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LAMP. 



LAMP, SAFETY. 



deposit is shaken to one end of the bag and removed, and the mouth 

 of the bag again tied up. 



Lamp-black is largely used as a pigment, chiefly in the manufacture 

 of printers' ink. It always retains a small quantity of undecomposed 

 hydrocarbons. 



LAMP. [LIGHTS, ARTIFICIAL.] 



LAMP, MONOCHROMATIC. If common salt be dissolved in 

 spirits of wine the mixture will burn with a yellow flame, and if no 

 other lights be burning at the same time, the effects will be extraordi- 

 nary. An arrangement for furnishing the lamp with a regulated 

 supply of the prepared spirit is termed a monochromatic lamp. 



LAMP, SAFETY. It has long been known that coal-mines, and 

 especially such as are deep, are occasionally infested with carburetted 

 hydrogen, a gaseous product, which, on account of its combustible 

 property is called jire-damp ; the word being the equivalent of the 

 German damp/, a vapour or exhalation. 



Several contrivances had been proposed for safely lighting coal-mines 

 subject to the visitations of this gas ; but the safety-lamp of Sir H. Davy 

 was the first one extensively employed. Davy began a chemical examina- 

 tion of various specimens of fire-damp, by which he confirmed the 

 previous statement of Dr. Henry, that the pure inflammable part of it 

 is carburetted hydrogen gas. He found that it required an admixture 

 of a large quantity of atmospheric air to render it explosive. Pro- 

 ceeding with his experiments Davy ascertained that explosions of 

 inflammable gases are incapable of being passed through long narrow 

 metallic tubes ; and that this principle of security ia still obtained by 

 diminishing their length and diameter at the same time, and likewise by 

 diminishing their length and increasing their number ; so that a great 

 number of small apertures would not pass explosion when their depth 

 was equal to their diameter. This fact led to trials upon sieves made 

 of wire gauze. He found that if a piece of wire gauze was held over 

 the flame of a lamp, or of coal gas, it prevented the flame from passing ; 

 and he found also that a flame confined in a cylinder of very fine 

 wire gauze did not explode even a mixture of oxygen and hydrogen, 

 but that the gases burnt in it with great vivacity. 



The experiments to which we have now alluded, served as the basis 

 of the safety-lamp, which Davy described as follows : " The apertures 

 in the gauze should not be more than Jj of an inch square. As the 

 fire-damp is not inflamed by ignited wire, the thickness of the wire is 

 not of importance ; but wire from jk to ^ of an inch in diameter is the 

 most convenient. Iron-wire and brass-wire gauze of the required 

 degree of fineness are made for sieves by all wire-workers ; and except 

 i lamp is to be used by a viewer for dialling, iron-wire gauze is 

 to be preferred : when of the proper degree of thickness it can neither 

 melt nor burn ; and the coat of black rust which soon forms upon it 

 superficially, defends the interior from the action of the air. The cage 

 or cylinder should be made by double joinings, the gauze being folded 

 over so as to leave no apertures. When it is cylindrical it should not 

 be more than two inches in diameter ; for iu larger cylinders the com- 

 bustion of the fire-damp renders the top incon- 

 veniently hot; and a double top is always a 

 proper precaution, fixed at the distance of half 

 or three-quarters of an inch above the first top. 

 The gauze cylinder should be fastened to the 

 lamp by a screw of four or five turns, and fitted 

 to the screw by a tight ring. All joinings iu 

 the lamp should be made with hard solder ; 

 and the security depends upon the circum- 

 stance that no aperture exists in the apparatus 

 larger than in the wire gauze." 



The annexed figure of the safety-lamp re- 

 quires but little explanation. The cylinder of 

 wire gauze is defended by three upright strong 

 wires, which meet at the top ; and to them a 

 ring is fixed, from which the instrument is sus- 

 pended. The lamp is screwed on to the bottom 

 of the wire gauze, and is supplied with oil by 

 the pip projecting from it. A wire, bent at 

 the upper end, is passed through the bottom of 

 the lamp for raising, lowering, or trimming the 

 wick. When the lamp is lighted and introduced 

 into an atmosphere gradually mixed with fire- 

 damp, the first effect of the fire-damp is to 

 increase the size and length of the flame. 

 When the inflammable gas forms as much as ^ 

 of the volume of the air, the cylinder becomes 

 filled with a feeble blue flame ; but the flame of 

 the wick appears burning brightly within the 

 blue flame. The light of the wick continues 

 till the fire-damp increases to one-sixth or one- 

 fifth, when it is lost in the flame of the fire- 

 damp, which in this case fills the cylinder with 

 a pretty strong light. The operation of the 

 wire gauze in preventing the communication 

 of flame is thus explained : Flame is gaseous matter so intensely 

 heated OH to be luminous. When the flame cornea into contact with 

 wire gauze it loses so much heat in consequence of the conducting 

 power of the metil, that it is cooled down below the point at which 

 ARTS AND SCI. DIV. VOL. V. 



gaseous matter can remain lumiiious ; and consequently the flame of 

 the gaseous matter burning within the lamp is incapable of passing 

 through it so as to set fire to and explode the mixture of fire-damp. 

 This cooling power is exerted even though the wire gauze, by effecting 

 it, be rendered red-hot. 



