132 THE COLLIERY GUARDIAN. August 21, 1914. MATERIALS FOR ROOF SUPPORT.* By A. W. Hesse. Upon a recent investigation of three different mines in West Virginia, made expressly for the purpose of inspecting timber conditions, with Mr. W. M. Foerster, forester for the Consolidation Coal Company, in Ken- tucky, the writer visited places in which props had been set in 1906, 1908, 1910, 1912, and 1913. The first observation made was that the use of props entirely without defect was an almost impossible prac- tice. In one mine in particular many posts in the newer work were found broken, due to knots, splits, bruises, or other defects. Moisture adhering to the roof of the mine appeared to affect the props considerably. This dampness soaks into the top of the post where the strain is greatest on the wood fibre. As soon as the tissues at this end weaken, a greater opening is made for the entrance of disease, and decay begins. This was evidenced by the fungus growth at the top before the lower end of the prop had begun to show signs of decay. The remedy to some extent is the use of sound caps. Evidence of this was also found, for in one mine small caps or none at all were placed over the posts; consequently compara- tively new props were split at the top, while in another mine heavy caps were used over props which had been standing since 1906. Incidentally, it might be well to mention that the latter were located in a room which had been boarded nearly shut. Timbers used as beams no doubt suffer the same conditions just recited. Another important question is : When is the proper time to do the timbering, before or after a fall? Going through a mine you will frequently find a 3 in. by 5 in. wooden mine rail across the entry. On a later visit you will perhaps find this has decayed and broken, letting down enough top to require several times as much more timber to hold the place. Would it have been cheaper to have used steel? If the roof is as previously mentioned in this article, it is the writer’s opinion that it would. Take, for example, a roof which disintegrates, and where top coal is carried to prevent exposure. Frequently a clay vein is crossed, leaving an opening to which the air has access. Experience will call for a certain sized timber, say an 8 in. round timber, to be 14 ft. long, to be used for a 12 ft. span. It is seen by the table that a 4 in. 7-5 lb. I-beam will carry the same load. The importance of the place and the length of time it is to be maintained should govern which should be used. Timber in a mine, if it carries approximately the safe load, will seldom last much longer than 18 months, and the replacement plus the first installation will be more than the cost of placing the steel. This table is presented with the idea that it will be used by mine officials in the proper selection of material when replacing or retimbering, and to give them some idea what their selection of sizes will carry in the weight of roof supported. COLLIERY ACCIDENTS. The Clifton Explosion. The adjourned inquest on the three men who were killed by an explosion at William Pit, Great Clifton, on August 4, was held on Tuesday. The victims were Isaac Smith (26), deputy; James Wright (23), examiner; John Wilkinson (62), pumpman. The explosion occurred while the miners were on holiday, and a few men were engaged in dealing with the water in the pit and other emergency work. The enquiry was conducted by Mr. E. Alter, coroner for West Cumberland, and amongst those present were : Mr. J. R. R. Wilson, H.M. inspector; Mr. G. A. L. Skerry, representing the Allerdale Coal Company; Mr. Crerar, on behalf of the relatives of Smith and the Cumberland Colliery Officials’ Association; Mr. T. Cafe, financial secretary of the Cumberland Mines Association, on behalf of the work- men of the colliery and the relatives of Wright and Wilkinson. Mr. Thos. Eadie, surveyor, produced plans of the working and an enlarged plan of the scene of the accident, in the Lick Bank seam, which had been worked since the begin- ning of March. The men were working 65 fathoms deep. He explained where the men were found and the effects of the explosion on doors and tubs. Dr.' Wm. Eadie said he saw the bodies of the deceased men after the explosion, and he examined them superficially. Smith had his right leg broken, badly smashed, showing that he had got the force of the explosion. The bodies were all scorched, Smith and Wright markedly so all round. to six on the day of the accident, and was told the pump was working well. When the shaft pumpman came up at six o’clock he said there was no water coming from the Lick Bank. Witness then described how he went down the pit and found the deceased workmen. Mr. Robert McFarlane, under-manager, produced his report-book, and stated that he went down the pit on Monday night at 10 o’clock to assist to get the pump away for the erection of a barricade. He had had charge of the mine since May last. He had had to do with making of exami- nations as to the ventilation. He had not signed the book before the 3rd. He commenced the examination at 11. He put his lamp to the roof, and inspected all round the pump house. It