CHAP, vm.] SOUNDING 205 



to warrant it. On a small-scale coast survey, if no plan of 

 the anchorage has been considered, necessary, the soundings 

 should at least have been thickened up to ensure, as far as the 

 scale will admit, that no hidden danger remains. Fishermen 

 should be interrogated, and their proceedings watched. 



Leading marks should invariably be run by the ship herself Leading 

 before recommending them. An original chart should indicate ^^ ^' 

 such marks, wherever they can be found, and are likely to be 

 serviceable. 



Clearing marks are particularly useful to the navigator, and Clearing 

 wherever they exist they should be noted on the chart and in ^^ ^' 

 the sailing directions, together with the best marks for fixing 

 the position of the ship. 



Shoal-banks, out of sight of land, or too far off to use marks. Sounding 

 can be sounded by starring round the ship, at anchor on it, or o^^gight^* 

 off its edge. For these, compass bearings of the sliip taken of Land, 

 from the boat, with distance measured by the mast-head angle, 

 will probably suffice in accuracy, the boats sounding in lines 

 radiating from the ship in all directions. 



It should be noted that this method of sounding covers the 

 ground very unequally, and is objectionable on that account. 



A large canvas ball or cylinder, on a light framework of 

 iron, and painted black, wdll be found very useful at the 

 mast-head when taking the angle for this purpose, as it will 

 clearly define the mast-head, and also indicates " Ship in 

 position." 



Boats or beacons can be moored in convenient positions, and 

 fixed by angles to one another and to and from the ship, also 

 at anchor, and the base obtained by mast-head angle, if it is 

 necessary to sound a bank a little more accurately. These 

 will then be used as marks, and the soundings fixed by angles 

 in the ordinary way. 



Having starred round the ship at anchor on a shoal, it is 

 sometimes advisable to leave a boat at the anchorage to mark 

 the position wliile the ship weighs and proceeds to search for 

 another shoal patch, which, when found, is connected with 

 the boat's position by her bearing from the ship and mast-head 

 angle taken from the boat. 



On suddenly striking shoal-water out of sight of land, the 

 ship may be anchored at once, and the shoal sounded out by 



