112 THE COLLIEBY GUABDJLAN. July 17, 1914. mixed dust zones, to determine the relation between the time of their operation and the passage of the flame. Matches and guncotton tufts were installed every 20 ft. throughout the mine. Results of Explosion. When the igniting shot was fired by the pressing of a button in the observatory, slight puffs of dust were noticed at the main entry and aircourse, accompanied by a very muffled report. Shortly afterwards more dust came from entrances, particularly the aireourse entrance, and issued for some moments. Externally the explosion was very mild. When the ventilating current was turned on after a cloud of rock dust had been expelled, the afterdamp, accompanied by an extensive cloud of black smoke attested to a considerable explosion in the interior of the mine. The flame of the explosion extended in the main entry and in the aircourse to the respective rock dust barriers, which were placed at points 550 ft. from the outside of the mine, or 700 ft. from the origin in each case. The barriers in both ■1 £ Fig. 2—Rice Concentrated Rock Dust Barrier in Main Entry after Explosion. cases operated, and flame was not communicated to the pure coal dust zones beyond or outbye the barriers. The ventilating door in the second butt was evidently thrown down by the shock wave from the cannon, as indicated by the elapsed time as recorded on the chronograph. When the flame reached it, about four seconds later, there had been sufficient time to permit the rock dust to settle, so that the flame passed overhead and ignited the coal dust beyond, with the result that there was quite a strong inflammation at the head of the butt entries, sufficient to break the track and throw down shelving. This indicated that the door frame had not been put up sufficiently strong, since for the proper operation of the rock dust device, the frame should not have been thrown down until reached by the main explosion. This was the case with the first left butt ventilating door, probably because this door opened inward. The barrier surrounding this first left butt door was thrown down apparently by the main explosion, although it is not perfectly clear from the time records whether it may not have been thrown down by the ■ Fig. 3.—View of Rice Box Barrier in Air- course after Explosion. explosion which came around from the second butt. In either case, there was apparently sufficient rock dust launched into the air to quench the strong explosion coming out of the butts. The pressures as recorded by the different manometers showed that the explosion was a very light one, partly due to the dust being mixed and, perhaps, also due to the very wet condition of the mine. The maximum pressures at E-1150 was 2-4 lb.; at E-750, 51b., and at E-550, no pounds. The pressures at E-750 and 550 show the effect of the concentrated barrier in extinguish- ing the flame. In the air course the pressure at A-1150 was 1'4 lb. and at A-750, lib. This latter pressure in view of the considerable development of force at the head of the butt entries, is rather surprising and indicates the ventilating door barriers in the butt entries if they did not stop the explosion on entering, did so on the return wave. At A-550 outbye the box barrier the pressure was zero. The velocity of the explosion was very slow; one of the slowest that has been recorded. It required 8'2 seconds to traverse a distance from the origin to the station at E-1150 in the entry, a distance of 150 ft. and 2’9 seconds to station A-1150 in the air course, also 150 ft. from the origin. The explosion required 6'5 seconds to reach station 750 in the entry, and 5’1 seconds to reach the corresponding station in the aircourse. The average velocity of flame between stations on the return aircourse, 182 ft. per second, was greater than the average velocity of name between stations on the intake entry, 131 ft. per second. it would not appear from the pressure and velocity records that the high velocity of the air current had much influence on the development of the explosion. About the only variation in the development of the explosion in the two entries was that the velocity of flame on the return side was somewhat greater than that on the intake side. While this may have been an effect of the ventilating conditions, it was probably more a matter of chance than from any effect of the air current, since the explosion was such a slow one. As the explosion was very light, the concentrated barrier in the entry was not broken up or injured. The shelves had dropped until the supporting chains were taut and about 80 per cent, of the dust had fallen from tnein, the remaining 20 per cent, still retained on the planks. The barrier operated 5’44 seconds after the snot was fired, while the flame reached it about 7 seconds after