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Gravelly Shoals Light is an automated lighthouse that is an active aid to navigation on the shallow shoals extending southeast from Point Lookout〔(Wobser, Dave, Gravelly Shoal Light ), at boatnerd.com.〕 on the western side of Saginaw Bay. The light is situated about offshore and was built to help guide boats through the deeper water between the southeast end of Gravelly Shoals and Charity Island. Architecturally this is considered to be Art Deco style.〔(Lighthouse Depot, Gravelly Shoal light. )〕 ==History== As part of President Roosevelt's New Deal and its program to "Put America Back to Work" the new light tower was put up for bid, and built in 1939.〔(Lighthouse Central, Gravelly Shoal Light Photographs, History and Directions, ''The Ultimate Guide to East Michigan Lighthouses'' by Jerry Roach ) (Publisher: Bugs Publishing LLC - July 2006). ISBN 0-9747977-1-5; ISBN 978-0-9747977-1-7.〕 It replaced an earlier gas-lit buoy. It also displaced the Charity Island Light,〔(Bostwick, Violet M., ''Charity Island Light'', Boatnerd.com. )〕 which was constructed in 1857, and operated until 1930.〔 Contemporary unmanned lights in the Art Deco style is the Indiana Harbor East Breakwater Light and its twin, the better known Port Washington Breakwater Light in Wisconsin.〔 Note that the document has a picture of the Indiana Harbor East Breakwater Light under "Indiana Harbor Light", and that it has the correct history and wrong picture under "Indiana Harbor East Breakwater Light"〕 When built according to its original specifications, the contractor warned that the foundation was inadequate to withstand the buildup of ice, and put in a bid for a contract modification. However, at the time jurisdiction over the light had just been transferred to the Coast Guard from the United States Lighthouse Service, and they chose to disregard the warning, and to accept the light as built. This resulted in substantial additional expense in due course, as the light had to be retrofitted.〔 This light is designed as an autonomous automated electrified station. It is under the control and maintenance of Coast Guard Station in Tawas City, Michigan. Ordinarily it displays a 15,000 candela light powered by a 120 volt electric lamp. Power is supplied through a submarine cable, which crosses the shoal from Point Lookout. The focal plane makes its flash (1-second every 5 seconds) visible for . It is supplemented by a standby 110 candela acetylene light with a half second flash every three seconds—which activates automatically if there is a power failure. In foggy weather, mariners are warned by twin compressed-air two-tone #3 diaphones, which operate on a 30-second cycle (3-second blast followed by 27 seconds of silence).〔 The National Data Buoy Center lists the Site Elevation as above sea level; an automatic readout for wind, waves and weather is operated there.〔(National Buoy Data Center with automatic readout of wind, waves and weather for Gravelly Shoal Light. )〕 The National Weather Service operates an automated weather observing station at the lighthouse. An added large steel tower atop the light is a radio beacon. The 1953 Coast Guard Light List indicates that the signal transmitted at 296 kilocycles, send forth a group of half-second dashes for 15.5 seconds, followed by 14½ seconds of silence. As of 2001, both the light and radio beacon served as active navigational aids.〔 Although it never had a resident lighthouse keeper, this light is a recognized 'significant light" by the National Park Service National Maritime Initiative.〔National Park Service (Maritime History Project, Inventory of Historic Light Stations. Significant Unmanned Aids. )〕 As of July, 2015, the light is for sale through an on line GSA auction process.〔(【引用サイトリンク】title=Summer 2015 Lighthouse Sales Be a Part of Maritime History Zone One—Boston/Chicago )〕〔(【引用サイトリンク】title=Gravelly Shoal Light Auction ) 〕〔 〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Gravelly Shoal Light」の詳細全文を読む スポンサード リンク
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