FLORA. , 161 
the lump-fish, and the bull-head. Nor are the crustacea 
unrepresented ; long-tailed crabs being abundant, while 
the common mussel may be gathered almost everywhere 
at ebb-tide. The seas, however, grow poorer as we advance 
towards the Pole, and many important species of fish do 
not penetrate further north than the Arctic Circle. 
‘Yet even where these are wanting, the ocean-waters 
teem with life; and a recent writer is fully justified in 
remarking that the vast multitudes of animated beings 
which people them form a remarkable contrast to the 
nakedness of their bleak and desolate shores. The colder 
surface-waters are, as he says, almost perpetually exposed 
to a cold atmosphere, and being frequently covered, even 
in summer, with floating ice, they are not favourable to 
the development of organic life ; but this adverse influence 
is modified by the higher temperature which constantly 
prevails at a greater depth. Contrary to the rule in the 
Equatorial seas, we find in the Polar ocean an increase of 
temperature from the surface downwards, in consequence 
of the warmer under-currents, flowing from the south 
northwards, and passing beneath the cold waters of the 
superficial Arctic current. 
‘Hence the awful rigour of the Arctic winter, which 
strikes the earth with a death-blight, is not perceptible in 
the ocean-depths, where myriads of organisms find a 
secure retreat from the frost, and whence they emerge 
during the long summer’s day, either to haunt the shores 
or ascend the broad rivers of the Polar world. Between 
the parallels of 74° and 80°, Dr Scoresby observed that the 
colour of the Greenland sea varies from the purest ultra- 
marine to olive-green, and from crystalline transparency to 
striking opacity ; and these appearances are not transitory, 
but permanent.* The aspect of this green semi-opaque 
water, which varies in its locality with the currents—often 
forming isolated stripes, and sometimes spreading over two 
* Scoresby calculated that it would require 80,000 persons, labouring continuously 
from the creation of man to the present day to count the number of organisms con- 
tained in two miles of the green water. 
M 
