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Chapter Page 



9. Handling an Unescorted Vessel in Ice 61 



Entry Into Ice 61 



Working Through Ice 62 



Speed of Advance 70 



Hazards in the Ice 71 



Release of a Vessel 72 



Precautions Against Being Beset 74 



Precautions When Beset 74 



Operating Boats and Seaplanes 76 



10. Operating an Icebreaker 77 



Propellers 77 



Performance 78 



Operating in Ice 79 



Anchoring 84 



Explosives 85 



Engineering Procedures 85 



11. Convoying in Ice 87 



Types of Convoy 87 



Distance between Ships 89 



Course and Speed of Convoy 91 



Conducting through Ice 93 



Towing in Ice 98 



Breaking Out Ships 101 



Convoy Signals 105 



12. Navigating in Polar Regions 107 



Signs of Proximity of Ice 107 



Signs of Open Water 108 



Abnormal Refraction 109 



Piloting 112 



Fixing Positions 115 



Magnetic Compass 116 



Dead Reckoning 117 



Radar in Ice 120 



Sonar in Ice 122 



Appendix A. A Proposed Ice Dock 123 



Index 126 



LIST OF FIGURES 



No. 



1. Relationship between freezing point and temperature of maximum 



density for water of varying salinity 2 



2. Idealized diagrams illustrating the distribution of temperature with 



air at 0° F., and sea water at its freezing point of 30° F 4 



3. Graph for prediction of approximate thickness of ice 6 



4. Course of thickness of ice formed in two typical sheltered harbors in 



the Northern Hemisphere at the latitudes indicated 8 



5. Synoptic diagram showing the general relationships between the various 



kinds of ice occurring in the sea 10 



6. Tabular iceberg off Scott Island 12 



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