National Geographic : 1936 Aug
NEW SAFEGUARDS FOR SHIPS IN FOG AND STORM BY GEORGE R. PUTNAM Commissioner of Lighthouses, Retired T HE most magnificent of all light houses was built before the dawn of New Testament history, but the most remarkable of navigational safeguards has come only in the past few years. Day and night a monotonous drone of dots and dashes goes out over the sea, pene trating the thickest rain and fog, to help bring the voyager safely home. Today radiobeacons are essential equip ment on our most important lightships and lighthouses, and apparatus for receiving radiobeacon signals is carried on all mod ern passenger liners and many other vessels. Thus, after more than 2,200 years, we approach the solution of one of mankind's oldest problems. The lofty Pharos of Alex andria, erected by the Ptolemies near the mouth of the Nile, has never been surpassed by any other lighthouse in height or in fame (page 174). Its name became the word for lighthouse in the Romance lan guages; the French use it in radiophare (radiobeacon). But the signal which this magnificent tower gave to mariners was the light and the smoke from an open fire. No progress was made in marine signal lights for many centuries. Only a hundred and twenty five years ago tallow candles burned in the famous Eddystone Lighthouse near the English coast, and until 1816 the May Island Light, off Scotland, still used a blaz ing coal fire to guide ships. Nearly all the major advances in lights and fog signals-the electric lamp, the incan descent oil-vapor light, the Fresnel lens focus ing the beam in the horizon of the mariner, the fast-revolving light making it possible still further to gather the rays into powerful beams, and the fog bells, followed by the whistle, siren, and diaphone-have been de veloped within a little more than a century. Only in the last 30 years has so neces sary an aid been employed as the lighted buoy, boon to the navigator who must bring his vessel into port at night through treacherous shoals and narrow channels. The most notable advance was made 15 years ago, when radiobeacons were placed by the U. S. Lighthouse Service on Ambrose Channel Lightship and two other stations in the approaches to New York. Thus was solved an age-old problem. Only the radio signal penetrates fog and rain that blot out the most brilliant light.* It can carry its message of safety through storms that drown the most powerful whistle. Above the pilothouse of a modern liner you will see a small rotating coil antenna mounted on a metal frame. This coil re ceives radiobeacon signals now sent out from important lighthouses and lightships - more than 120 of them on the coasts of this country. THE RADIOBEACON AT WORK In approaching the coast, the navigator of a ship with this coil picks up a radio beacon signal-perhaps the four dashes from Nantucket Shoals Lightship, or the single dots from Ambrose. By rotating his radiocompass coil until the signal fades away ("taking the minimum" it is called), he determines the direction from which the signal comes, even from distances of more than a hundred miles (page 170). Anyone who has stood on the deck of a liner in a dripping fog, and has wondered at the courage of the navigators going ahead toward the unseeable, must realize what a blessing this is to tense nerves-how valu able is this gift of science to better naviga tion and to safety at sea. Radiobeacon systems now are being ex tended throughout the world, and radio di rection-finders are being placed on more and more vessels, recently even on fishing craft. There also are direction-finding sta tions on shore which give radio bearings to ships asking for them. These radiobeacons have added some 1,500,000 square miles of water to the area served by United States aids to navigation. In fact, their signals may carry far beyond this area. While off Nova Scotia, for ex ample, the Bremen once took bearings on the radiobeacon at Col6n, Panama, more than 2,000 miles away. * Other Government agencies have done pioneer work and have cooperated in the development of radio navigational aids, including the Navy, the Army, and the Department of Commerce, espe cially the National Bureau of Standards and the Bureau of Air Commerce.