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Scott's Last Expedition

Saturday, June 10th 1911

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.

The condition now rapidly approaches unstable equilibrium, B C tending to rise, A B to descend.

Owing to lack of sun heat the effect will be more rapid in south than north and therefore the upset will commence first in the south. After the first start the upset will rapidly spread north, bringing the blizzard. The facts supporting the theory are the actual formation of a stratus cloud before a blizzard, the snow and warm temperature of the blizzard and its gusty nature.
It is a pretty starting-point, but, of course, there are weak spots.

Atkinson has found a trypanosome in the fish – it has been stained, photographed and drawn – an interesting discovery having regard to the few species that have been found. A trypanosome is the cause of ‘sleeping sickness.’

The blizzard has continued all day with a good deal of drift. I went for a walk, but the conditions were not inviting.

We have begun to consider details of next season’s travelling equipment. The crampons, repair of finnesko with sealskin, and an idea for a double tent have been discussed to-day. P.O. Evans and Lashly are delightfully intelligent in carrying out instructions.

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