WIRE-GAUZE SAFETY-LAMP. 



furface, by diminiftiing the fize or increafing the depth of 

 the aperture, all flames, however rapid their motion, may- 

 be arretted. Precifely the fame law applies to explofions 

 afting in clofe veffels : very minute apertures, when they 

 are only a few in number, will permit explofions to pafs 

 which are arrefted by much larger apertures, when they fill 

 a whole furface. A fmall aperture was drilled at the bottom 

 of a wire-gauze lamp, in the cyhndrical ring which con- 

 fines the wire-gauze ; this, though lefs than one-eighteenth 

 part of an inch in diameter, pafled the flame, and fired the 

 external atmofphere, in confequence of the whole force of 

 the explofion of the thin ftratum of the mixture included 

 within the cyhnder driving the flame through the aperture ; 

 though, had the whole ring been compofed of fuch aper- 

 tures, it would have been perfeftly fafe. Nothing, fays fir 

 Humphrey Davy, can demonftrate more decidedly than thefe 

 fimple fafts and obfervations, that the interruption of flame 

 by folid tiffues permeable to light and air, depends on no re- 

 condite or myfterious caufe, but to their cooling powers 

 fimply confidered as fuch. 



When light, included in a cage of wire-gauze, is intro- 

 duced into an explofive atmofphere of fire-damp at refl;, the 

 maximum of heat is foon obtained, the radiating power of 

 the wire and the cooling effefts of the atmofphere, more 

 efficient from the mixture of inflammable air, preventing it 

 from ever arriving at a temperature equal to that of dull 

 rednefs. In rapid currents of explofive mixtures of fire- 

 damp, which heat common gauze to a high temperature, 

 twilled gauze, in which the radiating furface is confiderably 

 greater and the circulation of air Tefs, preferves an equal 

 temperature. Indeed the heat communicated to the wire 

 bycombuftion of the fire-damp in wire-gauze lamps is com- 

 pletely in the power of the manufadlurer, for by diminifti- 

 ing the apertures, and increafing the mafs of metal, or the 

 radiating furface, it may be diminiftied to any extent. One 

 important circumftance, however, is not here adverted to 

 by fir Humphrey Davy ; by increafing the thicknefs of the 

 wire and diminiftiing the aperture, the quantity of light 

 tranfmitted is greatly reduced, and its power of illumination 

 rendered nearly inefficient. Hence the power of the manu- 

 faAurer to conilruft a lamp perfeftly fafe and fufficiently 

 Luminous mull be limited by certain conditions. However, 

 fir Humphrey Davy informs us, he has lately had lamps made 

 Df thick twilled gauze formed of wires the one-fortieth of 

 an inch, fixteen to the warp and thirty to the weft, which 

 being rivetted to a fcrew cannot be difplaced, from its flexi- 

 bility it cannot be broken, and from its ftrength cannot be 

 cruftied, except by a very fl;rong blow. 



From fome very ingenious experiments on the combuftion 

 9f inflammable fubilances at low temperatures, fir Hum- 

 phrey Davy difcovcred that a coil of platina wire, one- 

 feventieth of an inch thick, remains at a white heat when the 

 quantity of coal-gas is increafed fo as to extinguifti the 

 flame of the lamp ; hence he has fuggefl;ed the advantage of 

 introducing a coil of fuch wire into the fafety-lamp, but we 

 do not learn that it has yet been found of praftical ufe. An 

 account of thefe experiments is given in the Phil. Tranf. for 

 1817. 



