HELIOPHYLLUM. 735 HELIOTKOPE. Perfect speciincns, which are quite common, are really btaiilil'iil objects. Sometimes the coral Ipraiuhcs, ami then two or more cups lu' calyces are found on the same stem. Heliophyllum Ilalli is the common species. HE'LIOP'OLIS (Lat., from Gk. 'HWou iriXis, UClioti iiolis. City of the Sun). The Greek name of the ancient Egyptian city On, situated im the east side of the Pelusiac brancli of the Nile near the apex of the delta. Its site is occupied by the modern village of Matariah. Heliopolis was the seat of worship of the god Tum or Atum. who later came to be regarded as one of the forms of the sun-god Re. Its sacred name was rer-Re, 'house or city of Re,' and of this the Greek name is a translation, as was also the Hebrew name licthsliemcsli. As On, it is often mentioned in the Bible. Although a very ancient and impor- tant city — according to Manetho. it existed in the time of the Second Dvnasty — it is seldom men- tioned in Egyptian texts before the Twelfth Dy- nasty. Amenemhat I. built here a splendid temple, on the site of an older sanctuary, and his son and successor, Usertescn I., erected before it two great obelisks, of which one is still standing. The obelisks known as Cleopatra's Needles, of which one is now in New York and the other in London, were originally erected at Heliopolis by Thothnies III. Under Rameses III. (about B.C. 1200) the temple was at the height of its influ- ence, standing second only to that of Anion at Thebes: 12,693 persons are said to have been engaged in its service. The theological school of Heliopolis had a strong influence upon Egyp- tian religious thought, and to it is due a very considerable portion of the religious literature of ancient Egyjit. Greek writers mention the great reputation for wisdom enjoyed by the Heliopolitan priests, and Thales, Solon, and Plato are said to have studied under them. Under the later dynasties Heliopolis seems to have declined, since Herodotus speaks only of the wisdom of its priests, not of the splendor of its buildings; and Strabo, at the beginning of the Christian Era, states that the place was practically deserted, though the temple end col- lege still existed. The ruins of the city and temple existed in a fair state of preservation far down into Arab times, but now little remains except the obelisk of Usertesen I. HELIOPOLIS (in Syria). See Baalbek. HE^LIOS (Gk. "HXiot. or in the epic 'HAios, Eelios ; connected with Lat. sol, Goth, saiiil, AS., Icel. sol, It. sul, Lith., Lett., OPruss. saulc, Skt. sura, svar, sun). The Greek name of the sun- god. He was, according to the Theogot>;/, a son of the Titan Hyperion and of Thea or Eury- phaessa, and is described by the same poet as giving light to lioth gods and men. He rose in the east from the marshy borders of Oceaiuis, into wliose dark abysses he also sank at evening. The later poets, however, gave him a splendid palace in the east, somewhere beyond Colchis, and de- scribed him as being conveyed, after the termina- tion of the burning labors of the day, in a winged boat of gold, along the northern coasts of the sea back to Colchis. In the earlier poets Helios is a distinct personality, all-seeing, the possessor of herds on Trinacria, a powerful deity. Later, much of his personality is obscured, and the real sun-god becomes Apollo, probably because the word Helios, denoting the actual sun, was not felt so fully as a proper name. Euripides contributes much to this fusion. His worship was widely spread. He had temples in Corinth, Argos, Tra;- zcne, Elis, and many other cities; l)ut his prin- cipal seat was Rhodes, where four white horses were annually sacriliced to him. A similar saeri- hce was olfered in his honor on the sunmiit of Jlount Taygetus in Laconia. In art, he was rep- resented as a young man in the full vigor of his strength and beauty, with flowing hair, and a crown of rays. Often he was represented in his four-horse chariot, as in a celebrated group by Lysippus at Rhodes, HE'LIOSTAT. An instrument used in as- tronomy, physics, and engineering to reflect the liglit from the sun or other luminous body in a certain desired direction. It consists of a mirror so mounted that it is capable of being moved by clockwork in such a direction and with such velocity that it will reflect tlic light of the sun to the same point imh'pendent of its motion. The first instrument of this kind is described by s'Gravesande (1088-1742) in his Phj/sices FJemcnta (3d ed. 1742). The helio- stat is used with the spectroscope (q.v. ), where it is desired to keep the sun's rays on the slit or in connection with a permanently mounted telescope, such as that constructed for the Paris Exposition of 1000. So large a telescope (see Telescope) it would have been next to impos- sible to moimt equatorially, and it was neces- sary to reflect the light from the heavenly objects under observation into its object-glass. The heliostat has also been used for observing eclipses, especially where it is desired to photo- graph the eclipse or make extensive spectroscopic observations. The term heliostat is also used to name an instrument which is more usually kno^^^l as the heliotrope, used by surveyors and engineers in making long-distance observations for distant stations. This consists of a mirror at the distant station which is so moimted and adjusted that it will reflect a -beam of light to the observing station. (See Engineering In- struments.) The heliostat of Thomas Drum- mond was an instrument of this kind, and was employed in geodetic surveying in England with considerable success. HE'LIOTAX'IS (Neo-Lat., from Gk. iJXws, hClios, sun -f rd|is, taxis, arrangement). Same as phototaxis (q.v.). See, also, Heliotropism. HE'LIOTBOPE. See Engineering Instru- ments. HELIOTROPE (from Lat. heliotropiim. Gk. ili.oTpbTn.ov, hrliotropion, heliotrope, sun-dial, frimi ijXios, helios, sun r|- rpoTri), trope, a turning, from TpiiTfiv, Ircpeiii, to turn), Hcliotropiiim. A genus of plants of the natural order Horaginacea; (q.v.). Many of the species have fragrant flowers which are used by perfumers. The Peruvian he- liotrope (Uclioiropium Pervi^Umum) . a small shrub, seldom more than two feet high, with ob- hmg-lanceolate wrinkled leaves and small lilac- blue flowers, is in almost universal cultivation for its fragrance, which resembles that of vanilla. The European or common heliotrope (Ilrliolro- jiiiim. Evropcrum) . a native of the south and west of Europe, is an annual with small white, or rarely pale-red, flowers. A white flowered spe- cies (nrliotropiiiin rnrn>if-firici>m) grows wild in the Southern United States. Heliotropium co-
