117 



overhanging and towering ice walls and cracked pinnacles seem un- 

 affected by such noises. Six-pounder shells will bring down from a 

 few pounds to a few tons of ice. They are most likely to produce 

 damage if fired into weak portions of vertical or overhanging walls. 

 Sometimes a lucky shot placed in a crack near a pinnacle or a corner 

 about ready to fall will serve to produce a sizeable growler. 



That a berg about the Grand Banks can be noticeably shattered or 

 affected by any such thing as the making of noises near it, or by weak 

 blows like those from an axe should be considered as conceivable, but 

 verging upon the extreme height of improbability. The above state- 

 ment is made in spite of the following experience with a seemingly 

 fragile berg. 



One day in August, 1928, the United States Guard Cutter Marion 

 was run alongside a small grounded berg oft" the Labrador coast for 

 the purpose of obtaining ice. While the berg was being attacked 

 with an axe it calved and pieces of large size thundered into the sea, 

 pushing the vessel well clear. The action of this berg was alarming 

 and impressive to those witnessing it, but it should not be taken as 

 showing the great liabihty of bergs to disintegrate because of small 

 blows. As a matter of fact the ice that calved off amounted to very 

 little when compared to the total mass of the berg. The parts that 

 fell off were located along an almost vertical, slightly undercut wall. 

 The ice was probably just about to come down of its own accord from 

 the internally strained, grounded berg. It did so when the ship was 

 gently bumped against it by the slight swell, and when the men on 

 deck struck at the ice surface opposite them with an axe. 



Because of the rapidity with which bergs break up themselves, and 

 because of the known physical properties of ice, it has been suggested 

 that the southernmost bergs be removed from the paths of navigation 

 by boarding and mining them. Some experiments along these lines 

 have been carried out in past years by the ice j^atrol, but without 

 much success. There are on the average 51 bergs south of the forty- 

 thu'd parallel each year, and to attempt to mine any large proportion 

 of them, even if feasible, would consume much valuable time that 

 might be devoted to ice scouting. 



It has already been shown that bergs in the warm waters south and 

 east of the Grand Banks have a life span of only 7 to 10 days. The 

 rapidity with which they break up from natural causes throws no 

 little element of risk into mining operations on them. The condi- 

 tions are brought out somewhat in the preceding section on ice dis- 

 integration, but to evaluate further the risks the next few paragraphs 

 have been written for the benefit of future ice patrol officers who may 

 be called upon to experiment again with the mining of bergs. 



Some bergs are very delicately balanced. Two turned over during 

 1929 while being passed by the ice patrol vessel. It is hard to see 



