152 ALEXANDER VON HUMBOLDT. 



These labours led to the invention of a kind of respirator, and 

 of four lamps of different construction suitable for employment 

 in various circumstances. 



The respirator was to prevent the inhaling of injurious gases,, 

 and to supply the miner with good air ; the lamps were con- 

 structed to burn in the most inflammable kind of fire-damp 

 without igniting the gas. They were the forerunners of Davy's 

 later invention, and were frequently made use of by the miners, 

 who availed themselves also to some extent of the respirator* 

 The experiments, however, for testing these inventions were 

 not unfrequently connected with considerable personal risk, 

 and an instance of one such experiment, which occurred at the 

 alum works at Berneck, on October 13, 1796, will be found in 

 the following extract: 'The air in the cross-cut was so im- 

 pure,' relates Humboldt, ' as to extinguish every light as com- 

 pletely as if immersed in water. The arm-lamp, though usually 

 one of the most effectual, burned only with difficulty, while 

 the ring-lamp remained as bright as in the purest upper air. 

 In order to ascertain whether it would be possible to extinguish 

 the flame, I crept through an opening in the screen shutting 

 off the passage which had been left for the purpose of allowing 

 access without removing the screen. I went in alone. The 

 air was so loaded with carbonic acid gas that I could not 

 obtain a light, nor ignite paper even for an instant at my 

 lantern. I penetrated to the distance of six or eight fathoms, 

 over ground strewed with the traces of burnt sulphur,. 

 and as I stood surrounded with rotten wood, my ring-lamp 

 continued to burn as brightly as at first. I placed it upon 

 the ground, in order to observe its behaviour in the lowest 

 stratum of air, when the quantity of carburetted hydrogen gas 

 suddenly deprived me of consciousness. I became exhausted, 

 and at last sank down insensible near the lamp. Fortunately 

 I had just before summoned the attendance of Bauer, the fore- 

 man of the mine, and he and Herr Killinger hastened to my 

 assistance and pulled me quickly back by the feet : I soon re- 

 vived in the fresher air of the mine. I had the gratification, on 

 regaining my senses, of seeing the lamp still burning.' 



Humboldt thus learned, from his own experience, how 

 brightly his lamp would continue to burn in gases which 

 were too noxious for human life. 



