They came down the glacier in plus temperatures:  nor was there anything abnormal for more than a week after they got on to the Barrier.  Then there came a big drop to a -37 deg. minimum on the night of February 26.  It is significant that the sun began to dip below the southern horizon at midnight about this time.  “There is no doubt the middle of the Barrier is a pretty awful locality,” wrote Scott.

Simpson, in his meteorological report, has little doubt that the temperatures met by the Polar Party were abnormal.  The records “clearly bring to light the possibility of great cold at an extremely early period in the year within a comparatively few miles of an open sea where the temperatures were over 40 degrees higher.”  “It is quite impossible to believe that normally there is a difference of nearly 40 degrees in March between McMurdo Sound and the South of the Barrier.”  The temperatures recorded by other sledge parties in March 1912 and those recorded at Cape Evans form additional evidence, in Simpson’s opinion, that the temperatures experienced by Scott were not such as might be expected during normal autumn weather.

Simpson’s explanation is based upon the observations made in McMurdo Sound by sending up balloons with self-recording instruments attached.  These showed that very rapid radiation takes place from the snow surface in winter, which cools the air in the immediate neighbourhood:  a cold layer of air is thus formed near the ground, which may be many degrees colder than the air above it.  It becomes, as it were, colder than it ought to be.  This, however, can only happen during an absence of wind:  when a wind blows the cold layer is swept away, the air is mixed and the temperature rises.

The absence of wind from the south noted by Scott was, in Simpson’s opinion, the cause of the low temperatures met by Scott:  the temperature was reduced ten degrees below normal at Cape Evans, and perhaps twenty degrees where Scott was.[353]

The third question is that of food.  It is this point which is most important to future explorers.  It is a fact that the Polar Party failed to make their distance because they became weak, and that they became weak although they were eating their full ration or more than their full ration of food, save for a few days when they went short on the way down the Beardmore Glacier.  The first man to weaken was the biggest and heaviest man in the expedition:  “the man whom we had least expected to fail.”

The rations were of two kinds.  The Barrier (B) ration was that which was used on the Barrier during the outward journey towards the Pole.  The Summit (S) ration was the result of our experiments on the Winter Journey.  I expect it is the best ration which has been used to date, and consisted of biscuits 16, pemmican 12, butter 2, cocoa 0.57, sugar 3 and tea 0.86 ounces; total 34.43 ounces daily per man.

The twelve men who went forward started this S ration at the foot of the Beardmore, and it was this ration which was left in all depots to see them home.  It was much more satisfying than the Barrier ration, and men could not have eaten so much when leading ponies or driving dogs in the early stages of summer Barrier sledging:  but man-hauling is a different business altogether from leading ponies or driving dogs.