Page 253 hydrography 3416 



3416. Leadsman 



In handlead sounding the leadsman sounds when directed to do so by the recorder, 

 measures the depth of the water with the k^adhne, and keeps a lookout over the sur- 

 rounding water for shoals, discolorations, or other objects which may be of interest to 

 the officer-in-charge. The leadsman must be a responsible person who takes his duties 

 seriously and is interested in the results obtained. When sounding from a launch or 

 small boat, the leadsman has a better point of view from which to scan the surrounding 

 waters than any of the other personnnel, because of the elevation of his position. He 

 should be the first to detect submerged rocks and shoals by sight. Even when the 

 bottom is not visible the leadsman frequently knows in advance from the sinking of 

 his lead that the water has shoaled, or deepened, even before he has obtained the 

 sounding, and where this may indicate a possible danger to the survey vessel he should 

 notify the officer-in-charge immediately. 



The leadsman usually has an assistant to haul in the leadline after each sounding. 

 When the leadsman is directed by the recorder to determine the characteristic of the 

 bottom, the assistant arms the lead. The intervals at which this is done are directed 

 by the officer-in-charge. Between the times when the lead is armed, the leadsman 

 should observe, by feeling with the lead, the relative hardness or softness of the bottom, 

 notifying the recorder when any change is detected, and especially any indication of 

 rocky bottom. On a survey ship two leadsmen usually alternate at handlead sounding, 

 relieving one another each hour, because a great effort is required to heave the lead 

 as far as necessary and it should not be required of one man throughout a 4-hour watch. 

 On a launch the coxswain and leadsman frequently alternate in heaving the lead, but 

 if the leadsman's assistant is experienced, he may alternate with the leadsman at their 

 respective duties. 



3417. Coxswain 



The coxswain on a launch, or the helmsman on a ship, steers the vessel in accord- 

 ance with orders issued by the officer-in-charge. Most sounding lines now are run by 

 steering compass courses. The coxswain must repeat, for the purpose of verification, 

 each order which is given him, and if the order given is for a change in course of a certain 

 number of degrees, he should also report the course on which he steadies. In launch 

 hydrography the coxswain also assists the officer-in-charge by keeping a lookout ahead 

 when he can do so in addition to steering. 



Most changes in course are ordered by the officer-in-charge immediately after a 

 fixed position has been plotted and the position of the vessel is known with reference to 

 the proposed line. The coxswain or helmsman shoidd quickly learn how soon after 

 a fixed position he may expect the order to change course and he should be listening 

 for such an order at this time and always be alert to comply with it in the shortest 

 possible time. 



Ranges may be run in small-boat hydrography and in a small percentage of launch 

 hydrography. A coxswain should be trained to keep the vessel on the range once it has 

 been placed on the sounding line and headed in the correct direction, and he should be 

 capable of selecting new objects as required for ranges on adjacent lines. (See 3142 

 and 3453.) 



342. The Operation of Sounding 



There is no essential difference in the methods employed in sounding from a ship, 

 launch, or small boat. Probably more than 99 percent of the soundings are now echo 



