formerly called Sejestan, and sometimes Nimroz, a khanat or principality of Asia, forming the southwest portion of Afghanistan, bounded on the north by Herat, east by Kandahar, south by the Great Desert, which separates Afghanistan from Beloochistan, and west by Persia. It lies between N. Lat. 30, 30, and 32, O., E. Long. 61, O. and 62, 30., and is nearly oval in form, about 100 miles in length from N. to S., and 60 in breadth, with an area of about 5000 square miles. Though this region is raised to a height of probably not less than 2500 feet above the sea, it is, in comparison with the surrounding country, very much depressed. From the southern foot of the great Caucasian Mountains, which traverse Afghanistan from E. to W., a vast expanse of desolate ground stretches to the S.W., gradually sloping downwards, till it is met on the west by a chain of hills extending southwards, and on the south by the elevated desert of Beloochistan. In the lowest part of this vast slope lies Seistan. The whole country is an extensive plain, except one small hill near the eastern shore of the Great Lake, or Hamoon. This is merely a sheet of shallow water, or swamp, into which the rivers flow from the surrounding countries, for none of the streams that enter Seistan can flow out from it again. They consequently stagnate in the more depressed places, and form shallow lakes, which are constantly changing their form and size. The largest of these is the Great Hamoon, about 70 miles long, and from 15 to 20 wide. The principal rivers that flow into Seistan are the Helmund, the Khash Rood, and the Ibrahim Joi, from the east; the Furrak Rood and Adrusund from the north; and the Bundau from the west. All these, even the largest, are rather mountain-torrents than perennial rivers, rushing down at one time with a full volume of muddy water, and at another with merely a small stream in the bottom of the channel, which, in the case of the smaller rivers, is left dry altogether. Most of the lakes and morasses are imbued with salt, so that the water is frequently not drinkable. The soil in some parts is rich and fertile, and along the banks of the Helmund it is well cultivated; but the climate is excessively hot, and the atmosphere unhealthy. Wheat, rice, and other grains, as well as cotton and tobacco, are grown. There are no forests here, but dense jungle of tamarisks cover, in many parts, the face of the country. Beasts of prey, such as leopards, wolves, jackals, hyenas, &c., abound here; there are also many wild-asses, wild-boars, deers, porcupines, hedgehogs, &c. Domestic animals do not thrive well here; horses cannot be kept, and cows are subject to a great mortality. The majority of the inhabitants are of Persian origin, but there are also many Afghans and Belooches, and a few Hindus. They live in felt tents, and are mostly employed in hunting and fishing. Their language is a broken Persian, and their religion Mohammedanism. They are governed by a khan who resides at Dovshak, but who has little power on account of the numerous petty chieftains in the country. Seistan was once a fertile and nourishing country, full of large and magnificent cities, whose ruins still lie strewn for miles over the plain. The rivers were embanked, and the soil enriched by a careful system of irrigation. All this prosperity was destroyed by the conquest of the country in 1383, by Tamerlane, who exterminated the inhabitants, and laid the towns in ruins. The present population is from 50,000 to 60,000.

SEJANT. See HERALDRY.

SEJANUS, Lucius Aelius, an infamous tool of the Emperor Tiberius, was a native of Vulsini, in Etruria, and was son of Scius Strabo, a Roman knight who flourished during the reign of Augustus and the beginning of that of Tiberius. After spending a very immoral youth, Sejanus at length gained the favour of the reigning sovereign, Tiberius. Once the wily youth had the emperor in his grasp, nothing could part them but the death of either, as it subsequently proved. Possessed of a body capable of enduring the most unheard of fatigues, endowed with a mind fit for the highest species of subtlety and cunning, of manners the most polite and insinuating towards his equals, the most cringing towards his superiors, and the most haughty and imperious to those beneath him, the weak emperor, in opening his bosom to Sejanus, disclosed himself unwarily to a most subtle intriguer. On the death of Augustus, in A.D. 14, Sejanus was sent by Tiberius, together with his son Drusus, to quell the insurgents in Pannonia. On the father of Sejanus being sent to Egypt, the son was chosen sole commander of the praetorian cohorts. He urged upon Tiberius the propriety of concentrating these bands all in one place, and he instructed him not to divide their powers of effective action by scattering them throughout the city. The emperor complied. The object of Sejanus was to popularize himself with the soldiery, and he succeeded to admiration. He dealt out honours to the praetorian guard with lavish hand, which came back to him in statues and busts in the public places of Rome. It was evident Sejanus aspired to the purple. There was, however, more than one obstacle in his path, which he resolved silently to remove. Drusus, the son of Tiberius, and the children of Germanicus, all stood in his way. He seduced the wife of Drusus, and by promising her immediate marriage, and a participation in the imperial power to which he aspired, induced her to poison her husband. Sejanus now divorced his wife Apicata, and solicited the emperor to permit him to wed the wife of the murdered Drusus. The emperor couched his answer in ambiguous language. Sejanus now required to act with caution. After various manoeuvring, he induced the emperor to shut himself up in the island of Capreae, where he had full scope for his machinations. The death of Livia, the mother of Tiberius, was soon followed by the banishment of Agrippina, the wife of Germanicus, and her two sons, Nero and Drusus. The path was now clear before Sejanus; yet Tiberius, who possessed more than his share of cunning, began to suspect him. The emperor had duplicity sufficient to conceal his suspicions. He made the tyrant joint consul with himself, and elevated him and his son to a pontificate. Sejanus felt the ground giving way under him, but what could he do to prevent it? Sertorius Macro was sent to Rome to assume the command of the praetorian cohorts, with a letter from Tiberius which he was to read to the senate. The emperor could never express himself clearly when he wished to say anything dangerous to the imperial power. The senate and the populace caught the drift of the royal epistle, however, which was plainly to have done with Sejanus. No word of consolation was spoken for the great criminal. He was conducted to prison, amid the bootings and yellings of the multitude, who tore down his statues and busts as he passed them by. Next day his body was dragged through the streets of Rome, and what remained of it was flung into the Tiber.

The chief authorities for the history of Sejanus are Tacitus, Suetonius, and Dion Cassius.