678 THE COLLIERY GUARDIAN. March 27, 1914. AN EXPERIMENTAL CHAMBER FOR THE STUDY OF MINE FIRES. The United States Bureau of Mines has recently installed at the Pittsburgh experiment station an underground chamber or furnace in which to carry on experiments relating to mine fires and spontaneous combustion as occurring in mines. A section of steel tube cylindrical in shape, 64 ft. in diameter and 27 ft. long, was laid on its side in a deep trench, and after lining this shell with firebrick and mineral wool, and stopping the ends with 13 in. brick walls, it was covered with 2 ft. of earth. The chamber was constructed so as to be as nearly airtight as possible, and in such manner as to retain to the greatest degree practicable any heat generated within its walls. At one end a motor-driven fan will blow in air at a rate which can be accurately measured, and at the other a stack is provided which can be opened or closed as desired. Through the top of the chamber at frequent intervals, pass small pipes for withdrawing samples of air or- gases and for inserting pyrometers for tempera- ture measurement in the interior. The chamber will hold six to eight tons of coal when one-third full. It is expected that different kinds of coal or- of the gob or waste material from mines will be placed in the chamber and a study made of spontaneous development of heat in them under various conditions. After an active fire has been started in the chamber either by this means or artificially, experiments will be made on controlling the fire by reducing the air supply or by sealing it off entirely. The progressive changes in composition of the fire gases or of the air surrounding the coal will be followed and temperature measurements made, in an endeavour to apply the data thus obtained to solving practical problems in the treatment of mine fires. These investigations are being carried on by Horace C. Porter, chemist, of the Bureau of Mines. A LARGE ELECTRIC WINDER. The General Electric Company of New York, through its subsidiary company, the South African General Electric Company, of Johannesburg, recently received a contract for supplying to the Crown Mines Limited an electric mine hoist to raise 16,000 lb. of ore per trip in a vertical shaft 3,540 ft. deep, at a speed of 3,500 ft. per minute. The weight of the empty ore bucket (or skip) is 8,700 lb. The rope is 2 in. in diameter, weighing 6'4 lb. per foot. The hoist will consist of two cylindro- conical drums, of which the smaller diameters are 12 ft. and the larger (cylindrical diameters) 20 ft. 8 in. The speed of the drums will be 53'5 revolutions per minute. To either end of the drum shaft there are connected two direct, separately excited electric motors, designed for 500 volts, and each capable of giving continuously an output of 2,000-horse power at 5.3'5 revolutions per minute. The total weight of each motor will be approximately 142,000 lb., exclusive of shaft and bearing. These two hoist motors will receive their power from a motor generator set which converts 50-cycle, three-phase power to direct current. The motor' generator will consist of one 5,000-horse power (continuous rating), three-phase, 50-cycle, 2,000-volt induction motor, operating at 375 revolutions per minute, direct-coupled to two 1,650-kilowatt, separately - excited, direct-current generators. There will also be one 60-kilowatt, shunt-wound exciter for exciting the fields of the two hoist motors and the two direct-current generators. The system of control will be the Ward- Leonard system. While the capacity of tie motor generator set is equivalent to 5,000-horse power con- tinuously, the intermittent output from the hoist motors may be at times 9,000-horse power, and the corre- sponding in-put to the motor generator set approximately over 11,000-horse’power. The total weight of the motor generator set will be approximately 138,000 lb., while its over-all dimensions will be approximately as follow :— Length, 30 ft.; width, lift. 6 in. ; height, 10 ft. Sin. The dimensions of the hoist motor armatures are so great as to make their transportation over the South African Railways impossible, and it will therefore be necessary to assemble and wind them on the spot. It is understood that the contract price for this electric hoist is approximately 125,000 dols. Mr. D. A. Thomas in America.—The Black Diamond publishes an interview with Mr. D. A. Thomas, in which the Welsh “coal magnate,” as he is called on the other side, makes interesting statements. In regard to labour con- ditions in England, he said he anticipated prolonged and tedious negotiations in the several districts and a very difficult situation for some time, but whether it would eventuate with a stoppage would depend largely upon the conditions of trade at the time. He did not think there was much likelihood of the coal tax being resuscitated in the near future. The possibility of large shipments of American gas coal to the Mediterranean was one that might require serious consideration a little later on, but he questioned whether English producers had any ground for alarm just now in view of the recent heavy