The principal objeftions to the ufe of wire-gauze fafety- 

 Lamps in mines, and alfo to other fafety-lamps, may be 

 briefly ftated ; namely, the accidents to which the lamps 

 may be unavoidably fubjeft, and the accidents which may 

 arife from negligence in the ufe of them ; the injury to 

 the health of the men, from remaining in explofive mixtures 

 of fire-damp longer than they would have done before the 

 introduftion of thefe lamps into mines ; and lalUy, the tempt- 

 ation they prefent to negleft the more expcnfive methods of 



ventilating mines, and trufting too much to the fecurity of 

 the lamp. The accidents which may happen to the lamp 

 from one or more of the mefties being broken, when made 

 of fuch flender wire, and expofed to the corrofive effefts of 

 mineral waters in the mine, or the rapid oxydation from 

 moifture alone, mufl: be very frequent, independently of ac- 

 cidents from the falling of pieces of coal on the lamp. The 

 breaking of a fingle wire being fufficient to enlarge the 

 aperture and occafion an explofion, it is obvious that ex- 

 treme caution is required in the ufe of the lamps, and a 

 careful infpeftion of them (hould be made every day before 

 they are delivered to the men. This we underftand is done 

 in extenfive collieries, a perfon being appointed for the fole 

 purpofe of infpefting and trimming the lamps. The acci- 

 dents which may arife from the negligence of a fingle man, 

 in extenfive mines where more than fifty or one hundred per- 

 fons are employed, are lefs eafy to guard againft ; the lives 

 of a great number are conftantly depending on the carefuU 

 nefs of each perfon ; and, however perfeft the inftrument 

 may be, no one can feel perfeftly fafe when the air in the 

 mine is in an explofive ftate. Some of the lamps were at 

 firft fo conftrufted that they could not be opened except by 

 the key of the infpeftor ; but we beheve this precaution is 

 not generally introduced, the great objeft being to get the 

 lamps made as cheap as poffible. We conceive it, however, 

 elfential to the fecurity of the miners, that the lamp ftiould 

 be clofed by a lock, to prevent the men from uncovering the 

 flame. The lamp itfelf, by the enlargement of the flame, 

 gives due notice when the air of the mine is in an explofiw 

 ftate, and at fuch times the proper remedy is to be fought 

 in ventilation ; for we conceive it to be neither wife nor hu- 

 mane to fuff"er the men to remain working in an explofiv« 

 atmofphere, unlefs under particular circumllances. Should 

 the invention of fafety-lamps induce coal proprietors to 

 allow their workmen to remain for a longer time inhaling 

 the fire-damp, or lead them to negleft the only permanent 

 fecurity, that of efficacious ventilation, we ftiould confider 

 the difcovery as injurious to the interefts of humanity. It 

 would, however, be extremely unfair to decry the merit of 

 any invention from the poffible mifufe of it. Were coal- 

 mines firft opening in a diftrift where they had never before 

 been worked, we believe that in moft; cafes it would be prac- 

 ticable to fecure a conftant and fafe ventilation through all 

 the works : but in diftrifts like thofe on the Tyne and the 

 Wear, there are numerous old excavations remaining filled 

 with impure air, of which the prefent miners have little 

 knowledge, having been worked out in remote periods. 

 Any communications accidentally opened with thefe old 

 workings may fuddenly fill a mine with a mixture of fire- 

 damp, in which cafe the fafety-lamp offers the only means 

 of fecurity with which we are acquainted. For viewing the 

 old workings or wajles of the mine, which cannot be ap- 

 proached with a common lamp or candle, the fafety-lamp is 

 a moft invaluable inftrument ; and in all cafes where the fteel- 

 mill was formerly ufed it affords a far more fecure and con- 

 venient light. Though we have thought it neceffary to ftate 

 the objeftions which may be urged againft the fafety-lamp, 

 we conceive that they apply principally to the mifufe of it ; 

 and the following ftatement made by fir Humphrey Davy- 

 offers the moft fatisfaftory proof of its utihty. " It has 

 now been (Jan. 181 7) for ten months in the hands of hun- 

 dreds of common miners in the moft dangerous mines in 

 Great Britain, during which time not a fingle accident has 

 occurred where it has been employed, whilft in other mines 

 much lefs dangerous, where it has not been adopted, fome 

 lives have been loft, and many perfons burned." 



The farther experience of another year, on a more ex- 

 4 A 2 tended 