took only 10 minutes. They first took the motor in by some planking. This would take about an hour. His report, written and signed at 11.10 p.m., stated : “ Noxious or inflammable gases, none; safe ventilation, good; condition of roof and sides, good order; general safety all right.” Previous inspections were general inspections during shifts, and were therefore not noted in the book produced, but in the shiftman’s book. He admitted that the whole district must have been charged with gas. Witness stated that he tested for gas in the ripping on Sunday night, and found nothing. He went down at five o’clock, took Mateer with him, and went along that level. Asked why he went, he said he had nothing to do, and thought he would just go along. He was quite sure he put his lamp to the roof. He did not make a report because he did not go down to make one. . He just went with the electrician to help him. The man in charge of the district was there, but witness thought as he was senior official he had better make the report. Mr. George McDonald, manager of William Pit since March 1 last, said three or four men were working at repairs. Smith and Wilkinson were known to him to be experienced men. He had no reason to doubt the com- petence of Wright. The fan was stopped at 6.30 on Saturday night, and operated afterwards as usual. Barnes informed him of the explosion. He informed witness about nine o’clock on Tuesday morning about the pump not work- ing, and said he would go down and find out for him the reason if he wished. He was down about an hour. Wit- ness went down with others after Barnes brought up Sanderson. He found nothing till he got to the bottom of the Lick Bank Dip. Then everything was in confusion, the doors and timber being blown about. In his opinion, the explosion was caused by gas. He did not suggest that a broken lamp was the cause. Table Comparing Strength of Steel and Wcod for Supporting Mine Roofs. Span. Ten feet. Twelve feet. Steel, weight per yard. Wood. Steel, weight per yard. Wood. Uniform load in lb. Re- quired Stand. T rail. Stand. I beam. White oak. Chestnut. White pine. Uniform load in lb. Re- quired Stand. T rail. Stand. I beam. White oak. Chestnut. White pine. Sawed. Round. Sawed. Round. Sawed. Round. Sawed. Round. Sawed. Round. Sawed. Round. In. Lb. In. Lb. 1,015 16 3 16-5 5 by 3 5 6 by 4 5 6 by 4 5 845 16 3 16*5 5 by 3 5 6 by 4 6 6 by 4 6 1,385 20 3 16’5 5 „ 4 51 6 „ 5 . 61 6 „ 5 61 1,155 20 3 16*5 5 by 5 51 6 by 5 61 6 by 5 61 1,920 25 3 19’5 6 „ 4 61 7 „ 5 71 7 „ 5 71 1,600 25 4 22’5 6 by 4 61 7 by 5 7i 7 by 5 71 • 2,450 30 4 22’5 6 „ 5 71 7 „ 1 8 7 „ 7 8 2,045 30 4 22*5 6 by 5 7 7 by 7 - 8 7 by 7 8 3,090 35 4 22 5 7 „ 5 71 8 „• 7 81 8 „ 7 81 2,580 35 5 29*3 7 by 5 71 8 by 6 81 8 by 6 81 3,810 40 5 29*3 7 „ 6 8 8 „ 8 9 8 „ 8 9 3,200 40 5 29*3 7 by 6 8 8 by 8 9 8 by 8 9 4,475 45 5 29-3 7 „ 7 81 10 „ 6 91 10 „ 6 91 3,735 45 6 36*8 7 by 7 81 10 by 6 91 10 by 6 91 5,225 50 5 36’8 8 „ 6 9 '-0 „ 7 ! io 10 „ 7 10 4,355 50 6 36*8 8 by 6 9 10 by 7 10 10 by 7 10 6,290 55 6 36-8 9 „ 6 91 10 „ 8 ioi 10 „ 8 101 5,245 55 6 36*8 8 by 8 91 10 by 9 11 10 by 9 11 7,140 60 6 36'8 9 „ 7 10 10 „ 10 ii 10 „ 10 11 5,955 60 7 45*0 9 by 7 10 11 by 8 11 11 by 8 11 7,890 65 6 44’5 10 „ 6 10 12 ,, 7 ill 12 „ 7 Hl 6,580 65 7 45 0 1<» by 6 10 10 by 10 Hi 10 by 10 Hi 8,955 70 7 45’0 10 „ 7 10.1 12 „ 8 12 12 „ 8 12 7,470 70 7 45*0 10 by 7 101 11 by 10 12 11 by 10 12 9,700 75 7 45*0 9 „ 9 11 12 „ 9 121 12 „ 9 121 8,090 75 7 52*5 10 bv 8 11 12 by 9 121 12 by 9 121 10,765 80 7 45*0 10 „ 8 11 12 „ 10 13 12 „ 10 13 8,980 80 8 54 0 11 by 7 11 12 by 10 13 12 by 10 13 11,940 85 7 52*5 10 „ 9 Hi 12 „ 11 13 32 „ 11 13 9,955 85 8 54*0 10 by 9 111 12 by 11 131 12 by 11 131 13,110 90 8 54*0 10 „ 10 12 12 „ 12 131 12 „ 12 131 : 10,935 90 8 60 8 10 by 10 12 12 by 12 14 12 by 12 14 14,180 95 8 54*0 12 „ 8 12 12 „ 13 14 12 „ 13 14 i 11,825 95 9 63*0 12 by 8 121 13 by 11 14 13 by 11 14 15,670 100 8 60*8 12 „ 9 12^ 12 „ 14 141 12 „ 14 141 : 13,070 100 9 63*0 11 by 10 121 13 by 12 141 13 by 12 141 Note —Loads given in table are the safe uniform loads that T rails will carry; other members show sizes necessary for these loads. Timber presumed as seasoned. For green timber use f loads. Factor of safety six (about). Fibre stress white oak, 1,200 lb.; White pine and chestnut, 800 lb. Timber to be placed narrow side against roof. has demonstrated that the absence of a clay vein under these conditions is worth about $100 or more. How- ever, such veins occur, and the proper thing to do is to take care of them in due time. That time is as soon as a support can be put under the roof at each side of the clay vein and said vein lagged over. The suggestion has been made to put a thin coating of cement over such an exposure. This sounds practi- cable and worth trying. However, should a place like this occur on the main entries, wood should not be used, nor should the mine foreman, nor officials above him, allow the use of steel mine rails for this purpose. A mine rail which is good enough for a roof support is more valuable for the purpose for which it was designed. Of course, it is practically impossible to tell just what