e the land was falling. Bowers mentions that the
crystals did not appear in all directions, which goes to show that the
air was not always rising, but sometimes was falling and therefore not
depositing its moisture. There is no doubt that the surfaces met were
very variable, and it may be that the snow lay in waves. Bowers mentions
big undulations for thirty miles before the Pole, and other inequalities
may have been there which were not visible. There is sometimes evidence
that these crystals were formed on the windward side of these waves, and
carried over by a strong wind and deposited on the lee side.

It is common knowledge that as you rise in the atmosphere so the pressure
decreases: in fact, it is usual to measure your height by reading the
barometer. Now the air on this last stretch to the Pole was rising, for
the wind was from the south, and, as we have seen, the plateau here was
sloping down towards the Pole. The air, driven uphill by this southerly
wind, was forced to rise. As it rose it expanded, because the pressure
was less. Air which has expanded without any heat being given to it from
outside, that is in a heat-proof vessel, is said to expand by adiabatic
expansion. Such air tends first to become saturated, and then to
precipitate its moisture. These conditions were approximately fulfilled
on the plateau, where the air expanded as it rose, but could get little
or no heat from outside. The air therefore precipitated its moisture in
the form of crystals.

Owing to the rapid changes in surfaces (on one occasion they depoted
their ski because they were in a sea of sastrugi, and had to walk back
for them because the snow became level and soft again) Scott guessed that
the coastal mountains could not be far away, and we now know that the
actual distance was only 130 miles. About the same time Scott mentions
that he had been afraid that they were weakening in their pulling, but he
was reassured by getting a patch of good surface and finding the sledge
coming as easily as of old. On the night of January 12, eight days after
leaving the Last Return Party, he writes: "At camping to-night every one
was chilled and we guessed a cold snap, but to our surprise the actual
temperature was higher than last night, when we could dawdle in the sun.
It is most unaccountable why we should suddenly feel the cold in this
manner: partly the exhaustion of the march, but partly some damp quality
in the air, I think. Little Bowers