SAFETY-LAMPS. 195 



tected at last in the very act of committing destruction. A 

 shower of sparks was seen to ignite the explosive gas ; and 

 what is rare in the history of coal-mine explosions those who 

 saw it lived to tell the tale. The good repute of steel-mills 

 was lost for ever. 



True, science has made known the conditions under which 

 alone the steel-mill is dangerous. It must be working in good 

 order, as can only happen when surrounded by pure, and there- 

 fore non-explosive, air. The sparks of a steel-mill can only 

 ignite fire-damp when darted from a pure atmosphere into a 

 locality where fire-damp has accumulated. This is an ex- 

 ceptional case, but exceptions of the sort are not rare ; so it 

 was absolutely necessary to find a substitute for the steel-mill. 



Before reverting to the labours of the Milbanke commis- 

 sion, and to the consequences of it in relation to safety-lamps, 

 it may be worth while to say that the Wallsend explosion in 

 1783 not only demonstrated the treachery of steel-mills, but 

 that an accident flowing out of it suggested the principle of 

 illuminating mines by reflection; a principle, by the way, 

 which Mr. Goldsworthy Gurney, about half-a-century later, 

 suggested, under the impression that it w r as absolutely new. 



The chapter of accidental suggestions, turned to practical 

 account, discloses many a case of romantic interest. The 

 stern historian of philosophy may be, perhaps, allowed to 

 express a regret that the interest which attaches to accidental 

 suggestions is so considerable. Truth -germs get so in- 

 crusted with mythologic concrete poetic fiction gets so mixed 

 up with philosophic fact, that the reasoner is often brought 

 sharply up by the prompting fear, lest such and such an 

 explanation be too pretty to be true. It is a pretty notion, 

 doubtless, that Apollo got the idea of his lyre from a tortoise- 

 shell with shrivelled tendons stretching from side to side. A 

 pretty notion, that a little dog belonging to the Tyrian Her- 

 cules coming back one day with a purple mouth, the cause 

 of the tint was traced to the little dog's having caught, and 



