LIGHTHOUSE, a structure on some con spicuous point of seashore, island or rock, or on the bank of rivers and lakes, from which a light is exhibited at night as a guide to mariners. Lighthouses are generally placed on salient points, each requiring structures specially designed to meet the exigencies of varied sites. When placed on headlands or large islands lighthouses are very much alike in general features, the differences being mainly in the height of the towers, depending on the dis tance at which the light requires to be seen, and the lighting apparatus. Towers erected on isolated, wave-swept rocks in the open sea, such as the Minet's Ledge and Spectacle Reef in the United States, the Eddystone, the Bell Rock, Skerryvore and Chickens Rock light houses in Great Britain, and that of Brehat in France, are triumphs of engineering.
The history of lighthouse build ing and illumination may be said to extend over a period of more than 2,000 years; but the regularly organized life-preserving system of modern lighthouse engineering goes back very little further than the beginning of the 19th century. None of the early lighthouse buildings now exist. The Pharos of Alexan dria (331 a.c.) gave its name to its successors. The Romans built lighthouses at Ostia, Ra venna, Puteoli and other ports. The Phoenician Pharos at Coruna, repaired during the reign of the Roman Emperor Trajan, was re-established as a lighthouse about 1634, and in 1847 had a dioptric apparatus placed in it. On the cliff at Boulogne there are the remains of a lighthouse ascribed to Caligula (40 A.D.), and at Dover there are remains of another Roman Pharos. Until the end of the 18th century the light houses of the United States and of Great Britain were few in number, and of an inferior description in the great essential of a lighthouse, namely, sending the greatest number of rays of light toward the horizon. In the United States of America the first act of Congress relating to lighthouses was passed in 1789. Many of the public lights in England were private property, as was also the case with the Isle of May in Scotland, the patent for which was ratified in 1641. There were only 25 lighthouse stations and six floating lights in England at the beginning of the 19th cen tury. The coast and harbor lights in Great
Britain and Ireland are now upward of 1,000 in number.
The early lighthouse towers had on their summits grates or chauffers, in which billets of wood or coal were burned, but though ex pensive to maintain —some of them using 400 tons of coal yearly— were uncertain in their appearance, varying with the ever-changing character of the atmosphere. Such coal-lights survived in Scotland till 1816, in England till 1822 and on the Baltic till 1846.
The difficulties of building are very great, the greatest usually being to effect a landing of men and material. At Minot's Ledge, off the Massachusetts coast, General Alexander got only 30 hours of work in the first year, and 157 in the second, and the earlier histories of the Bell Rock, Skerry vore, Dhuheartach, Chickens, Eddystone in Great Britain and others tell the same tale. The cost of lighthouses may vary much; for in stance, Spectacle Reef, on Lake Huron, cost $300,000• an ordinary land station, fully equipped, will cost much less — as a matter of fact, about $25,000 to $50,000. Light-vessels cost about $45,000.
These towers are constructed of steel, or hard stone, such as granite, or cement-concrete faced with hard stone, and of such a mass and strength as to prevent their being overturned or destroyed by the waves. A typical stone lighthouse is built of granite, say 140 feet in height, with a diameter at the base of 42 feet and at the top of 16 feet, and contains 58,580 cubic feet, or about 4,308 tons of masonry. A staff of four light-keepers is attached to such rock lighthouses, three residing in the light house and one on shore, the reliefs being fort nightly, 'so that each man has six weeks on the rock and two weeks ashore. At land light house-stations, where women and children can be stationed, the keepers' families reside with them, and the staff consists of three men when there is a fog-signal, and two men when there is only the light to attend to. It is considered essential that a constant watch be kept in the light-room during darkness to ensure the proper exhibition of light.