November 3, 1916. THE COLLIERY GUARDIAN. 865 CURRENT SCIENCE The Atmospheric Problem in Deep Mines. In reporting on the ventilation of the Morro Velho Mine, Brazil, Mr. G. Chambers (Mining and Engineer- ing World) says that as depth has been attained, the necessity for modification in the distribution of the air becomes imperative. Some years back boreholes were made, and the temperatures taken, the readings enabling a rock temperature grade to be constructed as a guide to what might be expected at great depths. Supposing the lode to continue the same in size and value to horizon 20 (a vertical depth of 7,6*26 ft.), it could be worked profitably to that point, and even a much greater depth, but from the grade on the tem- perature chart the rock at horizon 26 would be no less than 126-5 degs. Fahr, at the moment of opening. . The increase of air temperature, due to the air becoming more dense as it passes down the mine, has been found under normal conditions to be approxi- mately 1 deg. Fahr, for every 180 ft., while -the increase in rock temperature is approximately 1 deg. Fahr, for every 125 ft. During the cold season an experiment was tried by night (when the temperature was consider- ably below the normal) in which a known volume of air was passed through a measured distance of the adit tunnel into the mine, the rock temperatures being taken throughout the distance of the tunnel and period of trial. At the end of five hours it was found that a considerable fall in the rock temperature had taken place, but as the sun rose the air became warmer, and the rock rose again to its original temperature. The drying of the air has always been considered necessary in conjunction with the cooling operation, but its importance was not so fully understood until information was gained from a valuable paper by Prof. John Cadman. Unfortunately, the drying of the atmosphere is somewhat antagonistic to a satisfactory solution of the dust question, which necessitates water- ing of' the roads and stopes to keep down the dust. However, the proposed distribution of the air will apparently do far more to overcome the dust trouble than the drying of the air will make against the efforts in this respect, as the allotted quantity of air, after passing one stope, or, at the outside, two, will go directly with what dust it has taken up, to the upcast and away to the surface, instead of the present system, in which the same air passes the bottom stopes, thence over the remaining stopes, with some slight addition of fresh air at each horizon, but accumulating dust all the way, until it finally reaches the highest stope, and thence goes to surface. With regard to the situation where the operation of cooling and drying should take place, it is considered that the increase in mechanical appliances underground represents a serious obstacle to the particular form of mining operations in use, and, further, on account of the principal cooling agent (water) being found on the surface in abundance, whilst underground there is very little, and that at a high temperature, it has been decided that the cooling plant should be installed on the sur- face. The plant designed for the purpose is one in which each operation will be performed to the most economical point, at the same time making use of ordi- nary cooling appliances which in practice have long since proved their reliability in cold storage, dry blast for furnace, and other installations, and in consequence it represents a thoroughly practical scheme, which will effectually remove the one serious obstacle against the company being able to work the mine to a great depth. The necessary power for driving the plant is not exces- sive, amounting to approximately 400 horse-power; and the provision of this power, with that of 200 horse- power for ventilation, and other additions necessary for the working into depth, has been satisfactorily arranged for. Natural Gas Operating Coal Mines. According to Mr. R. P. Hines (Coal Trade Bulletin), in mining and loading a large quantity of bituminous coal, the Consolidation Coal Company makes extensive use of electricity, generated at a gas power central station and distributed to the