118 STEPHENSON'S MERITS AS AN INVENTOR, CHAP. VII. 



vidual on the subject ; and by the time that the first 

 public intimation had been given of his discovery, 

 Stephenson's second lamp had been constructed and 

 tested in like manner in the Killingworth pit. The 

 first was tried on the 21st of October, 1815 ; the second 

 was tried on the 4th of November ; but it was not until 

 the 9th of November that Sir Humphry Davy pre- 

 sented his first lamp to the public. And by the 30th 

 of the same month, as we have seen, Stephenson had 

 constructed and tested his third safety-lamp. 



Stephenson's theory of the " burnt air " and the 

 " draught " was no doubt wrong ; but his lamp was 

 right, and that was the great fact which mainly con- 

 cerned him. Torricelli did not know the rationale of 

 his tube, nor Otto Griirike that of his air-pump ; yet no 

 one thinks of denying them the merit of their inven- 

 tions on that account. The discoveries of Volta and 

 Gralvani were in like manner independent of theory ; 

 the greatest discoveries consisting in bringing to light 

 certain grand facts, on which theories are afterwards 

 framed. Our inventor had been pursuing the Baconian 

 method, though he did not think of that, but of inventing 

 a safe lamp, which he knew could only be done through 

 the process of repeated experiment. He experimented 

 upon the fire-damp at the blowers in the mine, and also 

 by means of the apparatus which was blown up in his 

 cottage, as above described by himself. By experiment 

 he distinctly ascertained that the explosion of fire-damp 

 could not pass through small tubes ; and he also did 

 what had not before been done by any inventor he 

 constructed a lamp on this principle, and repeatedly 

 proved its safety at the risk of his life. At the same 

 time, there is no doubt that it was to Sir Humphry 

 Davy that the merit belonged of having pointed out 

 the true law on which the safety-lamp is constructed. 



The subject of this important invention excited so 

 much interest in the northern mining districts, and 



