y a lamp of this kind was actually
proposed; but it was but a rude sketch compared to its present state of
improvement. Sir H. Davy, after a succession of trials, by which he
brought his lamp nearer and nearer to perfection, at last conceived the
happy idea that if the lamp were surrounded with a wire-work or
wire-gauze, of a close texture, instead of glass or horn, the tubular
contrivance I have just described would be entirely superseded, since
each of the interstices of the gauze would act as a tube in preventing
the propagation of explosions; so that this pervious metallic covering
would answer the various purposes of transparency, of permeability to
air, and of protection against explosion. This idea, Sir Humphry
immediately submitted to the test of experiment, and the result has
answered his most sanguine expectations, both in his laboratory and in
the collieries, where it has already been extensively tried. And he has
now the happiness of thinking that his invention will probably be the
means of saving every year a number of lives, which would have been lost
in digging out of the bowels of the earth one of the most valuable
necessaries of life. Here is one of these lamps, every part of which you
will at once comprehend. (See PLATE X. fig. 1.)

[Illustration: Plate X.

Fig. 1.
A. the cistern containing the Oil
B. the rim or screw by which the gauze cage is fixed to the cistern.
C. apperture for supplying Oil.
E. a wire for trimming the wick.
D. F. the wire gauze cylinder.
G. a double top.

Fig. 2.
A. the reservoir of condensed air.
B. the condensing Syringe.
C. the bladder for Oxygen.
D. the moveable jet.]

CAROLINE.

How very simple and ingenious! But I do not yet well see why an
explosion taking place within the lamp should not communicate to the
external air around it, through the interstices of the wire?

MRS. B.

This has been and is still a subject of wonder, even to philosophers;
and the only mode they have of explaining it is, that flame or ignition
cannot pass through a fine wire-work, because the metallic wire cools
the flame sufficiently to extinguish it in passing through the gauze.
This property of the wire-gauze is quite similar to that of the tubes
which I mentioned on introducing the subject; for you may consider each
interstice of the gauze as an extremely short tube of a very small
diameter.

EMILY.

But I should expect the wire would often become red-h