depot,
each unit of four men being entitled to 2/3 of a gallon, and the
units of three and five men in proportion.

The return journey on the Summit had been made at good speed, taking
twenty-one days as against twenty-seven going out, the last part of it,
from Three Degree to Upper Glacier Depot, taking nearly eight marches
as against ten, showing the first slight slackening as P.O. Evans
and Oates began to feel the cold; from Upper Glacier to Lower Glacier
Depot ten marches as against eleven, a stage broken by the Mid Glacier
Depot of three and a half day's provisions at the sixth march. Here,
there was little gain, partly owing to the conditions, but more to
Evans' gradual collapse.

The worst time came on the Barrier; from Lower Glacier to Southern
Barrier Depot (51 miles), 6 1/2 marches as against 5 (two of which
were short marches, so that the 5 might count as an easy 4 in point of
distance);from Southern Barrier to Mid Barrier Depot (82 miles), 6 1/2
marches as against 5 1/2; from Mid Barrier to Mt. Hooper (70 miles),
8 as against 4 3/4, while the last remaining 8 marches represent but
4 on the outward journey. (See table on next page.)

At to the cause of the shortage, the tins of oil at the depot
had been exposed to extreme conditions of heat and cold. The oil
was specially volatile, and in the warmth of the sun (for the tins
were regularly set in an accessible place on the top of the cairns)
tended to become vapour and escape through the stoppers even without
damage to the tins. This process was much accelerated by reason that
the leather washers about the stoppers had perished in the great
cold. Dr. Atkinson gives two striking examples of this.

1. Eight one-gallon tins in a wooden case, intended for a depot at
Cape Crozier, had been put out in September 1911. They were snowed up;
and when examined in December 1912 showed three tins full, three empty,
one a third full, and one two-thirds full.

2. When the search party reached One Ton Camp in November 1912 they
found that some of the food, stacked in a canvas 'tank' at the foot
of the cairn, was quite oily from the spontaneous leakage of the tins
seven feet above it on the top of the cairn.

The tins at the depots awaiting the Southern Party had of course been
opened and the due amount to be taken measured out by the supporting
parties on their way back. However carefully re-stoppered, they
were still liable to the unexpected evaporation and leakage a