pit. The
_first_ was tried on the 21st October, 1815; the _second_ was tried on
the 4th November; but it was not until the 9th November that Sir Humphry
Davy presented 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.

[Picture: Davy's and Stephenson's Safety Lamps]

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
concerned him. Torricelli did not know the rationale of his tube, nor
Otto Gurike that of his air-pump; yet no one thinks of denying them the
merit of their inventions on that account. The discoveries of Volta and
Galvani 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 Stephenson's numerous friends considered
his lamp so completely successful--having stood the test of repeated
experiments--that they urged him to bring his invention before the
Philosophical and Literary Society of Newcastle, of whose apparatus he
had availed himself in the course of his experiments on fire-damp. After
much persuasion he consented, and a meeting was appointed for the purpose
of receiving his explanations, on the evening of the 5th December, 1815.
Stephenson was at that time so diffident in manner and unpractised in
speech, that he took with him his friend Nicholas Wood, to act as his
interpreter and expositor on the occasion.