1906. No.3. AMUNDSEN’S OCEANOGRAPHIC OBSERVATIONS IN 1901. 83 
The charts for 50, 100, 200, 300, and 400 metres (Pl. V) demonstrate 
clearly that there are special conditions in this region. 
The reason why the tongue of ice, extending eastwards, is formed 
to the south of this region, is no doubt difficult to decide so long as 
no fuller investigations have been made. It may be caused by the con- 
dition of the atmosphere and the winds; the great variations from one 
year to another may seem to indicate that the winds are of much im- 
portance in this respect. But the following consideration may also 
perhaps be worthy of notice. In the region where the bottom-water is 
formed on the surface, there is a maximum of density, approaching 
28-10 or 28:12 on the surface. The lighter surface-water of surrounding 
regions, especially the much lighter polar water to the west, whose 
density is not much increased by cooling, since it is protected by the 
overlying ice, will have an increased tendency to flow in this direction. 
But, owing to the Earth's rotation, it will be deflected towards the right, 
and there may thus be a tendency towards a cyclonic movement round 
this maximum of density, by which movement the ice would be carried 
southeast- or eastwards south of it. 
In the atmosphere there may also be a tendency towards a similar 
cyclonic movement, for there will be a tendency towards a barometric 
minimum over this cold but more or less open sea where the air is 
heated by contact with the water-surface, whilst it will be much colder 
over the adjacent fields of snow-covered ice. 
Why the seals especially choose this tongue of ice for their breeding 
place, is a difficult question. It may be mentioned that this seal is 
a very social animal, generally found in great shoals; it will na- 
turally choose for its breeding place ice-masses, where the hundreds 
of thousands do not risk being too much disturbed by the breaking 
up and scattering of the ice. On the other hand the seal wants 
flat, and not too thick ice to lie on, where it is easy to get up and 
down from the floes. The Greenland seal does not therefore like 
the old humocky Polar ice with high edges, but generally seeks ice which 
is only a few feet thick, z. e. such as is formed in the Norwegian Sea. 
There should not be much risk of the ice freezing together to form a 
solid ice-field; for, if this should happen, the seal could not get into the 
water. This does not happen as a rule on this tongue of ice, where 
there is sufficient movement to break the floes if they should freeze 
together. It nevertheless sometimes happens that the whole ice-mass 
does freeze solid, to the great misfortune of the seals, which are then 
