Show fg q UH COL C EO 0 Q sy f kis pa N X f icv i at sf vf V A L aj wi 1 4 e fi V W t BC SI ewt M 5 yc at 71 r 1 61 i c yd c f 4 3 casatta saTta ta WA q cc HE recent loss of life in the seng collier wales affords another example ot of the explosive na turo lure of coal dust the public has heard a good deal about the dau dan gers ot of firedamp and of its dread ed aftermath chokedamp which speedily edil overcomes comes its confused victims less has been said ot of the dangers ot of coal dust but they are becoming better appreciated and measures to protect miners from them are arc being demised the bureau of mines at washington niton has lately been doing good work nork in its studies of 0 the ex of coal dust and in allied experiments seeking to find practical ways to lessen casualties from this cause what hat american officials haie done in this direction has been an amplification ot of similar efforts abroad A surprising feature of the whole subject is that the danger lurking in this dust was as so long unsuspected IU in fact tor for man years vears people actually refused to recognize any menace in this material it was not until convincing ei dence was vas adduced by the scent ilic investigator that the stubbornness of generations gave wa nay then unbelief sur rendered before the indisputable proof of the dan gers of coal dust when floating in the tha air according to the recent report of a british government committee it may now nom be consid i ered established besand all doubt that coal dust suspended in the air Is capable of being ignited without the presence of any inflammable gas and of spreading an explosion throughout the dusty galleries of mines the first require requirement ent Is that minears mi the dust shall be stirred up b some means and mixed the ajr air in cloudlike cloud like form when ignited in this state it is capable of producing just such destructive effects as are so often observed after a collier disaster Is this stuff dangerous the chemists say that it Is because there Is more surface tor for the oxygen to attack and this action induces heat according to the british research commission the degree ot of inflammability ot of any combustible material can be defined as the rela tive live ease with which its oxidation can be effected so as to produce flame in other words the finer the dust from any particular kind of 0 coal the greater its inflammability the best evidence of this lies in the tact fact that a sample of coal which ordinarily would not ignite until it had been exposed to a temperature ot of 1065 1 oga degrees centigrade would when in the forin of dust explode at a temperature of degrees centigrade gunpowder explodes at a temperature of degreed centigrade so you can see how closely coal dust Is allied to gunpowder we have been burning coal for hundreds ot of years and et there Is a lot about it we do not know in tact fact the true chemical nature of 0 this uel fuel remains target a master investigators have hane shown that coal Is not the simple sub stance it was once thought to be in fact it is a compound of vegetable table cellulose which forms its base cemented by the changed resins and gums of tile the primordial plants the latter bodies arc readily decomposed at comparatively low ion temperatures tempera fares lures and it Is from this part of the coal that tho the first of the explosive gases come when coal Is in the form of a dust it Is in the condl condi tion to respond quickest to the action of heat you have seen the cloud of dust advancing along a country road ahead of a coming storm well an explosion in a mine virtually duplicates this occurrence the explosion sets up disturbing air curren currents tg and these stir up the coal dust in the galleries what follos follows ss that initial blast heats the dust to the point ot of ignition and the fine particles mixed with the air become an explosive e it flashes up at once and transmits kindred waves throughout the whole range ot of the dust cloud and in this fashion generates a series of 0 explosions which aro are successively shely fed by the whirling dust that the disturb it is substantially a chain ot of explosions which lengthens to the tha furthest limits of the available fuel upon winch it feeds the heedlessly bared flame of a miners miner s lamp may start the ball rolling either by igniting a 13 small volume of firedamp or by setting off a cloud of coal dust which has been created by a miners blast undoubtedly many of the worst colliery disasters sisters di have base been more directly due to coal dust than to adv an other cause and vet jet firedamp was vas until quimp recently held responsible for most of these it did not occur to the miners or to their employers that the gath ering particles of coal were a source of danger the opera operatives tiNes were too busy getting out mer charitable coal to give ghe any heed to the accumulate Ingi ing dust lust andret and let as behave we have seen the mine gal ceries were slowly but surely becoming little less perilous than magazines of powder once the biard was nas realized the mining world cast about for preventive agencies naturally the first seemed to be water nater and mine road nas were nere liberally saturated to lay th dust and thus prevent ltv ta rising so as to form an explosive mixture with kith the atmosphere in lieu of this the next precaution was in the form of dustless zones the powder particles being scrupulously removed for a considerable dis tance the idea was nas to establish in this manner a sort of void through which waves naves could not be propagated theoretically this is all right but again the ventilating air currents carry with nith them a measure of coal dust arid and make it impracticable to maintain the defensive zones just how some one stumbled on the idea of dl di coal dust with nith a non explosive dust Is not a matter of history bat somebody did ronce conceive lve the plan and the value of this remedy Is dally daily growing in favor because of its effectiveness in general terms the german mine authorities touched upon this method as tar far back as 1984 but the subject was not brought forward eclen until after the explosion in the altofts collim colli erv england two years later W E garforth Gart orth was the aba mine manager while traveling through the underground workings atte after an explosion of coal dust ho he noticed that although great damage had been dono done in some borne places there nem a ere at others no perceptible destructive et ef facts curiously just at these cheso apparently immune places fine stone dust had been whirled into the air vuth nith great violence and then settled upon the roadways like a thick carpet mr G anforth Gart orth noticed this peculiarity on other occasions and came to tho the conclusion that stone lust dust might be useful to dilute coal dust and so BO render the latter harmless just in the same fashion as air Is used to dilute firedamp A line fine example of how well rock dust may be distributed by natural means is to be seen in the illinois long vail field where the bits of shale that fall from the root roof and the pack walls keep the coil dust covered up explosions han have e never happened in this district though min ing has boen been going on there for over 40 years it took the british some sears before they reached the point of action but in july 1908 experiments peri ments on a large scale with stone dust were commenced on the completion of the allots research gallery mr garforth being placed in charge this gallery consisted of a tube feet in length having a diameter of seven and a half feet and being built of the shells of disused boll ers and tor for more thin than two years investigations were carried out with nith the most painstaking care it was proved conclusively that tho the admixture of an incombustible dust with the coal dust rendered the initiation of an explosion correspond bingly difficult to effect at the testing gallery gallen the ordnance center of the british government it was found that coal dust containing a large proportion of shale was insensitive to ignition by means of a charge of gunpowder in these latter experiments sen sensitive coal dust was rendered inert by an admixture with 85 cpr cent of shale dust but this seemed to call tor for too much protective stone dust to make the method practicable ible the apigian authorities have set the pace in this matter they did it by bv placing boards in the mine galleries just under the root roof in the form of shelves and upon these they laid heaps of ancona bastible bus tible dust riot not fine fina enough to be disturbed by the normal air currents they allowed something like nine bushels per square yard of working there was left sufficient space above aboe the top of the dust heap tor for the blast of an explosion to sweep oval the pile and thus to blow it broadcast in a cloud thus tho the same destruct destructive he blast that would otherwise have stirred up the coal dust and ignited it was nas made to set in motion an antidote which smothered the inflammable particle of coal european experiments have shown n that a 40 per cent admixture of stone dust with coal dust waa vas sufficient to prevent an explosion of course this depends upon the chemical nature of the coal and the results so tar far obtained are the reward of the first efforts to lessen bessen this hazard it Is quite probable that some kindred but less bulky medium will be discovered that will answer bet ter in tact fact a 2 per cent mixture of sodium ill bl carbonate caro onate has a very remarkable smothering or checking effect |