CHAP. VIII.] SOUNDING 197 



Before running in on the new line it is a wise precaution to 

 pick up in a similar manner another object on the beach as 

 nearly as possible at the end of the next line to be run out from 

 the shore. When close in shore it is often impossible to fix, 

 and the lines may therefore be irregular without some such 

 assistance. 



In sounding out a small harbour, circumstances must guide 

 the direction of the lines. 



A point of land or a reef is often prolonged under water by a sounding 

 narrow shoal ridge, which, unless carefully searched for, may °f Land or 

 escape detection. Radiating lines of soundings at close Reef, 

 intervals are necessary, supplemented by cross-lines in cases 

 where the geological features suggest the possibility of such 

 prolongation occurring. All rocky points likely to be rounded 

 closely by a ship should receive such close examination. 



In planning lines of soundings it is desirable to call attention 

 to one particular element of danger. This lies in the elbow 

 formed by changing abruptly the direction of parallel lines of 

 soundings, the area of unexamined ground thus being unduly 

 great compared with the remainder. 



Two observers being in a boat near the required spot, the To Pick 

 fixing angles are clamped on their sextants. Manoeuvring the posttfon^" 

 boat to bring on the more sensitive of the two angles, the by Sex- 

 direction of the arc of that circle is estimated, and the boat Angles, 

 steered to keep on it by preserving the exact angle between 

 the two objects. The other angle will then gradually be 

 brought on and the precise spot will have been reached. 



In sounding off breakers it is frequently a good and safe Danger 

 plan to steam round them as closely as may be considered 

 prudent, cutting in their tangents and sounding at the same 

 time. The lines may afterwards be run off and on at right 

 angles to the line of breakers, but it will not now be necessary 

 to do more than approach the danger-line that has been 

 first run, and the safety of the ship or boat is less imperilled 

 by thus having a definite limit within which she must not 

 pass. 



In turbid waters pinnacle rocks are seldom discovered by the Pinnacle 

 ordinary lines of soundings. If an indication is obtained, it 

 is very possible that it may be by getting a deeper sounding 

 than usual, the scour round the base of the rock making a 



