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 with nitrous acid and alcohol (O. and E. Fischer, Ann., 1881, 206, p. 152). The last reaction is most important, for it established the connexion between this hydrocarbon and the rosanilines. Triphenylmethane is a white crystalline solid, melting at 92° and boiling at 358°. It separates from benzene and thiophene with one molecule of the “ solvent of crystallization.” On oxidation it gives triphenylcarbinol, (C6H5)3C·OH, and reduction with hydriodic acid and red phosphorus gives benzene and toluene. It combines with potassium to give (C6H5)3CK, which with carbon dioxide gives potassium triphenylacetate, (C6H5)3C·CO2K. Fuming nitric acid gives a paratrinitro substitution derivative which on reduction gives paraleucaniline; the salt of the carbinol formed on oxidizing this substance is the valuable dye rosaniline.

TRIPOD (Gr., Lat. tripus), in classical antiquities, any “three-footed” utensil or article of furniture. The name is specially applied to the following: (1) A seat or table with three legs. (2) A stand for holding the caldron used for boiling water or cooking meat; when caldron and stand were made in one piece, the name was given to the complete apparatus. (3) A sacrificial tripod, or altar, the most famous of which was the Delphic tripod, on which the Pythian priestess took her seat to deliver the oracles of the god, the seat being formed by a circular slab on the top, on which a branch of laurel was deposited when it was unoccupied by the priestess. Another well-known tripod was the “Plataean,” made from a tenth part of the spoils taken from the Persian army after the battle of Plataea. This consisted of a golden basin, supported by a bronze serpent with three heads (or three serpents intertwined), with a list of the states that had taken part in the war inscribed on the coils of the serpent. The golden bowl was carried off by the Phocians during the Sacred War; the stand was removed by the emperor Constantine to Constantinople, where it is still to be seen in the Atmeidan (hippodrome), but in a damaged condition, the heads of the serpents having disappeared. The inscription, however, has been almost entirely restored (see Frazer on Pausanias, v. 299 seq.). Such tripods were usually of bronze and had three “ears” (rings which served as handles). They also frequently had a central upright as support in addition to the three legs. Tripods are frequently 'mentioned in Homer as prizes in athletic games and as complimentary gifts, and in later times, highly decorated and bearing inscriptions, they served the same purpose. They were also used as dedicatory offerings to the gods, and in the dramatic contests at the Dionysia the victorious choregus (a wealthy citizen who bore the expense of equipping and training the chorus) received a crown and a tripod, which he either dedicated to some god or set upon the top of a marble structure erected in the form of a small circular temple in a street in Athens, called the “street of tripods,” from the large number of memorials of this kind. One of these, the “monument of Lysicrates,” erected by him to commemorate his victory in a dramatic contest in 335 is still in existence (see Frazer, ii. 207).

 TRIPOLI, a Turkish vilayet (regency) of North Africa. It is bounded N. by the Mediterranean (between 11° 40′ and 25° 12′ E.) and has a coast-line of over 1100 m. Tripoli comprises at least five distinct regions—Tripoli proper, the Barca plateau (Cyrenaica), the Aujila oases, (q.v.) and the oases of Ghadames and Ghat—which with the intervening sandy and stony wastes occupy the space between Tunisia and Egypt, extend from the Mediterranean southwards to the Tropic of Cancer, and have a collective area of about 400,000 sq. m., with a population estimated at from 800,000 to 1,300,000. Towards the south and east the frontiers are undefined. But on the west side the conventional line laid down by agreement with France in 1886 was more accurately determined in 1892, when the terminal point on the Mediterranean was shifted from Borj-el-Biban to Ras Ajir, 18 m. to the south-east, in 33° 12′, N. 11° 40′ E. From this point the line passes along the Wad Magla and across the Erg (sand) dunes in such a way as to leave Ghadames to Turkey. In consequence of frontier collisions the boundary as far as Ghadames was precisely defined in 1910. South of that point the rival claims of France and Turkey remained in dispute.

For some distance east of Tunisia the seaboard is low and sandy, and is often regarded as a part of the Sahara, which, however, begins only some 80 m. farther south, beyond the Jebels Nefusi, Yefren and Ghurian (Gharian). The “Jebel,” as this system is locally called, terminates eastwards in the Tarhona heights of the Homs (Khoms) coast district, has a mean altitude of about 2000 ft. and culminates in the Takut (Tekuk) volcano (2800 ft.) nearly due south of the capital. It is not a true mountain range, but rather the steep scarp of the Saharan plateau, which encloses southwards the Jefara coast plains, and probably represents the original coast-line. The Ghurian section is scored in places by the beds of intermittent coast streams, and on its lower slopes is clothed with a rich sub-tropical vegetation. South of these escarpments, the vast Hammada el-Homra, the “Red Hammada,” an interminable stony table-land covering some 40,000 sq. m., occupies the whole space between Tripoli proper and the Fezzan depression. The now uninhabited and waterless Hammada formerly drained through several large rivers, such as the Wadis Targelat (Uani, Kseia), Terrgurt, Sofejin, Zemzem and Bel, north-eastwards to the Gulf of Sidra (Syrtis major). Southwards the table-land is skirted by the Jebel Welad Hassan, the Jebel es-Suda, the Jebel Morai-Yeh, and other detached ranges, which have a normal west to east trend in the direction of the Aujila oases, rising a little above the level of the plateau, but falling precipitously towards Fezzan. The Jebel es-Suda (Black Mountains), most conspicuous of these ranges, with a mean altitude of 2800 ft., takes its name from the blackened aspect of its limestone and sandstone rocks, which have been subjected to volcanic action, giving them the appearance of basalt. Eastwards this range ramifies into the two crescent-shaped chains of the Harūj el-Aswad and Harūj el-Abiad (“Black” and “White” Harūj), which rise some 700 ft. above the Red Hammada, and enclose an extensive Cretaceous plateau. Rocks of Cretaceous age cover, indeed, an immense area of the northern part of the vilayet, recent eruptive rocks being represented by the lavas and ashes of the craters of Takut and Manterus. The later palaeozoic formations occur in Fezzan.

Beyond the barren Ghadama district in the north of the Hammada the dreary aspect of the wilderness is broken by