Page:Encyclopædia Britannica, Ninth Edition, v. 13.djvu/215

 I O N I O N are arranged in the following table, where the numbers in the column headed indicate the ratio between the ob served density and the theoretical density on the air scale corresponding to the formula I 2 (879). 203 V. Meyer. Meier and Crafts. Temperature. Density. D I) Temperature. Density. I) D 253 3 -400 8-89, 8-83, 8-84, S 8.3 445 8-70, 8-78,8-75 586 8-87, 8-71, 8-71 !)!&amp;gt; 677, 682 8-06, 8-58 04, 757, 770, 765 8-05, 8-28 93 842 C-fiS. 6-80, 6-80 77 831, 878 8-04,8-11 92 10:27 5-75, 5-74 65 1039, 1059, 1030 7-18, 7-02,6-83 81 1270. 1280 fi-07,5 57 fi6 1570 5-67, 5-60,5-71, 5-81 85 1390 5-23, 5-31 GO Meier and Crafts were of opinion that the highest tempera ture they employed was probably as high as that estimated by V. Meyer at 1570, and the latter chemist subsequently acknowledged the justice of their criticism of his deter minations of temperature, which were conducted by a calorimetric method, whereas Meier and Crafts employed an air thermometer. V. Meyer has since extended his observations to a still higher temperature, and has obtained the values 4 53, 4-55, 4 57, which are not far removed from the theoretical value 4 39, corresponding to the formula I for the iodine molecule (op. cit., 1880, p. 1010). An important series of observations by Meier and Crafts (Comptes Rendus, xcii. 39) on the density of iodine at various temperatures under various pressures show that at temperature below 700 and pressures below atmo spheric pressure the density is constant, and corresponds to the formula I 2, and that the density diminishes more rapidly with rise of temperature. From the earlier results obtained by Meier and Crafts, A. Naumann has calculated the rate of dissociation of iodine, on the assumption that the decomposition is expressed by the equation I 2 = I + I, and has shown that it is in accord ance with the general law of dissociation deduced from the dynamical theory of gases. He points out as especially remarkable that dissociation probably extends over 1200, since it is only half completed at a temperature of about 1270, and commences at least 600 lower. The observations of Meier and Crafts indicate that the density of iodine begins to be abnormal at a temperature between 600 and 700. The dissociation of bromine appa rently does not commence at so low a temperature, and at a temperature at which the ratio of the observed to the theoretical density is -66 for iodine, it is 8 for bromine. Chlorine is much less readily dissociated than bromine. These results are in accordance with the general chemical behaviour of the halogens. It has yet to be proved, however, that the dissociation is of the character indicated above, and that the molecules of the halogens do not undergo a less simple decomposition such as is contem plated in Sir Benjamin Brodie s calculus of chemical operations. (H. E. A.) ION&quot;, of Chios, one of the five Greek tragic poets of the canon, was born in Chios, probably in the 74th Olympiad, 485-480 B.C. Although he seems to have lived much in his native island, where he met Sophocles in 441 B.C., he paid frequent visits to Athens, making the acquaintance of ^Eschylus, and becoming a warm admirer of Cimon and a severe critic of the rival statesman Pericles. His first tragedy dates from the 82d Ol., between 452 and 449 B.C. ; and he is mentioned as third to Euripides and lophon in the tragic contest of 429 B.C. In a subsequent year he gained both the tragic and dithyrambic prizes, and in honour of his victory gave a jar of Chian wine to every Athenian citizen, a gift which would imply an ample fortune. From a passage in the Peace of Aristophanes (830 seq.), which was produced in 421 B.C., it is gene rally concluded that Ion died before that year. The names and a few fragments of eleven of Ion s plays remain ; the latter give him a place only inferior to the three great tragic _masters of Greece. He is credited by the scholiast on Aristophanes (loc. cit.) with having composed comedies, dithyrambs, epigrams, pa3ans, hymns, scholia, encomia, and Regies ; and he is the reputed author of a philosophical treatise on the mystic number three. His historical or biographical works were five in number, and included an account of the antiquities of Chios. See Mate s Language and Literature of Antient Greece, iv.; Ala- haffys History of Classical Greek Literature, i., 1880 ; Welcker s Gmechischen Tragddicn, iii. ; and Kayser s Ilistoria Tramcorum Grwcorum. IONA, or ICOLMKILL, a small island of the Hebrides, on the west coast of Scotland, in the county of Argyll, is situated about 8 miles south of Staffa and 1 miles west of the south-western promontory of Mull, from which it is separated by the shallow Sound of lona. Its length is about 3J- and its breadth 1 miles. The total area is about 2000 imperial acres, of which about 600 are under cul tivation. Along the north-western shore patches of green pasture alternate with small irregular rocky elevations, cul minating in the north of the island in Dunii, which has an elevation of about 330 feet. From the base of Dunii to the shore there is a stretch of low land consisting of shelly sand covered partly with grass, but towards the east ex hibiting a surface of unbroken and dazzling whiteness. The southern part of the island consists of a combination of rocky elevations and grassy ravines, the rocks in the south-west corner presenting a bold and precipitous front to the sea. Geologically lona is composed of Laurentian gneiss of great variety of character and very contorted stratification. Its deficiency in natural features of special interest is compensated for by the striking and various views obtained of the surrounding archipelago of islands, including the neighbouring Mull and Jura, and the distant mountains of Skye. Fronting the sound is the small village of lona or Buile Mor, consisting of about fifty cottages. There are two churches (Established and Free) and a school. Oats, barley, and potatoes are grown on the island, and it affords sustenance for about 300 cattle, 600 sheep, 20 horses, and 60 pigs ; but the inhabitants are dependent for support as much on fishing as on agriculture. Population in 1861, 264; in 1871, 236; in 1881, 243. The relics of antiquity still remaining consist of part of the cathedral church of St Mary, the nunnery, some small chapels, a building called the bishop s house, and a number of ancient tombs or crosses. The cathedral, dating from the 13th century, is built in the usual form of a cross, and consists of nave, transept, and choir, with a sacristy on the north side and chapels on the south. A great portion of the walls and the central tower, about 75 feet in height, are still standing. It contains a number of old tombs. To the north are the remains of the conventual buildings which from a Norman arcade still standing appear to have been of an older date than the cathedral. The chapel of St Oran or Odhrain situated in the cemetery, on the south side of the monastery, dates probably from the llth century, and its western doorway presents a Norman arch with the beak-head ornament. The cemetery, called in Gaelic Eeilig Oiran, the burial-place of kings, and said to contain the remains of forty-eight Scottish, four Irish, and eight Danish or Norwegian monarchs, possesses a largo number of monumental stones. The remains of the nunnery exhibit traces of Norman architecture. Of the numerous crosses erected in the island the finest are Maclean s cross and St Martin s cross, which are still almost entire. Both