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 “wood-tin,” and these, though not unknown in the matrix, are generally found as rolled pebbles. By the disintegration of tin-bearing rocks and vein-stones, the cassiterite passes into the beds of streams as rolled fragments and grains, or even sand, and is then known as stream tin or alluvial tin. This detrital tin-ore was probably used as a source of the metal before the primitive miners had learnt to attack the solid tin-bearing rocks.

Pure cassiterite may be colourless, or white, as seen in certain specimens from the Malay Peninsula; but usually the mineral is brown or even black, the colour being referred to the presence of ferric oxide or other impurity. Occasionally the tin-stone is red. In microscopic sections the colour is often seen to be disposed in zones, following the contour of the crystal. A brown variety, with rather resinous lustre, is termed “rosin tin.” The usual lustre of crystals of cassiterite is remarkably splendent, even adamantine. The mineral has a high refractive index, and strong bi-refringence. Certain transparent yellow and brown specimens, cut as gem-stones, exhibit considerable brilliancy.

The hardness of cassiterite is 6.5, so that it cannot be scratched with a knife, and is nearly as hard as quartz. Its specific gravity is about 7; and in consequence of this high density, the tin-stone is readily separated during the process of dressing, from all the associated minerals, except wolframite, which may, however, be removed by magnetic separators.

Cassiterite usually occurs as veins or impregnations in granitic rocks, and is especially associated with the quartz-mica rock called greisen. The usual associates of the tin-stone are quartz, tourmaline, apatite, topaz, beryl, fluorite, lithia-mica, wolframite, chalcopyrite, &c. The presence of fluorine in many of these minerals has led to the opinion that the tin has been derived in many cases from an acid or granitic magma by the action of fluorine-bearing vapours, and that cassiterite may have been formed by the interaction of tin fluoride and water vapour. Cassiterite occurs as a pseudomorph after orthoclase felspar in some of the altered granite of Cornwall, and it has occasionally been found as a cementing material in certain brecciated lodes.

Among the localities yielding cassiterite may be mentioned Cornwall, Saxony, Bohemia, Brittany, Galicia in Spain; the Malay peninsula, and the islands of Banca and Billiton; New South Wales, Queensland and Tasmania. Fine examples of wood-tin, occurring with topaz, are found in Durango in Mexico. Deposits of cassiterite under rather exceptional conditions are worked on a large scale in Bolivia; and it is notable that cassiterite is found in Liassic limestone near Campiglia Marittima in Tuscany. Cassiterite has been worked in the York region, Alaska.

 CASSIUS, the name of a distinguished ancient Roman family, originally patrician. Its most important members are the following.

1., surnamed Vecellinus (Vicellinus, Viscellinus), Roman soldier and statesman, three times consul, and author of the first agrarian law. In his first consulate (502 ) he defeated the Sabines; in his second (493) he renewed the league with the Latins, and dedicated the temple of Ceres in the Circus; in his third (486) he made a treaty with the conquered Hernici. The account of his agrarian law is confused and contradictory; it is clear, however, that it was intended to benefit the needy plebeians (see ). As such it was violently opposed both by the patricians and by the wealthy plebeians. Cassius was condemned by the people as aiming at kingly power, and hurled from the Tarpeian rock. Another account says he was tried by the family council and put to death by his own father, who considered his proposal prejudicial to the patrician interest. According to Livy, his proposal to bestow a share of the land upon the Latins was regarded with great suspicion. According to Mommsen (Römische Forschungen, ii.), the whole story is an invention of a later age, founded upon the proposals of the Gracchi and M. Livius Drusus, to which period belongs the idea of sharing public land with the Latins.

See Livy ii. 33, 41; Dion Halic. v. 49, viii. 69-80; Cicero, Pro Balbo, 23 (53), De Republica, ii. 27 (49), 35 (60); Val. Max. v. 8. 2.

The following Cassii are all plebeians. It is suggested that the sons of Spurius Cassius either were expelled from, or voluntarily left, the patrician order, in consequence of their father’s execution.

2., consul 73 With his colleague, Terentius Varro Lucullus, he passed a law (lex Terentia Cassia), the object of which was to give authority for the purchase of corn at the public expense, to be retailed at a fixed price at Rome. It is doubtful whether this Cassius (who is often called by the additional name Varus) is identical with the Varus who was proscribed by the triumvirs, and put to death at Minturnae (43). According to Orosius he was killed at the battle of Mutina.

See Cicero, In Verrem, iii. 70, 75, v. 21; Livy, Epit. 96; Appian, ''Bell. Civ.'' iv. 28; Orosius v. 24.

3., prime mover in the conspiracy against Julius Caesar. Little is known of his early life. In 53 he served in the Parthian campaign under M. Licinius Crassus, saved the remnants of the army after the defeat at Carrhae, and for two years successfully repelled the enemy. In 49 he became tribune of the plebs. The outbreak of the civil war saved him from being brought to trial for extortion in Syria. He at first sided with Pompey, and as commander of part of his fleet rendered considerable service in the Mediterranean. After Pharsalus he became reconciled to Caesar, who made him one of his legates. In 44 he became praetor peregrinus with the promise of the Syrian province for the ensuing year. The appointment of his junior, M. Junius Brutus, as praetor urbanus deeply offended him, and he was one of the busiest conspirators against Caesar, taking an active part in the actual assassination. He then left Italy for Syria, raised a considerable army, and defeated P. Cornelius Dolabella, to whom the province had been assigned by the senate. On the formation of the triumvirate, Brutus and he, with their combined armies, crossed the Hellespont, marched through Thrace, and encamped near Philippi in Macedonia. Their intention was to starve out the enemy, but they were forced into an engagement. Brutus was successful against Octavian, but Cassius, defeated by M. Antonius (Mark Antony), gave up all for lost, and ordered his freedman to slay him. He was lamented by Brutus as “the last of the Romans,” and buried at Thasos. A man of considerable ability, he was a good soldier, and took an interest in literature, but in politics he was actuated by vanity and ambition. His portrait in Shakespeare’s Julius Caesar, though vivid, is scarcely historical.

See Plutarch, Brutus, passim, Crassus, 27, 29, Caesar, 62, 69; Dio Cassius xl. 28, xlii. 13, xliv. 14, xlvii. 20; Vell. Pat. ii. 46, 56, 58, 69, 70, 87; Cicero, Philippics, xi. 13, 14, ad Att. v. 21, xiv. 21, ad Fam. xi. 3, 15, 16; Appian, ''Bell. Civ.'' ii. 111, 113, iii. 2, 8, iv. 60-62, 87, 90, 111-113, 132; Caesar, ''Bell. Civ.'' iii. 101.

4., the brother or cousin of the murderer of Caesar, quaestor of Pompey in Further Spain in 54 In 49, as tribune of the people, he strongly supported the cause of Caesar, by whom he was made governor of Further Spain. He treated the provincials with great cruelty, and his