686 CAUSES OF EXPLOSIONS IN MINES. 



IJermancnt magnet of each lamp is thus caused to return to its normal posi- 

 tion, and in so doing it again acts on the pin of the stop-cock and thus 

 turns off the gas. 



This system was introduced by Mr. Fox at the Fulham Station about 

 .eight months since, and altogether forty lamjDS scattered about in various 

 parts of the company's extensive premises have been used to test the prin- 

 •ciple. About two months ago the number connected up was reduced to 

 twenty-three, in order to enable the company's engineer.j Mr. F. McMinn, 

 to make an official trial of the system bj^ direction of the governor and di- 

 rectors of the company. The trial ranged over six weeks and in its results 

 enabled Mr. McMinn to report most favorably upon the merits of the sys- 

 tem. For all |)ractical purposes, however, the invention may be said to 

 have had an eight months' trial. — London Times. 



CAUSES OF EXPLOSIONS IN MINES 



Mr. "VY. Galloway, in Nature, has the following seasonable remarks on 

 this subject : 



Before the invention of the safety lamp, the only means of guarding 

 ao-ainst the ignition of firedamp consisted in the employment of an appa- 

 ratus called the "steel mill." The light obtained by its aid was feeble and 

 'uncertain, and Mr. Buddie informs us that explosions were known to have 

 Ibeen caused by the sparks emitted by it. When Davy made his brilliant 

 invention in 1815-16, the steel mill was laid aside for ever, and it was then 

 imagined that colliery explosions had almost become phenomena belong- 

 ing to a paflt order of things. So confident, indeed, was Davy in the eflicacy 

 •of his lamp, that he believed it could be safely employed for carrying on 

 work in an explosive atmosphere. But one explosion followed another in 

 :an unaccountable manner; and a select committee was appointed in 1855 to 

 inquire into the nature of accidents in mioes. In 1850 Mr. Nicholas Wood 

 made a seiiics of experiments, which proved that when a Davyjamj) is sub- 

 jected to an explosive current traveling at the rate of 8 or 9 feet per second^ 

 thelflame soon passes through the wire gauze. This was corroborated about 

 '1867 by exjperiments conducted by a committee of the North of England 

 Institute of Mining Engineers. In 1872-73, the writer demonstrated, also 

 by experiment, that when. a lamp burning in explosive gas is traversed by 

 a violent sound-wave, such as that j^roduced by a blasting shot, the same 

 result follows, that is, ignition is communicated to the outside atmosphere. 

 Theatmosphere of a j)art of a mine may become explosive before the men 

 escape, either by the -sudden influx of a quantity of firedamp from some 

 natural cavity in which it had existed in a state of tension, or by a partial 

 or total cessation of the ventilating current; and I propose to consider 

 how such an event could produce an explosion, supposing all the men to be 

 provided with -safety-lamps. This will happen (1) if the inflammable gas 

 ,pa&ses over. a furnace at the bottom of the upcast ; (2) if it is carried against 



