June 16, 1916. THE COLLIERY GUARDIAN. 1151 contain externally acquired wet, as well as that inherent to the coal. He had noticed differences in samples brought in wet as compared with samples which had laid over for a day or two, and it was this latter policy which seemed to be the best, for even so the coal would not lose its inherent moisture, seeing that it acquired it again if left alone. Another point was that he had in mind a place where there was a great deal of pyrites, in an ironstone mine which had been under water for *20 years, and he did not know what its exact description would be, but the water coming from the mine was slightly alkaline, and the pyrites itself on exposure to air gave a moisture which was strongly acid. He did not know whether that was a peculiar state of things or a normal one. So- long as the ironstone was submerged and the pyrites in the working was not -exposed, the water remained slightly alkaline. Air. G. L. Kerr, speaking with regard to the amount of moisture in coal, said that his experience with two seams which he knew very well did not agree with what had been said with regard to the moisture in the seams proper and the carboniferous limestone. He had noticed that coals of inferior quality usually carried 'a high percentage of water, and this was borne out by one seam at Kembleton and another at North Ayrshire, both of which were at the very bottom of the carboniferous limestone and contained very high percentages of water. Dr. J. S. Haldane said he had really nothing to add to- what was in the paper. What was aimed at at the Doncaster laboratory was -to get definite measurements of everything, and that Mr. Winmill had been able to do with extraordinary' success. First of all, he tried to get a definite measurement of the heat produced when a given amount of oxygen was absorbed, and that, he (the speaker) thought, had been done very well. It was now known that the absorption of oxygen, which was much more easy to measure, was a definite measurement- of the heat production, and it was the heat production that was the important thing practically in connection with gob-fires and underground temperatures.' We had now7 got a solid basis to go on with regard to the pyrites theory. In a paper 12 years ago by Mr. Mea-chem and himself they rather went in for the pyrites theory and resuscitated it. It had seemed to him then that pyrites was probably responsible for gob-fires, but there was only a little of it in the coal, and whatever there was in the coal that was -responsible for the heating was very quickly exhausted. That seemed rather to indicate pyrites. When, however, the Barnsley seam was attacked by Mr. AVinmill, the pyrites theory was blown to atoms. There was no oxidation of pyrites, and there was a great deal of oxidation of the coal, and now data had been obtained which threw an enormous light on the pyrites question. It was a great surprise to him to find that when the unoxidisabl-e crystalline Barnsley pyrites was pounded to powder it was just as oxidisable as the pyrites from the Bullhurst seam in North Staffordshire. It was a typical pyritic looking seam, but there was actually no difference. He had made a good many enquiries of mineralogists who- knew a good deal about marcasite and ordinary cubical pyrites, but they all gave different opinions, but he had not gone into it very deeply, because it was desired at Doncaster to go direct to the . point whether the stuff was oxidisable or not, whether it produced heat, and exactly how much heat it did produce. He felt himself very doubtful as to whether one crystalline form of pyrites produced a different- amount of heat from others, but -it was at any rate clear that when it was broken up it oxidised, however stable .it might have been before. They had not tried some of the very stable forms of pyrites, but he did not feel much doubt that they .would oxidise readily when the crystalline surface was broken, because the Barnsley crystalline pyrites was extremely stable, but- was not stable when disseminated in the coal. The crystals remained absolutely bright for years, yet if they were pounded in the laboratory they gave oxidation and heating like anything. Those members of the institution who were at the laboratory at Barnsley would remember a sample which Mr. AVinmill had put in a vacuum flask, and which was heating at the rate of about a degree a minute. This was ordinary Barnsley pyrites, just pounded up, and yet it heated so rapidly that the thermometer could be seen moving, and the glass would have been fused in a very short time if the air supply had not been shut off. That demonstration must have given an idea of the capacity of pyrites when the crystalline surface was broken. Mr. R. AV. Dron asked if Mr. Winmill, in carrying out his experiments, had dealt with the effect of pres- sure. The subject was suggested to him when Mr. Ellison mentioned, at the beginning of the discussion, the case of a heap taking fire. He himself had a heap of duff which was lying by. As long as the heap did not get to a height of more than 10 or 12 ft. there was no trouble, but as soon as it extended to 18 or 20 ft. it began to heat. This was a poor substance, containing about 30 or 40 per cent, of ash, and not a material that one