A and B are designed to permit passage of vessels south of the cold 

 water and consequently south of the fog. As cold air masses more 

 frequently pass over the northern routes (tracks E and F), clear 

 weather can be expected along these tracks more often than would 

 be experienced farther south. Strict adherence to the prescribed 

 routes, therefore, is strongly recommended. Vessels which adhere to 

 the tracks in force travel through an area that is constantly being 

 crossed by other vessels and conditions therein are known. On the 

 other hand, a vessel that deviates from the prescribed route may 

 pass immediately into an area in which ice conditions are unknown 

 and usually into waters where fog is more prevalent. 



The ice along the edges of an ice field, particularly on the lee side, 

 is ordinarily light and easily penetrated as it is there that the ice is 

 being scattered by wind and sea, broken up and eventually melted. 

 As a vessel continues on into the ice field, the ice gradually becomes 

 heavier and more close packed, resulting in the speed being diminished 

 accordingly. Some ships wisely return to open water before the 

 situation becomes acute. Others, however, continue on and assume 

 the risk of being caught in the ice or damaged. A greater percentage 

 of fog will be found over water partly covered with ice, adding to 

 the risk already taken in attempting to cross through an ice field. 



When field ice is encountered by a vessel, the master must decide 

 either to attempt passage through it or to follow the safer procedure 

 of rounding it. It is believed that the proper action to take would 

 be never to enter field ice, especially when the opposite edge is beyond 

 the limit of vision. Even in passing through isolated strings of ice, 

 utmost caution must be exercised inasmuch as what often appears 

 from the edge to be small pieces may be found on contact to be large 

 and heavy with a tremendous destructive power. Oftentimes, in 

 crossing through field ice strings, collision with larger pieces cannot be 

 avoided and, although hull plating may withstand the shock, there 

 is always the danger of damaging the propeller or rudder. Field 

 ice, then, should always be avoided if it is at all possible to do so. 



For example, close packed field ice containing numerous bergs and 

 growlers entered the area at the northeast shoulder of the Grand 

 Banks in February, 1939, and Canadian tracks E and F were impass- 

 able until May 16. The boundaries of the ice field were described 

 in the regular ice broadcasts and vessels were advised to shape their 

 courses to pass south of the southern limits. The vessels that heeded 

 this suggestion traversed the area safely with little loss of time and 

 distance, while those that attempted a more direct course experienced 

 delay of several days' time and a few sustained damage. The expenses 

 incident to repairs as a result of field ice damages and the cost due 

 to loss of time must represent a considerable sum of money. This 