Although the inventor of this lamp expressed himself fully satisfied 

 of its security, yet others have entertained strong doubts on the 

 subject. During the session of parliament for 1835 a committee was 

 appointed to inquire into the Accidents in Mines. The evidence of 

 Mr. Buddie was strongly in favour of the safety of the lamp ; he stated, 

 that for many years he had had not less than 1000, and sometimes 1500 

 lamps in daily use, and that he never knew in one solitary instance an 

 explosion to happen from them ; and he mentioned also that he had 

 been with them in all possible varieties of explosive mixtures. On the 

 other hand abundant evidence, and especially that of Dr. Pereira, was 

 adduced before the committee to show, that in strong currents of 

 explosive mixtures the lamps could not be trusted, as the flame passed 

 through them ; indeed Sir H. Davy seems himself to have been aware 

 that an objection might possibly be urged against them on this head, 

 and he proposed the use of a tin shield where such currents occur. 

 Dr. Turner remarks : " If a lamp with its gauze red-hot be exposed to 

 a current of explosive mixture, the flame may possibly pass so rapidly 

 as not to be cooled below the point of ignition ; and in that case an 

 accident might occur with a lamp which would be quite safe iu a calm 

 atmosphere. It has been shown by Messrs. Upton and Roberts, that 

 flame may in this case be made to pass through the safety-lamp as 

 commonly constructed; and I am satisfied, from having witnessed 

 some of their experiments, that the observation is correct. This then 

 may account for accidents in coal-mines where the safety-lamp is 

 constantly employed. An obvious mode of avoiding such an evil is to 

 diminish the apertures of the gauze ; but this remedy is nearly imprac- 

 ticable from the obstacles which very fine wire gauze causes to the 

 diffusion of light. A better method is to surround the common safety- 

 lamp with a glass cylinder, allowing air to enter solely at the bottom 

 of the lamp through wire gauze of extreme fineness, placed horizontally, 

 and to escape at top by a similar contrivance." 



In mentioning the names of other inventors of safety-lamps, we must 

 especially allude to the late George Stephenson ; because some inju- 

 dicious friends of Davy have sought to brighten the fame of that' great 

 chemist by disparaging the self-taught engineer. In 1815 Stephenson 

 was engine-wright at the Killingworth Colliery, near Newcastle. 

 Terrible explosions having taken place, he turned his ingenious mind 

 to the devising of some kind of lamp which would not prove dangerous. 

 Dr. Clanuy of Sunderland had taken up the subject two years before, 

 but had not yet surmounted the difficulties. In the month of August, 

 Stephenson drew out a sketch for a lamp, which, after conferring with 

 Mr. Nicholas Wood and other colliery engineers, was sent to a lamp- 

 maker at Newcastle. The new lamp was ready on Oct. 21st, and was 

 tried successfully on the same day. Stephenson then made a few 

 improvements, and caused a new lamp to be ready by Nov. 4th. Again 

 he experimented and made improvements, and a still more complete 

 lamp was ready by Nov. 30th ; and the " Geordy " lamp, as the miners 

 familiarly called it, at once came into use at Killingworth. During 

 these very months Davy was at work on the experiments which led to 

 his safety-lamp ; and it is now clearly proved, by the evidence collected 

 in Smiles's ' Life of George Stephenson,' that the illustrious chemist 

 and the humble engine-wright arrived by wholly independent paths at 

 a knowledge of the facts concerning the passage (or rather the non- 

 passage) of flame through tubes and small apertures. The coal-miners 

 of the north did justice to Stephenson in a very public way in 1817. 



The merits and defects of safety-lamps have formed a subject for 

 many committees of inquiry. The parliamentary committee of 1835 

 has already been adverted to. A great explosion near Sunderland in 

 1839 led to the formation of a South Shields committee, the members 

 of which devoted three years to the collecting of evidence relating to 

 the causes of colliery explosions ; and one of the results to which they 

 arrived was, that the safety -lamp might in some circumstances be a 

 source of danger rather than security, if it induced a neglect of 

 measures for ventilating the mines. There was a committee of the 

 House of Lords appointed in 1849 to inquire into the causes of these 

 terrible disasters ; this was followed by similar committees of the 

 House of Commons in 1852 and the next two years ; and the result of 

 all the inquiries was to show that any one among a large variety of 

 safety-lamps would render useful service, provided care be taken in 

 the using. It is, however, painfully evident that this amount of care 

 is tint always taken ; for the miners are too often thoughtless in the use 

 of their lamps. 



In briefly noticing some among the many kinds of safety-lamp 

 devised since the time of Davy, it may be useful to mention that they 

 depend for their safety on two principles the obstructive action of 

 wire-gauze, and the protective shield afforded by a glass cylinder. Of 

 the Davy lamp enough has been said in former paragraphs ; the method 

 of arrangement has only been slightly altered since his day. 



The Stephenson lamp has a gloss cylinder inside the wire-gauze 

 cylinder. The air is supplied through a triple circle of small holes in 

 the metal bottom. Inside the top of the glass cylinder is a sort of 

 metal chimney full of small holes. The lamp gives a steady light by 

 being protected from the currents of the mine. It has a few advan- 



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