SEA ICE 181 



with them considerable fall of temperature, they helped to reunite these shattered 

 fragments through freezing the interstitial strips and patches of open water. 



Plate LIII. Fig. 2 shows the appearance of the sea in McMurdo Sound near 

 Hut Point at the end of February 1909. 



Pancake Ice {eierkuchen eis). We observed that ice of this type developed when 

 the surface of the sea was bemg gently rippled by the wind during a comparatively 

 low temperature. At first the sea presented a soupy appearance. On the first 

 occasion which we saw this (on February 18, 1908) we thought, as it had been 

 immediately preceded by a very heavy three days' blizzard, that this soupy appear- 

 ance was due to large quantities of partly water-logged drift snow. This idea 

 subsequently proved to be incorrect. The pancake ice shown on Plate LIII. Fig. 2 

 developed gradually out of countless ice crystals, which on this occasion also imparted 

 a distinct soupy appearance to the sea. It might also be likened to the aspect of 

 melted paraffin wax floating on the water. Little by little these crystals of sea ice 

 felted themselves together into small cakes, which, jostled by the gentle breezes, 

 continually collided along their growing edges. The latter, being very flexible, become 

 gradually turned up so as to form raised rims, and the whole pancake became slightly 

 saucer-shaped. 



Plate LIV. Fig. 1, photographed by Brocklehurst, illustrates the growth of 

 pancake ice at about the same period. 



Plate LIII. Fig. 3 shows the appearance of the wake of the Ximyod as she cut 

 her way through the pancake ice about March G, 1909. At the time the pancakes 

 were beginning to be more or less firmly cemented at their edges, and thus made 

 a tough surface, which seriously handicapped the Nimrod, and for several hours 

 held her up completely. In time the whole of the interstitial water between 

 the pancakes freezes, thus producing a continuous firm surface of ice. If this ice 

 lasts for the whole of the winter and following spring it forms an excellent surface 

 for sledging ; the raised rims of original pancakes, by this time rounded off through 

 evaporation, much reduce the friction of the runners of the sledge on the ice. 



Plate VII. Fig. 2 shows the appearance presented by the sea ice formed in very 



calm and quiet water. This photo was taken on March 20, 1908. The temperature 



at the time these crystals grew was about -10°F. The ice flowers tasted very 



salt and bitter. A few days later the temperature rose to about +5° to -1-8° F., 



and the centres of the ice flowers rapidly disappeared, forming tiny briny pools ; 



these were surrounded with a fringe of the outer ends of the petals of the ice 



flowers. These outer petals or extremities of the crystal plates of ice were 



evidently formed of freshwater ice of the nature of hoar frost collected fi-om the 



moisture in the air. Their thaw point was evidently near to 32° F., whereas that 



of the crystals containing the strong brines was probably close to 0° F. Evidently 



the centres of these ice flowers are formed of the residual brines squeezed out of 



the gradually congealing sea ice when it crystallises in calm cold weather. The 



2 A 



