M. Travers, G. Senter and A. Jacquerod (Phil. Trans. A. 1903, 200, p. 105) carefully examined the behaviour of a constant volume gas thermometer filled with helium. For the pressure coefficient per degree, between 0° and 100° C., they give the value .00366255, when the initial pressure is 700 mm. This value is indistinguishable from that which they find for hydrogen. Thus at high temperatures a helium thermometer is of no special advantage. At low temperatures, on the other hand, they find, using an initial pressure of 1000 mm., that the temperatures on the helium scale are measurably higher than on the hydrogen scale, owing to the more perfectly gaseous condition of helium. This difference amounts to about 1⁄10° at the temperature of liquid oxygen, and about 1⁄5° at that of liquid hydrogen.
The liquefaction of helium was achieved by H. Kamerlingh Onnes at Leiden in 1908. According to him its boiling point is 4.3° abs. (−268.7° C.), the density of the liquid 0.154, the critical temperature 5° abs., and the critical pressure 2.3 atmospheres (Communications from the Physical Laboratory at Leiden, No. 108; see also [Liquid Gases]).
References.—A bibliography and summary of the earlier work on helium will be found in a paper by Ramsay, Ann. chim. phys. (1898) [7], 13, p. 433. See also M. Travers, The Study of Gases (1901).
(R. J. S.)
HELIX (Gr. ἕλιξ, a spiral or twist), an architectural term for the spiral tendril which is carried up to support the angles of the abacus of the Corinthian capital; from the same stalk springs a second helix rising to the centre of the capital, its junction with one on the opposite side being sometimes marked by a flower. Sometimes the term “volute” is given to the angle helix, which is incorrect, as it is of a different design and rises from the same stalk as the central helices. Its origin is probably metallic, that is to say, it was copied from the conventional treatment in Corinthian bronze of the tendrils of a plant.
HELL (O. Eng. hel, a Teutonic word from a root meaning “to cover,” cf. Ger. Hölle, Dutch hel), the word used in English both of the place of departed spirits and of the place of torment of the wicked after death. It is used in the Old Testament to translate the Hebrew Sheol, and in the New Testament the Greek ᾃδης, Hades, and γεέννα, Hebrew Gehenna (see [Eschatology]).
HELLANICUS of Lesbos, Greek logographer, flourished during the latter half of the 5th century B.C. According to Suidas, he lived for some time at the court of one of the kings of Macedon, and died at Perperene, a town on the gulf of Adramyttium opposite Lesbos. Some thirty works are attributed to him—chronological, historical and episodical. Mention may be made of: The Priestesses of Hera at Argos, a chronological compilation, arranged according to the order of succession of these functionaries; the Carneonikae, a list of the victors in the Carnean games (the chief Spartan musical festival), including notices of literary events; an Atthis, giving the history of Attica from 683 to the end of the Peloponnesian War (404), which is referred to by Thucydides (i. 97), who says that he treated the events of the years 480-431 briefly and superficially, and with little regard to chronological sequence: Phoronis, chiefly genealogical, with short notices of events from the times of Phoroneus the Argive “first man” to the return of the Heraclidae; Troica and Persica, histories of Troy and Persia.