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NAVIGATIONAL AIDS, Improved Signals and Marks Installed partment of commerce has recent- ly completed an elaborate re- vision and modernization of aids to navigation in Duluth-Superior harbor on Lake Superior. Before going into details in connection with the recon- struction of the system of naviga- tional signals and marks in this har- bor, let us consider briefly the value of general aids to navigation on Lake Superior as exemplified by the voy- age of a 600-foot bulk freighter after passing through the locks at Sault Ste. Marie, bound for Duluth. Shortly after the big freighter has passed Whitefish Point Light station it is not unusual for a ‘‘pea soup’’ fog to blot out the light and every other visible evidence of the surroundings. It is in circumstances like these that the radio beacons, installed at Manitou, Passage Island, EKagle Har- bor and Devil’s Island, serve as in- valuable aids in making it possible for the vessel to maintain her sched- ule with complete safety if she is equipped with a direction finder and if it is used with intelligence and care. Without seeing a light or any other landmark all the way up Lake Superior the skipper is able to con- tinue with confidence at his regular speed as he can and does take bear- ings from the various radio beacons from which he is able to determine with accuracy his position on the course until he hears the signals from the Duluth radio beacon dead ahead. T= lighthouse service of the de- Distance Off Determined When the fog signal is heard the speed is checked down and since this signal is synchronized with the radio beacon, it is possible to determine accurately the distance off (within 10 per cent) by the simple device of noting the time of the fog signal. For practical navigation, as sound travels about one mile in five seconds, hav- ing noted the elapsed interval be- tween the known time of sending and hearing the fog signal, the distance is established at once, Very often, peculiarly enough, the fog lifts sufficiently for entering Du- luth harbor without difficulty. Then guided by the flashing lights of the The author, F. P. Dillon, is superin- tendent of lighthouses, in charge of the eleventh lighthouse district, with office at Detroit. The eleventh lighthouse dis- trict extends from Lake Erie to Duluth, but does not include Lake Michigan, which .is in the twelfth district. 14 buoys and the steady lights of the ranges, the vessel confidently moves around Rice point and finally comes alongside of the great ore chutes, and without ceremony begins the business of loading from nine to twelve thous- and tons of ore. Before the break of day she has disappeared downbound on her schedule, guided by the sig- nals of the lighthouse service, New Lights and Marks In August, 1933, the sum of $90,- 500 was allotted from public works appropriations for the lighthouse service, department of commerce, for the revision of aids to navigation. Du- luth-Superior harbor and approaches, New light signals and marks at Duluth- Superior harbor. Upper—Electric range light, St. Louis river. Point Light..No.6 MARINE REVIEw—February, 1935 Lower—Rice _ BY F. P. DILLON*® Plans were made by the superintend- ent of lighthouses, Detroit, which in- cluded a low power radiobeacon at Superior Entry Light station. A variety of construction work was involved, embracing design and erec- tion of steel towers on shore and on marine foundations, equipping towers with tank houses, pole line and ca- ble connections and various types of lanterns to suit conditions. Steel buoys, complete with light- ing equipment, were provided, includ- ing acetylene accumulators. The re- arrangement and improvement of the entire buoyage system was effected, including all other aids to naviga- tion. Because ice conditions at times make buoy marking unreliable, per- manent sets of range lights were es- tablished for service throughout the season. The navigation season for Duluth- Superior harbor averages about eight months. Fog or thick weather is of- ten encountered. Shipping is char- acterized by bulk cargo carriers and package freighters, many vessels be- ing about 600 feet long. Vessel freight receipts consist mainly of coal. Such materials as limestone, slag, coke, oils, steel products, auto- mobiles and miscellaneous freight are of much less tonnage. Of the freight shipped, iron ore and wheat rank highest in tonnage, and in much less quantity are such items as flour, grains, dairy products, scrap iron and wool. Confusion Eliminated From 2000 to 12,000 vessels have entered and departed from these har- bors in a single season in late years. These are busy ports even in depres- sion times. The vessels are of mod- ern type designed to be loaded and unloaded quickly. The ore and coal docks have loading and unloading equipment which is the marvel of the shipping world. The vessels move in and out of the ports continuously, day and night, in all kinds of weath- er, on schedule, and often dock with- out the assistance of tugs. Delays are thus cut to a minimum. The movement of this vessel traffic im- poses heavy responsibilities on the masters of the vessels and on the lighthouse service, whose duty it is to establish and maintain the marks and signals for safe navigation of the waterways. To safeguard the traffic in Duluth- Superior harbor, the boundaries of