Argolis. See Argos.
Argon, a gas which is fairly widely distributed in the free state and is a constant constituent of the atmosphere, of which it forms about 1 per cent by volume. It was discovered by Lord Rayleigh and Professor Ramsay in 1894. During their determinations of the density of nitrogen they noticed that the density of nitrogen derived from the air differed from the density of nitrogen derived from ammonia and other compounds of nitrogen, and after a series of very careful experiments they succeeded in isolating a new gas, which they named Argon. The gas occurs in sea and river water, in plants, in the blood of animals, and the gases issuing from volcanoes and mineral springs. It is always in the free state and never in combination, and is associated with nitrogen. It is colourless, odourless, and tasteless, and may be liquefied and solidified. It is heavier than air, and is chemically a very inert substance. It is usually referred to as one of the rare gases of the atmosphere. Argon is manufactured in fairly large quantity from air, making use of the inertness of the substance compared to oxygen and nitrogen, the chief constituents of the air. Several methods are in use, e.g. nitrogen may be removed by passing it repeatedly over red-hot magnesium; thus the nitrogen is absorbed and the argon left. When oxygen and nitrogen of air are absorbed by a mixture of 90 per cent calcium carbide and 10 per cent calcium chloride previously heated to redness in vacuo, a gas becoming richer and richer in argon is obtained. Another method of preparing argon is by fractionation of liquid air. It is used for filling electric bulbs.
Ar´gonaut, a molluscous animal of the genus Argonauta, belonging to the dibranchiate or two-gilled cuttle-fishes, distinguished by the females possessing a single-chambered external shell, not organically connected with the body of the animal. The males have no shell and are of much smaller size than the females. The shell is fragile, translucent, and boat-like in shape; it serves as the receptacle of the ova or eggs of the female, which sits in it with the respiratory tube or 'funnel' turned towards the carina or 'keel'. This famed mollusc swims only by ejecting water from its funnel, and it can crawl in a reversed position, carrying its shell over its back like a snail. The account of its floating on the surface of the sea, with its sail-shaped arms extended to catch the breeze, and with the six other arms as oars, is a mere fable. The argonaut, or paper-nautilus, must be carefully distinguished from the pearly-nautilus or nautilus proper (Nautilus Pompilius).
Argonauts, in the legendary history of Greece, those heroes who performed a hazardous voyage to Colchis, a far-distant country at the eastern extremity of the Euxine (Black Sea), with Jason in the ship Argo, for the purpose of securing a golden fleece, which was preserved suspended upon a tree, and under the guardianship of a sleepless dragon. By the aid of Medea, daughter of the King of Colchis, Jason was enabled to seize the fleece, and, after many strange adventures, to reach his home at Iolcos in Thessaly. Among the Argonauts were Hercules, Castor and Pollux, Orpheus and Theseus.—Bibliography: A. R. Hope Moncrieff, Classic Myth and Legend; Kingsley, The Heroes; N. Hawthorne, The Wonder-book.
Argo-Navis, the southern constellation of the Ship, is almost entirely invisible in Britain. It contains Canopus, next to Sirius the brightest
fixed star. In the great nebula in Argo is situated the remarkable star Eta Argûs. It is variable, generally faint, but in 1837 it became temporarily one of the brightest stars in the sky.
Argonne, a district of France, between the Rivers Meuse, Marne, and Aisne, celebrated for the campaign of Dumouriez against the Prussians in 1792, and for the military movements and actions which took place therein previous to the battle of Sedan, in 1870.
Argonne, Battle of. When, in the autumn of 1914, the Allies retreated towards the Marne, the German Crown Prince's army endeavoured to invest Verdun. His right wing advanced through the thick and extensive forest of Argonne, but took precipitate flight after the battle of the Marne before the army of General Sarrail. In the summer of 1915 the Crown Prince endeavoured to hack his way through the French Argonne lines, using much heavy artillery, poison-gas, liquid-fire, and tear-shells. A final effort to break through was made in September, between Le Four de Paris and Vienne-le-Château, but, after gaining a footing in the first line of French trenches, the Germans were hurled back by a dashing counter-attack. The great salient from the Argonne to St. Mihiel was the salvation of Verdun.
Ar´gos, a town of Greece, in the north-east of the Peloponnesus, between the Gulfs of Ægina and Nauplia or Argos. This town and the surrounding territory of Argolis were famous from the legendary period of Greek history onwards. Here, besides Argos, was Mycenæ, where Agamemnon ruled. Modern Argos is a straggling place of 10,000 inhabitants, with some ancient remains. The territory Argolis forms a nomarchy of Greece. Pop., Argolis and Corinthia, 153,172. The capital is Nauplia.