in the Coal-Mines of Germany. 385 



as to push the flame by half an inch aside, and at last to extin- 

 guish it. Other safety-lamps of 308 and 184 meshes to the 

 square inch, gave the same results. Lastly, a common mining 

 lamp was placed before the hole. The flame of the lamp was 

 pushed 1£ inch aside, and was blue coloured, but did not kindle 

 the fire-damp which was streaming out. On removing the 

 lamp, the blue flame disappeared, without being extinguished. 



From these observations it follows, that the inflammation 

 of the gas issuing from the hole, and kindled by a lamp, is not 

 continued backwards ; and this is owing to the strong stream- 

 ing of the gas. Hence it appears to follow, that if holes are 

 bored against a rising gallery filled with an explosive mixture, 

 an explosion is not to be feared with a common lamp, and still 

 less with a safety-lamp. 



As the fire-damp of the artesian well in the principality of 

 Schaumburg contains 16 per cent, olefiant gas, and only 5 per 

 cent, nitrogen (see last No., p. 146), it was to be expected 

 that many of the lamps, which were quite safe in the ex- 

 plosive mixtures of the coal mines, would no longer be safe 

 in this case. 



The results of my experiments made with this fire-damp 

 were, that all the thirty wire-gauzes, without exception, pro- 

 duced explosions. But a safety -lamp of 620 apertures to the 

 square inch was, under all circumstances, quite safe. 



The experiments enumerated shew, that in many coal-mines 

 wire-gauzes of larger apertures than now in use may be em- 

 ployed. Such a contrivance would be useful to the work- 

 men, as complaints are frequently made of the obscure light 

 afforded by the safety-lamp. Indeed, I have had myself op- 

 portunities of observing this during my frequent visits to mines 

 filled with fire-damp. The size of the apertures in the wire- 

 gauzes employed in any coal-mine may be easily ascertained 

 by experiments in excavations made in the mines. But even 

 in coal-mines charged with the most dangerous explosive 

 mixture^, wire-gauzes of 620 apertures to the square inch, 

 appear td restrain the flame within its narrow bounds, and to 

 prevent explosions. 



Finally, I have to remark, that the Royal Academy of 

 Sciences at Brussels announced last year a prize-question, — 

 " llechercher et discuter les nioyens do soustraire les travaux 



