UNITED STATES LIGHTHOUSE SYSTEM. The theory of coast lighting is that each coast shall he so set with towers that the rays from their lights shall meet and pass each other. so that a vessel on the coast shall never be out of sight of a light. The United States is proceeding upon this theory and lights are being installed upon this plan. The cost of the lighthouse estab lishment for the first century of its existence in the United States was $93,250,000. The first lighthouse on this continent was built at the en trance to Boston harbor and was supported by light-dues of Id. per ton on all inemning and out going vessels except coasters. When the United States, in 1789, accepted the cession of the title to and jurisdiction over the lighthouses on the coast, and agreed to maintain them thereafter. they were eight in number, and were placed in the care of the Treasury Department. Up to 1820 the number of lights increased from S to 55. and each seems to have been built to meet immediate want without regard to any general system. Un der the Fifth Auditor of the Treasury. Stephen Pleasanton. who was popularly known as general superintendent of lights from 1820 to 1852, the number of lighthouses increased from 55 to 325, and numerous buoys and other aids to gation were erected. In 1852 Congress passed b an act constituting the Lighthouse Board as it now exists. The board, finding from the experi ence of the keepers of the lights at highlands of Navesink that the lenticular apparatus could be managed by the average light-keeper after in struction by an expert, and that its use was more economical in oil than was the reflector apparatus in use, pushed its substitution with vigor, find, as they had anticipated, with a diminution of the annual expenditure for oil.
The construction of lighthouses in the United States varies greatly. Those built on the New
England coast previous to 1840 were either of rubble masonry, in the shape of conical towers, or wooden frame towers built on the roofs of the keepers' dwellings. The stone towers were gen erally three feet thick at the base, tapering to two feet in thickness at the top, and from 20 to 50 feet in height. The iron-pile structure was introdueed next, and great improvement followed in the combination of the framework, in the ar rangement of elevated apartments for keepers, and making disk pile and other improved foun dations. There are a large number of screw-pile lighthouses, chiefly in Southern waters, and where dry foundations are found, iron plates have been used to form the structures in later years. A number of brick towers and iron skeleton towers are also in use. The lights in the various light houses are classed in six groups or orders, de pending upon their size. The first-order lights, which are the largest, have a lenticular appa ratus which stands nearly 12 feet in height, and is 6 feet in diameter. Such a light costs from $4250 to $S400. The lights of the second order are 4 feet 7 inches in diameter; those of the third, 3 feet inches; those of the fourth, inches; those of the fifth, 143/4 inches; and those of the sixth or smallest order are 11% inches. The total number of lights in the United States in 1900, including coast, lake and river lights, lightships, and lighted buoys, was 3163. (See table at end of article.) The river lights, of which there are about twice as many as the others, are considered as separate and distinct from the lighthouses, and are maintained from a separate fund.