LIGHTS. ARTIKICIAL. 



LIGHTS, ARTIFICIAL. 



Art*4>d prMpI* ot UM mod* of admitting air to act on the wick 

 hoa bean ih MM most generally followed lino* hii time ; UK! many of 

 the Mbaeuueni inventions havo had relation merely to MOM modifio*- 

 boa ..f thu arrangement. Tb eWor lamp. ORB of the modem kind., 

 U* a provision for ending op air through the im.-ri. .r of the wick, M 

 ia Ihe Argand; but the action of Uu air on tha cit. i -i ilie wiok 

 U mad* DOT* decided. The wick pane* through a bole in the centre 

 of cap or eon*; and the air i* admitted to a* to art on the flame close 

 to this bole, and in a huriionUl direotiuo, while the flame is yet amall ; 

 so that the uposure of the gawoua product* to the air 1* much more 

 intimau than in the ordinary Um|, and the combustion more com- 

 plete. NiLb'a oryrfito c.iKleni'n , Uinp bu a Oat wick, willi a combining 

 cap fixed to the upper part of the gba holder, circular at the bane, but 

 Uperinff upward! to an oblong alot or opening, to allow the flame to 

 emerge from the flat wick. Archer'e pnuurt lamp ha* the oil placed 

 ia flexible bag, with a wick holder, a moveable diak, and a coiled 

 print. Clark 'nature lamp ha* a (trainer or percolator on ti. 

 part of the supply pipe, to prevent impurities from patting into the 

 lamp. Bright! tfoMe-tricli Uiup hai hollow cylindrical wick* made in 

 atldaoed *tat ready for use ; the wiclu are of two different height*, 

 ao that one or both parU may be uied, according as a weak or a 

 strong light U needed. Among muneroui uiodern arraugeinonu 

 of uil lamps, aame are especially intended for the uae of colza or 

 mpe-eeed oil 



. In chemical experiment* the spirit-lamp hai long 



bun a valuable piece of apparatus ; but the uae of spirit instead of oil, 

 M a food for lamp* intended for domestic purposes, ia a modern inno- 

 vation, and baa led to much mechanical ingenuity in the construction 

 uf the apparatus. 



The term spirit is rather a vague one, since there are many kinds 

 of apirit which are inflammable enough to be used for this purpose ; 

 but the kind here alluded to U more generally the ipirit of turpentine, 

 or the liquid dintilled from common turpentine by being separated 

 from the resin which is a component ingredient in the lout-named sub- 

 atanoe. When brought to it* purest state, thia spirit is called by the 

 French chemiat* aiai/j/iint ; and hence the name for some of the 

 modern spirit-lamps. Turpentine being a very abundant produce of 

 the American forests, camphino boa long been in use in the United 

 State* for lighting shops and public buildings ; and it seems to have 

 been from that country that the practice was borrowed and introduced 

 into England. When the import duty on turpentine was lowered 

 some yean ago, the price became reduced sufficiently to direct the 

 attention of lamp makers to the practicability of using cauiphine as a 

 substitute for oil. Many different form! of lamp have resulted from 

 these inquiries; and different procewes have also been adopted for 

 freeing the turpentine from a small quantity of oxygen which it 

 contains. Young's ("rain lamp ia one of those varieties. The 

 piineiplea of its construction are that, on account of the inflam- 

 mability of this liquid, provision shall be made for keeping cool the 

 reservoir where it is deposited ; that no tube or metal conductor of 

 any description u allowed to pan into or through the liquid from the 

 burning part of the lump; that a non-conductor of heat is placed 

 between the burner and the liquid ; that the cotton wiok hang* down 

 from the burner into the spirit, so as to supply spirit to the flame by 

 capillary attraction, without the intervention of any metallic or con- 

 ducting substance ; and that the admiaainn of air to the interior of the 

 wick ia managed without the necessity of pawing an air-tube through 

 the liquid. All these features and a few others are rendered necessary 

 in the camphine or spirit lamps, on account of the extreme inflam- 

 mability of the liquid ; an inflammability such that the arrangement* 

 for an oil-lamp would not be available for a oamphine-lamp without 

 much danger. Whether the oomphine-lamp* receive the name of 

 P***>, or Htrn. or Victoria, or Paragox, or Imperial, or any other of 

 the many which have been applied to them, they all present in c<mim..n 

 reservoir, generally of glass, placed between the supporting pillar and 

 the burner ; the spirit is contained in this reservoir, and a cotton 

 wick dips down into it. The chief points in which the several 

 varieties of the lamp differ are in the arrangement* for admitting air 

 to the ftafnt. 



The increased demand for camphine has rained the price ; and it 

 bec-me* a variable commercial question whether oamphine or oil IK- 

 the matt profitable. In a scientili,,- sense, spirit has a great advantage 

 over oil All lamp-oils contain some oxygen, which neutralises a part 

 of the hydrogen and carbon, and also some oxide or other substance 

 which damps the brilliancy of the flame; whereas rectified oamphine, 

 being composed almost wholly of hydrogen and carbon, contain,. 

 wpthing bat what ia stuceptible of combuatTon. Whether the lump I,,- 

 so constructed a* to admit of this perfect combustion, and also so a* to 

 avoid danger, are questions for the consideration of the manufn. 