drop in freights from Durham to the Mediterranean. The present dock facilities at Cardiff were by no means sufficient, and any little pressure for coal had led to con- gestion, delay and demurrage. Steps should be at once taken to prepare for the increased requirements which would certainly arise during the next few years. The practice of mixing coal which has developed on an extensive scale during recent years had tended to reduce the shipping capacity of the existing docks by the time occupied in sorting the empty wagons after shipments. Frankly, he did not anticipate that the ratio of increase for the past 10 or 20 years was likely to continue. Any increase must come from the further development of collieries already in existence. As to the possibilities of American coals, he thought that the opening of the Panama Canal would lead to a gradual and considerable increase in the use of American coal, and that American coal might make inroads into some of the markets now held by Welsh coal, such as those on the eastern side of the South American continent; also that American coal might displace Welsh or German coal in the Mediterranean, but it was all a matter of freights. While the cost of production had grown enor- mously in recent years, a comparison between the average cost of American coal now and what it was 20 years ago would show a diminution. He should expect the cost of production of American coal from now on to increase with the altered conditions of labour which were likely to arise. Speaking of the tolls question, Mr. Thomas said senti- ment would play a very insignificant part in deciding what routes the steamship owner would send his ships. He would be guided entirely by commercial conditions, and would use the coal which he found the cheaper, whether of American or of British origin. He believed the tendency will be towards an increase in American exports of coal, both to South America and to the Mediterranean ; but this would be slow and gradual and would be some time before it ran into millions of tons. It was not so much a question of American and British owned tonnage as the relative freights from the United States and the United Kingdom, the step taken by America towards a free trade policy, though only a short one, by inducing a return freight, was all in favour of coal exports. Further, it might be found practicable, under modern conditions and by increasing sufficiently the size of the steamers, to reduce the cost of coal freight as to make it a paying proposition for boats to return in ballast. Two very large steamers of carrying capacity of 14,000 tons were now under construc- tion by an Italian company to convey coal under this policy from Hampton Roads to the River Plate. Speaking very broadly and generally, and admitting exceptions in particular localities, he did not think American coal pro- ducers, or for the matter of that, coal producers in any country, need have any alarm in regard to competition from oil. The quantity of oil would have to be increased 25-fold in order to displace the total consumption of coal at the present time. To a representative of the New York Evening Journal, Mr. Thomas stated that his visit is not for the immediate acquirement of more coal properties in West Virginia, but to complete arrangements for the building of a 1,500-mile railroad in north-west Canada. He said his interest in producing coal in Wales was secondary to his interest in coaling depots all over the world, and the unsettled labour conditions in the Old World made it all the more imperative that he should look to America for coal for the future. Asked about the action of certain Congressmen from coal- producing States in urging the United States to enact legislation prohibiting the sale of any but American coal on the Panama Canal, Mr. Thomas said : “ Such legislation is entirely unnecessary. Panama is the natural outlet for American coal, and American producers will unquestionably reap the benefits that will accrue through the operation of the new waterway. When one considers that in the past 10 years American coals have supplanted Welsh coals in the West Indies, one does not need to give serious consideration to the fear of competition at Panama from Welsh or German coals. The canal will play an important part in commerce, and I am therefore giving it a great deal of study. To have my coal interests international appeals very strongly to me, and I am hoping to extend my opera- tions from time to time, so that my producing interests will be situated so advantageously from a geographical standpoint that my coaling depots will be assured of a constant supply of coal and at competitive prices, no matter where they may be located. I see a great future for your better grades of American coals from the operation of the Panama Canal. Your coals are at present impregnable so far as the West Indies are concerned. The west coast of South America will take a great deal of tonnage from American shippers when the canal is opened up, while at the present moment Americans are increasing their ship- ments to the east coast of South America and to the Mediterranean.” THE TEACHING OF MINING SCIENCE.