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BOILING-POINT heating flues are inside the water-vessel and (2) those in which the furnace is external to the water vessel. The first type is not much used in this country for stationary boilers, but it is commonly used for locomotive and marine boilers. The locomotive boiler consists of a fire-box of rectangular form which is more or less surrounded by the long cylindrical water-vessel. A large number of tubes run from the fire-box to the smokestack through the water-vessel, and thus allow the heat from the hot furnace gases to reach the water. The common stationary boiler in this country belongs to the second class. In its simplest form it is a single cylindrical vessel placed over the furnace and its hot flues. As more commonly used now, it consists of a large number of water tubes, the furnace gases passing around these tubes and thus heating the water. The Babcock and Wilcox boiler is one of the best of this type. The water is contained in a large number of straight tubes which are inclined at an angle of about 15° from the horizontal and connected with a drum above, which contains part of the water and the steam. The furnace is below the tubes, and the hot gases pass up and along the water tubes. These are compact, efficient and safe, if properly constructed. When the tubes are straight, they have the great additional advantage of being easily inspected and cleaned.

Boilers are generally rated in horsepower, and as applied to boilers this is a conventional term. A boiler of 1 H. P. is one which evaporates 30 pounds of water per hour from feed-water of 100° F. into steam at 70 pounds gauge pressure.  Boiling-Point, the temperature at which a liquid is transformed into vapor. The boiling-point varies with different liquids, while it changes with the amount of atmospheric pressure to which it may be exposed. When the boiling-point is normal at the sea-level, in high altitudes, where the air-pressure is light, liquids boil more slowly. So well-known is this that the heights of mountains are approximately measured by ascertaining the degree of temperature at which water boils. In highly elevated regions many substances cannot be cooked by boiling. A further fact is that when water contains foreign substances in solution the boiling-point is raised; in other words, the greater the amount of these substances a liquid contains, the higher within certain limits is the boiling-point of the liquid. Under normal atmospheric pressure, ether boils at 35° C., pure alcohol at 78°, while aniline boils at 183° C. Water boils at 100° Centigrade or 212° Fahrenheit.  Bois de Boulogne. See.  Boise, Idaho, the capital of the state, and the county seat of Ada County, on the Boise River, about 48 miles east of

its junction with the Snake River. It is reached by the Oregon Short Line Railroad (now part of the Union Pacific system.) It lies in an important mining district and besides a military post it has a federal assay office, U. S. Court and land offices, together with a soldier's home, a penitentiary and the state capitol. Its civic institutions, besides the city hall, include a public library, several schools and academies, a business college and a natatorium. The Boise River is utilized considerably in the region for irrigation purposes, as well as for water power for the city's manufactures. The latter embrace saw mills, wood-working factories, foundries and machine shops. In the vicinity there is much farming carried on, as well as stock-raising, while Boise has become noted as a wool market. Population (1910), 17,358.  Bo′ker, George Henry, an American poet, was born at Philadelphia in 1823, and died there in 1890. He wrote several plays, which were successful on the stage, among them Calaynos, a Tragedy, and Francesca da Rimini. His war poems, written during the Civil War, were published in a volume entitled Poems of the War. He was appointed minister to Constantinople, and after four years was transferred to St. Petersburg. In 1882 he published a volume of verse, The Book of the Dead.  Bokhara, meaning “treasury of sciences,” a city of central Asia, the capital of the khanate or province of Bokhara, a vassal state of Russia, is situated on a plain near the river Zerafshan. It is more than eight miles in circumference, and is surrounded by mud walls twenty-four feet high, pierced by eleven gates. The palace of the khan, built on a hill at an elevation of 300 feet in the center of the city, is surrounded by a brick wall nearly seventy feet high. Bokhara is the center of religious life in central Asia, and is said to have 365 mosques. The finest occupies a square of 300 feet, and has a cupola 100 feet in height. Joined to it is a tower of about twice the height, from which criminals are hurled. The city has long been noted as a seat of learning, and besides a vast number of schools has about eighty colleges. The River Zerafshan is utilized for irrigating, and the drain of water is said to have lessened the population by one half, but there are still about 75,000 people. Silks, woolens and swords are manufactured, slave markets are held, and the bazaars are rich with the wares of Europe and Asia. The Transcaspian railroad opens communication with the ports of the Caspian Sea, but the trade is almost wholly in Russian hands. The area of the state of Bokhara is about 80,000 square miles, with a population of about 1,250,000.  Boldrewood, Rolf. See . 