When the mixture of the two gases is to be em ployed in Newman's blow-pipe, the chest is first ex hausted of air, and then the gaseous mixture in a bladder, screwed on at N, is to be forced into the chest by the condensing syringe. The proportions of the two gases, which Dr Clarke found to produce the greatest heat, are, two volumes of hydrogen and one of oxygen gas. The intensity of the heat is much greater when the gases are pure ; the oxygen procured from manganese does not produce nearly so great a heat as that got from the hyper-oxymu riate of potass. The intensity of the heat may be regulated, by allowing the gas to issue in a more or less copious stream, which is done by turning the stop-cock. The heat, Dr Clarke thinks, is greater than that produced by the largest galvanic batteries. Most substances hitherto tried. are fused by it, so that it is difficult to find supports for holding the subject of experiment to the flame. The supports employed by Dr Clarke were, charcoal, platina, a piece of tobacco•pipe, black lead. Lime, strontian, and alumine, were fused. The metal of strontian was got, and retained its lustre for some hours. The alka lies were fused and volatilized almost the instant they came in contact with the flame. Rock-crystal fused into a transparent glass full of bubbles. Quartz gave the same result, Opal fused into a pearly white enamel. Flint fused rapidly into-a white frothy enamel. Blue sapphire melted into greenish glass balloons, ramified singularly. Foliated talc fused into a greenish glass. Peruvian emerald melted into a transparent and colourless glass, without bub bles. Lapis lazuli fused into a transparent glass
with a slight tinge of green. Pure foliated native magnesia, from America, is the most difficult of fusion ; it is, however, at last reduced to a white opaque enamel. Agalmatolite of China fuses into a limpid colourless glass. Iceland spar is next in difficulty of fusion to the native magnesia ; it does at last melt into a limpid glass,. and, during the pro cess, gives an amethyst-coloured flame as strontian does; the fusion of pure lime and of all its com pounds, is attended with a flame of the same colour. Diamondfirst became opaque, and then was gradually volatilized. Gold fused along with borax, on a piece of tobacco-pipe, was nearly all volatilized. Platina wire, nth of an inch diameter, melted the instant it was brought into contact with the flame of the gas; the melted platina ran down in drops, and the wire burnt as iron wire does in oxygen gas. Brass wire burnt with a green flame, differing from the green flame that salts of copper give. Copper wire melted rapidly without burning. Iron wire burnt with bril liant scintillation. Plumbago melted into a bead which was attractable by the magnet. Blend or native sulfuret of zinc melted, and metallic zinc ap peared in the centre of the melted mass. Metalloid oxide of manganese, crystallized in prisms, was re duced to a metallic state.—See Dr Clarke's Account ?this Experiments, in the Journal of Science, edited at the Royal Institution, October 1816. (v-)