 but in a chemical point of view, oamphine seems better fitted for 

 combustion than oil 



it ia not aluM from turpentine that the npirlt may be procured ; for 

 tar and naphtha also, if subjected to careful distillation and reoti- 

 BoaUoo, will yiatd a spirit or oamphine differing but little from that 

 rU*d by turpmUne. ManalM.I'i Amsub lamp is founded on an 

 UfMiou* mode of combinlni; air with ipirit vapour. Beniole ia a 

 compound of hydrogen and carbon, procured from coal-tar. The 

 mod*) of employment adopted by Mr. Mansfield oonsUU of lending a 



stream of atmospheric air, or of common gas, through a reservoir 

 charged with beniole; the benzole vaporises rapidly, and in so 

 combines with the air or go*. The re.. - arrangement is, 



that benzole and similar hydro-carbons contain too im 

 burned in the ordinary way in lumps ; and that an extra dose 

 of hydrogen is required to ensure jierfect combustion. ll<>lliday' 

 A'ojwMa lamp is another apparatus for using a cheap hydro-carbon 

 very rich in the hut-named element; the iiaphthalic vapour, as it 

 issue* from the jet, is made to mix rapidly with atmospheric air 

 before combustion. Many analogous arrangement* have been planned 

 by Donovan, Lowe, Ceale, and others, and have been made more 

 or le** applicable to alcohol, oil of tur|*-ntiti. and wood spirit, as 

 well a* to iwuxolo and nuphtlio. Mechanically couxi'l. i. <l. Hnlliday'it 

 arrangement ia ingenioua. The admiaaion of air to mix , 

 hot vapour is regulated by making the burner revolve on the 

 the wick tube; there are perforations in both; when tin- liule* arc 

 .'iiii-i.l.-ii 1 . tin! current U at it* maximum ; but it gradually diminish*)) 

 as the burner is turned round. We may im-nti.m also /HiivjKne and 

 pttroltum among the liquids now used a* food for lamps ; paraffine 

 being deemed in many respects superior to comphinu. 



Of the late M. Soyer'n ipirit lamp, intended to give beat rather than 

 light, a brief notice will be found under COOKING APPARATUS. 



A few words may be added concerning two important nutters con- 

 nected with lamps ; namely, the comparative illuminating powers of 

 different kinds, and the means of' carrying off the product* < : 

 bustiun. 



Poctet, Dr. Ure, and Dr. Fyfe have all instituted experiments 

 bearing on the former of these two questions. I'tv u-nted 



on candles only. He determined what would be the value of .! 

 kinds of candle, sufficient to produce a given intensity of light, as 

 determined by Carcel's lamp as a standard. They rank , 

 following order, the first being the cheapest : tallow candles, six to 

 the pound ; ditto, of eight to the pound ; pressed tallow ; stt 

 spermaceti; wax. Thin relation was as to price only. The r. 

 irrighti of material consume >1 followed a dilt'erent order of arrangement, 

 the spermaceti being the least, an 1 tin- pressed tallow the greatest. 

 In Dr. lire's list the relative quantities of light for a given price, or 

 the relative cheapness of a given quantity of light, among never, 

 of lamps and candles, are placed in the following order : Hot oil lamp, 

 with southern whale-oil; Carccl lamp, with sperm-oil; hot-oil 

 with sperm nil; hot-oil lump, with common olive-oil; h.,( ,,il Limp, 

 with cocoonut-oil ; French lamp, with sperm-oil; mould tallow 

 candles ; Palmer's spread-wick candles ; ateario acid candles ; c<* 

 stearine; spermaceti caudles ; wax candles: the first heiiur. in point of 

 economy, the cheapest, and the last the dearest. Dr. Kyfe's . 

 meuU were of a more extensive character, embracing a larger number 

 of sources of illumination. Assuming a given intensity of gas-light OH 

 a standard, he experimented on ten varieties of candles, and found 

 their relative cheapness, in producing the given degree of light, to rank 

 as follows: tallow with single wick, cocoa, compo- 

 with double wicks, wax, diaphane, margarine, .-p. 

 position. In another table, comparing gas, oil, and candles to 

 he assumed an Argand gas-flame as a standard of intensity and price, 

 and gives the following arrangement in renpeet to the ration of relative 

 cheapness, the intensity of light being unit 



Argnod gm.il.ime )-oo 



Solar lamp J-oo 



Naphtha ........ 3-00 



Solar oil in Argand lamp 



Whale-oil 



Sperm-oil . . . 



Tallow-candle (two wickc) 



Cocoa candle . . 



Tallow candle (one wick) 



Composite . . 



Palm .... 



Wax .... 



Diaphane 



Margarine . 



Spermaceti 



Computation 



3-98 

 6-00 

 8-00 

 1S-70 

 13-10 

 13-30 

 14 30 

 18-90 

 35-00 

 27-10 

 28-40 

 29.20 



According to this table, composition candles are nearly thirty times 

 as costly OR gaa for on equal intensity of light. 



Dr. 1 araday has Introduced an important arrangement for gal 

 off the products of combustion in gas and oil lamps. 'I'M- arose out 

 of n complaint, on the part of the members of the Ath. i 

 that the air of their lilirary was vitiated and tl 



' l>y the lamps then used. I'r. Faraday investigated the u 

 and shortly afterwards communicated 



Engineers the mode wlii.-li lie ]m.|i. .,., .1 (., adopt for remedying tho 

 evil. In paper oommnnicoti >'ly lie addi ig proof 



of tho magnitude of tin- product raulting i .-,ti..n. " A i 



oil, win prodaoW pint and a quarter of water, and a ; 



of gas more than half pounds of \\.it.-r; tin- 



weight Ix-ing due to the ali-orpti..i 

 one part of hydrogen taking eight part* (by weight) . 

 water. A London Argand gas-lamp, in a closed shop-window 

 produce in four hours two pints and a half of water ; a pound nf oil 



