SCIEXTIFIC EESULTS 



121 



Mention should be made of published reports appearing from 

 time to time regarding the sudden breaking up even of large bergs 

 as a result of bursting, or of a resonant sound. Bowditch (1925, p. 

 264) states that bergs have sometimes been split by the single blow 

 of an ax. The top of an iceberg has been described as often being 

 '* rotten " when it will topple down if a shot be fired at it. or even 

 if a voice be raised in the neighborhood. Eskimos are said always to 

 keep perfectly quiet when obliged to pass a berg at close quarters. 

 The phenomenon is said to be due to an unequal contraction of differ- 

 ent parts of the berg by which the imprisoned air is compressed 

 beyond the structural strength of the ice so that it explode^. But we 

 have not been able to produce any such effects, either by the ship's 

 Avhistle or by the report of a C-pounder gun fired close to a berg, 



An Iceberg in the advanced Stages of Disintegration 



Figure SO. — June 15, 1922, in latitude 42° 43' N., longitude 51° 27' W., the water 

 temperature was 48° F. The broken ice and small growlers can be seen Hoating 

 away to leeward. (Official photograph, international ice patrol.) 



though we have carried out many such experiments under various 

 conditions. 



Barnes (1927, p. 162), after carefully observing a large iceberg 

 for a period of two weeks off Newfoinidland, states that the greatest 

 calving and cracking occurs in the early morning at and immediately 

 after sunrise. Closer examination shoAved^- that the water which 

 had been melted on the exposed surface of the ice during the day 

 froze again at night. The sun's rays of the following morning pene- 

 trating the ice before surface melting started, he believed to be the 

 factor responsible by which the ice expands unequally. This does 

 not happen later in the day because the heat from the sun is absorbed 

 by the great quantities of melt water bathing the entire surface. 



*2Zeusler (1925. p. .38) states that the greatest amount of disintegration was noticed at 

 noon and shortly after sunset. Ricketts (19.30, p. 113) points out that the air-exposed sur- 

 face of the bergs does not always freeze at niglit since he (Ricketts) observed water pour- 

 ing from all visible surfaces of a berg on a cloudy night southeast of the Grand Bank. 



