Page:The New International Encyclopædia 1st ed. v. 10.djvu/825

* IONIAN SEA. 735 IONIZATION. and that of Otranto, and it forms a number of deep inlets on the coast of Greece, the chief of whieli is the Gulf of Corinth. IONIC DIALECT. See Greek La.nguage. IONIC ORDEK. One of the three orders of Greek architecture, so called because it was first and principally used in the Greek cities of Asia Minor. It is not a development of the Doric order, as was formerly supposed, but was co- existent with it. It is of a more elaborate char- acter than the Doric. The base of the column consists of a plain, square plinth, two trochili, with moldinus, and a torus fluted horizontally. The shaft is more slender than the Doric, the height var3'ing from eight to ten times the lower diameter of the shaft, and the entasis is slight. It contains twenty-four semicircular flutes, deeper than in the Doric shaft. The capital is composed of an ovolo, enriched with egg-and-dart molding, and of a spiral roll, resembling a cushion, the ends of which are called volutes. Above this roll is a very low abacus, connecting the capital with the architrave. The latter usually consists of three bands, crowned by a cor- nice enriched rith mold- ings. The frieze is an un- interrupted surface, often decorated with sculpture in relief, and the cornice has two divisions : a pro- jecting block, divided into cogs and dentils, above which still farther projects the corona, capped with moldings. In the buildings of At- tica a special variety of the Ionic order, called the Attic-Ionic, was used. In this the base consists of two tori and only one trochilus — a debasement of which form was adopted by Roman architects, and is now generally used. The Attic cornice is without dentils. A very beautiful but unique example of the Attic - Ionic order, widely imitated at present, is that of the Erechtheum (q.v.) at Athens. In this the upper part or necking of the shaft is enriched by an exquisite band of floral ornaments, and the channel of the spiral roll of the capital is double, while between the roll and the ovolo there is a torus of braided pattern. The Ionic order was generally used in the Greek cities of Asia Minor for peripteral temples (as at Ephesus, Prienc. etc. ), but in Greece proper its use was confined to small prostyle and amphi- prostyle buildings (Temple of Wingless Victorv-, Athens), for circular buildings (Philippeum at Olympia). and in the interior of Doric temples (Bassse, Tegea). There was. however, a general increasing tendency to use it in Greek architec- ture. The principal change in its form was in that portion of the spiral roll which connects the volutes. In the best period this was curi-ed. but later it became a straight line — a degradation IONIC OUUKft. which was adopted by Roman architects, and is still generally used. See CoLUMX, and the special articles on the technical terms mentioned. IONIZATION ( from ion, from Gk. iuv, pres. part, of livai, iemi, to go). The modern theory of electric conduction is that an electric current consists of the motion of minute particles of matter which are charged positively and nega- tively, the motion of the oppositely charged par- ticles being in opposite directions. These charged particles are called 'ions,' and they are in no case identical with molecules; in fact, there is no evidence of a molecule as such being charged. The formation of these ions is called ionization. In metals and all solid conductors there are ions probably always present, but in what state it is not known. In a liquid ions are produced by dissolving in it some salt or acid, which 'dissociates' in the act of solution (q.v.). In ordinary gases ions are probably always present to a limited extent, although in a pure dry gas there may be none ; but in any case their number may be enormously increa.sed in many ways. If, the Rontgen or X rays (q.v.) are passed through a gas, it is ionized, as is shown by its becoming a good conductor; similarly, if uranium rays (q.vi) or rays from any radio-active substance, or ultra-violet light, or the cathode rays pass through a gas, it is ionized. If the temperature of certain gases is raised, they become con- ductors; or if a spark is passed between two balls joined to an electrical machine or induction coil, the gas on all sides becomes a conductor; if there is a 'brush discharge' ofi' points, the same is true. JIany gases when formed by elec- trolysis in liquids are found to be ionized. The whole subject of ionization is still tinder investigation ; but several facts seem to be now assured : ( 1 ) The ions are not molecules. (2) The negatively charged ions have less mass than the positively charged ones, and move more rapidly under the action of a given electric force. (3) The ionization of any one gas, however produced, gives the same result ; e.g. the ions of oxygen gas are always the same. (4) The negatively charged ions of all gases are identical. It seems probable, but not certain, that the charge carried on an ion of any substance in the gaseous state is the same as that carried on an ion of the same substance in a liquid, e.g. a hydrogen ion in hydrogen gas. and a hydrogen ion produced by dissolving sulphuric acid in water. The masses of the ions in the two cases are quite difi'erent. the gaseous one being about one-tliousandth as heavy as the other. (It may- be that in the case of the liquid-electroljrte the ion drags with it a quantity of uncharged mat- ter.) According to the latest experiments of J. J. Thomson, the mass of a negatively charged ion is of the order 10"" grams; the ratio of this mass to the charge carried is about 10"', the charge carried by each ion being about 6.5 X 10"'° electrostatic units. It requires energy to ionize a gas. and some experiments of Rutherford give as an approxi- mate value of the number of ergs necessary to ionize a gas 1.9 X 10-'° ergs per ion. Similarly in the ionization of a salt or acid by going into