242 Scientific Labors and Charade?- of 



of them refuse to pass to the other ? Will it pass through a tube ? 

 This brought him to the grand discovery ; for it appeared, tliat the 

 flame of the most explosive mixture would not pass through a small 

 tube, — that the communication was more easily prevented, in pro- 

 portion as the tube was of a better conducting substance, and there- 

 fore operated by cooling the flame below the point of kindling. It 

 was only then to surround a lamp with a transparent envelop com- 

 municating with the surrounding air by metallic tubes, and thus the 

 air might enter freely to feed the lamp, while the flame would not be 

 communicated to the surrounding atmosphere, in the most explosive 

 state in Avhich it ever could exist in a coal mine. Subsequent ex- 

 periments proved, that in case the diameters of the tubes were very 

 small, their lengths might be diminished to mere apertures ; and 

 hence it was only necessary to surround the lamp with wire gauze, 

 and the air would enter freely to supply the lamp, while the flame 

 could not pass through the apertures of the gauze. 



The experience of fourteen years, while tlie safety lamp has been 

 in constant and extensive use in the coal mines of England, 

 without the occurrence of a single explosion,* is the best comment 

 upon the correctness of the principles which led on step by step to 

 its construction, as well as the highest testimony in favor of the bene- 

 fits which this invention has conferred upon society. We are not 

 aware of any other example of a great invention so purely philosoph- 

 ical as this. Most inventions have been partly at least the suggestion 

 of accident. But here our philosopher commenced, not with con- 

 structing a lamp, but with inquiring into the nature and properties of 

 the agent which he had to control. He began, like the Philis- 

 tines of old, by learning where lay the secret of its might ; this being 

 discovered, it was shorn of its strength as easily as the giant of Israel. 

 But he did more than simply disarm the foe : he made him his slave. 

 In the most explosive mixtures, the flame of the lamp is greatly en- 

 larged, and its light much augmented ; and by this change, it gives to 

 the miner instant v/arning of the approach of danger. 



These researches on the specific nature of explosive mixtures of 

 carburetted hydrogen and common air, led to the more general in- 

 quiry. What is the nature of flame'? It is somewhat remarkable, 

 that in all the researches which had been made, and the tlieories which 

 had been proposed, on the subject of combustion, the nature of flame 



* Graham's Elements of Chemistry, 1829. 



