A Plating lamp has been made by Mr. Merryweather, of Whitby, England, some years since. If a coil of small p]atina wire be placed around the wick of a spirit-lamp, and rendered red hot, the wire continues ignited for some time after the flame is blown out. The lower part is constructed of tin, in the body of which is a reservoir, large enough to contain a quart of alcohol. The bottom of the interior of the reservoir is con cave, in order that the cotton wick may take up the last drop of the spirit. After the wick has been spread in the form of a coronet at the top of the lamp, a pla tina-wire cage, containing one piece of spongy platina, is to be pricked into the centre of the wick, and to be kept near ly in contact, but not to touch it. After the reservoir has been filled with alcohol, the wick is to be inflamed, and a minute afterwards the spongy platina becomes incandescent, when the flame of the wick is to be suddenly blown out, and the glass cover to be immediately placed over the platina. Without any further care or attention, the platina ball will keep ig nited for thirteen or fourteen days and nights. If a tube is connected with a re servoir (containing a sufficient quantity of alcohol) and the bottom of the reser voir of the lamp, the platina ball may be kept ignited for years, as the spongy pla tina does not appear to be in the least deteriorated by being kept in a state of constant ignition. Two objections to this lamp, the expense of the alcohol and the odor are removed, since equal parts of alcohol and whisky answer as well as pure alcohol ; or one-third of al cohol and two-thirds of whisky, which cost two cents for eight hours. Whis key consists of 4 parts of alcohol and 8 parts of water. As a remedy for the second objection, an apparatus for condensing the vapor is made of tin, which is to be suspended from a nail in the wall. The glass tube of. the lamp is to be inserted into the tin tube of the condensing apparatus, which will com pletely destroy the strong odor of the vapor, and the liquid is drawn off by the stop-cock at the side of the condenser.
Spirit-lamps are those used with cot ton wicks and alcohol, and though the flame is slight the heat is intense, and its action on metals, &c., effective. As the alcohol approximates pure hydrogen, and has little carbon, it fixes much oxy gen, which confers the heat, and there being no carbon, there is little light and no smoke ; so that it forms no carbonic acid, and the gases are concentrated into aqueous vapor, giving out great heat for all chemical purposes. The heat is great est just within the summit. Sometimes four burners are used, and one and two chimneys above each other, to place over the whole, allowing air to enter at the bottom, and in this case the highest de grees of heat are attained at an easy ex pense. The spirits or alcohol should have 0.85 spec. gray., i. e., six pints should weigh five pints of water.
Spirit-lamps produce little flame but intense heat, since white light and flame result from the joint action of hydro gen and carbon. They are to be trimmed with a twisted cotton wick and alcohol, and they have the advantage of intense heat, without smoke or chemical combi nation with substances applied to them.
Sometimes several wicks are combined in a hollow cylinder, raised above the ta ble, and a chimney may be added, with which it becomes a powerful furnace. The alcohol should be about -84 or •85. Pyroligneous ether may be substituted for alcohol, as cheaper in some countries.
Double wick, and Argand oil-lamps with separate rack-work, are very pow erful and luminous, with free access of air.
To prevent the breaking of lamp-glasses by sudden heat, cut or scratch the base of the glass with a diamond, and after wards sudden heat may be applied with out dancer.