AEROPLANE

See Arronavtics. ZEROSTAT, a name indicating a balloon or flying machine; also a, balloonist or aeronaut. It is derived from aerostatics, a science treating of the equilibrium of elastic fluids or that of bodies sustained in them, and accordingly | embraces zronautics, or zerial sailing. orator and statesman; speeches rank next to those of his rival Demosthenes;. member of emba y sent to Philip of Macedon (347), whose policy he defend- — ed against Demosthenes; exiled to Rhodes. ZESCHINES (V. cent. B.C.), A then i an philosopher) friend of So crates; wrote dialogues on virtue, riches, death, etc. Z=SCHYLUS (525-456 B.C.), father of Gk. tragedy; b. Eleusis; fought in Grecian wars against Persia, and present at battles of Marathon, Salamis, Artemisium, and Plateea; began writing for theatre at an early age, and produced about seventy dramas, of which only seven — surive: The Suppliants, Persoe, Seven against Thebes, Pro me the us, Agamemnon, Choephoroe, and Eumenides. He was the ~ greatest of Gk. tragic poets and differed from his rival Sophocles in that his plays deal with the larger i ues of fate, and by their grandeur of conception, while Sophocles deals more particularly wit: the personal amenities of human life, Tradition tells that he was warned he would meet his death by the fall of a house, whereupon he retired to the fields and was killed by an eagle letting a tortoise fall on his bald head. 4ESCULAPIUS (cla ical myth.), god of medicine; s. of Apollo and Coronis; © f. of Hygeia (health) and Panacea (all healing), A. searched out the hidden powers of plants and herbs, and discovered cures for the various diseases _ which afflict mankind. He was slain — by Zeus with a flash of lightning for eT ee eee ne C — a e ee ee O a e a e having restored several persons to life, — 4ESIR, a race of gods who, according — to Scand in avian mythology, controled: for a time the destinies of that country. Nerthus, the protector of sailors and ee, is given prominence among them. Phrygian fabulist and philosopher; originally a slave, but received his freedom from his master, Iadmon; travelled through Greece and Egypt, and resided chiefly at court of Croesus, king of Lydia. The Delphians accused him of having stolen a sacred ve el from temple of Apollo, and put him to death by hurling him from a high rock, 561 B.C.; famous for the fables, which were narrated by him on various occasions, but never committed to writing. ZESTHETICISM, generally applied to the pose of complete attachment to zsthetical principles, whose apostle was Wilde (q.v.); an absurd and ephemeral side-i ue of the Atsthetic movement represented by Keats, Tennyson, Ro etti, and Morris; cleverly burlesqued a at and Sullivan’s opera, Patience 1881). 4:STHETICS (perceptible by senses), applied by Baumgarten, XVIII. cent., to science of taste or beauty, though used mcre nearly in Gk. meaning in ing with the conditions of sensuous Perception. Plato, following his ideal theory, affirmed an absolute beauty, from which was derived the beauty of particular things; Beauty not clearly separated from the Good and the True. Aristotle defined the beautiful as a mean between extremes, and resolved it into order, symmetry, definitene , and a certain magnitude relative to the perceptive capacity. aimed at immediate pleasure, with no ethical purpose. In modern times Baumgarten limited sxsthetics to the confused conceptions from the senses; the clear conceptions of truth were apprehended by reason, the higher intellectual power. Le ing (Laocoon) distinguished the provinces of poetry and painting, and excluded from the plastic art the representation of the repulsive. Kant affirmed the subjectivity of beauty and defined it according to his categories; the beauty of art inferior to that of nature. According to Schelling, the identity of subject and object is clearly seen only in artistic perception. Hegel affirmed the beautiful to be the realization of the abstract ideal; the appearance of the Idea in a sensuous medium. Schiller, Winckelmann, Fichte, and Herbart have also written on the subject. ZEST I VAT I ON (zool.), state of torpor undergone by some animals, (e.g.), snails, during the hot season, contrasted with hibernation; (bot.) folded arrangement of a flower bud before summer. ZETHELFLZED, dau. of Alfred the Great; m. Aithelred, Earl of Mercia; sent expedition against Welsh; constantly in conflict with vikings. ZETHELING, Anglo-Saxon term applied to those of noble or kingly birth, almost exclusively confined to sons of royal family of We ex. A:STHELRED (d. 716), king of Mercia; ravaged Kent, and destroyed abbeys and churches; afterwards abdicated (704), and became abbot of Bardney. ZETHELRED I. (866-71), king of West Saxons; s. of Aithelwulf; won great victory over Danes at Ashdoun:; suce, by bro., Atlfred the Great. (968-1016), king of the English; succ. 979; ‘unready’ or ‘redele ’ means lacking in counsel; adopted foolish policy of buying off Danish invaders; m. Emma. dau. of Richard, Duke of Normandy, es paving way for Norman Conquest. ZETHELSTAN (895-941), Saxon king: s. of Edward the Elder; grandson of Atlfred the Great; succ. 925; won brilliant victory at Brunanburh over allied Celts and Danes; praised by chroniclers as wise and vigorous ruler. A: THER, ETHER.—From early times philosophers have recognized the nece ity of some medium filling all apparently empty space; hence various ‘Atthers’ have been supposed to exist, the properties of which varied according to the physical phenomena for whose explanation they were nece ary. The only ze. theory to survive is the one invented by Huygens to explain the propagation of light. More recent work has shown that the properties nece ary for the propagation of light are just those required for the explanation of electromagnetic phenomena. The modern view is that the whole universe consists of a perfectly continuous, incompre ible medium, as a whole completely at rest, frictionle and unresisting to the ordinary motion of matter through it. The medium po e es considerable rigidity, which property might be conferred on it. if throughout the whole medium there exists a system of vortex filaments or rings of exceedingly small dimensions. The elasticity of the «. is regarded as ‘perfect’, The property of the x. analogous to rigidity is probably electric in its origin, and it is accompanied by a quasi-inertia, which has to do with magnetism. The two properties together enable transverse electro-magnetic waves to be transmitted through it at a definite speed. The inertia of the e. corresponds to density in the case of ordinary matter, and it is po ible that the inertia or density of the «.is exceedingly great, much greater than that of any known material. Is THH AUTHER AT REST?—The theory of a motionle ee. was at first unable to explain the negative results of Michel son and Morley’s experiments which seemed to show that the «.near the earth was carried along with it; but FitzGerald’s hypothesis overcame the difficulty. He supposed that the dimensions of material bodies are slightly altered when they are fin motion relative to the «#. The idea has gradually extended, and is now generally taken as the basis of all theoretical investigation on the motion of vongeranle bodies through the #. See