National Geographic : 1913 Jan
THE PIGEON POINT LIGHTHOUSE, ON THE RUGGED PACIFIC COAST, CALIFORNIA This light gives each 10 seconds a flash of 4 seconds' duration and 160,000 candle power. The fog signal is a first-class air siren, giving each 30 seconds two blasts in quick succession a traveler on a cable. The total cost of the work at St. George Reef was about $712,000, making it the most expensive lighthouse that has been built in this country. These two exposed light sta tions on the Pacific coast are the only ones having five keepers (see pp. 16-18). Of lighthouses built on piles in the water, the original Minots Ledge struc ture has been mentioned. Brandywine Shoal light, in 6 feet of water in Dela ware Bay, completed in 1850, was the first in the United States built on iron screw-piles. These were bored down 6 feet into the sand bottom, the broad screws at the ends of the piles also fur nishing additional bearing surface; this structure has stood 62 years, but now must be rebuilt on account of the piles having been damaged by the ice. LIGHTS ON THE FLORIDA REEFS Five pyramidal iron skeleton light houses have been built in the water along the Florida reefs; these are supported on iron piles forced about 10 feet into the coral rock or sand. The piles are driven through large cast-iron discs, with a shoulder bearing on the disc; these discs are about 8 feet in diameter and give a broad support for the structure. Sombrero Key, with its light 142 feet above the sea, is the tallest of these reef lighthouses (see page 22). The keepers' quarters are carried within the skeleton tower, and they thus live 37 feet above the water. LIGHTS ON SAND BOTTOM-THE 14-FOOT BANK LIGHT The first lighthouse built in the sea distant from the land and not on a rock foundation was the Rothersand. This notable engineering work stands in 20 feet of water, on a sand foundation in the North Sea, o1miles from the Ger man coast, in the approach to Bremen. The first attempt to place a lighthouse in this position resulted in failure, but a structure was finally completed in 1885.