Galvanism, as a source of light and heat.
Batteries of great dimensions, such as contain from 5,u00 to 10,000 square inches each, of zinc and copper surface, are capable of furnishing abundance of sensible heat and much light. If the con nection between the two ends of the bat tery be made by a very small wire, such as the fine watch spring wire, the wire becomes red-hot for a considerable length, and if the power of the battery be great, itibecomes white-hot, and ultimately fus ed.
Let the end of the wires of the battery be each provided with a pair of tweezers, one pair of which being insulated from the hand by coveringthe surface with dry cloth ; place between each pair of tweez ers a small bit of charcoal, made in a close vessel, from box-wood, or lignum vita. The moment the contact is formed be tween the bits of charcoal, a vivid light is produced, much more brilliant than that occasioned by burning in oxygen. If the contact be frequently severed by a sort of tremulous motion, the light may be kept up for some time.
The foils and small wires of metals are deflagrated by placing them in the icur rent. Let one of the conducting wires be brought in contact with an iron dish, fill ed with mercury. Let the foil or small wires be attached to the other conducting wire, and be brought in contact with the surface of the mercury, which, constantly presenting a clear surface, is very conve nient in these experiments. A very bril
liant effect may also be produced, by pre senting the foils to the surface of a sheet of tinsel.
In flaming oils, alcohol, &c. by gal vanism, some thin metallic substance, or a small piece of charcoal, should be co vered with the substance to be inflamed. The moment the contact is made, as in deflagrating the metal, the oil takes fire.
The galvanic spark, with great facility, fires a mixture of oxygen and hydrogen gases.
A very brilliant discovery has lately been made by Mr. Davy, Professor at the Royal Institution, and confirmed by others, which consists in the deconvo= sition of the two fixed alkalies. It is per formed by placing a bit of the alkali in the solid state, and a little moistened,up on a plate of platina, connected with one end of the battery, and bringing into con tact with it another piece of platina, from the other end of the battery. A por tion of black matter is soon formed, in which is found imbedded small me tallic globules ; which substance is found to be the base of the alkali, and has been deprived of its oxygen by the gal vanic agency. These globules are so in flammable, as to decompose water, with a brilliant flash and slight explosion. See ALKALI.
This discovery will be of great import ance to chemistry, and will probably soon make a serious change in its arrangement and nomenclature.