Greenland and the Antarctic Continent. 355 
There is another class of facts which shows still more con- 
clusively the probably low flat nature of most of the Antarctic 
regions. I refer to the character of the great ice-barrier, and 
the bergs which break off from it. The icebergs of the southern 
ocean are almost all of the tabular form, and their surface is 
perfectly level, and parallel with the surface of the sea. The 
icebergs are all stratified ; the stratifications run parallel with 
the surface of the berg. The stratified beds, as we may call 
them, are separated from each other by a well-marked blue 
band. These blue lines or bands, as Sir Wyville Thomson 
remarks, are the sections of sheets of clear ice; while the white 
intervening spaces between them are the sections of layers of 
ice where the particles are not in such close contact and pro- 
bably contain some air. The blue bands, as Sir Wyville sug- 
gests, probably represent portions of the snow surface which 
during the heat of summer becomes partially melted and 
refrozen into compact ice ; while the intervening white por- 
tions represent the snow of the greater part of the year, which 
of course would become converted into ice without ever being 
actually melted. It is therefore more than probable that each 
bed with its corresponding blue band may represent the for- 
mation of one year. Judging from the number of these layers 
in an iceberg, some of these layers must be of immense age, 
occupying a period probably of several thousand years in their 
formation. And as the ice is in a constant state of motion 
outwards from the centre of dispersion — probably the South 
Pole — the bergs before becoming detached from their parent 
mass must have traversed a distance of hundreds of miles. 
The fact that these bergs must have travelled from great 
distances in the interior is further evident from the following 
consideration. The distance between the well-marked blue 
lines is greatest near the top of the berg, where it may be a 
foot or more, and becomes less and less as we descend, until, 
near the surface of the water, it is not more than two or three 
inches. This diminution in the thickness of the ice-strata 
from the top downwards has been considered by Sir Wyville 
to be mainly due to two causes — compression, and melting of 
the ice, particularly the latter. But in my paper on the 
Antarctic Ice (Quart. Journ. of Science, Jan. 1879) I have 
shown that, although compression and melting may have had 
something to do in the matter, this thinning of the strata from 
the top downwards is a necessary physical consequence of con- 
tinental ice radiating from a centre of dispersion. Assuming 
the South Pole to be this centre, a layer which in, say, lati- 
tude 85° covers 1 square foot of surface will, on reaching 
latitude 80°, cover 2 square feet ; at latitude 70° it will 
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