210 



HYDROGRAPHICAL SURVEYING [cHAr. viii. 



Alterna- 

 tive 

 Method. 



winch, and to the derrick or davit aft. A shp is attached to 

 this with a broad projecting palm of sheet-iron to the catch 

 (see Fig. 57). 



To this the lead is attached, and hove forward by the winch. 

 When up to the boom, the rounding-line is let go, and on 

 striking the ^^•ater the palm releases the catch, and the lead 

 falls free to the bottom. 



The roimding-line is at once rounded aft again, ready foi 

 the slip to be again attached when the lead comes up. 



Fig- 57- 



a. The broad palm 



b. A spring to keep slip in place. 



There are varieties in the detail of the fittings, according 

 to different ideas. 



By dropping the lead well away from the ship, the chances 

 of the lead-line fouling the screw, if the helm is over, are 

 much lessened. 



Another plan has recently been tried with successful results. 

 By its means the lead can be slipped from any desired 

 position as it travels forward, and it has the advantage 



