87 
Chapter XI. 
DENUDATION. 
Wind-action . — The winds in South Victoria Land prove to be as strong and as 
constant as any oceanic trade-wind. Around Winter Quarters the bare land-surfaces 
are usually covered to a depth of six inches by a loose cloak of rook-debris. Below 
this the earth is permanently frozen throughout the year, and here rock-surfaces due to 
fracture often seem to remain quite unweathered. The layer of rock -debris consists of 
a mixture of occasional boulders, 
abundant small stones and rock- 
chips, embedded in a matrix of 
impalpable flour, and all would 
seem to be rapidly disintegrating. 
Many of the boulders seem to have 
no very definite outer boundary, 
and the protected surface may be 
seen to pass gradually through a 
state of crumbling (547) into im- 
palpable powder (446). This cloak 
is usually damp for a week or two 
in summer, but: becomes dry and 
loose when frozen during winter. 
Here decomposition and disintegra- 
tion proceed simultaneously, and 
any particles loosened by frost from 
the upper surfaces are at once blown 
away by the wind ; the fine material 
which remains is always an inch or so below the loose layer of stones at the top 
of the deposit. 
The loose stones are often smoothed and pitted (325) in the manner peculiar to 
the wind-worn stones of desert regions, * and some of the harder ones have a superficial 
glaze. Some of the boulders are too granular to receive polish ; gradually crumbling 
away, they for a time leave patches of small angular fragments, still too large to be 
transported by the wind, to mark the spots they once occupied. 
The wind has carried away the smaller rock-fragments from the summits of 
Observation Hill and Castle Bock. Those which remain are upwards of two inches 
in diameter. The summit of the former, which is composed of trachytic lava, is 
* Walther, Abhand. math.-phys. Cl. d. k. sachs. Ges. Wiss., 1891, Bd. xvi, p. 447. (Dreikaoter.) 
Fig. 50. — Hollowed Granite-boulder with Incrustation of 
Calcium Carbonate, near Descent Pass. 
