502 HYDROGRAPHICAL SURVEYING [chap. xxi. 



as possible. Care is necessary to prevent the flags becoming 

 fouled aloft as the beacon is lifted . 



It should be made a practice for the ship's artisans to examine 

 and report the condition of the beacons on being recovered, 

 draining the casks, and tightening the hoops where necessary. 



An examination of the moorings, and whether the mooring 

 chain has become entwined round the anchor, will frequently 

 give a ready clue as to the reason of a beacon being out of posi- 

 tion, and afford useful knowledge for safeguarding this in future. 



Should it be necessary to replace at any time a beacon that 

 has become dismasted, dragged, etc., but which may still 

 occupy about the position we require, it is generally a better 

 plan to drop the new beacon first close to and with reference to 

 the original beacon, whose position may be known but is not 

 determined at the time owing to the weather conditions, such 

 as mist, etc. ; sufficient room must be left to manoeuvre the 

 ship clear of botli beacons when subsequently engaged in picking 

 up the damaged beacon. 



As a useful guide, it may be stated that the time occupied for 

 one vessel with a speed of 8 knots when engaged in picking up 

 successively ten beacons moored in about 20 fathoms at dis- 

 tances of 4| miles apart (which necessitates steaming not less 

 than 40 miles), should not under normal circumstances exceed 

 seven hours, and has in the \^a'iter's experience often been less. 



As a rough guide, not more than forty -five minutes should be 

 allowed for the interval between recovering successive beacons 

 when moored at this distance. 



SECTION XX. 



THE PROTECTION AND DISTINaUISHING OF BEACONS 

 BY NIGHT. 



Lighting of Beacons. 



No suitable means have yet been found in practice for hght- 

 ing the beacons in such a lasting manner as will indicate their 

 presence at night to passing vessels. 



It is out of the question to attempt to constantly renew 

 any lamp of whatever character that it may be possible to 

 attach in the first place to the staff, either from the ship or from 

 a boat in suitable weather ; the delays and risk of damage in- 