mines of the company in West Virginia. The power plant is at Hutchinson, which is centrally located with reference to the dis- trict to be served, practically all of the mines being within a radius of 12 miles from this point. The instal- lation comprises four 23J in. by 32 in. horizontal twin tandem natural-gas engines, each rated at 1,500 b.h.p., and direct connected to a 1,280 k.v.a. 2,300 volt three- phase 60 cycle revolving field alternator. In order to raise the voltage to 23,000 volts, at which pressure the power is delivered at the station end of the transmis- sion lines, three 1,500 k.v.a. oil-insulated water-cooled single-phase 60-cycle transformers are used. At first, two main 23,000-volt transmission lines were taken from the station, but a third has lately been completed 'to serve two large new mines now being opened. The first of these original circuits is about 13 miles long, and extends in a southerly direction from the plant, while the second is about 11 miles long, and takes a northerly direction. The branch lines taken from these circuits total about 14 miles in length. The third line is approximately four miles long. At the mines, the 23,000-volt alternating current power is converted into 275 volts direct current for use inside the mine, by rotary converters■ used in connec- tion with the necessary step-down transformers. The equipment inside of the mine operated by electricity includes haulage and gathering locomotives, coal- cutting and drilling machines, and pumps for removing water from the mine, and fans for ventilating. Other banks of transformers reduce the voltage to 2,200, or even to 220, for use on tipple motors, car haul motors, ventilating fan motors, hoist motors, etc., and also for AND TECHNOLOGY. use in lighting the mine buildings of the company and the miners’ houses. The number of mines served from the central power plant is 19, the total connected load in transformers and rotary converters for these mines being approximately 5,445 kw. Briquetting Anthracite Smalls. A description of how small sizes of anthracite are cleaned and prepared into a size suitable to domestic use, was given by Mr. A. L. Stillman in a paper read before the New York Retail Coal Dealers’ Association, the plant described being that of the Lehigh Coal and Navigation Company. The Lehigh Company started with the pitch binder, but discarded it as its deficiencies became manifest, and adopted the Dutch oil process, controlled by the Ge neral Briquetting Company, of New York, a plant of 150 to 200 tons per working day being installed. At the culm bank, the surface dirt is removed from the culm by a short preliminary washing process.' In this way about 10 per cent, of the ash content is removed. Then the coal dust is conveyed to the main washery, and treated until the ash is brought down to 15 per cent., as compared with 30 per cent, in the original culm. The treated material, dried, now receives its oil addition. The oil, a black, asphaltic material, solid at ordinary temperatures, is melted by contact with steam coils. It has a very high melting point, a very high heat value, and strong adhesion. It distils a slight whitish smoke, but of little odour, and no soot, in strong contrast to pitch binders. The foreman easily determines the proper proportion of oil, usually about 5 per cent., and when the right consistency of the mass is determined, the next step is in order, namely, the mastication or inter-compounding of the coal and oil. The apparatus for this purpose is known as the edge runner, whereby the coal oil mixture is crushed and mixed until homogeneous. In this method the small grains of coal are each not only coated, but thoroughly inter-penetrated with the oil, and the result is a won- derful cohesion, a firm exterior shell, and consequently practically no breakage and great resistance to weather. From the edge runner the digested material goes to the third step, the moulding and pressing. The presses are twin cylinders, with the moulds on the exterior, pressing against each other in their rotation. The mass, now at a temperature of about 150degs., passes through the presses, is moulded into shape, and then is carried up