1236 THE COLLIERY GUARDIAN. June 30, 1916. 4,493 men, and above ground 1,952. This shows a reduction of 1,625 men employed compared with the year 1914. The number of tons mined per man for the year 1915 was 532 tons, while that of the year 1914 was 467 tons. The number of mines in operation during the year was 280, which is an increase of 16 over the previous year. During the year 58 mines were opened, while 72 were abandoned. There were 18 separate accidents, causing the loss of 18 lives, 15 of which occurred underground iand three above ground; 28 serious accidents occurred underground and five above ground, and 27 slight accidents occurred underground and six above ground. 7-17 tons of coal was mined per lb. of explosives used in bituminous and anthracite fields, while 3*91 tons of lignite coal was mined per lb. of explosives used. The average number of days worked per month in the province was 16-9. There were 131 prosecutions instituted for contravention of the Mines Act, and convictions obtained in practically every instance. There were 306,461 tons of coal mined in the Crow’s Nest Pass district per man killed in the mines, 359,864 tons per man killed in the Lethbridge district, 121,335 tons per man killed in the Edmonton district, and 157,316 tons per man killed in the Calgary district. Dominion Goal Go.'s Production.—Eor the first quarter of the year the production of the Dominion Coal Company shows an increase of 253,000 tons compared with the first quarter of 1915. The coal mines have worked through the winter months as steadily as is the custom in the summer months. The outputs actually obtained in the first quarter of 1916 compare with the same period of 1915 as follow :— 1916. 1915. Tons. Tons. Glace Bay Mines .......... 1,126,000 ...... 864,871 Springhill Mines ........... 100,000 .... 98,791 i,226,000 ....... 963,000 Increase ................. 253,000 tons. RETARDER FOR STEEP CHUTES.*' The accompanying illustration shows diagrammatic- ally a retarder used in the chutes at the Rendham Colliery of the Jermyn Coal Company. Sometimes the space in a breaker is so distributed that it is necessary to put in chutes with steep slopes. In such cases the coal moves too rapidly, and is badly broken. Of course, the best plan is to have the chutes at just the right angle to let the coal slide slowly, but the next best thing is to retard the coal if it moves too rapidly. The device illustrated consists of a number of hinged gates set in the chute, so that they will close by their Diagrammatic View of Retarder. ■7d Eccentric own weight if released. They are raised by wires or by rods, which are moved by bell cranks which may be operated by eccentrics, the motion being transmitted to the bell cranks by wires or rods. The gates are so moved that alternate ones are closed or open at the same time. Thus, in the illustration, No. 1 and No. 3 are closed, while No. 2 and No. 4 are open. The coal will collect above No. 1 and No. 3, and when they are raised, it will slide down until stopped by No. 2 and No. 4, which will then be closed. In this way the coal slides only a few feet at a time, and does not acquire such high velocity as to be broken. * Coal Age. LAW INTELLIGENCE. HOUSE OF LORDS.—June 27. Before Lords Parker, Sumner, and Wrenbury. A Pit Prop Cargo. Dampskibssilskabet Svendberg v. Love and Steward Limited. — The plaintiffs, who are owners of the Danish steamer “ Chassie Maersk,” appealed against a judgment of the Court of Session regarding the carriage of pit props from Petrograd to Granton. The dispute related to measurement. According to the bill of lading, the quantity shipped was for a cargo of 595 fathoms, but it was tsigned by the master “ under dispute for quantity,” and it was afterwards alleged that the amount shipped was regarded a not inconsiderable part of the cargo the result of the measurement had not been proved. As to this, part of the measurements were taken by one person only, who was not called at the trial. This person appeared to have communicated the result of the measurement to another person, who was called as a witness, and it was quite clear that what was said by the former to the latter was not admissible. The appellants had, therefore, failed to prove the figure on which their claim was based, and it did not appear to him (Lord Parker) that they could fill up the gap in that evidence by inferences to be drawn from the capacity of the ship or the manner -and extent to which she had been loaded. The other judges concurred, and the appeal was dismissed. CURRENT SCIENCE AND TECHNOLOGY. By-Products of the Gas Industry. At the 100th meeting of the Waverley Association of Gas Managers, Prof. Thomas Gray spoke of the possi- bilities of increasing the yield of ammonia, which at present, in the different systems of carbonisation, expressed in terms of sulphate, ranges from about 20 lb. to 361b., and from coal distilled in horizontal retorts is usually 241b. to 261b. In the present state of our knowledge of the subject, there is nothing to indicate a prospect of any substantial improvement of the ammonia yield, but a similar criticism of the still pre- valent system of recovering this product from the gas, which involves the handling and storage of large volumes of liquor, with the attendant unavoidable loss of ammonia and the transport—often to considerable dis- tance's—of a