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FORCE-PUMP time-rate of change of the angular momentum of the body. Or, still again, moment of force is the angular rate at which the energy of the body is changing. For unit of force see and.

In popular usage force is a very much-abused word, and is misused often to indicate acceleration, momentum, power, energy etc. The student of science cannot be too careful in avoiding this error.  Force-Pump. See.  For′est. Forests may be considered as the climax of the world's vegetation, but conditions favoring their development do not exist everywhere. There are many types characteristic of different regions. The prevailing type of temperate regions is the deciduous forest. Sometimes it is nearly pure, as in beech-forests, oak-forests, etc.; but the more common type in the United States is the mixed forest, consisting of a mingling of numerous trees, as maple, elm, hickory, oak, beech, walnut, poplar, gum, etc. The deciduous forests of the United States are much finer than those of Europe, where the varieties are not so numerous and the trees are not so well-developed. Coniferous or evergreen forests are common in mountain regions and on sterile soils, extensive forests of this kind occurring in the lake-states, gulf-states and in the western mountains. The greatest of all forests are in the rainy tropics, as in the Amazon region, where the forests form jungles dripping with moisture, the trees being interlaced with vines and covered with air-plants. The scientific handling of forests is called forestry, (see ) which involves not so much the preservation of forests, as proper care and cutting, by means of which they may be preserved and still yield the timber necessary for the world's use. A division of forestry has been organized by the Department of Agriculture in Washington, which has charge of this subject in the United States. Foreign countries, as France and Germany, are far in advance of the United States in the proper management of forests.  Forest-Reserves are areas reserved for the preservation of forests and the protection of other natural resources. They are withdrawn from occupation, except conditionally. The national reserves are called national forests, and number 160 in the United States, including four in Alaska and one in Porto Rico. There are four state-forests.

The law as to national forests encourages every industry that will not jeopardize their safety and maintenance. Each is subject only to restrictions that prevent waste and injury to the forests. Any settler can obtain $20 worth of timber a year for home-purposes free. The forester marks the trees, and the pioneer cuts them. Should the settler need more than $20 worth, he files an application, and in 1911 over

40,000 such free-use permits were issued. Only mature trees may be cut. They must be so cut as not to hurt young growth. Tops and brush must, if necessary, be burned. Cutting must begin within six months from the date of the permit, and be completed within a specified time. For municipal and mining purposes the government grants rights of way. It also issues grazing permits; lets cattle be driven through the forests between pastures outside; and builds driveways for stock in reserves where grazing is not allowed.

California has the largest, North Dakota the smallest, national forests. The New York reserves are mainly in the Adirondacks, but partly in the Catskills; the Pennsylvania ones at the heads of its three principal rivers.  Forest-Service is a branch of the Department of Agriculture that cares for the national forests and also promotes forestry throughout the country, forestry being the art of growing forests and keeping them up. The service originated in 1897 when Mr. Cleveland was president, and until Feb. 1, 1905, was under the Department of the Interior. It comprises the office of the forester and four branches. These are operation, silviculture, grazing and products. The forester's office includes inspection, law, information and dendrology, the science that deals with the natural history or life-story of a tree. Operation includes maintenance, accounts, organization, engineering and lands. Silviculture includes extension, silvics and management, silvics being the science that treats of a forest. Grazing includes control and development. Products include wood-utilization, wood-preservation and publication. The forester is Henry S. Graves, and his force in 1911 numbered 2,624 men. Positions are filled by civil service examinations, and technical qualifications of a high order are required