CHAP. XXI.; SURVEYING FLOATING BEACONS 473 



ships engaged may be employed to the best advantage when 

 favourable opportunities of weather occur, a factor upon which 

 aU beacon work is more especially dej)endent. 



When the vessels are so employed it may be taken as a safe 

 indication of a proper organisation. 



SECTION I. 

 SURVEYING FLOATING BEACONS, MOORINGS, AND FLAGS. 



Beacons. — The beacons now in use are the well-known 

 cask type of surveying beacons, of the pattern of 1912, which 

 embody various improvements (f)rincipall\ consisting of in- 

 creased strength in the design as a whole), and include six 

 galvanised iron tie-rods connecting the top and bottom pieces, 

 also stouter sized poles and lengthened iron collars on the poles. 



Moorings. — ^These are now universally of galvanised chain, 

 size tV inch to yV inch — dependent upon the circumstances of 

 depth, etc. — and are usuallj/ prepared beforehand in lengths 

 of 35 fathoms. 



Wire rope, size 2 inches to 1| inches special one-strand rope 

 unit, can be used with advantage in deep water. 



Owing to the liability to chafe, hemp moorings should be 

 avoided, unless the depth renders it necessary. 



In depths not exceeding 100 fathoms, about one and a half 

 times the deftth should be used for the length of the moorings. 



Anchors. — The total weight of the anchors, backed with 

 sinkers, in depths under 100 fathoms, should never be less than 

 about one quarter of a ton, or about 500 pounds, and in a 

 tideway this weight should be increased. 



Various forms of anchors and sinkers have been used. 



(«) Sinkers: 5 c^vt. Service pattern, fiat bottomed, and 



mushroom shaped. 

 (6) Anchors: 3 to 4 cwt., Admiralty pattern, with stock, 



backed with additional sinkers where necessary, 

 (c) Boats' Anchors: Service pattern, 100 to 120 pounds' 



weight, backed up with eight i-cwt. sinkers, either 



passed through or secured to the anchor stock. 



Of these, the boats' anchors, (c), have proved the most 

 effective, and held the best. 