load a roof will place on a support, but we know that if a certain wood timber when new has carried certain roof conditions satisfactorily, it is easy to determine the equivalent structural steel necessary to do the same. With this in mind a table has been prepared showing what different sizes of steel rails will support when uniformly loaded; then taking these loads, the sizes of equivalent standard I-beams and the different wood beams have been calculated. Thus, taking a 20 lb. mine rail, it is seen that the safe uniform load it will carry on a 10 ft. span is 1,3851b., then following this line to the right, under the same conditions, it is seen that the 3 in. 16-5 lb. I-beam will do the same and save 3-5 lb. per yd., or about 141b. to a beam of 12 ft. length. Under white oak is found a 5 in. by 4 in. sawed or 5| in. round timber for this load, while chest- nut and white pine require a 6 in. by 5 in. sawed or 6J in. round timber. Quite frequently a requisition * From Coal Age. Wilkinson was scorched about the face, and the skull was badly fractured, and Wright was badly burnt. They had been dead some hours. Wilkinson had probably died in a minute or two, and the others had not lived long. Wilkinson had gone into the water, and drowning and the injury to his brain were the cause of his death. Smith and Wright’s deaths were due to shock, plus suffocation by afterdamp. Thomas Sanderson, the survivor, who gave his evidence with difficulty, said he was a coal miner, and had worked at William Pit, QJifton, for 17 years. Wright and Smith were working with him on the day referred to, and he had been working since 6.45. He was working at the water. The miners had not been working getting coal since Friday afternoon. On Monday the ventilation was all right. On Tuesday there was nothing in the report book to show that the working had been inspected. Witness was in charge. The water had risen since the day before. They were all working together, and all went well until about 20 minutes to 8, when Wilkinson said the water was rising. They then started the pump, and after a few minutes there was a sudden report and a flash. The explosion started, he thought, somewhere about the electric machinery. Witness was 3 yds. from it. Wilkinson was at the switch. There was a partition between them to protect the motor. The explosion knocked the partition down. He did not think there was any necessity to go round the pit. He had the impression that the regulations of the Act as to inspection only applied to where men were working. He had never been told by an official that it was not necessary to examine the whole of the district. Witness, further examined, said he had found gas, and knew gas would accumulate in the absence of ventilation. With the door previously referred to open—and it was open when he passed it—no air would go round the workings and gas would accumulate. When working with Wright and Smith he saw no gas. John Henry Barnes, surface foreman, said all the men were skilful workmen. He went to work about 10 minutes By the Inspector : He did not ask anybody if they had been round the workings, and made no enquiry about the ventilation. It did not occur to him when the men were not working. He had no reason to think there was anything wrong. The fan was going then. Gas accumulated when the fan was not going, and had to be got out. He could not suggest the origin of the explosion, but all the evidence pointed to it having occurred in the gateway. Witness, further examined, said a canvas sheet had been blown half a dozen yards up the road. It had been a violent explosion, but he would not say there had been a iot of gas. He did not think a flame had passed round the faces, but a blast. He had seen indications of heat at the gateway. He thought there would be a report. It would have an effect on every ventilation district; there would be a blast right through. He did not think Sanderson, when he was standing, would have felt any- thing before he saw the flash. Evidence was also given by Mr. John Wilson, under- manager, Buckhill Colliery; Michael Rafferty, Great Clifton, deputy overman ; Richard Walker, assistant elec- trician at the colliery; Fred Taylor, and Mr. E. A. Hail- wood, managing director of Ackroyd and Best, the makers of the lamp, who gave evidence at his own request. Mr. Wm. Charles Mountain, Newcastle-on-Tyne, said he visited the colliery on August 14, and made a thorough inspection of the pump house and surroundings to see if the explosion could in any way be connected with elec- tricity. His final conclusion was that electricity had nothing to do with it. The explosion had occurred outside. If the door was closed there would be sufficient air to ventilate the pump house, but with it open it was impossible for gas to be there, as practically all the air would pass through the pump room. He explained experiments he had made for the Home Office, with a view of discovering whether an explosion of gas could be caused by a motor coal cutter. With an explosive mixture of 10 per cent., and making the motor spark as much as he could, he got an explosion. He could not get an explosion with anything