possesses an alkaline reaction, and is readily decomposed by acids with liberation of selenium. It forms numerous double salts.
Numerous determinations of the atomic weight of selenium have been made. The earlier results of J. J. Berzelius from an analysis of the chloride gave values from 79.2 to 79.35. Later determinations by V. Lenher (Jour. Amer. Chem. Soc., 1898, 20, p. 595), from the analysis of silver selenite and the reduction of the double selenium ammonium bromide, give values from 79.277 to 79.367; whilst J. Meyer (Ber., 1902, 35, p. 1591) by the electrolysis of silver selenite in the presence of potassium cyanide obtained the value 79.22.
SELEUCIA (Gr. Σελεύκεια), the name of several ancient Greek cities named after Seleucus I. Nicator, founder of the Seleucid dynasty. The following are the most important.
1. Seleucia on the Tigris, at the mouth of the great royal canal (Naharmalka, mod. Radhwaniya) from the Tigris to the Euphrates, about 50 m. N. of Babylon and 15 m. S. of Bagdad. It was founded by Seleucus Nicator (see Seleucid Dynasty), ruler of Babylonia from autumn 312. Seleucus, departing from the precedent of Alexander the Great, who, after his return from India, had settled in Babylon, preferred to build a new capital of a decidedly Greek character. The new city “was founded with the object of exhausting Babylon” (Plin. vi. 122; Strabo xvi. 738); a legend says that the Chaldaean priests, when they were consulted about the right hour for the initiation of the city, tried to frustrate the design of the king by naming a wrong hour, but that by chance the work was begun in the moment predicted by the stars and the decree of fate accomplished (Appian, Syr. 58). Seleucia was peopled with Macedonians and Greeks; Syrians and Jews were admitted to the citizenship (Joseph. Ant. xviii. 9. 8). It obtained a free constitution. A great many other Greek cities were founded in Babylonia by Seleucus I. and Antiochus I., while Babylon and the other ancient cities (Sippara, Erech, Ur, Borsippa) decayed into mere villages. Here the Chaldaean priests continued to teach their astrological wisdom (we possess many astrological tablets in cuneiform writing from the time of the Seleucids and the earlier Arsacids); but Seleucia became the centre of the new Hellenistic civilization (see Hellenism). A great many Greek authors were born here (e.g. the Stoic Diogenes of Babylonia, 2nd century), though the inhabitants of Seleucia in Babylonia generally are simply called Babylonians by the Greeks. In the time of Pliny the town was said to have 600,000 inhabitants (vi. 122). Seleucia suffered from the rebellion of the satrap Molon of Media, who was put down by Antiochus III. the Great in 220 (Polyb. v. 54). Antiochus IV. Epiphanes once more restored the Seleucid supremacy in the east; but after his death (163) the decay of the empire began and was accelerated by the intrigues of the Romans. In Babylonia the governor Timarchus rebelled and was acknowledged by the Roman senate. But he was defeated and killed by Demetrius I. (c. 158), who was hailed as deliverer (Soter, “saviour”) by the inhabitants (Appian, Syr. 45. 4 f.; Trogus, Prol. 34; Diod. 31. 27a). Soon after, the great conquests of the Arsacid king Mithradates I. began; Babylonia became subject to the Parthians (c. 140). The Greek towns were very unwilling to submit to the foreign rule, and welcomed Antiochus VII. Sidetes, when in 130 he attempted to restore his empire; but his defeat by Phraates II. in 129 ended the Seleucid rule in the east. Seleucia and other towns were cruelly punished by Phraates and his prefect Himerus, who also devastated Babylon (Justin xlii. 1; Trog. Prol. 42; Diod. xxxv. 19. 21; cf. Posidonius ap. Athen. xi. 466 b). Seleucia, however, maintained her self-government and her spirit of Greek independence (Plin. vi. 122; Tac. Ann. vi. 42; cf. Joseph. Ant. xviii. 9. 8 f.), and remained the greatest commercial town of the east. The Arsacids did not dare to bring their host of barbarian soldiers and retinue into Seleucia, but fixed their residence opposite to it on the left bank of the Tigris in Ctesiphon (Strabo xvi. 743; see Ctesiphon). In all the wars with the Romans Seleucia inclined to the western deliverers; from A.D. 37 to 43 it was in open rebellion against the Parthians (Tac. Ann. xi. 8 f.). Vologaeses I. (A.D. 50-91) “founded the town Vologesocerta (near Ctesiphon) with the intention of draining the stormy Seleucia” (Plin. vi. 122). Trajan occupied Seleucia in 116. In the war of Marcus Aurelius and L. Verus against the Parthians, Seleucia was taken by Avidius Cassius in 164, and then the. Romans did what the Parthians had not dared to do: they burnt down the great Greek town with 300,000 inhabitants (Dio Cass. lxxi. 2; Zonar, xii. 2; Capitol. Vit. Veri, 8; Eutrop. 8. 10; Ammian. Marc. xxiii. 6. 24; xxiv. 5. 3). The great plague, which laid waste the Roman empire during the next years, is said to have sprung from the ruins of Seleucia. The destruction of Seleucia may be considered as the end of Hellenism in Babylonia. (See also Seleucid Dynasty and Hellenism.) (Ed. M.)
