Shelters to Iceholes

Time out of number one is coming across rediscoveries.  Of such a nature is the building of shelters for iceholes.  We knew a good deal about it in the Discovery, but unfortunately did not make notes of our experiences.  I sketched the above figures for Nelson, and found on going to the hole that the drift accorded with my sketch.  The sketches explain themselves.  I think wall ‘b’ should be higher than wall ‘a.’

My night on duty.  The silent hours passed rapidly and comfortably.  To bed 7 A.M.

Thursday, June 8.—­Did not turn out till 1 P.M., then with a bad head, an inevitable sequel to a night of vigil.  Walked out to and around the bergs, bright moonlight, but clouds rapidly spreading up from south.

Tried the snow knife, which is developing.  Debenham and Gran went off to Hut Point this morning; they should return to-morrow.

Friday, June 9.—­No wind came with the clouds of yesterday, but the sky has not been clear since they spread over it except for about two hours in the middle of the night when the moonlight was so bright that one might have imagined the day returned.

Otherwise the web of stratus which hangs over us thickens and thins, rises and falls with very bewildering uncertainty.  We want theories for these mysterious weather conditions; meanwhile it is annoying to lose the advantages of the moonlight.

This morning had some discussion with Nelson and Wright regarding the action of sea water in melting barrier and sea ice.  The discussion was useful to me in drawing attention to the equilibrium of layers of sea water.

In the afternoon I went round the Razor Back Islands on ski, a run of 5 or 6 miles; the surface was good but in places still irregular with the pressures formed when the ice was ‘young.’

The snow is astonishingly soft on the south side of both islands.  It is clear that in the heaviest blizzard one could escape the wind altogether by camping to windward of the larger island.  One sees more and more clearly what shelter is afforded on the weather side of steep-sided objects.

Passed three seals asleep on the ice.  Two others were killed near the bergs.

Saturday, June 10.—­The impending blizzard has come; the wind came with a burst at 9.30 this morning.

Simpson spent the night turning over a theory to account for the phenomenon, and delivered himself of it this morning.  It seems a good basis for the reference of future observations.  He imagines the atmosphere A C in potential equilibrium with large margin of stability, i.e. the difference of temperature between A and C being much less than the adiabatic gradient.

In this condition there is a tendency to cool by radiation until some critical layer, B, reaches its due point.  A stratus cloud is thus formed at B; from this moment A B continues to cool, but B C is protected from radiating, whilst heated by radiation from snow and possibly by release of latent heat due to cloud formation.