The life of George Stephenson, railway engineer - Lighthouse ...

116 LIFE OF GEORGE STEPHENSON. [chap.xi.
October ; and it was made and delivered to him on the 21st of
October, after which it was tested at the blower in the Killing-
worth pit, on the evening of the same day. Up to this time
nothing was known of the nature or results of Sir H. Davy's ex-
periments. But on the 31st of October Davy communicated the
fact which he had now discovered to the Rev. Dr. Gray, then
Eector of Bishop Wearmouth (afterwards Bishop of Bristol), in
a communication intended to be private,* but which was inadvertently
read at a public meeting of coal-miners held at Newcastle
on the 3d of November following. In that letter he stated,
— " When a lamp or candle is made to burn in a close vessel
having apertures only above and below, an explosive mixture of
gas admitted merely enlarges the light, and then gradually ex-
tinguishes it without explosion. Again,—the gas mixed in any
proportion with common air, I have discovered, will not explode
in a small tube, the diameter of which is not less than one-eighth
of an inch, or even a larger tube, if there is a mechanical force
urging the gas through the tube.'' This was the first public inti-
mation of the result of Sir H. Davy's investigations ; and it has
been stated as probable that the information was conveyed to
Mr. Stephenson by some of his friends who might have attended
the meeting. Supposing this to be so, it contained nothing which
he had not already verified by repeated experiments. The fact
that explosion would not pass through small tubes was by this
time perfectly well known to him. He had been continuing his
experiments during the end of October and the beginning of
November; his second and improved lamp, constructed on this
very principle, was already completed, and it was actually tried
in the Killingworth mine on the 4th of November, the very day
following the meeting at which Sir Humphry Davy's discovery
was first announced. Whereas the Tube Safety Lamp, which
the latter had constructed on the principle above stated, was not
presented to the Royal Society until the 9th of November follow-
ing. Thus, Mr. Stephenson had invented and tested two several
tube lamps before Sir Humphry Davy had presented his first
lamp to the public.
* Paris's Life of Davy, 4to ed., p. 314.