GAL 



GAN 



oak; the buds undergo a morbid action, 

 enlarge into a globular form, consti- 

 tuting a nidus for the larva of the insects, 

 and eventually become the galls of com- 

 merce. 



GALLI'NiE [gallus, a cock). Galli- 

 naceous birds, so named from their affi- 

 nity to the common cock, and consti- 

 tuting the fifth order of the class Aves. 



GALL-INSECTS. Coccidee. A family 

 of homopterous insects, the females of 

 which are apterous, and assume, at the 

 period of ovi-position, a globular form 

 analogous to the galls produced by the 

 GallicolcB. 



GALLS. Protuberances found on cer- 

 tain plants, occasioned by the puncture 

 of an insect. They differ in consistency, 

 from the hard nut-gall, to the soft and 

 spongy berry or apple-gall. The Aleppo 

 galls are extensively used in dyeing and 

 in the manufacture of ink. See Gal- 

 licolcB. 



GALT. A provincial name applied in 

 the east of England to a series of beds of 

 chalk marl, the geological position of 

 which is between the upper and the 

 lower Greensand. 



GALVANISM. A form of electricity 

 named after Galvani, and usually elicited 

 by the mutual action of various metals 

 and chemical agents upon each other. 

 The additional discoveries of Volta led 

 to the term Voltaism, or Voltaic Electri- 

 city ; and its effects on the muscles of 

 animals newly killed, suggested the term 

 Animal Electricity. 



1. Galvanic Circle. If, between two 

 plates of different metals, a fluid be inter- 

 posed capable of exciting a chemical effect 

 on the one plate, while it has little or no 

 influence on the other ; and if a com- 

 munication be then formed between the 

 plates at some point, by means of a wire 

 or other conducting substance, a con- 

 tinued current of electricity will pass 

 along the conductor from one plate to the 

 other, so long as the chemical action is 

 excited. This constitutes a simple gal- 

 vanic circle. 



2. Galvanic Pile. This arrangement 

 consists of a number of pairs of plates, 

 similar to those above described, placed 

 alternately with an acting fluid inter- 

 vening between each pair, and having 

 the two ends of the series connected by a 

 wire. The effect is thus m.ultiplied by 

 each pair of plates. The end of the pile 

 which gives out the electric fluid is called 

 the positive pole, while the other end in 

 which the wire terminates, and which 



147 



receives the electric matter, is called the 

 negative pole of the pile. 



3. Galvanic Battery, or Trough. An 

 apparatus for accumulating galvanism, 

 consisting of plates of zinc and copper 

 fastened together, and cemented into a 

 wooden or earthenware trough so as to 

 form a number of cells ; the trough is 

 then filled with diluted acid. 



4. Galvano-meter {uerpov, a measure). 

 An instrument which indicates the 

 feeblest polarization of the magnetic 

 needle, or slightest current in the con- 

 necting wire of a voltaic circle. 



5. Galvano-scope {(TKoireco, to examine). 

 An instrument by means of which the 

 existence and direction of an electric 

 current may be detected. A magnetic 

 needle is a galvanoscope. 



6. Galvano-magnetic induction machine. 

 A machine principally used for medical 

 purposes, and consisting of an induction 

 spiral connected with a hydro-electric 

 battery, which is fitted up with an appa- 

 ratus for establishing and breaking con- 

 tact with great rapidity. 



GA'MMUT. An old term in Music, 

 now applied to the diatonic scale, and 

 also called the harmonical hand, in con- 

 sequence of Guido having arranged the 

 musical notes upon the figure of a hand. 

 The term gammut, or gamm'ut, was de- 

 rived from the Greek letter yd/jL/jia, ap- 

 plied by Guido to a note which he added 

 below the " supernumerary " note, with 

 the addition of ut, which is the same as 

 do in the syllabic scale. 



GAMOPE'TALOUS (la/ueuj, to marry, 

 ireraXov, a petal). A term applied, in 

 Botany, to a corolla consisting of cohering 

 petals, in order to avoid the inaccuracy 

 of the word mono-petalous. 



Gamo-sepalons. A corresponding term, 

 denoting a calyx formed of cohering se- 

 pals, and therefore preferable to the more 

 common term mono-sepalous. 



GA'NGLIONE'URA (7^77X^0^, a 

 nerve-knot, vevpov, a nerve). A term 

 applied by Rudolphi to the Articulate 

 and Molluscous divisions of the Animal 

 Kingdom, which are characterized by a 

 ganglionic disposition of the nervous 

 system. In the former class, the ganglia 

 are arranged symmetrically along the 

 middle line of the body, and communi- 

 cate by a double chord ; these are termed 

 homogangliata. In the latter class, the 

 ganglia are dispersed in an unsymmetri- 

 cal manner, apart from one another and 

 from the middle plane ; these are called 

 heterggangliata. 



H2 



