April 19, 1918. THE COLLIERY GUARDIAN. 797 in several important steel plants. Since the benzol is now generally extracted from the gas, it is the practice to burn a certain amount of tar along with the gas, to give it luminosity and higher radiating power. About 12 gals, of tar,, together with from 8,000 to 8,200 cu. ft. of gas—the quantity depending upon its calorific value—are required per ton of ingots produced, and it is found that furnaces fired in this way can be depended upon to produce from 10 to 15 per cent, more steel than when heated with producer gas. These figures are based on work at stationary furnaces, and it may be stated that the surplus gas and the tar obtained in the production of a ton of coke will furnish the necessary fuel to produce a ton of ingots from an open-hearth furnace. Without considering the value of the other by-products recovered, this statement illustrates the importance of the by-product oven as a fuel supply to a blast furnace and steel plant. Separation of Gas. Early in the development of the by-product oven in America, the principle of the separation of the richer portion of the gas, which comes off during the early 40 30 SO too 0 °7o CH, 60 40 50 30 SO 20 too 3 2 20 7 6 S 6 5 4 3 Fig. ____3 4. _____to Average Hourly analysis or coke oven Gas from One Oven. Coal 25% Volatile. Coking Time > /5"Average Width per Hour. _________I I WOV. 19,21,22 24 1917 !2 13 14 IS 16 Hours Coking Time. \1oComb. J—- 40 .20 10 !5 20 Specific Gravity. Hours Coking Time B. T.U. PER Cu. Candle Power io .30 5 20 40 20 Fig. 5. COAL 25% VOLATILE. COK/NG TIME /.IS" AVERAGE WIDTH PER HOUR. ; Nov 19,21,22,24, 19/7 ___3 4 S 6 7 8 3 !O !2 !3 M IS !6 !7 €00 SOO 600 SOL part of the coking period, from the leaner portion, was developed in. a practical way. This has enabled the oven plants to produce gas for sale having a calorific value much higher than could possibly be produced in ordinary gas works from the same coal. The accompanying charts (figs. 4 and 5) show the com- position of a gas from an oven running on a coal of about 25 per cent, volatile matter, analyses being taken each hour during the coking period. At the time these analyses were made the oven was coking at the rate of about 1-15 in. of width per hour. This chart shows plainly the progressive decrease in the percentages of methane and the progressive increase in hydrogen and carbon monoxide, as the coking proceeds. The separation of the rich from the lean portion of the gas is probably not advantageous when the surplus is to be used for fuel purposes, as, of course, separa- tion introduces some complications into the apparatus, but where a higher calorific value than the average is desired, the separation method is of great value, and can be accurately controlled. Recovery of Benzol. The benzols are recovered in the form of a “light oil,” containing usually about 60 per cent, of benzol, 12 per cent, of toluol, and 6 per cent, of solvent naphtha, although these percentages vary considerably with the details of the coking process and the light-oil recovery. Before the war the light oil produced was used largely for enriching illuminating gas, and the refined products were employed in the manufacture of paints, varnishes, and other similar industries. Since the beginning of the war the enormous demand for the high explosives, picric acid, and trinitrotoluol, has resulted in the equipment of practically all the plants in the United States for the recovery of these products, and it is estimated that the plants now built or building have a capacity of 120,000,000 gals, of light oil per year. The removal of the light oils from the gas practically destroys its luminosity, but the reduction in calorific value is relatively small, about 10 B.T.U. per cubic foot per gallon of light oil recovered per ton of coal. When the demand for high explosives ceases after the war, a large amount of the benzol now produced will probably be sold as motor benzol; a mixture of benzol, toluol, and solvent naphtha in the proportions in which they occur in the light oil. Motor benzol has a fuel value from 18 to 20 per cent, higher than gasoline, and may be used alone with the ordinary carburetter if a somewhat larger proportion of air is used, or it may be mixed with gasoline in any proportion. Pure benzol freezes at 5-18 degs. Cent., and toluol at - 92 degs. Cent. No trouble is experienced from freezing, even in the coldest weather, when proper percentages of toluol or gasoline are mixed with the benzol. The dye and colour industry in the United States, which has greatly expanded during the war, will furnish a large market for benzol, the raw material for aniline. Also, it seems not. improbable that trinitrotoluol will be widely utilised as an industrial explosive. It is claimed that it can be manufactured more cheaply than nitro- glycerine, and as a commercial explosive it has many advantages over nitroglycerine compounds. It is very stable and ignites only at high temperatures, and even then does not explode. It does not freeze, as does nitroglycerine, and on many counts it has advantages on the side of safety and convenience. When used alone it produces large amounts of carbon monoxide, but this can be entirely prevented by com- bination with other bodies, such as ammonium nitrate, for example, if these are added in proper proportion to produce complete combustion. COAL OUTPUT IM 1917. An advance proof of the report relating to the output of coal and other minerals in Great Britain in 1917 has been issued by the Home Office. These statistics are stated to be substantially complete, and a summary of them appears below. The output of coal from mines under the Coal Mines Act, which from 287,411,869 tons in 1913 fell to 265,643,030 tons in 1914, and to 253,179,446 tons in 1915, rose in 1916 to 256,348,351 tons, but in 1917 it fell again to 248,473,119 tons—a decrease of 7,875,232 tons on 1916. The comparison with 1916 for each of the inspection divisions is as follows:— Increase or decrease. - 1,848,887 - 4,041,894 + 1,123,331 + 302,435 - 3,572,807 + 162,590 1917. Scotland ................. 34,245,744 ... Northern ................. 43,228,230 .. York and North Midland 69,128,836 ... Lancashire, North Wales and Ireland............. 