* By G. A. Lodge. Coal has been known in this country since the time of the Romans, and probably to the Britons. The industry appears to have become fairly well established during the 17th century. The methods of working were crude and the conditions unpleasant and sometimes cruel. Under such circumstances the fittest only would survive, but these were men, who, though perhaps barren of the graces of life, could look death in the face without flinching, and though knowing little of science were yet able to grapple with the forces of nature and win the treasure of coal and iron. We may picture the miner of the early 19th century a man strong in body, brave and self-reliant, and therefore brooking inter- ference badly. Perhaps because of these qualities, and the uncomfortable conditions of his work, he, in some cases, gave way to excesses and gained an unenviable reputation. Many of our mining students to-day are descended from men of this type and possess their good qualities, but in the majority of cases are free from their bad ones. These students are working miners engaged in the pit during the day. They began their labours at 13 or 14 years of age, sometimes they have attended evening continuation classes, but more often they have indulged in a “ rest ” or a “ good time ” until reaching 18 or 20 years. They are thus adult students, and we should hope to get this state of things altered, but one of the surest ways of getting hold of the boys in the future is to get hold of their fathers now. We can only expect a sensible reduction in incidental accidents by educating the miner in the subjects relating to safety in mines. There are thousands of miners ignorant of the elementary principles of safety, and the miner, owing to the difficult conditions of working, is subject to less supervision than any other worker. Hence the necessity for cultivating his intel- ligence. In the early days of mining the stewards or managers were practical pit men, with little or no education except that gained by experience. Many could barely write their own names. Examinations of colliery managers were instituted in 1872. At first these were very elementary; sometimes a few lessons in decimals and composition from the village schoolmaster were sufficient for success. The Science and Art Department first held mining examinations in 1863. In 1898 the West Riding County Council adopted the system of local mining courses, and included arithmetic and elementary science, with the idea of giving a better all- round training. In 1911 their classes were attended by 617 students, mostly working miners. In 1909 the first local classes in testing for gas in the pits were formed at Batley. In 1912 it became compulsory for deputies and shotfirers to pass in one or more of the three subjects—gas testing, hearing and air measurement; 48,775 candidates themselves in 1912. There is no doubt a genuine desire to improve the education of the miner. A scientific education to enable him to understand and overcome the dangers of his calling is at any rate essential, and at the same time something should be done to broaden his ideas and enlarge his interests. Even the dull ones should be catered for. Success in educating depends to a great extent on the teacher. If we are to be increasingly successful we must be ever trying to improve oui' methods and our understanding of our students. Our teaching must be alive and create interest, make a two-hour lesson seem to last only one hour. Our methods must be varying ones; a well arranged and suitable lesson for to-day may be unsuitable five years hence. Our teaching must bring out what is best in the student, and must aim at cultivating understanding. A writer has said that “ stupidity may be directly cultivated by making a full memory of facts the one thing needful in school, and it may be cultivated nearly as readily by calling for no real effort on the part of the student.” The students themselves should take a great part in the lesson. All of them have had experience of some kind, and by working from such experience interest may be aroused and understanding result. When students are adult a well arranged class discussion is of great value. The value of experiments in the teaching of mining science can hardly be over-estimated; a prior discussion of the problem to be dealt with and the method to be employed will arouse interest and eagerness. With adult students whose faculties are often less flexible than those of youngsters, the more nearly the form of the experiment comes within the range of their experience the better they will understand and appreciate it. The influence of the teacher should extend beyond the class room. True education should mould the life of the student. Associations of mining students are being formed in connection with some centres. The influence of teachers will be felt in these, and the use- fulness of the movement will depend largely on the teachers work. * From a paper read at a recent meeting of the Mining Section of the West Yorkshire branch of the Association of Teachers in Technical Institutions.