LAMP OF DAVY.

743

The parts of the lamp are,

,, The brass cistern a, d,fig. 61 5, which contains the oil. It is pierced at one side ofe c entre with a vertical narrow tube, nearly filled with a wire which is recurved above,1 the level of the burner, to trim the wick, by acting on the lower end of the wire e with® fibers. It is called the safety-trimmer.

The rhn b is the screw neck for fixing on the gauze cylinder, in which the wire-S a uze cover is fixed, and which is fastened to the cistern by a screw fitted to b.

'4 An aperture c for supplying oil. It is fitted with a screw or a cork, and communi-ties with the bottom of the cistern by a tube at f. A central aperture, for the wick,^te w; > re -g auz e cylinder, fig. 614, which should not have less than 625 apertures tosquare inch.

j °- The second top, -J of an inch above the first, surmounted by a brass or copper plate,0 which the ring of suspension may be fixed. It is covered with a wire cap in the

figure.

Four or six thick vertical wires, g' g' g' g’, joining the cistern below with the topP lat e, and serving as protecting pillars round the cage, g is a screw-pin to fix the cover,0 that it shall not become loosened by accident or carelessness. The oil-cistern fig. 615s drawn upon a larger scale than fig. 614, to show its minuter parts.

When the wire-gauze safe-lamp is lighted and introduced into an atmosphere graduallyrxed with fire-damp, the first effect of the fire-damp is to increase the length and size. the flame. When the inflammable gas forms so much as l-12th of the volume of theair ) the cylinder becomes filled with a feeble blue flame, while the flame of the wickPPears burning brightly within the blue flame. The light of the wick augments till the. re -damp increases to l-6th or l-5th, when it is lost in the flame of the fire-damp, whichthis case fills the cylinder with a pretty strong light. As long as any explosive mixture; as exists in contact with the lamp, so long it will give light; and when it is extinguished,btch happens whenever the foul air constitutes so much as l-3d of the volume of thetnosphere, the air is no longer proper for respiration; for though animal life will con-Wue where flame is extinguished, yet it is always with suffering. By fixing a coil of... fidtfium wire above the wick, ignition may be maintained in the metal when the lampSe « is extinguished; and from this ignited wire the wick may be again rekindled, onfififying it into a less inflammable atmosphere.

, We have frequently used the lamps where the explosive mixture was so high as to_ a t the wire-gauze red-hot; but on examining a lamp which has been in constant uselb l * lree months, and occasionally subjected to this degree of heat, I cannot perceive that, e gauze cylinder of iron wire is at all impaired. I have not, however, thought it pru-in our present state of experience, to persist in using the lamps under such circum-in !l ces ’.k ecause I have observed, that in such situations the particles of coal dust floatingTh' G a * r ’ ® re at gas burning within the cylinder, and fly off in small luminous sparks,is appearance, I must confess, alarmed me in the first instance, but experience soonthat it was not dangerous.

in® • es ^ es the facilities afforded by this invention to the working of coal-mines abound-fltrn 111 ^ re_t t am P) it h as enabled the directors and superintendents to ascertain, with thetin. ^ St P rec i s io n an d expedition, both the presence, the quantity, and correct situation of

the

of aon

§as. Instead of creeping inch by inch with a candle, as is usual, along the galleries

tnme suspected to contain fire-damp, in order to ascertain its presence, we walk firmlyfilin'^ 1 saia-lamps, and, with the utmost confidence, prove the actual state of thean p 6 ’ "^serving attentively the several appearances upon the flame of the lamp, inand Xarn W at i° n of this kind, the cause of accidents which happened to the most experiencedfire aaut ‘ ous miners is completely developed; and this has hitherto been in a great meas-“ f! a ^ ter more conjecture.

fie 1 ls . not necessary that I should enlarge upon the national advantages which mustbp c * sar *W result from an invention calculated to prolong our supply of mineral coal,e X p'. se . * U'ink them obvious to every reflecting mind; but I cannot conclude withoutHie assln S .my highest sentiments of admiration for those talents which have developedbusies, and controlled the power, of one of the most dangerous elements whichfif'Sci 11 eilter P r ise has hitherto had to encounter.”—See Letter to Sir H. Davy , in Journalfiiost : nce ’ ’■ I 1 ’ 3 °2, by John Buddie, Esq., generally and justly esteemed one of theM| WC H n i) C fi° a Tminers in the kingdom.

of hh’iT, 1 e ’ in a fetter dated 21st August, 1835, which is published in Dr. Davy ’s life" In th r -n r Hum ?hrey, says

C’otnrnon 6 |- e , en ! :e Seven in my last examination before a committee of the House of1000 to S j 500 i 6a filter nearly twenty years’ experience of ‘ the Davy ’ with fromCoal mini o. ° femps in daily use, in all the variety of circumstances incidental tong, wit out a single accident having happened which could be attributed to