dilute liquor containing only 2 per cent, of valuable material, can scarcely be justified. A more general adoption of the semi-direct process of recover- ing ammonia from the gas in the form now practised' in some of the smaller gas works is desirable; and the pro- posal to combine a direct system of ammonia recovery with arrangements for the fractional condensation of the tar on the lines suggested by Purves appears to call for the serious consideration of the gas engineer. With regard to synthetic ammonia, Prof. Gray remarked that it was safe to predict that the development of this process, if it proved to be a commercial success, would not render the recovery of ammonia in connection with existing coal distilling plants unremunerative, though it would undoubtedly have a very serious influence on prices. In view of this possibility, the need for an enquiry into existing methods of dealing with ammonia as a by-product of the manufacture of gas, for the pur- pose of determining the best methods of preventing loss and of reducing the cost of converting it into sulphate, was urgent. The total output of tar in the United Kingdom is approximately million tons. The London Gas Light and Coke Company separated from 16J million gals, of tar : 81,500 gals, of 90 per cent, benzol, and 19,600 gals, of 90 per cent, toluol. One ton of tar yields 0-95 gal. of 90 per cent, benzol, and 0-23 gal. of 90 per cent, toluol, and the possible output of these products from 1| million tons of crude tar may be estimated to be about 14 million gals, of 90 per cent, benzol, or, making allowance for the higher yields from the richer tars, about 2 million gals., and the possible output of 90 per cent, toluol from tar distillation about one-quarter of these figures. The major portion of the lighter hydrocarbons remains in the coal gas. It has been the practice in coke works for a considerable number of years to recover these by scrubbing the gas with creosote oil, and subsequently to distil them from the solution, with the help of steam. This practice has only been extended to gas works since the outbreak of war. The yield of crude benzol per ton of coal carbonised in coke ovens is usually from 2 to 3 gals., and is probably of the same order in gas works. Practical working yields of finished commercial pro- ducts, obtained per ton of coal carbonised in a large coke works, and of pure products, over the more limited period during which these have been manufactured, are given below :— Commercial Products. Gals. 90 per cent, benzol .... 1-70 90 per cent, toluol 6-31 Solvent naphtha ....... 0-11 Pure Products. Gals. Pure benzol ............ 0-88 95 per cent, at 90 degs. benzol ............. 0-72 Pure toluol ............ 0-33 Xylol ................ 0-05 Solvent naphtha ....... 0-05 Total ...... 2-12 Total ..... 2-03 The following figures, based on the results of the car- bonisation of nearly 100,000 tons of coal in horizontal retorts, show the yields of unwashed, distilled products per ton of coal :— Gals. 96 per cent, at 90 degs. benzol............ 1-23 90 per cent, toluol ....................... 0-23 Solvent naphtha .......................... 0'05 Total ................. 1-51 The loss on washing may be assumed to be 10 per cent. The output of benzol, expressed as 90 per cent, benzol, from coke ovens in Great Britain may be esti- mated to be 17,000,000 to 20,000,000 gals. (68,000 to 80,000 tons) per annum. If the whole of the metal- lurgical coke produced in the United Kingdom—approxi- mately 12,000,000 tons per annum—were made in by-product recovery ovens, the output of 90 per cent, benzol might be raised to 25,000,000 to 30,000,000 gals. (100,000 to 120,000 tons), a similar production might be expected from gas works, if oil washing of illumi- nating gas were universally practised. Up till quite recently the bulk of the benzol produc- tion was absorbed by the pure chemical and dye indus- tries, but in the few years immediately preceding the war the amount which was consumed as motor spirit greatly exceeded that used for all other purposes. Thus the consignment of benzol in Germany during 1910 totalled 67,790 tons, of which 32,300 tons were used in colour works, and 33,322 tons as motor spirit; of the benzol produced in Germany during 1913, the probable consumption in motors was stated to be 80,000 tons, and for 1914 the estimate was 95,000 tons. This new development of the use of benzol took place principally in France, which imported supplies from Great Britain, Germany, and Belgium. In 1908 Great Britain exported 2,000,000 gals, of benzol and toluol, of which 1,000,000 gals, went to France; in 1913 the amount exported had risen to 6,650,000 gals., of which France absorbed 6,320,000 gals. The British export to the United States, on the other hand, reached its maximum value of 178,000 gals, in 1911, and fell to 4,700 gals, in the following year. According to a recently published estimate, the yearly production of benzol by American iron and steel companies now falls not far short of 25 million gals., and it is evident that the United States is no longer dependent on foreign supplies. So far as the chemical industries are concerned, ignoring for the moment the present abnormal demand for the manu- facture of explosives, the output of benzol is very greatly in excess of. requirements, and the motor industry seems to offer the