the shot; the rock dust that sifted down apparently made a sufficient dust curtain to extinguish the flame. The box frames were found lying on the floor of entry, only one being damaged to any great extent. The bottom boaras were all suspended from the chains and only one had been broken. All of the dust had fallen from the boards, which were supported in a tilting position. The boxes operated at period 4’9 seconds, while the flame reached the boxes about period 5'5. The rock dust showed good distribution along the air- course. The record indicated that this stopping had been blown down at least partially when struck by the shock wave from the igniting shot at a period 0'473 after the shot. The stopping was probably built unneces- sarily light. It had operated effectively since flame did not penetrate inbye the stopping. The door in No. 2 butt had been thrown down by the shock wave at period 0'429, while flame reached this point it is estimated after a period of about 4 seconds. The dust compartment of No. 1 left door fell, according to the time of rupture of the wires, after a period of 4'9 seconds, the flame reaching this point possibly a little before. It is probable that the flame passed into No. 2 butt over the dust pile, which had fallen possibly enough in advance so that much of the dust in the air had settled. The woodwork of both doors had been broken to fragments by the return wave from the butts and the fragments thrown out to the aircourse, and both outbye and a short distance inbye on it. The failure of No. 2 butt door is undoubtedly due to the frame being braced too lightly. It should not have gone out with the shock wave. Also, it would be better to hang some of the boards from the roof by chains, as in the case of the box barriers, in order to retain some of the dust for delayed flame. The results are valuable as showing the effectiveness of the concentrated barrier and the box barrier in a weak explosion. Their method of operation permits a surer and more effective scattering of the dust than does the open shelf type of barrier in which the amount of dust blown off the shelves depends upon the strength of the air current. In a weak explosion, the amount blown off might be too small to effectively quench the flame. COAL MINING IN NEW SOUTH WALES. The report of the Under-Secretary of Mines for 1913 states that the mineral production of the State, valued at 1112,095,084, was again a record. The output of ccal was 10,414,165 tons, valued at £3,770,375, which shews an increase of 528,350 tons and 11110,360 in value. Dur- ing the last two years the output has expanded by 1,259,140 tons. The coal exported during 1913 amounted to 6,231,724 tons, valued at £3,342,003, an increase of 178,606 tons and £109,274 in value. The following particulars are extracted from the report of Mr. A. A. Atkinson, Chief Inspector of Coal and Oil Shale Mines. The output and average price of the coal raised in the various districts in shown in the following table :— Output. Average value District. 1912. 1913. 1912. 1913. Tons. Tons. s. d. s. d. Northern 6,913,810.. . 7,402,627...8 1T5...7 9'91 Southern 2,172,800.. . 2,081,472...6 1'06...6 1'13 Western 799,205.. . 930,066 4 11-98...5 1'85 Total & average.. 9,885,815... 10,414,165...7 4'85...7 2'89 The number of coal mines in operation, 115, was eight fewer than in 1912, owing to the closing of several small collieries. The number of persons employed was 18,966, as against 18,051, the number employed below ground being 14,256, as against 13,278. Taking the output of the Northern district, more than one-half was got from the Greta seams in the lower coal measures, and a large addition may be expected as soon as the Richmond Main No. 2 and Aberdare South Collieries are in operation. At the former a very up-to- date plant is being installed. The Borehole seam in the upper coal measures contributed two-thirds of the remaining output. The quantity raised per person employed was 549 tons, or, taking only those employed below ground, 732 tons; this is including the small quantity of shale, 16,985 tons, raised during the year. There are now 233 coal cutting machines at work, of which 80 are of percussive, six of the revolving bar, and 147 of the chain breast type; the increase is 19, con- fined to the last type mentioned. Electricity was the motive power in the case of 153 machines, the remainder being driven by compressed air. By electricity 2,203,265 tons were gotten, and by compressed air 633,451 tons, the total being a decrease of 59,896 tons, as compared with 1912. The quantity cut represents 27 per cent, of the total output. Turning now to the exports, 3,465,787 tons were shipped to Australasian ports, the average value per ton being 10s. 6-08d., and 2,765,937 tons to foreign ports (10s. ll-99d. per ton). Thus 