218 Appatatus for re-lighting the Miners’ Davy. 
Description of the Figures. 
Fig. 2 (Plate III.) shows a cast-iron urn resting in a vessel of 
lime-water, or cream of lime, to absorb the carbonic acid gas 
formed. It is topped with two folds of wire-gauze at A. At 
BBB are three or more sockets, the orifices of which are covered 
with wire-gauze. In these sockets are fixed tubes of tin C, 
which move up and down to any height like the sliding pipes of 
a perspective or opera glass ; they terminate in a funnel-shaped 
orifice, or they may be jointed, to incline at any angle to receive 
the explosive medium for combustion. The ‘** Davy” will be 
the index of the requisite height; the tubes should be raised 
within half an inch of the base of the fire-damp, floating on the 
roof, so that a due admixture of inflammable air and its sup- 
porter may enter the funnel of the tube, together. 
Fig. 3 exhibits a view of the internal insulated wire-gauze, 
being that which imprisons the wick of flame ; it does not touch 
the surrounding cast-iron case or urn, nor even the upper wire~ 
gauze, on its top. This cage may be made two or three folds. 
The lamp is fed by an oil cistern exterior to the urn,.and a fold 
or two of wire-gauze in the communicating pipe will prevent any 
retrogression of flame where the cistern is to be supplied with 
oil. The wick may be of asbestos, which will never need re- 
newal; and the lamp, first lighted, is screwed tight into the 
socket. 
Fig. 4 represents the oil cistern of Davy’s safe-lamp with two 
separate wicks. A exhibits one of these wicks surrounded by a 
platinum cage. B the reserve wick, with an appendage which 
serves at once toelevate the cap and depress the spiral platinum 
wire to ignite the wick ;' a the cap attached to the axis f by the 
wire l. c¢ a spring, that when at freedom reacts on the wire 
attached to the cap, which then fails and protects the wick, when 
not required; d is a spiral platinum wire attached by e to the 
axis f, which moves by a button exterior to the wire-gauze, 
The reserve wick is tipped with sz/phur. When the wick of the 
lamp A is extinguished by reason of excess of fire-damp, the 
singular combustion of the platinum wire begins, and continues 
until there exists no longer any of the hydrocarbonate. The 
platinum wire before extinct becomes dull red; this will indicate 
an approach to the free atmusphere the moment after, by a se- 
mirotatory movement of the button, the cap is raised, and the 
top of the platinum brought in contact with the wick tipped with 
sulphur, which ignites it. i ' 
XXXVIII. On 