only possible outlet for the surplus production. The consumption of imported motor spirit in the United Kingdom has increased from 54,000,000 gals, in 1910 to nearly 119,000,000 gals, in 1914, and as the use of benzol for this purpose has long passed the experimental stage, the gas works and coke ovens of this country may be expected to supply a con- siderable proportion of this demand, if adequate facilities for the distribution of benzol to the consumer are pro- vided. Reports on the use of benzol as a motor spirit state that it gives 15 per cent, more mileage per gallon than petrol, and these confirm the evidence of tests of the calorific value, which show that the heating power per gallon is greater, though the value per pound is less. The following statement shows the net calorific values in British thermal unite of the two fuels :— Per lb. Per gal. Benzol (specific gravity 0-883) 17,270 ... 152,500 Petrol (specific gravity 0-72). 18,750 ... 135,000 In order to counteract the tendency to freeze at winter temperatures, it is desirable to include the toluene frac- tion with the benzol, and, for use in abnormally cold localities, to mix the latter with petrol. Inferior Coal for Firing Kilns. The use of steam in kiln fireplaces requires some consideration, for its ability to reduce the cost of fuel in boilers is well known. If a jet of steam is allowed to inject a quantity of air into a closed ash-pit, just below the fuel on the grate, or even if the air and steam are forced into the lower layers of fuel on the bars, the first effect is to burn the coal at a more rapid rate, and if the fuel be in large pieces, the steam and air will rapidly make holes in the fire, and a bad .and irregular com- bustion will occur. If, on the contrary, the coal is small and one which “ lies heavily ” instead of burning brightly, or tends to burn dully and to die out unless it is frequently stirred, the use of a steam jet to blow in air and steam has quite a different result. In this case the air and steam lift up the fuel, making it more open, and the net result is that with the simple aid of a steam jet and air-pipe the fuel can be made to burn almost as well as a better quality of coal without these aids. As the dull-burning fuels are usually cheaper, the combined use of a cheap fuel and a steam jet may result in an equally satisfactory production of heat at a lower cost than when using better coal and no steam. It is impor- tant to notice that the steam requires to be heated to the temperature of the kiln or fire, and that this will absorb the heat from a certain amount of coal. There is there- fore a loss of heat, though this may be more than counterbalanced by the lower price of the inferior coal. On the other hand, a careless fireman will use three times as much steam as a more careful one, and will upset all ordinary calculations. Whilst the steam is decomposed into oxygen and hydrogen in the firebox, and these gases re-combine with the production of great heat in the kiln, there is no gain in an ordinary kiln, for the decomposition of the steam absorbs a certain amount of heat from the gases used, and this is given out again when the gases reunite to form steam. The saving in fuel which is effected is due merely to the steam, being the vehicle which carries a supply of air to an otherwise slow- burning fuel. A blast of air of the same size and power would do equally well if it were produced by a blower or fan, but the ease with which steam may be used, and the simplicity of the jet, make it more convenient than the use of an air-pump or compressor. All that the steam jet does is to make the coal burn more brightly, so that the heat inside the kiln is increased, and the draught, being dependent on the rate at which the fuel burns, is also increased, though it bears no direct ratio to the amount of steam used. In a fan-created draught, on the contrary, the draught is directly dependent on the size and capacity of the fan. Whereas, in single kilns, there is no need to fear that steam will injure the goods in the kiln, provided, the steam is not used until they are at a dull red heat, in continuous kilns the use of steam jets is not advisable, nor is it necessary. The gases do not go direct up the chimney, but pass through one chamber after another, gradually becoming cooler until they finally have no appreciable heating power. When the steam in these gases comes into contact with goods which are suffi- ciently cool, it condenses, and may cause serious damage to the goods, so that the use of steam jets for such kilns cannot be recommended. This cannot well occur in single kilns. When steam is applied to single kilns each fireplace should have a separate steam-pipe, a 1 in. pipe being usually ample. These pipes and the main connecting them to the boiler should be well lagged, so as to prevent undue loss by condensation. The end of the steam-pipe nearest the fireplace should be fitted with a brass reducing piece, so that the jet of steam is jin. or rather less in diameter. The air pipe which leads into the fire- place is 2 in. in diameter, and may be of iron or steel. If a grate is used, the air pipe may be passed rather beyond the middle of the grate, the ash-pit beneath being closed by a tight- fitting door, duly luted. If the coal is burned on a solid bottom, the air-pipe is carried to about the middle of the