would have expected to have any spontaneous com- bustion, and, moreover, the seams had never troubled him in any way. The only thing he could see to account for it was the extra pressure due to the height, for when 10 ft. were taken off the top the trouble imme- diately stopped. Sir William Garfortii said that, personally, he was very pleased at what had taken place that afternoon. They all knew the large masses of coal that had been lost through spontaneous combustion. He hoped the information which was now available would enable similar large masses of coal to be saved in the national interest, and it was evident that in the future the prac- tical men would have questions to ask which would be answered in a reliable way by the scientific men. Pro- bably the scientific men would ask for further time, but if in the course of the next few years it was possible to prevent that which had taken place in the past, then the papers from Dr. Haldane, Air. Winmill, and Air. Graham would be looked upon as the finest work that tlie institution had done. He had often said that this question was a far more difficult one than that of coal dust, because with coal dust, they knew they were guilty in allowing the dust to be blown from the tubs and put on the roads, making grey roads into black roads. Then they diluted it to such an extent that there was no danger. In the case of spontaneous combus- tion, however, they did not understand the matter, and be hoped that in the future they would be able to help themselves, and help other countries by reducing the danger, and by being able to get the large areas of coal which had been lost. Air. AVinmill, in replying, said he was extremely grateful to the various gentlemen who had been good enough to criticise what had been put before the meet- ing, and to have pointed out ways in which, he should have managed his experiments to give more definite results. Prof. Louis had pointed out that it was com- monly known that there were two forms of pyrites. That, however, was also- commonly denied, and. it was difficult to know where the truth was. .■ Since there seemed to be- a division of opinion as to how far these two forms of pyrites were, really different forms, it was stated defi- nitely in the paper where the pyrites was taken from, and how it had been in the seam, so that anybody who understood mineralogy could, in. the light of the obser- vations in the paper, determine whether the pyrites in the different seams was marcasite or true pyrites. So far as his experience went, there was no difference in the heat production of the two forms of pyrites. AVith the non-oxidisable form, which might be called true pyrites, he was not very much concerned; it gave the same results as the finely-divided Bullhurst pyrites. The estimation, of pyrites was almost an impossible . task, and though he had had great difficulty in getting con- cordant results by different methods, in general the argument was not in the least altered by an error of 1 per cent, in the amount of pyrites. The degree of oxidation of the pyrites had been determined, of course, from the amount of .sulphate produced, but, in general, the estimation of the pyrites in the coal was scarcely affected by errors in the analytical methods of coal. He also confirmed Prof. Louis that the sulphur was con- tained as an organic compound. Air. Alackey and him- self were more at variance apparently than in reality. He had been concerned with the analysis of a sample which was partly ground up in a bottle, and he there- fore could deal * with very small quantities. Air. Alackey, on the contrary, had to deal with a sample of a product of coal where an analysis of a small quantity introduced very considerable errors, and he was per- fectly correct in saying that heating in an air bath was the only satisfactory way of drying such a sample. As a matter of fact, however, drying coal in a vacuum over sulphuric acid ’at ordinary temperature was not accurate, since dry coal absorbed moisture much faster than sulphuric acid did, and therefore the vapour pressure of water -over the practically dry coal was less than the vapour pressure over the sulphuric acid, so that the sulphuric acid could not take up any more water. As regards the firing of stacks of coal, Air. Smith had mentioned that his stacks did not fire, but in this case the speaker was not at all sure that the position of the stacks and their nature was not partly responsible for their non-liability to fire. They were placed on the top of a hill, there was a great deal of large Steel Plate D New Arrangement of Automatic End Gate. coal, and there was a perpetual breeze blowing through the stack; and it was very difficult for a stack to fire in those circumstances. They had heard that several people had had difficulty with stacks firing, and that heaps of 10 to 12 ft. high in general did not fire, but- that as soon as the heaps were about 18 ft. high they fired almost invariably, unless the coals were of a special kind, non-liable to fire. He did not think this could be properly attributed to pressure, but was, he believed, a question of heat insulation. The heap must be a certain size before the centre of it was properly insulated, and, moreover, he had shown that the actual mechanism of