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use great care to avoid damage to the hull of the vessel through col- 

 lisions with the ice cakes. 



4. If the ice is thick and drifting rapidly, wait for a change in di- 

 rection of the ice movement, which may be accompanied by an im- 

 provement in ice conditions. Take into account the time of ebb and 

 flood : ice generally becomes more compact on the flood but begins to 

 break up on the ebb. 



5. The ice edge is usually not straight, but often has projecting 

 tongues between bights. Enter at such a bight, for here the surge will 

 be least. 



6. Enter at the slowest possible speed, to reduce the force of the 

 initial impact on the stern. Once the bow is in the ice and is cutting 

 or pushing ice aside, increase power to avoid losing headway and 

 adjust revolutions thereafter in accordance with the state of the ice. 



7. Always enter the ice on a course perpendicular to its edge. Fail- 

 ure to observe this precaution may result in a glancing blow which will 

 very likely damage the bow plating on the side toward the ice, and may 

 swing the stem into the ice with resulting damage to rudder and 

 propeller. 



WORKING THROUGH ICE 



Some guiding principles of working in pack are: 



(1) Keep moving, 



(2) Work with the ice, not against it, 



(3) Do not rjish the work, 



(4) Respect the ice ; do not fear it, 



(5) Stay in open water or leads, 



(6) Watch the propeller, 



(7) Xever hit a large piece of ice if you can go around it ; if you 

 must hit it, hit it head on. 



The type, thickness, and area of ice which can be attempted depend 

 on the type, size, strength, and shaft horsepower of the vessel employed. 

 Ice covering up to five- or six-tenths of the sea surface is passable by 

 all powered vessels, for a way can always be found around individual 

 blocks or masses of ice. Independent navigation by vessels in ice 

 covering more than six-tenths is more difficult ; the master's experience 

 in ice navigation, and the existence of leads or areas of open water are 

 the things that count. Bearing in mind the contour of the coast, the 

 position of islands, and the direction of the wind and permanent cur- 

 rents, one may form an idea of the direction in which the ice may be 

 getting thicker or breaking up. 



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