AS OBSERVED IN THE WEDDELL SEA. 
809 
Very often there was first opening and then closing of the space between two 
floes. Take an imaginary case, namely an area which has been almost stationary : 
when movement starts the bigger floes will take some time to reach their proper 
speed ; but, on the other hand, they will go on travelling after smaller floes have 
stopped moving. In the early stages, therefore, the big heavy floe will be attacked 
by smaller floes overtaking it ; in the latter stages it itself will be the attacker of 
other smaller floes ahead ; by reason of its size and weight it is pretty sure to take 
the upper hand whatever happens. Light pressure only may result, but, even so, 
it will only still further complicate the floe surface and create possibilities of yet 
further differences in speed. 
Besides the forward motion imparted by the wind, there was also a swinging or 
turning tendency in almost every floe ; this was either an effort to trim them- 
selves to the wind, or the result of pressure from another Hoe ; but, as the floes 
were continually hindered by each other, and the wind was not necessarily constant 
in direction, this swinging habit seemed to have no end. The process was' of course 
more easily seen and realised when the pack was loose. For instance, on April 6, 
1916, the floe on which the Endurance party was camped swung as much as 180° 
in one night ; the ice at the time was described as being fairly open and travelling 
fast ; but it was still open-pack, not drift-ice. When the ice was closer, the actual 
swinging was not so obvious, but the effects were greater ; and one saw the type 
of pack produced which is so dangerous to sail through, and which the 
navigator calls “ screwing pack.” 
The screwing or shearing habit resulted in pressure being located mainly at the 
jutting corners of floes. By one or other of the methods to be described, a hummock 
was formed of loose ice-blocks mixed up with a certain amount of snow ; when 
movement ceased it settled downwards and became covered with falling and drifting 
snow, and in the end it would simply appear as a trifling inequality on the ice- 
surface, no bigger than a haycock. 
Pressure worked in three ways : — 
(а) Bending ; 
(б) Tenting ; 
(c) Rafting. 
These are the old terms given by early whalers and Arctic explorers, and are practi- 
cally self-explanatory. Collectively, or when not particularised, the term generally 
used is “ hummocking.” Taken as a whole, hummocking resembled fairly closely 
the experiments which geologists make to illustrate mountain-building. 
(а) Bending was characteristic of thin and very plastic ice. The most impressive 
result of this nature was the formation, in March 1915, of an arch 3 feet high and 
8 feet span, formed of young-ice about 8 inches thick. 
(б) Tenting was, on the other hand, confined to heavy floes, which being thicker 
