382 Prof. Bischof on the Employment of the Safety-Lamp 



six lines in diameter, the phenomena alluded to, viz., the en- 

 largement of the flame, and the red heat of the wire-gauze, 

 were soon decreased. The lamp must therefore sometimes 

 be removed from the apparatus for collecting the explosive 

 mixture before continuing the experiments. On that ac- 

 count, the safety of the above-mentioned cylinder, and still 

 more that of the two following, could not exactly be so proved 

 as that of the two smaller cylinders. Indeed, the experiment 

 made on applying the cylinder No. 20, had shewn that the 

 transmission of flame through the wire -gauze, is not pro- 

 duced till the lamp has remained for a long time in the ex- 

 plosive mixture, as the saving power of the wire-gauze decreases 

 as its temperature increases. 



The results of my numerous experiments are, 



First, Cylinders of 101 apertures to the square inch, are 

 perfectly safe when placed in the apparatus filled with the strong- 

 est explosive mixture, formed by the blower in Gerhard'' 's mine, 

 but cylinders of 58 apertures are no longer safe. 



Secondly, The diameter of the cylinders of 101^ apertures 

 may increase to two inches without a decrease of their security 

 being observable. 



The experiments I have made near the blower in the gal- 

 lery of Welles weiler, gave in general the same results ; but it 

 was distinctly evident, that the fire-damp produced by this 

 blower afforded a stronger explosive mixture than that of the 

 former one, which accords with the chemical analysis. Thus 

 the lamp No. 20 was scarcely two minutes in the apparatus 

 ere an explosion happened, whilst, when filled with the fire- 

 damp of the gallery of Gerhard's mine, an explosion took 

 place only after twenty minutes. Also the enlargement of 

 the flame and the heat of the wire-gauze were greater than 

 in the fire-damp of Gerhard's mine. There is no doubt the 

 effects produced by the blower of Wellesweiler would have 

 been yet more intense, if the quantity of fire-damp of this 

 blower had been as considerable as that of the blower of 

 Gerhard's gallery. 



In order to establish whether a safety-lamp, burning for a 

 long time in explosive mixtures, is heated so much as to effect 

 an explosion on the outside of the lamp, I caused an officer of 

 mines to make such an experiment. He allowed a new safety- 