40-16 per cent, of the out- put was reserved for home consumption. In 1913, 298,612 tons of coke were made, valued at £208,989 at ovens, being increases of 57,453 tons and £46,535 in value. This gives a mean value of 14s. per ton at ovens, of which there were 768 working, out of a total of 966 built or in course of construction. In the Northern district the Australian Coking and By-Products Company have erected a bench of 48 Coppee and Otto ovens, the first installation of by-product ovens in the State. During the year 18 fatal and 129 non-fatal accidents were reported, each of the former causing one death. In 1912 there were 29 accidents, causing 30 deaths and 145 persons injured. The following summarises the causes:— Deaths. Persons injured. Explosions — Falls 8 58 Shaft accidents 1 1 Haulage accidents . Other miscellaneous 3 below 18 ground 1 31 On surface O 27 Total 18 135 Total, 1912.... 30 145 The death-rate works out at 0-949 per 1,000 persons employed, or 579,508 tons raised per life lost. A recent estimate shows that 48-5 per cent, of the total output of the State is obtained from collieries where the miners use safety lamps. Several firms have ordered electric lamps. Sirocco fans have been installed at the Pelaw Main, Stockton Borehole, and Bellbird Collieries, and a Waddle fan at the Excelsior No. 2 Mine. Several of the mines, however, are still ventilated by furnaces. During the year there were several fires in colliery workings, both in connection with spontaneous combus- tion and fires accidentally brought about. At the New Winning Colliery, in which there are two sealed areas, 250,000 cu. ft. of free C02 have been discharged into the area, with the result that the temperature has been considerably reduced. At the North Bulli Colliery an explosion and fire was caused by an enclosed electrical coal cutter, and this was followed some weeks later by another explosion with the same machine. It is men- tioned that the internal capacity of the motor case showed that the volume of the explosive mixture inside the case would not exceed 1 cu. ft. The machine was Sullivan flame-tight machine, working at 250 volts. Three instances of spontaneous combustion at East Greta Colliery were dealt with during the year. The report contains an account by Mr. Senior Inspector Humble of his visit to England with reference to the provision of rescue stations. A piece of land at Kurri Kurri has been set apart for a rescue station, but nothing yet has been decided as to the type of apparatus to be finally adopted. The Acting-Electrical Inspector reports that the use of electricity has greatly increased, and its usefulness as a means of obtaining motive power is being more appreciated. The increase has chiefly taken the form of sub-haulage gear, pumps, and coal cutting machinery. A large central power station has been erected at the Richmond Main Colliery, part of the plant being now in operation for driving the main ventilating fan, air com- pressors, and haulages at Pelaw Main, and the main winding engine at Richmond Main. Other large power stations are being built at Stanford Merthyr and North Bulli Collieries, high-tension transmission being used in both cases to supply underground substations. The advantages of using high-tension three-phase current is becoming generally recognised, and quite a number of mines have changed to this system. The South Coast Mines. In the 17 mines included in the South Coast mining district of New South Wales, 4,256 persons were employed last year in or about the mines, the amount of coal raised per person being 489 tons. There were only two fatal accidents, while the number of men injured totalled 36. The Chief Inspector for Mines states that about 48-5 per cent, of the whole output of coal in the State is obtained from collieries where the miners use safety lamps. As the workings get deeper year after year this proportion is more likely to increase than decrease, since with greater depth there is more likelihood of firedamp being frequently dealt with. Last year 10 of the South Coast collieries reported the presence of inflammable gas —and the desirability of having a lamp giving as good a light as possible with a maximum of safety has been brought home to managers. Two fires occurred in one colliery; both were caused by an electric coal cutting machine. No accidents were reported as a result of the use of electricity for the transmission of power. At the present time mining operations on the South Coast of New South Wales are brisk, and most of the collieries are kept going at full strength. The governors of the Imperial College of Science and Technology have appointed Dr. A. N. Whitehead, F.R.S., to the newly-constituted Chair of Applied Mathematics, and Dr. C. G. Cullis to the Professorship of Economic Mineralogy.