x PRACTICAL PURPOSE 259 



an unsteady flame, he corrected the defect by using 

 several tubes of reduced diameter instead of a single 

 tube, to supply the air. This lamp was found to burn 

 better than the first lamp, and was used with safety in 

 a dangerous mine early in November, 1815. A few 

 weeks later he had a third lamp constructed in which 

 small holes in metal plates took the place of the tubes, 

 but in this device he was forestalled by Davy, who 

 presented to the public on November 9th, 1815, his 

 safety-lamp having wire gauze surrounding the flame. 



It is not our intention, however, to revive the angry 

 controversy which arose over the respective claims of 

 Stephenson and Davy as the discoverer of the miner's 

 safety-lamp ; all we wish to do is to use the invention 

 to illustrate the different methods by which the same 

 end may be reached. Stephenson made a lamp and 

 then proceeded to test and perfect it ; Davy, when he 

 took up the problem of the cause and possible prevention 

 of explosions in mines, first inquired into the nature 

 of the explosive gases and of flame, and was soon able 

 to announce his discovery " that explosive mixtures of 

 mine-damp will not pass through small apertures or 

 tubes ; and that if a lamp or lanthorn be made air-tight 

 at the sides, and furnished with apertures to admit the 

 air, it will not communicate flame to the outward 

 atmosphere." Davy discovered a principle and then 

 constructed a lamp based upon it. Stephenson made 

 a lamp and was led by it to a principle. Though there 

 may be differences of opinion as to who was the inventor 

 of the safety-lamp, the establishment of the principle 

 of its construction was undoubtedly discovered by 

 Davy, and was a notable advance of scientific know- 

 ledge. It was, however, left to practical men to devise 

 the improvements which removed some of the defects 



