306 SCOTT'S LAST EXPEDITION 



to sea by blizzards or some such transporting agent. The pack 

 extends in normal years in December from about 66 to 71 S. 

 Lat., a distance of 300 miles from north to south, and at times 

 evidently fills the whole width of the Ross Sea. 



Pack may be heavy or light, closed or open the latter condi- 

 tions being entirely dependent on local winds and currents. Thus 

 heavy pack if open may offer no insuperable bar to navigation, 

 whereas in closed pack, whether heavy or light, little progress 

 can be made by ships. Heavy pack is usually associated with 

 hummocks or pressure ridges rising to a height of four or five 

 feet above the general level of the floe. These hummocks and 

 pressure ridges are callect upon to furnish ice for cooking and 

 other purposes in the pack, being comparatively free from salt, 

 owing, as mentioned previously, to the fact that the salt in the 

 ice goes into solution and drains away, whenever the temperature 

 rises above zero. 



Towards the end of February the Ross Sea becomes com- 

 paratively free of pack and offers no bar to navigation. 



SNOW 



Precipitation from the atmosphere occurred always in the 

 form of snow in these regions bordering on the continent; some- 

 times, when the temperature was high, in the form of delicate six- 

 rayed stars, or at lower temperatures in the form of hexagonal 

 plates, little granular balls, or at still lower temperatures fine 

 needle-shaped forms. 



Not long, however, do they keep this form after falling. 

 Immediately ' the mighty molecule ' starts its work, some crystals 

 grow at the expense of others, the whole grows more compact, 

 becomes hard, and while still containing much air is white and 

 called neve. Later it completes its change by expelling the air 

 and becomes the well-known blue ice. 



During the summer one can see the whole transformation 

 taking place before one's eyes in the course of a few days. 



CRYSTAL FORMS 



Not only in the form of snow, however, do these crystal forms 

 occur. In crevasses, on the roof of the stables, on windows, and 

 so on, countless varied forms are to be seen, each single form 