25,300,206 ... South Wales .............. 48,507.902 ... Midland and Southern... 28,062,201 ... Total decrease... - 7,875,232 The number of persons employed at mines under the Coal Mines Act was 1,021,340. These figures show a decrease of 106,550 persons on the pre-war year of 1913, but an increase of 23,277 persons on the figures for the year 1916. The rate of the decrease on the pre-war figures in the output of coal is about 13'5 per cent, and in the number of persons employed at mines under the Coal Mines Act about 9’4 per cent. MANCHESTER GEOLOGICAL AND MINING SOCIETY. A meeting of the Manchester Geological and Mining Society was held on Tuesday last, Mr. Pickup, the president, being in the chair. The following gentle- men having been duly nominated were elected: — Members — Federated:—J. Hewitt, Clifton Vale House, Pendlebury; J. Kane, Glenside, Wattstown, Rhondda. Associate members:—W. B. Davies, Brynheulog, Pentre, Rhondda; R. E. Michael, 46, Llanwit-road, Treforest, Glam.; H. Foster, 17, Silver- well-street, Bolton; A. S. Harding, Brighton Villa, Castle-street, Abertillery, Mon.; A. Timmins, Argyll Lodge, Runcorn. The “ Bold ” Timber Tram. An apparatus described as the “Bold” timber tram was exhibited by Mr. J. C. Thompson, who explained that, in working some of the coal seams in the St. Helens district of Lancashire, a large amount of timber was required. It was a difficult matter to convey timber which was too long to be placed in the coal trams, especially along poor and inclined roads underground. Some of it would slide on the tram and get out of balance, with the result that it caught the sides of the road, or of the adjacent braces on a double haulage road. Attempts had been made to minimise those diffi- culties, and the “Bold” tram, after being in use for a period of over 18 months, was found to meet the requirements quite satisfactorily. In the con- struction of this tram, a standard box frame, wheels and drawbar were used, the over-all dimensions of which did not exceed those of an ordinary tram, so that when empty it could ride in the cage along with the coal trams. A plate was fitted underneath the frame so as to provide a receptable for the chain and lever when not in use. Two horns were arranged to support the timber and folded towards the middle of the tram when out of use, or when the tram was being loaded or unloaded. When in use they were maintained in an upright position by the pressure of the timber on the cranked centres, the latter also preventing side movements. The raising and lowering of the horns could be assisted by inserting a bar or pick point in either of the holes provided in the ends. A bar secured across the centre of the tram had a notch at either end, into which a chain link fitted. The chain, with a tightening lever, was secured to the bar. The tightening lever was made in the form of an elongated jaw which received the chain tongue, the jaw being bent to one side and provided with a hole at the end so that a pick point could be inserted for additional leverage in tightening the chain. A pin or stud in the open end of the shackle rested in the head or tongue and prevented any movement of the chain and timber in transit. The chain could be adjusted to various loads by insert- ing the proper links into the slots at the end of the bar. Discussion. The President, in moving a vote of thanks to Mr. Thompson, said this was one of the little problems which mining men delighted to solve, and it would be a good thing if other members, who could hot devote the necessary time or material to the prepara- tion of a long paper, would submit similar descriptions of any device adopted at collieries in order to get over difficulties due to particular circumstances. Mr. Siddall, in seconding, asked whether Mr. Thompson would give an account of a particularly neat device which he had observed at the Bold Colliery in connection with the grooving on a big drum. It showed Mr. Thompson was a man of most ingenious mind. The vote of thanks was carried. Mr. Thompson, in reply, said he agreed with the president it was a pity these small things were not brought forward. The number of things which were not quite according to orthodox arrangements, but had been adapted by men connected with collieries, was amazing. One thing which always appealed to him was the lashing chain, a most ingenious and perfectly simple device, but in many respects unapproached by any other form of fastening that was available. He was told by some of the men at the colliery that a similar thing to that he had described had been seen years ago, but he had not been able to verify this. Many of the men objected to the device at the commencement, but they were now asking why it had not been adopted earlier. The grooving Mr. Siddall mentioned worked splendidly. The drum was 22 ft. in diameter. Recently he had been interested in certain quotations received at collieries in connection with winding. Engineering people would not agree to divide the angle so that there would be as much rope on one side as on the other. They suggested that a narrower drum should be put on, because long shafts were very expensive and very unsatisfactory from the engineering stand- point. So they might be, but there was another side to the question. The ropes which Mr. Siddall had mentioned cost about £800, and they had to be taken off at the end of 3J years, although they might be as good then as when they were put on. One did not like to shorten the period of 3J years, and he con- sidered it was a less disadvantage to have a wide drum and get the most out of the ropes, than to have a narrow drum with a reduced cost of engine, but a considerable increase in the cost of the ropes. The grooving was done to minimise trouble with the rope and get them near the edge of the drum. Coal Washing. The discussion on Mr. T. J. Drakeley’s paper (Colliery Guardian, January 18, 1918) was resumed. Mr. S. Hunter, in the course of a written contribu- tion, said the author appeared to have overlooked the paper he (Mr. Hunter) read on “ Coal Washing ” at the meeting of the society in April 1916, when he described a number of washeries laid out for washing all kinds of coal, including the dust, mixing and