SEA-FISHERIES LABORATORY. 185 
dilution of the sea-water, due to the influence of the land, 
than over the greater part of the North Sea; also there is 
a much more thorough mixture of the water of different 
regions than we find in the latter sea. Therefore, it is 
not to be expected that such sharply-bounded isohaline 
areas, or such positive indications of a flooding by water 
from without, as are observed in the North Sea* will be 
found in our area. Neither are seasonal changes in the 
positions of the isohalines, at least those delimiting water 
areas of the lower degrees of salinity, so sharply marked. 
There is no indieation, none at least so far, of the 
existence of a more or less permanent layer of cold bottom 
water.t This is just barely indicated by the temperature 
differences at Station V. There are no indications of the 
inflow of cold bottom water from the sea North of the 
British Islands, for though the channel between Galloway 
and Ireland is relatively deep, the sea bottom between Islay 
and Ireland is shallow, forming a “ barrier,” while the 
depth of water at the opening to St. George’s Channel is 
such as to admit only of the entrance of surface Atlantic 
water. It has been estimated{ that the flow outwards 
through the North Channel is such that a water-particle 
will travel from the Irish Sea to the Scotland-Shetland 
Channel in about eighty days; at which rate the water- 
volume leaving the Irish Sea annually is at least equal to 
the entire volume of that sea, that is, 3,000 cubic 
kilometres. The planktonic fauna and flora of our area 
is, therefore, affected, not by the Sub-Arctic region, but 
by that of the Atlantic or Biscay latitudes, a conclusion 
* See D’Arcy Thompson, Natwre, Dec. 17, 1908. 
{+ Such as is known to exist in the North-Western part of the North 
Sea. Cf. Second Report Fishy. and Hydrogr. Invests. in the North Sea 
and Adjacent Waters, Pl. I [Cd. 3358], 1907, p. 11. 
‘t Knudsen, Publications de Circonstance. Cons Perm. Internat. 
Faplor. Mer, No. 39. Copenhague, 1907. 
