444 Mr. W. Galloway on Safety-Lamps. [June 18, 



in those cases in which safety-lamps only were used. It is no doubt 

 highly probable, however, that when once an explosion of firedamp has 

 been initiated in one way or another, and large bodies of air are driven 

 through the passages of a mine with great velocity, explosive accumula- 

 tions will be dislodged from cavities and goaves, and pressed through the 

 safety-lamps with the velocity requisite to pass the flame. 



In the beginning of the year 1872,. when I was giving attention to this 

 subject, it appeared to me to be probable that the sound-wave originated 

 by a blown-out shot, in passing through a safety-lamp burning in an 

 explosive mixture, would carry the flame through the meshes of the wire 

 gauze, in virtue of the vibration of the molecules of the explosive gas. 

 It had long been known*, indeed, that if an explosive current were made 

 to impinge upon a lighted safety-lamp in a direction perpendicular to its 

 axis, and with a velocity of 8 to 14 feet per second, the flame would pass 

 through the meshes after a short time, and ignite the explosive mixture 

 on the outside ; but it does not seem to have been suspected that the 

 same result might be produced by the passage of an intense sound-wave 

 through a safety-lamp burning quietly in an explosive mixture. The 

 explosion at Cethin Colliery in 1865 is a good example of one that may 

 have been caused in this way, by the firing of a shot. Several days after 

 the explosion the safety-lamp of the overman was found, securely locked 

 and uninjured, lying at the distance of a few yards, within an abandoned 

 stall which was known to have contained firedamp : shot-firing was 

 carried on in this mine, and it is not improbable that a sound-wave from 

 an overcharged or blown-out shot had passed through this lamp and 

 ignited the explosive mixture shortly after the overman had entered it : 

 moreover the Inspector of Mines says f he has no hesitation in stating 

 that, in his opinion, the gas in this stall had been ignited, and was there- 

 fore the origin of the explosion ; but he is unable to state by what means 

 it was fired. 



It is certain that, in every fiery mine, safety-lamps are placed in an 

 explosive mixture from time to time, either by accident (as when men 

 retire hurriedly, perhaps into disused places, after the fuse of a shot has 

 been ignited) or by design to test the quality of the air, as the overman 

 at Cethin Colliery may have been doing ; and it is equally certain that 

 shots are fired, occasionally, which blow out the tamping and cause a 

 violent concussion of the air. If, therefore, the explanation which is 

 brought forward in this paper to account for the relation between explo- 

 sions and shot-firing be the true one, then the question as to how often 

 explosions of this kind are likely to occur would resolve itself into one of 

 probability as to how often an ordinary Davy or Clanny lamp, burning in 

 an explosive mixture, would be traversed by a sound-wave of a certain 

 amplitude of vibration. 



* Transactions of North of England Institute of Mining Engineers, vols. i. & xvii. 

 t Keports of the Inspectors of Mines, 1865, p. 118. 



