it is doubtful whether all the necessary requirements of sensitiveness,
resistance to strong currents, satisfactory light, self-extinction, perfect
combustion, etc., can ever be combined in one lamp. The object of the
present paper is to show that with the assistance of the fire-damp
detecter, the tin shield, or any other description of lamp, is made as
sensitive as the Davy, while its other advantages of resisting velocity,
etc., are not in any way interfered with. As a proof of this I may mention
that a deputy of experience recently visited a working place to make his
inspection. He reported the stall to be free from gas, but when the manager
and steward visited it with the detecter, which they applied to the roof
(where it would have been difficult to put even a small Davy), it drew a
sample of the atmosphere which, on being put to the test tube in the
tin-shield lamp, at once showed the presence of fire-damp. Out of
twenty-eight tests in a mine working a long-wall face the Davy showed gas
only eleven times, while the detecter showed it in every case. The
detecter, as will be perceived from the one exhibited, and the accompanying
sectional drawing, consists simply of an oval-shaped India rubber ball,
fitted with a mouthpiece. The diameter is about 2¼ inches by 3 inches, its
weight is two ounces, and it is so small that it can be carried without any
inconvenience in the coat or even in the waistcoat pocket. Its capacity is
such that all the air within it may be expelled by the compression of one
hand.

The mouthpiece is made to fit a tube in the bottom of the lamp, and when
pressed against the India rubber ring on the ball-flange, a perfectly tight
joint is made, which prevents the admission of any external air. The tube
in the bottom of the lamp is carried within a short distance of the height
of the wick-holder. It is covered at the upper end with gauze, besides
being fitted with other thicknesses of gauze at certain distances within
the tube; and if it be found desirable to further protect the flame against