firing might be rather a complicated business depending rather on the distance the air had travelled and become saturated with moisture. Such conditions could only occur in heaps of a certain size. The instance mentioned by Air. Alowat as to alkaline water running from .pyrites was certainly most remarkable. Normally, with the pyrites oxidising it would be acid. As regards the definite percentage of moisture in superior or inferior coals, he imagined that if anyone told a Barnsley man, for instance, that a Barnsley coal which had a high percentage of moisture was an inferior coal he would be extremely offended. In reply to a suggestion by Sir William Garfortii that the microscopist had the advan- tage over the chemist, in that he could produce some- thing definite, whereas the chemist, even when the sample had. been in the retort, did not always get the information, Air. Winmill claimed that lie could, produce definite information from laboratory methods. Sir AVilliam Garfortii suggested that, with the com- bined help of the microscopist and the chemist, much practical information could be obtained. For instance, one might get to know a certain stage at which a fire was going on, and from that he could begin to make his own arrangements for dealing with it. With the combined efforts of the chemist, microscopist, mining engineer, and colliery manager there should be every possibility of getting practical results, and that was what was wanted. Air. AVinmill agreed that the microscopist certainly had a great chance, and he certainly gave the chemist things to look at, and if it were possible to learn .any- thing by looking, it was naturally a great advantage. With regard to gob-fires, he did not believe enough was known definitely yet. So far, they had not got very much information as to the relation of the chemical constitution - of coal with the microscopical. Prof. O’Shea said he would like to mention a point which perhaps confirmed what Air. AVinmill had said with regard to the equilibrium between the amount of moisture given off by coal and that absorbed by sulphuric acid. In his experience he had found that it was possible for dry coal to absorb moisture from sulphuric acid. They could take a sample of coal dried in the oven, and, after placing it in a desiccator over sulphuric acid, it would be found that the dry coal had absorbed moisture. On putting it back again in the oven that moisture could be driven off. On the motion of Air. Arnold Lupton, a vote of thanks was passed to the president and council of the Geological Society of London for the use of their rooms for the meeting. A hearty vote of thanks to Sir AVilliam Garfortii closed the proceedings. AUTOMATIC END GATE.* This device consists of an end gate A, hinged at the top, the hinge rod B working in a curved slot in a casting C, at the upper forward corner of the car box. This end gate is provided with the ordinary double latches D, hinged in the centre and moving up and. down at their ■extremities. In the closed position of the gate these latches drop into suitable keeps or catches E. A lever F, pivoted at its upper end, extends down below the bottom of the car. To this is attached a locking bar G, which passes through suitable guides and which extends over-and retains the latch bars I) within their catches E. AVhile the car is filled with coal and is on the. regular track, the gate is held shut by the locking bans G upon either side, holding the latch bars D securely in the catches E. AVhen the car reaches the dump, however, a block properly placed upon either side of the track strikes the depending lever F and forces it backward, thus with- drawing the locking bars G from above the latches. As the car tilts in the dump, the hinge bar B slides outward and upward in its curved slots, thus lifting the latches D clear of the catches E and allowing the end gate to swing open, releasing the coal in the car. As the car returns to a hori- zontal position, the gate closes and the latches D drop into their places in the catches E. As the car moves off the dump, the depending Lever F .returns to a vertical or nearly vertical position, pushing the locking bans G into their places above the latches D and locking the latter in place. A car equipped with this type of end gate, which has been patented by G. AV. Stickler, of Lansford, Penn., has been in operation for somewhat over three months with- out failing to open at the dump or close again after the contents of the car have been discharged. This device does away entirely with the necessity of wedging the latches of the ordinary end gate in the closed position, as well as the labour required to remove these wedges and release the latches from the catches when the car arrives at the-dump for unloading. * Coal Age. Hull Coal Exports.—The official return of the exports of coal from Hull to foreign countries for the week ended June 6 is as follows:—Amsterdam, 98 tons; Alexandria, 1,914; Christiania, 258; Christiansund, 52; Dunkirk, 3,705; Genoa, 6,128; Guernsey, 133; Harlingen, 148; Jersey, 45; Rouen, 7,676; Rotterdam, 275; Treport, 838—total, 21,270 tons. Corresponding period June 1915—total, 25,992 tons. These figures do not include bunker coal, shipments for the British Admiralty, nor the Allies’ Governments.