stances out of account. The ice is found in some pathways 
of commerce in much greater forcethanin others. Accor- 
_ding to the excellent map appended to Dr. Neumayer’s 
pamphlet, the drift-ice extends farthest into the South 
Atlantic Ocean, where it makes its way to the 4oth 
parallel of latitude, while in the Pacific Ocean its 
boundary coincides nearly with the 52nd parallel; in the 
Indian Ocean the limit lies between the 4oth and soth 
degree of latitude. Clearly the cause of the ice pushing 
its way so far into the Atlantic Ocean is to be found in 
the fact that most of the icebergs there met with have their 
origin about Graham’s Land and the South Shetlands lying 
far to the north, and, according to Towson’s observations, 
they sail northward at a daily rate of ten miles in an 
easterly direction, when once they are exposed to the 
combined influence of the current and the westerly winds 
It is easy to see that these attempts to fix an aver- 
age boundary are fraught with difficulty, and therefore, 
also, with uncertainty, especially when it is taken into 
consideration that all parts of the ocean have not 
been equally explored—many, indeed, not at all, or only 
by single vessels. By an uncritical examination of all 
the collected facts relating to the subject, one might 
be led to very false conclusions. Therefore we ought to 
examine most narrowly any conclusions which may be 
drawn at first from the frequency of observation ; but for 
so complicated an inquiry, the material within reach is by 
no means sufficient, and therefore we must seek for help 
from some other quarter. Those parts of the ocean are 
best compared which have been explored by a nearly 
equal number of ships. But this at present is the case 
only along the regular routes in the South Atlantic, the 
Indian, and the South Pacific Oceans, and therefore in 
these cases an immediate comparison is admissible. By 
such a comparison it is immediately perceived that in 
each of the oceans places are found which are almost 
free from drift-ice, and that throughout the whole year. A 
specially valuable means of determining such places as 
are free from ice, is the fact that, towards the equator, a 
gap in the ice-boundary is shown, through which a ship 
coming from lower latitudes may sail to the 60th degree 
south without having to passthrough ice. These ice-free 
areas may be set down as follow :— ; 
1. To the south-west of Cape Horn the boundary of 
the drift-ice reaches down to about 57° S. lat. 
«. 2, Between the 6oth and 80th degree of E. long. the 
boundary is found in 61° S. lat. 
3. Between 160° E. and 175° W. long. it has the same 
limit as in No. 2. 
Of course, icebergs, which are influenced more by sur- 
face currents and the prevailing winds than by under- 
_ currents, are occasionally found in these clear areas; 
especially is this the case in years which are exception- 
ally abundant in ice, as was the case in 1854-5. 
Let us inquire, now, what kind of explanation can be 
‘given of these phenomena. These will naturally result, 
in some measure, from the considerations previously ad- 
vanced : either the place of their origin must be placed 
far to the south of the places indicated, so that the ice- 
bergs have a long journey to make before reaching the 
highways of commerce ; or the conditions of temperature 
within the region indicated are favourable to the melting 
and disintegration of the ice; or finally the direction of the 
NATURE 
65, 
current is such that the icebergs cannot reach the north, 
The winds, so far as the present question is concerned, 
can exercise no influence, for all round the Pole they are 
nearly the same forthe same parallels. With regard to 
the currents which are open to direct observation, it is 
difficult to come to any fixed .conclusions, for these ob- 
servations refer only to the surface-currents, which 
are almost universally caused by the prevailing winds. 
Besides, the observations as to currents of the usual 
kind, for special purposes, are not to be relied on. 
That an interchange of water takes place, besides 
that in the way of the general drift, through powerful 
currents, we know through many instances which need 
scarcely be mentioned. The question is concerning the 
position of these currents, their exact course in the various 
oceans. But for this purpose the drift-ice offers a capital 
means of solution, while the warm currents born of the 
water from the equator, in virtue of their southerly direc- 
tion against the advance of the ice, and in virtue of their 
temperature, must be highly unfavourable to the con- 
tinuance of this. Further, it is evident that the in- 
terchange of water occurs along such routes as are 
determined by the rotation of the earth and the configu- 
ration of the lands and the bottom of the seas. These routes 
will lead to places lying as far as possible from the Pole. All 
three would agree in furnishing strong proofs that the area 
is free from ice, if only we assume that the warm waters 
of the equator proceed southwards towards the places 
referred to. 
In reference to that principal current of the ocean 
which is always referred to in a theoretical view, it may 
be said that the factshas been established that the equa- 
torial waters, in their powerful currents from east to west, 
are made to diverge by the east coast of the Continent, 
and turned towards the Poles in both hemispheres. We 
find the direction taken by the south in a current along 
the east coast of America, of Africa, and Australia, from 
which it then makes its way towards the south-east, and 
when not to be recognised as a surface-current, it will be 
found to have assumed the form of an under-current of 
much greater force. The warm South American current 
will probably split on the point of Graham Land; one 
part makes for Alexander Land, the other towards that . 
part where Weddel, after he penetrated the pack-ice, 
reached water free of ice. The Australian branch tends 
towards Victoria in the south of New Zealand, and made 
it possible for Sir James Ross to reach the 78th degree 
of S. latitude, while the Mozambique or African current 
flows towards the Pole, beyond Kerguelen Land, between 
Termination and Kemp Lands. Inthe first two cases we 
have positive proof ; while with respect to the last, the 
evidence for a correct judgment can only be obtained by 
researches inthe high south. The direction of the axis 
of the ice-free area is, in agreement with the general direc- 
tion of the current, according to the present condition of 
our knowledge, from north-west to south-east ; at least 
this is true for the Indian and Pacific Oceans, while the 
wedge-shaped form of South America must tend to 
modify the general rule. 
We know from several voyagers that a girdle of pack- 
ice lies around the Poles, whose position and strength are 
liable to change, though in a less degree than is the case 
with the drift-ice. Naturally in this case, the evidence 
