^^I^ 



the most powerful lic.ht of this country, estimated 6o.000.000 caxdi.e 

 power: the xavesink lighthouse, new jersev 



"The electric light at Navesink, on the highlands just south of New York harbor, is the 

 most powerful coast light in the United States. This light shows each 5 seconds a flash of 

 one-tenth second duration estimated at 60 million candle power. Although, on account of 

 the curvature of the earth, the light itself cannot be seen more than 22 miles, its beam has 

 been reported to have been observed in the sky at a distance of 70 nautical miles (see 

 page 33)- 



every 20 seconds and giving a double 

 flash of about 940.000 candle power 

 every 10 seconds. The light is suffi- 

 ciently powerful to be visible 40 miles, 

 but because of the earth's curvature it 

 can be seen only 21 miles (see page 42). 



Occulting lights are less efficient, the 

 occultations being obtained by revolving 

 a screen around the light, by a drop shut- 

 ter, or by blank panels in a revolving 

 lens. With gas lights, flashes or occulta- 

 tions may be obtained by automatically 

 intermitting the gas supply, a small pilot 

 light still remaining. 



The earlier lighthouses all showed 

 fixed lights, and were equipped with 

 lamps giving only moderate candle 

 power. There is always danger of mis- 

 taking the identity of a fixed light, as it 

 may be confused with other hghts on 

 shore or on vessels, or one lighthouse 

 mistaken for another, and marine dis- 

 asters have resulted from such mistakes. 



All countries have, therefore, long since 

 undertaken to change the fixed liglils at 

 important coast points and give them a 

 distinctive characteristic, and also to in- 

 crease the brilliancy of illumination. 



To indicate the steady progress made 

 along these lines, during the past two 

 years this service has changed 47 lights 

 from fixed to flashing or occulting, and 

 at 68 light stations has substituted in- 

 candescent oil-vapor lamps for oil-wick 

 lamps, the latter greatly increasing the 

 brilliancy, with a diminished consumjjtion 

 of oil. 



D.WM.XRKS 



In addition to the lights, many other 

 marks are provided to assist navigators. 

 The light-towers themselves are painted 

 and shaped to make good landmarks in 

 the daytime, and special beacons and 

 spindles are placed usually to mark 

 shoals or other dangers. Nature and 

 man also provide many landmarks valu- 



39 



