galti (galt)

[Also gault, golt; galt2 (gâlt), n. [ Gree e growene as a galte , fulle grylych he lukez! Morte Arthure (E. E. T. S.), l. 1101. IMG:content-2056.png:[blocks in formation] galvanocautery (galva-nō-kate-ri), n.; pl. galvanocauteries (-riz). [ galvanic + cautery .] In surg ., a cautery in which a galvanic current is used to heat the cauterizing part of the ap- paratus. galvanoglyph (galva-nō-glif), n. [ galvanic + Gr. γλύφειν , engrave.] A picture produced by galvanoglyphy. galvanoglyphy (gal-va-nog'li-fi), n. [As gal- vanoglyph + -y.] A method of producing an electroplate which may be used in a printing- pre . The e ential features of the proce are the use of a zinc plate covered with a ground, and etched as a matrix for an electroplate, the reverse plate thus obtained being used in printing. The picture obtained by this method is called a galvanoglyph . galvanograph (gal'va-nō-graf), n. [ galvan- ic + Gr. γράφειν , write.] 1. A plate formed by the galvanographic proce .-2. An impres- sion taken from such a plate. galvanographic (gal"va-nō-graf'ik), a . [ gal- vanography + -ic.] Pertaining to galvanog- raphy. vanograph + -y.] A proce for producing plates which will give impre ions after the manner of a plate used in copperplate engrav- ing. The drawing is made on a silvered plate in viscid paints, in such a way as to leave the dark parts slightly raised. An electrotype is taken from this, which may be used as an engraved plate, the dark lines now being de- pre ed precisely as in a copperplate. An impre ion from such a plate is called a galvanograph . gal van ologist (gal-va-nol'ō-jist), n. [ galva- nology + -ist .] One who describes the phenom- ena of galvanism. gal van ology (gal-va-nol'ō-ji), n. [ galvanic + Gr. -λογία, λέγειν , speak: see -ology .] description of the phenomena of galvanism. galvanomagnetic (gal"va-nō-mag-net'ik), a. Same as electromagnetic . galvanometer (gal-va-nom'e-ter), n. [ galvan- ic + Gr. μέτρον, & measure.] An instrument for detecting the existence and determining the strength and direction of an electric current. In all galvanometers the principle of action is the same. It depends upon the force which Oersted discovered to be exerted between a magnetic needle and a wire carry- ing a current-a force which tends to set the needle at right angles to the direction of the current, and whose intensity, other things remaining the same, depends di- rectly upon the strength of the current. The term galvanometer is applied to an instrument for measuring the strength of electric currents by means of the deflection of a magnetic needle round which the cur- rent is caused to flow through a coil of wire. Aperiodic galvanometer, a dead-beat or thoroughly damped galvanometer. - Astatic galvanometer, an in- strument which consists of a pair of similar needles mag- netized, with their poles turned opposite ways, and stiffly connected at their centers, so that both will swing together. The one tends always to turn in a direction opposite to the other under the earth's magnetic attraction, so that if the needles were perfectly alike they would form a perfectly astatic pair, or a pair that would not tend to a ume any particular direction from the magnetic influence of the earth. One of the needles, ab , is nearly in the center of the coil, CDEF, through which the current pa es; the other, a'b ' , just above the coil. When a current traverses the coil in the direction of the arrows, the action of all parts of the current upon the low- IMG:content-2057.jpg:[ocr errors] er needle tends to urge the austral pole a toward the back of the figure and the boreal pole b to the E IMG:content-2058.jpg:[merged small][ocr errors] of the current is as the sine of the angular deviation. Any sensitive galvanometer in which the needle is di- rected by the earth's magnetism can be used as a sine galvanometer , provided the frame on which the coils are wound is capable of being turned round a central axis. S. P. Thompson , Elect. and Mag., p. 167. Tangent galvanometer, a very short magnetic needle delicately suspended so as to turn in a horizontal plane. The point about which it turns is at the center of a ver- tical coil of copper wire through which the current is pa ed. The diameter of the coil is at least ten or twelve times the length of the needle. The needle is therefore usually not more than half an inch long; and, for conve- nience of reading its deflections, long light pointers of aluminium or of gla fiber are cemented to its ends. In use the instrument is placed so that the vertical coil of copper wire is in the plane of the magnetic meridian. The current is then sent through the coil, and the angle by which the needle is deflected is read off. The strength of the current then is proportional to the tangent of the an- gle of deflection, whence the name of the instrument. - Thomson's mirror galvanometer, the most sensitive galvanometer yet invented. Its needle, which is very short, is rigidly attached to a small, light, concave mirror, and suspended in the center of a vertical coil of very small diameter by a silk fiber. A movable magnet is provided for bringing the needle into the plane of the coil when the latter does not coincide with the magnetic meridian, and also for rendering the needle more or le astatic. Needle, mirror, and magnet weigh only about 14 grains. At a distance of two or three feet from the mirror is a solid wooden stand, with a graduated scale, facing the mirroг. In the stand, just under the center of the scale, a hole is cut, and a fine wire is stretched upright acro it. A strong lamp stands behind the opening, so that its light will fall on the mirror and be reflected back on the scale. An image of the wire will thus be constantly thrown on the scale, and the slightest motion of the needle and its mir- ror will produce a much greater motion of this image. As the current flows the one way or the other the index will move to one side or the other. This galvanometer was devised for use in connection with the Atlantic sub- marine cables. It was long the only instrument with which signals could be read through long submarine lines; and it is still employed to a great extent, though now super- seded by the siphon-recorder of the same inventor. IMG:content-2059.png:[graphic] needle, a'b ' , is affected principally by the current CD of the coil, which urges the austral pole a ' to the front of the figure and the boreal pole b to the back. Both needles are thus urged to rotate in the same direction by the cur The Century Dictionary and Cyclopedia: Dictionary galvanoscopic galvanoscopic (galva-no-skop'ik), a. [ vanoscope.