Observations from aboard ship show a low percentage of 

 clear days but aircraft pilots usually reported good weather 

 over the continent and their aerial photographs show high 

 atmospheric transparency. Thus it seems that astronomers 

 should take an active interest in investigating portions of the 

 Antarctic Continent for possible use in making astronomical 

 observations. Perhaps the ice-free "oases" recently dis- 

 covered by the Navy near the Antarctic Circle would furnish 

 satisfactory bases. Along with excellent "seeing," the long 

 winter night permits uninterrupted observations and long 

 photographic exposures. 



ICEBERGS AND SEA ICE 



On 23 December 1946 the HENDERSON crossed the Ant- 

 arctic Convergence and entered the polar water mass. The 

 well-marked boundary of this water mass was very apparent. 

 While running about 20 miles, the surface water bucket tem- 

 peratures dropped abruptly from 39 to 33 degrees F. A 

 similar abrupt temperature drop when crossing this boundary 

 was revealed when the injection temperatures of both the 

 CURRITUCK and the CACOPAN were checked. The change 

 from blue to gray in the color of the water, the appearance 

 of new types of birds, the clearing of the sky, and the quieting 

 of the sea were other striking observations that were noted. 



The HENDERSON left the convergence and had traveled 

 about 25 miles in a southerly direction when the ship encoun- 

 tered the first iceberg; this berg was one of a large field of 

 bergs that extended to the south. Throughout the "entire 

 antarctic passage, the bergs were seldom observed to be 

 isolated; they appeared rather to be collected into fields. 

 The northernmost limit of bergs as noted by the CACOPAN 

 was roughly 60°S. Distribution of both bergs and pack ice 

 as noted by the HENDERSON is shown in figure 1. 



As antarctic bergs are formed largely by the calving of 

 shelf ice, they are typically tabular in shape (fig. 26). How- 

 ever, melting and wave erosion result in the formation of an 

 ice foot and of sea caves along the waterline and, after much 

 weathering, the bergs begin to lose their original tabular 

 form. They become pyramidy (fig. 27) and often are gro- 

 tesquely carved. Pyramidy bergs frequently display uplifted 

 and tilted waterlines formed by calving which results in a 

 sudden change in the center of mass. 



51 



