OYAMA                                                      1406                                                        OZONE

vigorously in pure oxygen than in air. Oxygen is continually given off by the leaves of plants in sunlight, and this is evidently the source of the atmospheric supply, for the gas is continually consumed by the breathing of animals, combustion and decay.

Oyatna (o-yak'mah), Marquis Iwao, a distinguished Japanese soldier, was born in the province of Satsuma in 1842. He was tutored in his early youth by Saigo Nanshu, who is considered by the Jananese the greatest military genius whom Japan has produced since the days of Iyeyasu, under whom he fought in the War of Restoration when the imperial forces fought against the men of the shogun. He was a military attaché through the Franco-Prussian war, and studied in Germany from 1872 to 1875. In 1877, when the Satsuma men under the leadership of Saigo Nanshu, his old master, took the field against the imperial forces, Oyama, at the head of a division of the imperial forces, took the field against them. He served with distinction as Chief of Police, Associate-Minister of the Interior and Vice-Minister of War, and in 1882 was given the portfolio of Minister of War. In 1884 he was appointed Chief of the General Staff, and 10 years later in the Chino-Japanese war commanded in the field the army entrusted to besiege Port Arthur. Twenty-four hours after the siege began he was being carried through the streets of the fortress, once thought impregnable, on the shoulders of his men. In the Russo-Japanese war he was Commander-in-Chief of the five Japanese armies in Manchuria and won the battle of Mukden against Kuropatkin, Russia's greatest general. Marchioness Oyama is a graduate of Vassar College.

Oys'ter, a common bivalve-shelled mol-lusk, extensively used as food. It is related to the clam and mussel, belonging to that group of mollusks with plate-like gills (Lam-ellibranchiata). The two valves of the shell in the clam and mussel are similar; but in the oyster one side (the lower one) is much larger. In clams and mussels the shell is closed by a pair of muscles, located at either end of the shell, but in the oyster there is a single muscle located near the center of the shell. The dark violet spot on the inside of an oyster-shell marks the position of that muscle. In structure and habits the oysters are much like the clams. The water is strained through the gills, and the minute food particles are thus separated. They are carried forward to the mouth by the action of cilia. The digestive and circulatory systems are fairly well developed. The nervous system consists of three chief clusters of ner%Te-cells with connectives and nerve fibers. Oysters were formerly distributed along the Atlantic coast, from the Gulf of St. Lawrence to the Gulf of Mexico, but are now rare north of Cape Cod. Chesapeake Bay is the center of

the oyster-beds. There are two kinds—a rounded form, found north, and a more southern, elongated form. They are found also on the coasts of England, Europe, Japan, the Cape of Good Hope and Australia. The fisheries are very extensive, and the animals are protected by laws. From May to September they are not caught, as that covers the period of breeding. The United States leads the world in the production of oysters, and far the largest supply comes from Maryland. In 1894 more than 29,000,000 bushels were taken on the coast of the United States, valued at more than $16,500,000. Oysters were used as food by the ancient Romans, and it is claimed that the Japanese engaged in oyster culture 18 centuries before Christ. See Brook's The Oyster.

O'zark Mountains, a range in Missouri. They start from Missouri River, cross part of Missouri and Arkansas, and enter Indian Territory. The Black Hills and the Washita Mountains of Arkansas are parts of the range. The highest peaks have an elevation of 1,500 to 2,000 feet.

O'ziums are the largest group of Pueblo Indians. Their village is situated on a small stream about 40 miles southwest of Fort Wingate near the western boundary of New Mexico. They number about 1,500, and are slowly decreasing. They are peaceable, industrious in their native arts, faithful to their ancient beliefs. In agriculture, housebuilding, pottery, weaving, social organization and ceremonial observances they resemble the Pueblos generally, of whom they and the Hopi may be considered the most typical tribes. They are a remnant of the Aztec empire.

O'zone is the active form of oxygen which is produced by the action of electricity upon ordinary oxygen and in other ways. It is not possible to convert oxygen gas entirely into this form. But, by cooling a mixture of oxygen and ozone to a low temperature, the ozone may be condensed to a deep blue liquid which is unstable and readily explodes. When mixed with air, as ordinarily obtained, ozone possesses a powerful odor resembling that of diluted chlorine and is the most-powerful oxidizing agent known, attacking india-rubber, paper and other organic substances and corroding mercury at ordinary temperatures. It is unstable and gradually changes to ordinary oxygen upon standing, while it undergoes this change instantly upon heating. It has been shown that ozone gas is one and one half times as heavy as oxygen ; hence chemists believe that the particles or molecules of this gas are made of three oxygen atoms, while ordinary oxygen molecules are made of two atoms. Very minute quantities of ozone probably exist in pure air, particularly that coming from the sea. The popular notion that this ozone is beneficial to health is not based on any certain facts.

H. L. Wells.