtained is much smaller in volume, but richer in methane and paraffins, than that obtained at high temperatures. In the year 1913 about 40 million tons of coal (or approximately one-fifth of the entire output) were carbonised in the United Kingdom, namely, about 20 million tons in gas Avorks, principally for the manu- facture of toAvns gas, and another 20,million tons in coke ovens, for the manufacture of hard metallurgical coke. In modern gas Avorks the retorts are heated by the com- bustion of a part of the coke produced, and the auxiliary plant is so designed that the Avhole of the valuable by- products, including, if necessary, even the benzol and toluol, can be recovered, so that the process becomes very economical. Turning now to the manufacture of metallurgical coke, although by using the by-product recovery system the amount of ammonium sulphate produced in coke Avorks increased from 17,435 tons in the year 1903 to 133,816 tons in the year 1913, nevertheless, out of the 20 million tons of coal carbonised in coking plants in the year 1913, no less than 6-5 million tons were treated in the old wasteful beehive ovens, equivalent to a dead loss to the country of nearly 2J million pounds sterling. Public interest Avould, therefore, justify the Government fixing by laAv a reasonable time limit beyond If the number of working days in the month be taken at 25 and the number of sb'ft hours at 12, there Avould be 300 hours during which the lamps would be in use in any month. Tn such circumstances a bulb of 300 hour capacity would have to be renewed every month, or 12 times in a year. If the price of each bulb is 36 c., the cost per annum would be 4’32 dols. per lamp per year. This maintenance would be far too heavy, as it covers the cost of bulbs only. Bulbs Last Over 600 Hours. At CroAv’s Nest the total number of approved bulbs received up to September 18, 1915, was 995, and as at that date there Avere 157 bulbs in reserve, 838 bulbs were broken, consumed or in use. The miners had broken 218 bulbs in service. It seems conservative to rate half of these as burned-out bulbs. The bulbs were destroyed by the mishandling of the miners, but not being new they would not have burned as long as bulbs from stock. The loss from negligence can therefore be calculated as being equivalent to 109 bulbs. This can be deducted from the Joss as previously obtained, leaving 729 bulbs destroyed by burning out. The same assumption, that the bulbs when unbroken have still half their life unexpired, may be applied to the bulbs in the lamps, 25Q in number. Assuming their life to be equivalent to that of 125 bulbs fresh from stock, and deducting them from the number already obtained, the bulbs actually consumed may be taken as 604. The number of lamp shifts of these 604 bulbs is 34,419. Each shift is taken at 11 hours, giving 378,609 lamp hours, or 627 burning hours per bulb, or 57 shifts of 11 hours, instead of the .minimum average as required by the Bureau for an acid battery, namely, 300 hours. Assuming the number of shifts in a year to be 300, then 5’26 bulbs will be needed per year, which at 36 c. would entail an expenditure of 1'89 dols. Where the Mannesmann Light Company, which supplies the lamps, maintains them at so much per shift it stipulates * Goal Age. the labour charge to this, the cost of opeiating is 3’7 c. per lamp shift. The custom in most American coalmines is to charge the miner at least 5 c. for the use of a safety lamp during one shift. Taking 5 c. as the charge, the balance left for the operator would be 1’3 c., and this Avould have to coArer amortisation and interest on invested capital. A small lamp plant of 300 lamps running 250 shifts per year Avould give a total of 90,000 lamp shifts, which at 1’3 c. would provide 975 dols. for amortisation and interest. Such a plant for the Manlite lamps, including the lights themselves, would cost about 2,750 dols. An amortisation charge of 30 per cent, and 6 per cent, interest would amount to 962’50 dols. So it will be seen that the electric cap lamp not only gives a good light and assures safety irom gas and other causes, but also is at 5 c. per lamp shift by no means an unsatisfactory investment. To the advantages of cap lamps already mentioned may be added those of cleanliness, lightness and general availability. Explosives Used in 1914.—According to Part II. of the General Report on Mines and Quarries for 1914, the quan- tity of explosives used in mines under the Goal Mines Act was 25,521,098 1b., and the number of shots fired was 46,089,646, the manner of firing being : By electricity, 22,834,030; by fuse, 13,493,488; by squibs, 9,762,128. The Northern Division proved to be the largest user of explosives, Scotland taking the second place. Of the total explosives used, 8,715,211 only were permitted explosives, the remain- ing 16,805,887 being other than permitted. Hull Coal Exports.—The official return of the exports of coal from Hull to foreign countries for the week end-E Tuesday, January 18, 1916, is as follows :—Aalesund, r tons; Amsterdam, 346; Alexandria, 1,800; Copenhagen, 1,086; Christiania, 330; Calais, 707; Dunkirk, 1,237; Guernsey, 156; Harlingen, 948; Rotterdam, 2,112; Rouen, 14,651; West Coast Africa, 703—total, 24,103 tons. These figures do not inchide bunker coal, shipments, for the British Admiralty, or the Allies’ Governments. Corresponding period January 1915—total, 36,909 tons.