3 50
T H E J O U R N A L OF I N D U S T R I A L A N D EATGINEERIXG C H E M I S T R Y
t h a t the outer portions of the flame flow in the direction along which the burner is traveling, and the portion of steel heated should be cooled-when intense hardness is required-by arranging t h a t cooling water shall follow as closely as possible the traveling burner, but not so close as to disturb the flame, because that is not only liable to put i t out, but prevents rapid heating and causes irregular hardening. The cost for hardening each square inch of surface is approximately only 0 . 5 cent. The flame required must be of the highest possible temperature, and burn close to, and eved under, water. This is obtained by adjusting the flame as for welding, and then increasing the pressure of oxygen, so that the flame changes color and appearance from a white cone to a bluish streaked tongue, when observed through smoked glasses. The essential to success in this method is the speed of heating. As the flame passes along, the surface is instantly cooled by the cold remainder of the forging or casting, leaving it of the maximum hardness of which the steel is capable when heated and quenched in cold water. To obtain a thin but intensely hard surface, the part to be hardened should be just below the surface of the water, the impinging flame blowing the film of water away. The normal depth of hardening is about in., can be i n , but a greater depth, up to about l/’g in or obtained by slightly prolonging the heating, a slight wavy or rotary movement being given to the flame to avoid burning the surface of the steel. Contrary t o what might have been expected, even with the hardest steels, there is no tendency for the hardened surface t o crack or flake away from the unhardened portion. In a number of cases made for examination, not a single instance shows any parting between the hardened and unhardened portions. TVhile RIessrs. Vickers are applying the process only to hightensile steels, and are interested in no further application, i t is of general engineering interest to note that cast-iron and “Blackheart” malleable-iron castings can also be given a glass hard surface by hardening in this manner.
THE SPONTANEOUS COMBUSTION OF COAL I N MINES The question of spontaneous combustion of coal in mines is discussed in Engineetizg (London), 97 (1914), 224, and the results of an English government investigation are reported. I n August, 1912, the Home Secretary appointed a DepartR. A . Redmayne, Chief mental Committee, consisting of Mi-, Inspector of Nines, Sir Arthur B. LIarkham, X I . P., and Messrs. C. E. Rhodes, Frank Rigby, and Herbert Smith, for the purpose of inquiring into the circumstances in which spontaneous combustion of coal occurs in mines, its causes, and the means of preventing it or dealing with it Considering that colliery temperatures vary widely from colliery to colliery, the committee, after taking much evidence from the inspectors, managers and men, suggest that the Inspector of Mines should be notified: (I) when gob stink or other signs of combustion are observed; ( 2 ) when the air temperature in any accessible part of the mine is z o o F. above the normal temperature in the main return air-way, or when it rises to 110’ F., ( 3 ) when any flash has been observed coming from any pack or waste. lTotification should also be made of the commencement of work for the purpose of discovering or combating a fire or anticipated fire The members of the committee, recognizing the importance of special conditions, propose t h a t in all the mines, in which safety lamps are used, or in which as much as 14 per cent of inflammable gas has been found in any ventilating district or return air-way of the mine, on any one occasion: ( a ) When smoke or other signs of a fire occur, all the workmen should a t once be withdrawn from the affected ventilating district, and not be re-admitted before the manager and two representatives of the men have made an inspection and have
s.
V O ~6. , NO. 4
entered their opinion, duly signed, that the mine is safe again; ( b ) when the actual fire has been located, or is known to exist, all the men working on the seam, and on other seams worked on the same level, should be withdrawn from the mine, except those engaged in fighting the fire, unless the seam be naturally wet throughout, etc.; (c) in the event of a fire being dammed off, all men should be withdrawn until the work has been completed. As regards rule ( b ) , four members would be ready to relax this rule provided incombustible dust be used on the roads; but they would require, in parts contiguous to the fire, a t least four parts of stone-dust to one part of coal-dust; that is to say, they would insist on more stone-dust than the Explosion in Nines Committee deems necessary. Four members again recommend in memorandum j that all timber should be removed from wastes and roads to be abandoned, as t h a t timber is clearly a very fruitful source of danger. Finally, AIr. Herbert Smith, who had signed only the first two memoranda, deprecates the use of stone-dust, which must be injurious to the health of the miners. I n South Africa, he points out, the working life of a miner is four or five years, and the mortality in the Yorkshire ganister-mines is also very high and medically ascribed to dust inhalation. SOME STATISTICS O N GERMAN UNIVERSITIES Some interesting statistics about German universities are given in the Chenziker-Zeiturzg, 38 (1914), 250. During the academic year, August, 191I-August, 1912, 4455 doctors’ degrees were given, S3 more than in the previous year; these were divided among the various faculties as follows: Theology, j j ; law and political science, 1265; medicine, 1343; philosophy and natural science, 1792. The percentage of students who receive degrees in the different universities and faculties varies from 87.6 per cent in law a t Erlangen to 0.2 per cent in law a t Berlin. The salary of rector varies in a n astonishing way a t different universities. This position is of course quite different from that of president in an American university, for the rector is elected from the faculty by his colleagues for a short term. In Berlin the rector’s salary is about $9,250, in Kiel $800, while in the Academy a t Rraunsberg it is slightly more than $20. The average is about $1,500. The salary of the deans of the various faculties varies even more, ranging from $5,500, the salary of the dean of the faculty of philosophy a t Berlin, to $5, the compensation of the head of the theological faculty a t Halle. ~~
D ~ S S E L D O R F CENTENNIAL EXPOSITION The centenary of the annexation of the Rheinland by Prussia will be celebrated in 1915 by an exposition at Diisseldorf. According to the Chemiker-Zeitung, 38 (1914), 2 2 3 , chemical and pharmaceutical industries will be represented more fully than ever before. I n the chemical section a special effort will be made t o show the history and development of pure chemistry during the century, its connection with other sciences and particularly with various industries.
THE RUBBER SITUATION I N JAPAN The rubber industry in Japan is in a very depressed condition. It takes a leading place among those industries that have grown up under the protective tariff and there are now about thirty firms with a capital of $2,300,000, engaged in it, but this very condition has reacted with the extremely limited demands of the market to cause a large drop in the price in the last two years. Although the price of raw material has also dropped, according to the Chemiker-Zeitung, 38 (1914), 134, the Japanese manufacturers have not yet felt the benefit of this; they are making no profits now and all except the strongest companies face the prospect of heavy losses in the future.
