115 



they have been reduced to the size of a ship's boat. Other bergs 

 will both calve and roll about much more than the average. 



The varying water temperatures in which a berg may be floating 

 have a great effect on its speed of disintegration, but it is doubtful 

 if the percentage of the total wastage due to calving, compared with 

 that due to direct melting from the berg, varies much under any 

 conditions met south of the forty-fourth or even the forty-eighth 

 parallel. The effects of calving are more noticeable in some cases 

 than others, however. For instance several bergs seen near the Tail 

 in 1929 had water lines showing that the upper parts of the berg were 

 rising higher and higher out of the water. They were very few in 

 number, and they may be explained by excessive calving, or by floadng 

 in very cold sub surface water during periods of warm bright weather 

 that were especialh^ destructive to large portions of their above-water 

 bodies. 



Nevertheless, despite low temperatures of surface water at all 

 places during the early season, and in many places until close to the 

 end of the ice period, and despite permanent low temperatures at 

 the lower levels reached by bergs in the "melting area," the constant 

 effect of the sea water moving about in intimate contact with the 

 water line and the great underwater surfaces of bergs must be the 

 most important factor working toward their destruction. Subaerial 

 melting from the bergs is a minor factor, but still it adds its quota 

 to the melting process of berg disintegration, as distinct from the 

 loss of mass through calving. Over the whole ice-patrol area the 

 sum total calving effect is probably much less than the total surface 

 melting effect in getting rid of the bergs. 



From a small boat that pulled about a berg which pitched heavily 

 while calving on July 15, many air bubbles were seen to be rising 

 through the smooth water and breaking at the surface within a dozen 

 feet or so of the vertical ice walls of one side. Some of these bubbles 

 appeared to be nearly 1 inch in diameter and these made a consider- 

 able disturbance at the surface like the large bubbles of marsh gas 

 that rise through shallow waters under certain conditions. Each of 

 the larger bubbles of gas in the case of the berg were undoubtedly 

 made up from the combined contents of many of the formerly im- 

 prisoned tiny air bubbles of the glacier ice. The separate air bubbles 

 in the bergs are generally less than one-thirty-second of an inch in 

 diameter, much smaller in size than the head of an ordinary common 

 pin. The particular berg of this instance was floating in surface 

 water of ten]perature 57° F. The continuous coming up of air 

 around it is good evidence of the rapid underwater wastage which 

 occurs whenever the water is that warm. 



When movement of the slight swell exposed portions of ice below 

 the average water line of the above berg it was seejiiHrtSPiBt'fee under- 