in a conveyor, cooled, and loaded. The finished “ boulet ” is ready foi the market, and can be sold at 4s. to 6s. per ton less han prevailing large size anthra- cite prices. Physical and chemical tests, as’ well as practical combustion, show a higher heat value per lb. of “ boulots ” than per lb. of anthracite. THE GERMAN AND AUSTRIAN COAL AND IRON TRADES. We give below further extracts from foreign periodicals that have reached us, showing the course of the coal and iron trades in Germany and Austria :— German Pig Iron Output in September. The report of the German Iron and Steel Makers’ Association gives the output of pig iron in September as I, 116,752 tons (1,145,239 tons in August) ; including foundry pig, 169,102 tons (167,645 tons); Bessemer pig, II, 302 tons (11,929 tons); basic Bessemer pig, 725,142 tons (729,543 tons); steel-iron and spiegeleisen, 195,744 tons (221,051 tons); and puddling pig, 15,462 tons (15,971 tons); Rhenish Westphalia produced 473,577 tons (479,212 tous); Siegerland, Wetzler and Hesse- Nassau, 71,975 tons (74,205 tons); Silesia, 60,637 tons (65,054 tons); North Germany, 21,091 tons (21,813 tons) ; Mid Germany, 34,875 tons (37,390 tons); South Germany and Thuringia, 22.241 tons (23,373 tons); the Saar district, 85,870 tons (89,946 tons); Lothringen, 184,068 tons (185,054 tons) ; and Luxemburg, 162,418 tons (169,192 tons). Austrian Iron Output in August. During August the Austrian ironworks distributed 54,351 tons of bars and sections (38,394 tons in August, 1915), 7,914 tons (8,574 tons) of girders, 8,594 tons (3,321 tons) of heavy plate, and 8,519 tons (6,723 tons) of rails. Fuel Traffic on the Rhine-Herne Canal in September. The total shipments of I coal, coke and briquettes in September amounted to 385,664 tons (230,312 tons last year), including: 55,741 tons (23,752 tons) from Aren- berg-Prosper; 65,164 tons (51,617 tons) from the State collieries; 40,699 tons (24,710 tons) from Bismarck; 20,021 tons (14,681 tons) from Concordia; 2,840 tons (1,743 tons) from Dortmund; 14,006 tons (12 249 tons) from Friedrich der Grosse; 6,170 tons (2,675 tons) from Hibernia; 22,577 tons (8,453 tons) from Koln-Neuessen; 13,092 tons (9,577 tons) from Konig Ludwig; 7,320 tons (1,305 tons) from Konig Wilhelm ; 44,453 tons (30,954 tons) from Mathias Stinnes; 125 tons (3,739 tons) from Minister Achenbach ; 5,144 tons (2,909 tons) from Nordstern, and 72,777 tons (39,728 tons) from Wanne- West. German Steel Union Report for September. The Steel Union reports that the deliveries in September totalled 244,212 tons (250.831 tons in August) in weight of raw steel, comprising 79,935 tons of semis, 85,542 tons of railway superstructure! material, and 78,785 tons of sections. SOUTH AFRICAN MINING IN 1915. According to the Annual Report of the Department of Mines and Industries for the Union of South Africa, the value of the coal raised, viz., 122,142,479, shows a decrease of .£116,417, the greater proportion of which is due to decreased outputs by Natal collieries, attributable to a large extent to a continued shortage of trucks, and the consequent difficulty of supplying the shipping demand. The following table shows the sales for each province : Tons of 2,000 lb. Value per ton. Province. ^1914. Iyl5.~^ Gl9U. 1915? s. d. s. d. Transvaal ............. 5,157,268...5,202,805... 4 5’55... 4 4*82 Cape...................... 53,621... 46,850...11 7*50...il 4*22 Orange Free State ... 699,217... 727,553... 5 5'58... 5 2*14 Natal ................. 2,567,817...2,304,116... 6 10*80... 6 9 50 Totals ............ 8,477,923...8,281,324... — ... — In addition, 24 tons of coke, valued at £31, were pro- duced in the Transvaal, and 7,255 tons, value £12,849, in Natal; and 26,050 gals, of tar, valued at £881, were produced by Transvaal coal companies. During 1915, 1,296,891 tons of coal were bunkered, and 506,539 tons exported, as compared with 1,343,240 tons and 651,210 tons respectively in 1914. In December 1915, 25,869 persons were engaged at coal mines, divided as follows : Whites, 1,274; Asiatics, 3,164; natives and others, 21,431. According to pro- vince, the distribution of labour was : Transvaal, 12,156; Cape, 784; Orange Free State, 2,233; Natal, 