2. A city on the north frontier of Syria towards Cilicia about 4 m. N. of the mouth of the Orontes, near the shore at the foot of Mount Pieria (hence called Seleucia Pieria). This town also was founded by Seleucus I. It served as the port of Antioch (Acts xiii. 4), and with Apamea, Laodicea and Antioch formed the Syrian tetrapolis. Considerable remains are still visible: the chief are those of a cutting through the solid rock nearly 1100 yds. long, which Polybius describes as the road from the city to the sea; the triple line of walls; amphitheatre, cemetery, citadel, temples. It was of great importance in the struggle between the Seleucids and the Ptolemies; captured by Ptolemy Euergetes in 246, it was recovered by Antiochus III. the Great in 219. It was recognized as independent by the Romans in 70, but little of its subsequent history is known. It had practically ceased to exist in the 5th century A.D. The district stretching inland was known as Seleucis.
3. Seleucia Tracheotis, sometimes called Trachea, a city of Cilicia on the Calycadnus (Geuk Su), also founded by Seleucus I. about 300 B.C., near the older Olbia. It had considerable commercial prosperity as the port of Isauria, and was even a rival of Tarsus. In 1137 it was besieged by Leon, king of Cilician Armenia. On the 10th of June 1190 the emperor Frederick Barbarossa was drowned in trying to cross the Calycadnus. In the 13th century it was captured by the Seljuks. There are many ancient remains, and on the Acropolis the ruins of a castle; many rock-cut tombs with inscriptions have been found. On the site is the modern Selefke, the chief town of the Ichili sanjak.
Other towns bearing the name Seleucia were:—(4) Seleucia in Mesopotamia, the modern Birejik; (5) in the Persian Margiana, founded as Alexandria by Alexander the Great and rebuilt as Seleucia by Antiochus I. (of Syria); (6) in Pisidia; (7) in Pamphylia; (8) on the Belus in Syria. The city of Tralles (q.v.) also bore the name for a short period.
SELEUCID DYNASTY, a line of kings who reigned in Nearer Asia from 312 to 65 B.C.
The founder Seleucus (surnamed for later generations Nicator) was a Macedonian, the son of Antiochus, one of Philip's generals. Seleucus, as a young man of about twenty-three, accompanied Alexander into Asia in 333, and won distinction in the Indian campaign of 326. When the Macedonian empire was divided in 323 (the “Partition of Babylon”) Seleucus was given the office of chiliarch (Gr. χίλιοι, a thousand), which attached him closely to the person of the regent Perdiccas. Seleucus himself had a hand in the murder of Perdiccas in 321. At the second partition, at Triparadisus (321), Seleucus was given the government of the Babylonian satrapy. In 316, when Antigonus had made himself master of the eastern provinces, Seleucus felt himself threatened and fled to Egypt. In the war which followed between Antigonus and the other Macedonian chiefs, Seleucus actively co-operated with Ptolemy and commanded Egyptian squadrons in the Aegean. The victory won by Ptolemy at Gaza in 312 opened the way for Seleucus to return to the east. His return to Babylon in that year was afterwards officially regarded as the beginning of the Seleucid empire. Master of Babylonia, Seleucus at once proceeded to wrest the neighbouring provinces of Persis, Susiana and Media from the nominees of Antigonus. A raid into Babylonia conducted in 311 by Demetrius, son of Antigonus, did not seriously check Seleucus's progress. Whilst Antigonus was occupied in the west, Seleucus during nine years (311–302) brought under his authority the whole eastern part of Alexander's empire as far as the Jaxartes and Indus. In 305, after the extinction of the old royal line of Macedonia, Seleucus, like the other four principal Macedonian chiefs, assumed the style of king.