GALVANIZED IRON is the some what fantastic name newly given to iron tinned by a peculiar patent process, whereby it resists the rusting influence of damp air, and even moisture, much longer than ordinary tin plate. The fol lowing is the prescribed process. Clean the surface of the iron perfectly by the joint action of dilute acid and friction, plunge it into a bath of melted zinc, and stir it about till it be alloyed superficially with this metal ; then take it out, and immerse it in a bath of tin, such as is used for making tin plate. The tin forms an exterior coat of alloy. When the metal thus prepared is exposed to humidity, the zinc is said to oxydize slowly by a galvanic action, and to pro tect the iron from rusting within it, whereby the outer tinned surface remains for a long period perfectly white, in cir cumstances under which iron tinned in the usual way would have been superfi cially browned and corroded with rust. GALVANISM. (From Galvani, pro fessor of anatomy at Bologna, the disco verer of some of the phenomona eopnect ed with this form of electricity in the year 1790.) Under this term are frequently included the phenomena of Voltaic elec tricity (which see). We shall here limit it to the apparent evolution of electricity by the contact of different metals ; this is best observed by the muscular contrac tions which areproduced in the leg of a frog recently killed, when two different metals, such as zinc and silver, tin and gold, &c., one of which touches the cru ral nerve, and the other the muscles, are brought into contact. Every time the metals touch each other the limb be come powerfully convulsed ; and if the experiment be made with a dead rabbit, so that one of the metals be in contact with the brain, and the other with the muscles of the extremities, the whole body of the animal is strangely agitated.
Similar experiments have been made up on the bodies of criminals shortly after execution. These results, which have till lately been considered to depend up on the effects of electricity excited by the contact of the metals upon the nervous and muscular systems, led Volta to hia celebrated researches, which terminated in the discovery of the Voltaic battery. Nearly all the cases, however, of the ap parent production of electricity by contact have been satisfactorily traced by Faraday to chemical action. (SeeVOLTAIC BATTERY.) GALVANOMETER. An instrument for ascertaining the presence of a current of electricity, especially Galvanic or Vol taic electricity, by the deviation which it occasions in the magnetic needle. The simplest form of a galvanometer is a netic needle poised upon a point, and surrounded by one or more coils of per wire covered with silk, the ends a and b being either left free, or terminating in two small copper cups containing mercury, for the convenience of munation with the source of electricity. When this needle is placed parallel to the coil, and in the magnetic meridian (as presented in the margin), it immediately deviates when the electric current passes through the coil ; and the deviation is ther to the east or west, according to the direction of the current. (See ELEcrno