The term spirit is rather a vague one, since there are ninny kinds of spirit which are inflammable enough to be used for this purpose; but the kind here Alluded to is more generally the spirit of turpentine, or the liquid distilled from common turpentine by being separated from the resin which is a component ingredient In the last-named sub stance. When brought to its purest state, this spirit is called by the French chemists eamphine ; and hence the name for some of the modern apirit-bunps. Turpentine being a very abundant produce of the Amencan forests, camphina has long been in use in the United States 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 oe turpentine was lowered some years ago, the price became reduced sufficiently to direct the attention of lamp makers to the practicability of using camphine as a substitute for oil. Many different forms of lamp have resulted from these inquiries ; and different processes have also been adopted for freeing the turpentine from a small quantity of oxygen which it contains. Young's lists lamp is one of those varieties. The principles 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 is allowed to pasta into or through the liquid from the burning punt of the lamp; that a non-conductor of heat is placed between the burner and the liquid ; that the cotton wick hangs down from the burner into the spirit, so as to supply spirit to the flame by capillary attraction, without the intervention of any meanie or con ducting substance; and that the admission of air to the interior of the wick is managed without the necessity of passing an aireube through the liquid. All these features and a few others are rendered necessary in the (emplane or spirit lamps, on account of the extreme intim Inability of the liquid; an inflammability such that the arrangements for an oil-lamp would not be available for a camphinolamp without much danger. Whether the camphinielamps receive the name of Vote, or tame or rietoria, or Paragon, or Imperial, or any other of the meny which have been applied to them,they all present in common a reservoir, generally of glass, placed between the supporting pillar and the burner ; time 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 arrangements for admitting air to the flame.
The increased demand for canipblue has raised the price; and it becomes a variable commercial question whether camphine or oil be the most profitable. In a scientific sense, spirit has a great advantage over oil. All lamp-oils contain mine oxygen, which neutralises a part of the hydrogen and carbon, and also sonic oxide or other substance which damn. the brilliancy of the flame ; whereas rectified camphine, being composed almost wholly of hydrogen and carbon, contain. nothing hut what is aunceptible of combustion. Whether the Imp be so es estructed as to admit of tide perfect ooinbustion, and also sore to avoid danger, are quoatlens fur the consideration of the manufacturer; but In a chemical point of view, camphine seems better fitted for combustion than oil.
It is nut elms from turpentine that the spirit may be procured p for tar and naphtha alao, If subjected to careful distillation and recti fication, will yield a spirit or camphine differing but little from that yrsided by turpentine. Mansfield's /levreete temp Is founded ou an ingenious mode of combining air with spirit vapour. Iknzole Is compound of hydrogen and carbon, procured from coal-tar. The
mede of employment adopted by Mr. Mansfield consists of sending a stream of atmospheric air, or of common gas, through a reservoir charged with bensole; the bentole vaporises rapidly, and in so doing cambium with the air or gate The reason for this arrangement is, that benzole and similar hydro-carbons contain too much carbon if burned in the ordinary way in lamps ; and that an extra dose of hydrogen is required to cneure perfect combustion. Holliday's Nopathe lamp is another apparatus for using a cheap hydro-carbon very rich in the last-named element ; the nephthalic vapour, as it Wiles from the jet, is rustle to mix rapidly with stmospliene air before combustion. Many analogous arrangements have lien planned by Donovan, Lowe, dcale, and others, and have been nutria mom or lees applicable to alcohol, oil of turpentine, and wood spirit, as well as to Leuze& and naphtha. Mechanically considered, Holliday's arrangement is ingenious. The admission of air to mix with the hot vapour is regulated by making the burner revolve on the top of the wick tube; there are perforations in both ; when the holes ate coincident, the current is at its maximum ; bat it gradually-diminishes as the burner is turned round. We may mention also pacuigne and petroleum among the liquids now used as food for lamp.; parathino being deemed in many respects superior to camphine.
Of the Into M. Soyer'a spirit lamp, intended to give heat rather than light, n brief notice will be found under COOKINCi AITAIIATUS.
A few words may be added concerning two important matters con nected with lamps ; namely, the comparative illuminating powers of different kinds, and the means of carrying off the products of com bustion.
Poctet, Dr. Urn, and Dr. Fyfa hero all instituted experiments bearing on the former of these two questions. Pectet experimented on candles only. He determined what would be the value of different kinds of candle, sufficient to produce a given intensity of light, its determined by Corcel'a lamp as a standard. They rank in the following order, the first being the cheapest :—tallow candles, six to the pound; ditto, of eight to the pound ; pressed tallow ; stearin° ; spermaceti; wax. This relation was as to price only. The relative weights of ninterial consumed followed a different order of arrangement, the spermaceti being the least„and the pressed tallow the greatest. In Dr. Ure's list the relative quantities of light for a given price, or the relative cheapness of a given quantity of light, among several kinds of lamps and candles, aro placed in the following order :—Ilot-oil lamp, with sogthern whale-oil; Cared lamp, with sperm-oil; hot-oil lamp, with sperm oil; hot-oil lamp, with common olive-oil; hot-oil lamp, with cocoanut-oil ; French lamp, with sperm-oil; mould tallow candles ; Palmer's spread-wick candles ; ateario acid candles ; cocoanut stearin° ; spermaceti candles ; wax candles: the first being, in point of economy, the cheapest, and the last time clearest. Dr. Fyfe's experi ments were of a more extensive character, embracing a larger number of sources of illumination. Assuming a given intensity of gaslight at a standard, he experimented on ten varieties of enudles, and found their relative cheapness, in producing the given degree of light, to rank as follows :—tallow with single wick, cocoa, composite, palm, tallow with double wicks, wax, diaphane, margarine, spermaceti, and com position. In another table, comparing gas, oil, and candles together, he assumed an Argand gas-flame as a standard of Intensity and price, and gives the following arrangement in respect to the ratios of relative cheapness, the intensity of light being uniform : According to this table, composition candles are nearly thirty times as costly RR gas for an equal intensity of light.