president’s address. 
II 
flow northwards along the coast, and cover the shallow 
spawning grounds with cold and brackish water from top to 
bottom. Under such circumstances the Herrings stop far out, 
and spawn in deep water inaccessible to the fishermen, with 
the result that the fishery is a failure. 
More recently the Danish investigators have shown that in 
the neighbourhood of Iceland, the Cod only spawn in spring 
in the Atlantic water on the southern side of the island, and 
that at the same time spawning Cod and the floating eggs of 
the Cod are quite absent from the Arctic waters on the northern 
and eastern sides, although young and spent fish are caught 
there later in the year when the warm Atlantic current has 
spread around the western and northern coasts of the island. 
This eastward migration of the Cod in relation with the 
eastward expansion of the Atlantic stream in summer is also 
shared by the Herring at the same season. 
It is clear that the parallel study of the physics and biology 
of the sea is providing us with a clue to the explanation of 
many of the hitherto inexplicable irregularities in the multipli- 
cation and wanderings of our sea-fishes. The conditions in 
the North Sea proper appear to differ from those in the border 
regions which have been discussed merely in the greater 
complexity of the factors concerned. Instead of two sharply 
contrasted streams, the North Sea consists of five or six 
masses of water of different origin, the distinctive characters 
of which are so quickly attenuated by mixture, or masked by 
coastal influences, that the investigation of the dominant 
influences at work presents difficulties of a special kind. 
Such results as those which have been mentioned are sufficient, 
however, to satisfy us that we are on the right road of inquiry, 
and that the steady prosecution of the work at sea. combined 
with the gradual perfection of our methods of experiment 
and observation, will produce their fruits in due season. 
One feature already made clear by the hydrographic 
investigations is that the Atlantic current, the time-honoured 
Gulf Stream, is not a constant, but a seasonal stream — a 
