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from time to time. On the other hand, it must be reduced occasionally 

 to examine the state of the ice and adapt the course accordinf^ly. 



Ice covering seven- to eight-tenths of the surface must be travei-sed 

 throughout at slow speed, so that any impacts with the ice will not 

 damage the hull. 



Once inside pack ice covering eight-tenths or more of the surface, 

 revolutions may be increased even to full with the object, not of 

 increasing speed, but of forcing a passage through the ice by using 

 the power of the engines. 



When darkness descends, or the visibility becomes poor, a vessel 

 working her way through leads or weak areas in close pack should 

 heave to or ride to an ice anchor. Otherwise she may unwittingly 

 enter thick ice from which it will be difficult to withdraw when the 

 visibility improves. On the other hand, when navigating at night or 

 with poor visibility through more broken ice, it is recommended not 

 to stop, but to proceed with caution at very slow speed. Under such 

 circumstances keep searchlights manned for immediate use. The 

 Edisto used 24-inch searchlights to aid the conning officer in picking 

 leads with some success. . The main criticism against using these lights 

 is that they are located behind the observer and the glare partially 

 blinds him. As an alternative, two portable lamps similar to "sealed 

 beam" automobile headlights can be rigged so that they can be installed 

 on the forward bridge bulwark and operated as necessary by bridge 

 lookouts. A portable damage control lamp has also been successfully 

 tested. 



HAZARDS IN THE ICE 



riie most serious danger is that caused by the pressure of the ice 

 on a vessel, which may result in the crushing of the hull or the nipping 

 off of the ship's bottom. This risk is greatest when navigating in 

 pack ice covering seven-tenths or more of the surrounding sea. Apart 

 from this hazard, a vessel beset by ice and therefore drifting with 

 it, may be forced into waters which are dangerous to navigation. In 

 the autumn there is also the risk of being forced to winter in the ice. 



Another danger is the meeting of masses of thick broken ice, espe- 

 cially those that bear signs of erosion by the sea on their upper sur- 

 faces. Such ice masses often have underwater spurs. The submerged 

 portions of such pieces are extraordinarily strong and are hardly 

 affected by melting. These can be very dangerous on impact with the 

 hull or screws of a fast-moving vessel. Dirty ice, broken away from 

 coastal regions, may sometimes be encountered at sea. This ice may 

 also be very strong. Furthermore, it nuist be remembered that the 



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