3 8 2 MINING 



the Durham and South Yorkshire coalfields. At Bullcroft Main it was found possible to 

 deal with running water and at Easington with sea water and tidal variations in level. 



It is in the cementation system that the greatest improvements have been made. It 

 would seem to have certain advantages in cost, while the preliminary estimates are more 

 likely to be accurate. At the Viktoria Colliery, in Westphalia, the cost was 150 per yd. 

 of depth. The system, as now applied, may be sub-divided into (l) the "systematic" 

 process, in which liquid cement is injected into surrounding boreholes from the surface, 

 much as in the case of the freezing system, with the object of filling up fissures and water- 

 logged cavities in the strata, the pressure being varied according to the necessities; (2) the 

 "methodical" process, in which the pressure is automatically regulated by the pressure of 

 the water; and (3) the "progressive" process, in which the ordinary drop-shaft system 

 is pursued, fissures being filled with cement injected under pressure by means of inclined 

 advance boreholes driven from the shaft bottom. 



In addition to the freezing system, mention may be made of the Stockfisch system, which 

 is a combination of percussion and flushing, the flushing liquid being of sufficient density 

 to keep out of the shaft any quicksand or loose rock liable to cave in. An installation at the 

 Diergardt Colliery is described by Krecke (Gluckauf, No. 14, 1912). In this system, as 

 in the Hoenigmann system, which has also been applied in Germany, and in the Kind- 

 Chaudron system, improvements in the boring trepan have been effected. 



By the ordinary methods some exceptionally rapid work has been done in the more 

 recently opened shafts, although, generally speaking, the increasing difficulties of depth and 

 strata militate against speed in sinking. At the Askern Main Colliery, near Doncaster, a 

 shaft of 23 ft. 6 in. in diameter (total excavation) in the middle coal measures was sunk 29 

 yds. I ft. in 7 days, at a labour cost of 9.05.3^. per yd. 



For preliminary protection from surface water, use has been made (as at Bentley and 

 Hatfield Main) of interlocking channel steel piling with satisfactory results. 



In the equipment of finished shafts, which now range up to 22 ft. diameter finished, 

 increased use is being made of concrete. 



THE USE OF ELECTRICITY. The most profound change in mining since the opening of 

 the present century has been the extension of the use of electricity. It has found its princi- 

 pal application for haulage, pumping, ventilation, signalling and shot firing, but its 

 employment for lighting and winding is also steadily growing, and the "All-electric 

 Colliery" is now an accomplished fact. New British regulations governing the instal- 

 lation and use of electricity in mines have been issued by the Home Office as provided 

 for by the Coal-Mines Act (Section 60) which also prohibits the use of electricity under- 

 ground telephone or signalling wires and approved handlamps excepted wherever 

 the percentage of inflammable gas in the air is found to exceed i}. Taken generally, 

 the main object and intention of the new British rules is to make armouring com- 

 pulsory in the future, although in some cases exempted until 1920. The new French 

 regulations also impose special restrictions on electric installations. 



The liability of the electric spark to ignite firedamp has formed the subject of many 

 experiments, but they have failed to establish the precise limits of safety. E. Lemaire 

 (Ann. Mines Belgique, ion, Vol. xvi, p. 321) has shown that explosive mixtures of air 

 and firedamp can be ignited by the finest filaments provided their temperature be 

 sufficiently high and quite independent of any break of contact spark. Such experi- 

 ments have enforced the use of strong globes with air-tight joints. 



THE COAL DUST QUESTION. During recent years there has been much investigation 

 of the part played by coal dust in colliery explosions. These investigations, which have 

 been attended by research on many collateral subjects, have been conducted at a num- 

 ber of centres, by means both of large-scale experiments in galleries and also of laboratory 

 tests. The testing stations are now for the most part under the control of the Govern- 

 ments of the various countries concerned, but were started through the enterprise of the 

 mine-owners. In England the gallery erected by the Mining Association of Great 

 Britain at Altofts, in Yorkshire, has been transferred to the Borne Office, and recon- 

 structed on a new site at Eskmeals, Cumberland. The Mining Association in 1910 

 published their first record of experiments; in 1912 the committee in charge of the 

 experiments at Eskmeals issued two reports, as well as an outline of the scheme upon 

 which it was proposed to conduct future investigations. In France the experimental 

 station at Lievin, erected by the Comite Central des Houilleres de France in 1907 and 

 extended in 1909, has been the scene of further researches, under the direction of J. 



