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7. Pancake ice. This is new ice formed after 2 or 3 days of freezing 



temperature 15 



8. Tidal currents acting on grounded ice produce the mushroom-looking 



pieces of ice, whose shape is visible at low tide 16 



9. Sea ice being subjected to great pressure 17 



10. Phase diagram for pure water in the vicinity of the freezing point 21 



1 1 . Hummockv ice floes in Eureka Sound 31 



12. Airplane photo of huge iceberg showing direction and effect of deep 



water currents. Although the berg stands about 280 feet above 

 water, it extends more than 1,000 feet below surface and is affected 

 by currents which run too deep to move neighl^oring ice 32 



13. Showing the effect of the propellers in keeping the stern of the ice- 



breaker clear of ice while hove to 52 



14. Mooring ship to the Antarctic ice shelf 54 



15. Unloading cargo from U. S. S. Yancey (U. S. S. Merrick in background). 



Lengths of telegraph poles hung vertically over side of ship are used 



as fenders 55 



16. Ships moored to ice showing tracks left in the ice from unloading opera- 



tions. Camp HIGH JUMP in the background 57 



17. U. S.C.G.C. A^ori/iwmd breaking through ice in McClure Straits, showing 



upended ice cakes which present a danger of fouling the propellers. . 64 



18. U. S. S. Edisto in drydock. Port propeller and external portion of 



shaft were sheared off by contact with the hard ice of the Lincoln 



Sea. Shaft is 18 inches in diameter 65 



19. A composite convoy in column following an icebreaker 88 



20. Line of bearing for breaking-out 89 



21. Wake left by U. S. C. G. C. Northwind after making her way through 



the ice. Note consistency of the ice left in the channel and the 

 tendency for the channel to fill up after passage of the icebreaker 90 



22. Herringbone method of breaking ice 96 



23. Modified herringbone method of breaking a wide lane 97 



24. Methods of making fast the tow lines when towing in ice 100 



25. U. S. C. G. C. Eastwind employing tactics of backing down on the bow 



of the U. S. S. T'Tyondoi to break her out of ice 102 



26. Diagram illustrating the conditions under which superior mirages va.&y 



be formed off large ice masses 111 



27. The ice dock when completed. The ship rests on ice buttresses 123 



28. After the ice has been removed from (A), a new layer of ice (B) forms 



below the ice layer, constituting the bottom of the future ice dock__ 124 



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