POUND                                                      1541                                                       .POWER

service in cleaning off insects as well as in manuring the ground. To make poultry profitable, they should be well-housed and well-fed, with sufficient space for obtaining gravel, grass, worms, garbage etc. Their houses should also be kept clean, as the richness of their manure makes the ground very foul. For laying-hens it has been found that sof food is very beneficial and that it should be given in the morning, with hard corn in the latter part of the day. Sitting hens should have a quiet nest, where they will not be disturbed during the 21 days required for incubation. Artificial incubation has been very largely adopted by poultry-raisers, most of the machines now sold working with great precision and regularity. The advantage of incubators is that they can be used at all seasons.

Pound, the English form of the Latin word, pondus, meaning weight, is now used in two distinct senses, first, a gold coin having the value of 20 shillings and, second, a standard of mass, equivalent to 7000. grains or 0.45359265 kilograms. The standard pound is not a "weight," but a "mass," and is kept at the Standard's office in London. The pound described above is the avoirdupois pound; the troy pound used only rarely by dealers in precious stones and metals has 5760. grains. The old English pound, which is said to have been the standard of weight from William the Conqueror to Henry VII, was derived from the weight of 7,680 grains of wheat all taken from the middle of the ear and well-dried. The pound weight of silver, the common money standard among the ancient Romans, w s introduced by them into the countries which they conquered, anc'! thus the term "pound" became the designation of a certain amount of coined money. The English pound is now considered as the simple equivalent in value of 20 shillings; but it originally denoted the actual p^und of silver that was coined into 20 shillings. From the time of Edward II the coins were more and more diminished in size until the reign of George I, when the pound (in weight) of silver was coined into 66 shillings; and this rate still continues, the term "pound" meaning 20 of these shillings.

Pout'er. See Pigeon. Pow'der, a general name for pulverised or minutely divided solid substances, has come to be specifically identified with gunpowder, a mixture of sulphur, charcoal and potassium nitrate. Gunpowder is now used in war far less than formerly, owing to the superior advantages of smokeless powders; but the production of it is considerable, and there is little likelihood that it will be superseded for such purposes as fireworks and military and naval salutes. The origin of gunpowder is obscure. The use of it for military purposes was suggested by Roger Bacon about 1266. But gunpowder was

known in India and China, where saltpeter is very abundant, from time immemorial. Gunpowder was used in cannons as early as the battle of Crécy (1346). Its quality was very gradually improved. The French took tlu step, under the direction of Lavoisier, of carefully pulverising the ingredients in separate wheel-mills. It was gradually discovered that the quality and purity of the ingredients, especially the charcoal and niter, need careful attention. The niter is purified and transformed into small crystals by a process of boiling in water, filtration and rotation in crystallising vessels. Willow-wood is commonly used for charcoal. Even the sulphur has to be distilled and finely powdered. The proportion of the ingredients may vary; but in military powder it often is 75 parts niter, 10 parts sulphur and 15 parts charcoal. The greater part of the powder now produced in the United States is used, not for guns, but for blasting. See Gunpowder.

Pow'derly, Terence Vincent, an American labor-leader, who came into prominence as General Master-Workman of the Knights of Labor, was born at Carbondale, Pa., Jan. 22, 1849. He entered the employ of a railroad as a switch-tender at 12 and as a machinist at 19. He joined the Knights of Labor in 1874 and was elected mayor of Scranton in 1877 and 1878. He was raised to the chief office in the Knights of Labor at their meeting in Chicago in 1879, remaining master-workman until 1893. He studied law and was admitted to the bar in 1894. He was appointed commissioner of immigration by President McKinley in 1897.

Pow'ell, John Wesley, an American geologist and anthropologist, was born at Mount Morris, N. Y., March 24, 1834, and served through the Civil War, in which he rose to the rank of major. After holding a professorship in Illinois Wesleyan University for. a number of years, in 1870 a survey of the Colorado and its tributaries was placed under his direction by act of Congress. His voyage through the canyon was a wonderful achievement. While engaged in this service he gave special attention to ethnology, and in 1879 was made director of the new bureau of ethnology; in 1881 he w-.s also appointed director of the United States Geological Survey. Major Powell in 1886 received the doctorate of philosophy from Heidelberg and of laws from Harvard; and in 1887 he was president of the Association for the Advancement of Science. His works include Explorations of Colorado River; Lands of the Arid Region; Contributions to American Ethnology; and Outlines of the Philosophy of the Indians. He died on Sept. 23, 1902.

Pow'er, a term used in physics and engineering to denote the rate of work. When an engine hoists a carload of coal from the bottom of a pit to the surface of the earth, it