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LEFT FORT COLLINS 177 FORTIFICATION square, polygonal, or in the form of a crown-work or star. They consist for the most part of a rampart, surrounded with a ditch and glacis; but in some cases an outwork is constructed for the defense of any side on which it may be more easily assailed. Paris is completely girdled with a chain of carefully planned forts, mostly pentagonal, in the shape of an enceinte, and situated at distances varying from a mile to IV^ miles from the inner line of bastions that encircle the city. In North America, generally, the name was also applied to a trading post in the wilderness with reference to the indispensable defenses, however slight, against the surrounding savages. FORT COLLINS, a city of Colorado, the county-seat of Larimer co. It is on the Cache la Poudre river, and on the Union Pacific and the Colorado and Southern railroads. It is the center of an important agricultural region and has manufactures of beet sugar, flour, bricks, etc. It is the seat of a Lutheran theological seminary and of the State agricultural college. It has a public library, a court house, hospital, and sev- eral excellent parks. Pop. (1910) 8,210; (1920) 8,755. FORT DODGE, a city of Iowa, the county-seat of Webster co. It is on the Minneapolis and St. Louis, the Illinois Central, the Fert Dodge, Deg Moines and Southern, and the Chicago Great Western railroads, and on the Des Moines river. It is an important manu- facturing center and has manufactures of clay products, brick and tile, oatmeal, shoes, etc. It is also an extensive coal regrion and in the neighborhood are large deposits of sand, clay, and sandstone. It is the seat of Tobin College and St. Joseph's Mercy Hospital. There is also a court house and a public library. It has the repair shops of four railroads which enter the city. Pop. (1910) 15,543; (1920) 19,347. FORTH, a river of Scotland, rising on ' the E. side of Ben Lomond, in Stirling- shire. After a sinuous course E. past Aberfoyle, Stirling, and Alloa, it unites with an arm of the sea called the Firth of Forth. Its chief affluents are the Teith, Allan, and Devon. The Firth at its mouth is 35 or 40 miles wide, from Fife Ness on the N., to St. Abb's Head on the S. shore, both washed by the Ger- man Ocean. It contains several islands, of which the chief are Inchgarvie, Inch- colm, Inchkeith, the Bass, and the Isls of May; the largest of these is but a few miles in circuit. Lighthouses are erected on Inchkeith and on the Isle of May. The Forth possesses many good harbors, and St. Margaret's Hope, above Queen's Ferry, is one of the safest road- steads in the island. Length of river, in- cluding its "links," 180 miles. FORTH BRIDGE, a remarkable work in engineering, spanning the Firth of Forth in Scotland; completed and for- mally opened on March 4, 1890. The construction was begun early in 1883, and the total cost up to the time of com- pletion may be given in round numbers as $16,000,000. Total length, upward of XVz miles; cantilever arms projection (outer), 680 feet; depth of cantilevers over piers, 342 feet; depth at ends, 41 feet; distance apart of lower members at piers, 120 feet; struts, largest diam- eter, 8 feet; ties, greatest length, 327 feet; central girder, span, 350 feet; cen- tral girder, depth at center, 51 feet; central girder, depth at ends, 41 feet; total amount of steel in bridge, over 50,000 tons, height of cantilever pier (masonry) above water, 209 feet. The designers of the bridge were Sir John Fowler and Benjamin Baker. FORTIFICATION, the art of increas- ing, by engineering devices, the fighting power of troops who occupy a position. The relation of fortification to the other great divisions of the art of warfare, strategy and tactics, may be divided as follows: Strategy determines the loca- tion of the position, which must conform to the general plan of campaign; tactics determines the best disposition of the troops on the position, for offense or de- fense; fortification improves the natural features of the position so as to increase the chances of success. Fortifications are commonly divided into two classes : "permanent fortifications" and "field- works." Under the former are included all works that are constructed for the defense of town, harbor, arsenal, dock- yard, etc., being carefully laid out and built with a view to durability and the resistance of an attack, whenever it may be made; under the latter, all works are classed that are intended to serve a tem- porary purpose, such as siege-work and batteries for an attack on a fortress, or lines of intrenchment hastily thrown up for the protection of an army in the field, or to check the advance of an enemy on an important strategical posi- tion. These works differ mainly in the manner in which they are built, the ram- parts and parapets of permanent works being faced or riveted with blocks of granite; the terre-plein of the rampart on which the guns are worked, the cheeks of the embrasures, casemates, bomb-proof buildings for magazines, etc., being formed of the same material; while field-works consist of mounds of earth formed of that which is thrown