418 POL three rows, the one higher up than the other, with appa rently but very slight indications of the fact that the figures of the upper rows were to be understood as standing at a more remote distance. The several rows would run con tinuously like sculptured friezes, and indeed this manner of composition is best illustrated by the friezes at Vienna recently found at Gjblbaxhi in Lycia, some of which present subjects and motives identical with those treated by Poly- gnotus. POLYHISTOR, CORNELIUS ALEXANDER, a Milesian and disciple of Crates, 1 who through the fortune of war became the slave and afterwards the freedman of Cornelius Lentulus (Suidas). He received the Roman citizenship from Sulla (Servius on ^n. x. 388), and wrote an enormous number of books on historical and geographical subjects, of which more than a hundred and fifty fragments have been collected (Miiller, Fr. Hist. Gr., iii. 206 #7.). His account of the doctrines of Pythagoras has been largely drawn from by Diogenes Laertius, but the most interesting of the fragments refer to the history of the Jews, for which Alexander drew on historical and poetical works of Jewish and Samaritan Hellenists. What has been pre served on this subject, mainly by Eusebius in the Pree- paratio Evangdica, is sufficient to throw a good deal of light, not particularly favourable, on the intellectual activity of the Hellenists of the 2d century B.C. See J. Freudenthal, Hellenistische Stud ten, i. ii. (Breslau, 1875), in which the subject of the sources of Tolyhistor is fully dis cussed. Plate III. POLYNESIA. In the last edition of the Encyclopedia Britannica Polynesia was used to denote all the intertropical islands of the Pacific Ocean eastward of the Philippine Islands to the north and the New Hebrides to the south of the equator. The New Hebrides and other islands west of that group were included under the term Australasia. Of late years these islands (sometimes also including Fiji) have been known as Melanesia, while the western islands of the North Pacific have been known as Micronesia. Thus Polynesia has been restricted to the central and eastern islands inhabited by the brown or Sawaiori race, becoming an ethnographic rather than a geographical term. Articles dealing with the western islands north and south of the equator will be found under MICRONESIA and MELANESIA. The present article is intended to give a comprehensive view of all the islands of the Pacific, their physical characteristics, natural productions, and the races of men found upon them. The name Polynesia is therefore here employed in a wide signification and solely as a geographical term. The western boundary of this region runs from the great barrier reef of Australia eastward of New Guinea and the Philippine Islands. All the inter- tropical islands of the Pacific eastward of this imaginary line are included, and also a few others which extend outside the tropic of Capricorn to nearly 30 S. lat. Any other divisions for geographical purposes, except those of groups of islands, appear to be unnatural and uncalled for. For ethnographical purposes special terms are used for the three different classes of people found in this wide area. If we exclude NEW CALEDONIA (q.v. which is of older formation than the rest, all the islands of Polynesia are either of volcanic or of coral formation. Some are purely coral, either in the shape of low atolls or of elevated plateaus. In a few atolls there are remnants of earlier volcanic rocks ; and most of the volcanic islands are more or less fringed with coral reefs. But, notwithstanding From the scholiast on Apoll. fth., i. 925, it would appear that olybistor was a Milesian only by education, for here the Carian Cher sonese is named as his birthplace. The dates seem to show that lie was not a personal disciple of Crates. this mixture, the islands must be divided broadly into 1 those which are volcanic and those which are of coral 1 formation. The coral islands must again be subdivided 1 into (1) atolls, or low islands which usually have a lagoon within them, and (2) elevated table-lands. The volcanic islands, with the exception of the Hawaiian archipelago, are all south of the equator. In Plate III. the great volcanic ridge is indicated by two lines which, ! commencing in 150 E., run in a south-easterly direction to about 140 W. long. With the exception of two curves, one in the lower line south of the New Hebrides, and one in the upper line at its eastern extremity, these are parallel, and are 10 apart. Within these two lines lie all 1 the volcanic islands of Polynesia, except two isolated j groups, viz., the Marquesas and Hawaiian Islands. On this ridge there are no atolls. The upper boundary line sharply divides the volcanic ridge from the atoll valley. This valley is indicated by a third line running for more than 50 of longitude parallel with the other two, at 20 distance from that bounding the northern extremity of the volcanic ridge. Eastward of 155 W. long, this line bends towards the south to exclude the isolated volcanic centre of the Marquesas Islands ; then, curving around the Tuamotu archipelago, it joins the central line. Within the area thus enclosed lie all the atolls or low coral lagoon islands of Polynesia, and there are no volcanic islands within this region except in three or four instances, where are found the remnants of former islands which have sunk, but have not been quite submerged. This is the region of subsidence stretching across fully 100 of longitude, and covering generally about 20 of latitude. Within the volcanic region there are a few coral islands, but these are all more or less elevated. Since their formation they have participated in the upward movement of the ridge on which they are situated. They are indi cated on the map by dotted lines. Two of the groups are within the lines marking the volcanic ridge ; and one, the Loyalty group, lies close to the lower line. The Volcanic Islands. Most of the volcanic islands of Polynesia are high in proportion to their si/e. The taper ing peaks, or truncated cones, which form their backbone present a picturesque appearance to the voyager as he approaches them. In some there are precipitous spurs jutting into the sea, while in others the land slopes gently from the central peak to the shore. Where there are these gentle slopes, and wherever there is any low land near the shore, there also will be found a coral reef fring ing the coast at a smaller or greater distance, according to the steepness of the land under the water. Where the trend downwards is very gradual, the edge of the reef will sometimes be one, two, or even three miles to sea ward. It has been thought that the absence of extensive reefs in some islands of the New Hebrides is due to " sub terranean heat." But the steepness of the slope of the islands under water is doubtless the reason why the reefs are small. As the reef-building coral polypes do not live and work below a certain depth about 20 fathoms, or 120 feet we easily see that the distance of the outer edge of the reef must be according to the slope of the inland beneath the water. Opposite to the larger valleys, where there is a stream flowing out to sea, there is usually found a break in the reef. This is doubtless caused either by the fresh water, or by the sediment which it contains, injuring the coral polypes and preventing them from effectively carrying on their work in these spots. The conviction of the present writer is that it is the sediment contained in the water especially during heavy rains and consequent freshets which prevents the growth of the coral, rather than the mere action of fresh water upon
the p:>lypes. Where there are streams of considerable-