Page:Encyclopædia Britannica, Ninth Edition, v. 10.djvu/53

Rh somewhat dangerous. In 1873 there entered 350 vessels with a total tonnage of 66,652 tons, 281 being Italian and 29 British. The principal exports are oil (of which 9628 tons were shipped in 1875), wine, oats, and cotton seed ; and the imports, ﬁsh from Norway, manufactured goods from France, petroleum from the United States, staves from Austria, and wheat and barley from Greece and Turkey. The population of the town in 1871 was 7578, and of the commune 9951. Gallipoli preserves the name and almost certainly occupies the site of the ancient Callipolis, the “Beautiful City,” founded, according to Dionysius, by a Spartan named Leucippus and a number of the citizens of Tarentum.  GALLIUM, so called in honour of France (Gallia), symbol Ga, atomic weight 69'9, a metal discovered, August 27, 1875, by M. Lecoq de Boisbaudran, in the spectroscopic examination of zinc—blende from I’ierreﬁtte in the valley of Argeles, Hautes 1’ rrénées, and since found to exist in blende from several other localities, notably in that of the mines of Istiilricli and Apfel at Bensberg, on the Rhine, which contains nearly 16 milligrammes per kilogramme. Its density and approximate atomic weight, and other of its characters, were predicted by Mendeljeff, in accordance with his law that the properties of the elementary bodies, as also the constitution and properties of their combinations, are periodic functions of their atomic weights (see article, ). Gallium may be prepared by a process the chief features of which are the treatment of the ore, which contains the metal in only very minute quantity, with zinc; the removal, from a hydrochloric acid solution of the gelatinous precipitate thereby produeezl, of various foreign metals by means of hydrogen sulphide ; the fractionation of the residual liquid with sodium carbonate, gallium being thrown down before zinc by that reager.t_: the formation of a sulphate from the re- sultant precipitate ; and, lastly, the electrolysis of a potash solution of the puriﬁed oxide obtained therefrom, the metal appearing on the negative platinum electrode. Solid gallium is greyish-white, of octahedral crystallization, and remarkably hard and resistant even at a temperature little below its melting point, and is but slightly malleable and ﬂexible, though thin plates of it will bear bending several times without breaking. It melts when held in the ﬁngers, its point of fusion being 30"'15 C. (86°'27 Fahr.). The liquid metal is of a silvery white colour, and adheres to glass, forming a mirror resembling that of mercury. It exliibits in a remarkable degree the phenomenon of super- fusion, but when some degrees below its melting point crystallizes immediately if a small fragment of the solid metal attached to a platinum wire be inserted into it. At 2l°'5 C. (76°'1 F ahr.) the speciﬁc gravity of the solid metal is 5956, and of the liquid 6069; the speciﬁc heat of the former between 12° and 23° C. is 0079, giving atomie heat 5'52, and that of the latter between 119° and 106° C‘. is 00802 (Berthelot, Compt. Renal, lxxxvi. 786-7). At a red heat in air gallium is not perceptibly volatilized. It is little affected by cold nitric acid, but dissolves readily in hydrochloric acid ; with potash solution it liberates hydrogen. It furnishes a deliquescent and very soluble chloride, GaCl3 or Ga__,Cl,,, a corresponding bromide and iodide, and an an11nonio—gallic alum. Its oxide is more soluble in ammonia than is alumina. Iu basicity it holds a place intermediate between aluminium and indium. It is precipitated by alkaline carbonates and barium carbonate, but not by hydrogen sulphide and ammonium sulphide in the absence of zinc. Gallium affords two brilliant lines in the violet part of the spectrum.

1em  GALLOWAY, (1796–1851), a Scottish mathematician, was born at Symington, in the upper ward of Lanarkshire, 26th February 1796. After receiving such education as the schools of his own and adjoining parishes could give, he entered in 1812 the university of Edinburgh, where he distinguished himself specially in mathematics. In 1823 he was appointed one of the teachers of mathe- matics at the military college of Sandhurst, and on the death of Sir John Leslie in 1832 he was an unsuccessful candidate for the vacant chair of natural philosophy in Edinburgh. In the following year he was appointed actuary to the Amicable Life Assurance Office, the oldest institution of that kind in London, and in this situation he remained till his death, November 1, 1851. Galloway was a voluminous though, for the most part, an anonymous writer, and took a leading part in the proceedings of the principal scientiﬁc societies of London. He contributed largely to the seventh edition of the Encyclopædia Britannica, and also wrote several scientiﬁc papers for the Ecliizbzcrgh and Foreign Quarterly; Reviews. His Encyclopædia article “Probability” was published separately.  GALLS. In animals galls occur mostly on or under the skin of living mammals and birds, and are produced by Acaridea, and by dipterous insects of the genus dish-u.s-. Signor Moriggia has described and ﬁgured a horny excres- cence, nearly 8 inches in length, from the back of the human hand, which was caused by Acar-us clomeslicus. What are commonly known as galls are vegetable deformities or excrescences, due to parenchymatous hypertrophy, and, according to the deﬁnition of Lacaze-Duthiers, comprise “ all abnormal vegetable productions developed on plants by the action of animals, more particularly by insects, what ever may be their form, bulk, or situation.” For the larvae of their makers the galls provide shelter and sustenance. The exciting cause of the hypertrophy, in the case of the typical galls, appears to be a minute quantity of some irritating ﬂuid, or virus, secreted by the female insect, and deposited with her egg in the puncture made by her ovi- positor in the cortical or foliaceous parts of plants. This virus causes the rapid enlargement and subdivision of the cells affected by it, so as to form the tissues of the gall. Oval or larval irritation also, without doubt, plays an im- portant part in the formation of many galls. Though, as Lacaze-Duthiers remarks, a certain relation is necessary between the “stimulus ” and the “supporter of the stimulus,” as evidenced by the limitation in the majority of cases of each species of gall-insect to some one vegetable structure, still it must be the quality of the irritant of the tissues, rather than the speciﬁc peculiarities or the part of the plant aff'ected, that principally determines the nature of the gall. Thus the characteristics of the currant-gall of Spatkegaster baccarum, L., which occurs alike on the leaves and on the ﬂower-stalks of the oak, are obviously due to the act of oviposition, and not to the functions of the parts producing it; the bright red galls of the saw-ﬂy Nematus gallicola are found on four different species of willow, Salix fra_qilis, S. alba, S. caprea, and S. cinerea, and the galls of a Cynipid, Bior/z-iza aptera, usually developed on the rootlets of the oak, have been procured also from the deodar. Often the gall bears no visible resemblance to the struc- tures out of which it is developed; eommonly, however, outside the larval chamber, or gall proper, and giving to the gall its distinctive form, are to be detected certain more or less modiﬁed special organs of the plant. The gall of C'ecidom_2/ia slrobilina, formed from willow-buds, is mainly a rosette of leaves the stalks of which have had their growth arrested. The small, smooth, seed—shaped gall of the