(Scorpion), Sagittarius (Archer), Capricornus (Goat), Aquarius (Water-Bearer) and Pisces (Fishes). The constellations bearing the same names coincided approximately in position when Hipparchus observed them at Rhodes, more than 2,000 years ago, with the positions they designate. The discrepancy now, however, amounts to the entire breadth of a sign, the sun’s path in Aries lying among the stars in Pisces; in Taurus among those of Aries; in Gemini among those of Taurus etc. This gradual retrogression of the signs through the constellations of the zodiac will continue till in about 25,868 years they accomplish a complete circuit. After this period the sign and constellation of Aries will coincide as they did in the time of Hipparchus.
Zodi′acal Light. If an observer in the tropical regions of the earth on a clear, moonless night watches the western sky from sunset till the last trace of twilight has disappeared, he will notice that the twilight seems to linger longer near the point where the [[../Sun, The|sun]] sank below the horizon and that gradually a nebulous band of light, broad toward the horizon and narrowing, first rapidly and then more slowly upward, begins to stand put clearly from the vanishing twilight, which spreads along a much wider arc of the horizon. This is the zodiacal light. When seen on a perfectly clear night, it will be noticed that it fades imperceptibly on both sides and toward the vertex and that its light is distinctly brighter toward the base than at higher points. Its width at its base may be said to vary from 10° to 30°, and the height of its vertex from 40° to 90°. It is most clearly seen in our latitude during the spring months after sunset and in the autumnal months before sunrise. This is due not to any change in the light itself, but to the fact that at other seasons of the year the ecliptic makes so small an angle with the horizon that light lying in or near it does not rise sufficiently high above the mists of the horizon to be seen after the twilight has vanished.
Zo'la, Émile, French novelist, was born at Paris, April 2, 1840, of a French mother and an Italian father, an eminent civil engineer. His distinguished son spent his boyhood at Aix, and was educated at Lycée St. Louis. Settling in Paris, he for a time was in the employ of Messrs. Hachette, the well-known publishing firm. His first venture in fiction was Les Mystères de Marseille, and in this and in Thérèse Raquin he at once displayed power in the critical analysis of human character. Soon after this he formed the naturalistic school of fiction, with Flaubert, Daudet and the Goncourts, chiefly marked by a hideous though powerful delineation of the crimes, weaknesses and loathsomeness of Parisian social life. The fruit in part of this was the series known as The Rougon-Macquart Family, modelled somewhat after Balzac's La Comédie Humaine. The more notable subsequent stories are L'Assommoir, Nana, Pot Bouille, La Joie de Vivre, Au Bonheur des Dames, Germinal, La Terre, La Bête Humaine, La Débâcle and Le Docteur Pascal. Their nastiness is somewhat sweetened by La Rêve (The Dream) and by a love-story entitled Lourdes. The latter forms one of a trilogy, which Zola called Les Trois Villes — Lourdes, Rome and Paris — all in the extreme realistic vein. His latest work, written in exile, occasioned by his courageous advocacy of the famous Dreyfus case, was entitled Fécondité. He was a knight of the French Legion of Honor, but was refused admittance to the French Academy. He died on Sept. 29, 1902.
Zone, literally a belt or girdle, a portion of the surface of a globe or sphere lying between any two circles of the same whose planes are parallel to each other, or that portion of the surface of a sphere cut off by the plane of a circle. As the earth's axis is inclined 23½° to the plane of the ecliptic or the sun's apparent path around the earth, the tropics of Cancer and Capricorn are located that distance north and south of the equator, respectively; and for the same reason the Arctic Circle and the Antarctic Circle are located 23½° from the north and south poles respectively. These circles are accordingly said to divide the earth's surface into five zones: to wit, the North Frigid, lying north of the Arctic Circle; the North Temperate, lying between the Arctic Circle and the Tropic of Cancer; the Torrid, lying on both sides of the equator, between the Tropic of Cancer on the north and the Tropic of Capricorn on the south; the South Temperate, lying between the Tropic of Capricorn and the Antarctic Circle; and the South Frigid, lying south of the Antarctic Circle. The area of a zone on any sphere is equal to the circumference of a great circle multiplied by the height of the zone.
Zoöl′ogy, the science of animal life. The scope of this subject broadened greatly in the latter half of the 19th century, and it came to include questions that might not at first sight appear to have a direct connection with zoölogy. For example, certain discoveries (those of Von Lenhossék) as to the nervous system of the earthworm opened the way to generalizations regarding the nervous system of higher animals, including that of the human body. Again, the studies of zoölogists on cells are helping to solve broad questions of development and heredity. Thus zoölogy comes into direct relation with the work of the anatomist, the physiologist and the psychologist. This relation is so close that medical schools are asking for a prepara-
