THE'TIS, daughter of Nereus and Doris, was married against her will by the gods to Peleus, by whom she became the mother of Achilles. She dwelt in the depths of the sea with her father, and had, like Proteus, the power of changing her shape. Her hand is said to have been sourrht by Poseidon and Zeus, who gave up the pursuit on Themis declaring that the son of Thetis would be greater than his father.
or CELESTIAL MOUNTAINS, a great mountain system, consisting of several ridges, mostly parallel, in central Asia, are situated to the s. and e. of lake Issyk-kul, in lat. about 42° north. They are said to extend in an e.n.e. direction from the vicinity of Samarkand, to long. about 96° e.—a distance of 1500 miles. As this range, however, was never visited by any European till P. Semenof, commissioned by the imperial Russian geographical society, explored a part of it in 1858, little has been actually ascertained character and dimensions. It is one of the four great ranges, trending in a general 'clirection from w. to e., which traverse central Asia—and these respectively are the AltaY-Sayan, or Altatan mountains, in lat. about 50° n.; the Thian-shan mountains, lat. about 42° n.; the Kuen-lun system. lat. about 36° n. ; and
the Himalaya mountains (q.v.). In long. 76° to 79° e., the Thian-shan mountains are divided into two great, nearly parallel ridges, and inclose between them a deep valley, about 15 m. in average breadth, through which the river Narin—the chief head-water of the Sir-daria—flows in a w.s.w. direction. East of these ranges, the mountains are known as the Tengri-Tagh; and of this subdivision the chief peak is the Tengri-Khan (i.e., specter-prince), in lat. 42° 23' n., long. 79° 40' e., and which rises to the height of 21,000 feet. East from the Tengri-tagh. the Thian-shan mountains continue in a double chain, and at an average height of 11,330 feet. In long. 90° e. is the volcano Pe-shan, which is believed to have been in activity prior to the 7th c.; and in the vicinity are several other volcanoes. These are remarkable as the only instances of volcanic fires at so great a distance-1500 miles—from the sea. In long. 88° e. is the huge mountain Lass of Bogdo-oola, perhaps the culminating point of the whole system, and certainly the peak on which there is the greatest accumulation of snow. There are several passes of from 10,000 to 13,000 ft. in height.