10,696. In salaries and wages the coal mines paid out £1,001,315, as compared with £991,822 in 1914. In addition, £617,819 (£643,158) was paid for machinery and stores. The total paid by all mines for machinery and stores was £12,082,371, as against £12,224,535 in 1914. Rather more than half this amount represents expenditure on South African products, including £1,099,578 on coal, £5,761 on coke, and £1,443,955 on explosives. The gold mines consumed 20,666 tons of smithy coals, 1,835,245 tons of steam coals, and 23,512 tons of other coals, together with 284 tons of imported coke, and 1,229 tons of local coke. Accidents in Mines. In 1915, 78 whites and 698 coloured persons were killed in accidents at mines, of whom four white and 49 coloured persons were killed at coal mines. Of the total of 53 killed, 23 natives were killed in Transvaal mines, one native in Cape mines, one white and nine natives in Orange Free State mines, and three whites and 16 natives in Natal mines. The accident death rate for the Transvaal, 3*02, again constitutes a record (3-05 in 1914). In the Transvaal collieries the death rate- from accidents was reduced from 2*22 per 1,000 in 1914 to 1-99 per 1,000 in 1915. This decrease is the outcome of improved vigilance and more careful supervision, falls of ground having been accountable in previous years for a very much greater number of accidents than was reasonable or justifiable. The Transvaal coal mines are, as a rule, free from marsh gas, and there is consequently little danger of serious explosions occurring. In the Orange Free State collieries the death rate from acci- dents increased from 1’35 per 1,000 in 1914 to 4-40 per 1,000 in 1915, through an explosion of gas at the Clydes- dale (Coalbrook) Colliery, by which eight persons were killed. This explosion was caused through non-observ- ance of the Regulations relating to fiery mines, which, on account of accumulations of gas, should have been strictly complied with, and the accident was therefore due to lack of supervision on the part of the manage- ment. The Natal collieries maintain a satisfactorily low death rate from accident, the figure being 1’70 per 1,000 for 1915, as compared with 1’86 in 1914. These mines, which are in the majority of cases fiery mines, are naturally a source of danger, the risk being increased by the existence of gob-fires in several instances, but fortunately there has been no serious loss of life from explosions during the year.. Gas occurs in practically every pit in Natal; at some it may be in such small quantities as to escape detection, but given opportu- nities, such as cavities in the roof, slackness in exami- nation or ventilation, it makes its presence felt. In addition to the 776 deaths, 2,213 persons were injured an mines within the Union during the year. The following table shows the principal causes of accident and the percentage of casualties :■— No. of deaths. Percentage Cause. ( * t A 1914. 1915. 1914. 1915. Falls of ground 275 . .. 279 .. . 37’01 . .. 35’96 Trucks and tramways 44 . .. 52 .. . 5’92 .. .. 6’70 Falling of material 60 . .. 66 .. . 8’07 .. .. 8’51 Explosives 156 . .. 167 .. . 2100 .. .. 21’52 Machinery Falling in shafts, excavations. 29 . .. 18 .. . 3’90 .. .. 2’32 etc 47 . .. 49 .. . 6’33 .. . 6*31 Trave Hing by cage or skip 41 . .. 36 .. . 5’52 .. . 4’64 Struck by skip, cage, etc 23 . .. 41 .. . 3T0 .. . 5’*28 Other causes 68 . .. 68 .. . 9 15 .. . 8’76 —.1 —... - ■ Totals 743 .. . 743 .. — — The extent to which the personal element affects accident occurrences is shown hereunder :— Deaths. Causes. t-------*------- No. Percent. Danger inherent to work or misadventure 481 ... 62 0 Defective plant or material.............. 9 ... 12 Fault of injured person— Carelessness ..................... 39 ... 5’0 Ignorance ........................... 6 ... 0’8 Disobedience to orders ............. 50 ... 6’4 Fault of management .................... 24 ... 3’1 Fault of gangers ....................... 94 ... 12’1 Fault of others......................... 26 ... 3*3 Joint fault ........................... 47 ... 6’1 Last year there were 17 separate accidents in con- nection with electrical plant at mines, causing eight