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THALLENE 328 THANET is distinguished by a green fluorescence, and, when illuminated by violet and ul- tra-violet light, exhibits a fluoi'escent spectrum containing light-green bands. THALLIUM, in chemistry, a triad metallic element discovered by Crookes in 1861, and widely distributed as a con- stituent in iron and copper pyrites in blende, native sulphur, and in many kinds of ores; symbol TL, at. wt. 203.64. It can be distilled with the sulphur by heat- ing pyrites to a bright-red heat, then dissolving out the excess of sulphur by boiling with caustic soda, collecting and washing the sulphide of thallium, con- verting it into sulphate, and precipitat- ing the thallium in the metallic state by the action of pure metallic zinc. The spongy metal is compressed, dried, and fused into a bright metallic button by heating under cyanide of potassium. It is a perfect metal, with high luster, not quite so white as silver, but free from the blue tinge of lead. It has a sp. gr. of 11.80-11.91, melts at 293% is a very soft metal with less tenacity than lead, and almost devoid of elasticity. It com- municates an intense green hue to a colorless flame, and its spectrum consists of one intensely brilliant and sharp green line, coinciding with the number 1442.6 on Kirchhoff's chart. THAMES, the most important river of Great Britain; usually said to rise about 3 miles S. W. of Cirencester in Glouces- tershire, near a bridge over the Thames and Severn canal, called Thameshead Bridge, but is more properly formed by the Isis, Churn, Colne, and Leach, which have their sources on the E. side of the Cotswold Hills, and unite near Lechlade, where the counties of Gloucester, Wilts, Berks, and Oxford border on each other. Proceeding from Lechlade, where it be- comes navigable for barges, it flows first E. N. E., then S. S. E., past Oxford and Abingdon to Reading, then N. W. past Great Marlow, and S. E. past Windsor to Staines. From Staines it pursues a circuitous course E., passing the towns of Chertsey, Kingston, Richmond and Brentford, separating the counties of Middlesex and Surrey, and passing through London. Below London its course E. to the Nore, between Kent and Essex, is 47 miles. Its total course is estimated at 250 miles. Its tributaries include the Windrush, Cherwell, Thame, Colne, Brent, Lea, and Roding, on the left; the Kennet, Loddon, Wey, and Mole, on the right. Thameshead Bridge is 376 feet above sea-level ; the junction of the Colne above Lechlade is 243 feet. At London Bridge the width of the river is 266 yards, at Woolwich 490 yards, at Graves- end 800 yards, and 3 miles below, 1,290 yards. The basin of the Thames has an area of 5,400 square miles, and belongs entirely to the upper part of the Second- ary and to the Tertiary formations. The depth of the river in the fair way above Greenwich to London Bridge is 12 to 13 feet, while its tides have a mean range of 17 feet and an extreme rise of 22 feet. By means of numerous canals immediate access is given from its basin to those of all the great rivers of England. THAMUGAS, "the Numidian Pom- peii," near the Aures Mountains, in Al- geria; 22 miles from Batna, which is half-way by rail from Constantine to Biskra. Here are in the solitude exten- sive remains of colonnades, temples, a forum, a triumphal arch in honor of the Emperor Trajan (founder of the city), and numerous statues and inscriptions coming down to the 5th century, when the Roman city was destroyed by the barbarians. THANE, a title of honor or dignity among the Anglo-Saxons. In England a freeman not noble was raised to the dig- nity of a thane by acquiring a certain amount of land (five hides in the case of a lesser thane), by making three sea voyages, or by receiving holy orders. The thanes had the right of voting in the Witenagemot, not only of their own shires, but also of the whole kingdom, on important questions. There were two orders of thanes: The king's thanes, or those who attended at his court and held lands immediately from him, and ordi- nary thanes, or lords of the manor, and who had a particular jurisdiction within their limits. On the cessation of his actual personal service about the king, the thane received a grant of land. After the Norman conquest, thanes and barons were classed together, and the title fell into disuse in the reign of Henry II. In Scotland, thane signified originally a count or earl, one who ruled a county, or even in some cases a province. After- ward the title was applied to a class of non-military tenants of the crown, and continued in use till the end of the 15th century. THANET, OCTAVE, pseudonym of Alice French, an American novelist; born in Andover, Mass., March 19, 1850. She published: "Knitters in the Sun"; "Otto the Knight"; "Stories of a Western Town"; "An Adventure in Photogra- phy"; "Expiation"; "The Heart of Toil"; "A Slave to Duty." THANET, ISLE OF. a district of Eng- land, in the county of Kent, at the mouth