CHAP. VIII.] SHIP SOUNDING 209 



may be quoted, though we have no knowledge of its having Belcher's 

 been practically tried. He suggests anchoring the boat as ing°a° ' 

 close to the bar as is safe, with the tide at flood, and veering Bar." 

 away a barricoe with a grapnel hanging at a given length of 

 rope. The barricoe is permitted to drift freely over the bar, 

 when the anchor catching, will give a shock to the barricoe 

 that will be seen by the watcher in the boat, and will indicate 

 that a less depth than the length of the cable allowed to the 

 anchor is on that part of the bar. 



The line attached to the barricoe, with presumably a tripping 

 connection with the grapnel, will bring the apparatus back to 

 the boat, when she can test another part of the bar in the 

 same manner. 



SHIP SOUNDING. 



The soundings over a certain depth — about 20 fathoms — can 



generally be most advantageously done from the ship. 



Where a steam- winch is fitted, soundings can be got with Usual 



Plan, 

 great rapidity ; and by dropping the lead from forward and 



heaving it up to a davit fitted on the taffrail, up-and-down 



casts can be got in 40 fathoms at a speed of about 4| knots 



without stopping with a 100-pound lead. 



If a long spar be fitted as a derrick aft, soundings can be 

 obtained in water up to 20 fathoms, by merely swinging the lead 

 and letting it go without heaving forward. 



A large field-board, about 42 inches by 36 inches, fitted with Ship's 

 legs to form a table, is necessary for ship's sounding. Board. 



A scale showing the distance on the sounding-board passed 

 over per minute of time at the average speed at which the ship 

 is travelling, is useful to ensure turning at the right moment, 

 and to avoid overshooting a certain spot, as when proceeding 

 from one line to another. The time must be noted at each fix. 



For deeper water a variety of methods have been devised Arrange- 



for getting the lead forward and dropping it rapidly. Expe- 



The following is now generally used : ^^^^°^^ 



° o ./ Sounding. 



The lower boom is got out and topped to an angle of 

 about 40°. 



An endless rounding-line of lead-line is carried through a 

 block at the end of the boom, by leading blocks to the steam- 



14 



