president’s address. 
9 
For two years now this work has made steady, if silent, 
progress ; and, when the time arrives for collecting the results 
obtained, 1 believe they will be found not only to have greatly 
broadened the basis of our knowledge, but to entail a complete 
revolution in the points of view from which many general 
problems have hitherto been regarded. At present T can 
merely give a few examples of the methods employed and of 
some of the earlier results of the work accomplished. 
The hydrographic results are based on the serial observations 
and samples collected at fixed stations on the periodic cruises 
at successive depths, supplemented by a net-work of observa- 
tions of surface temperature made on board trans-Atlantic 
and North Sea steamers making regular voyages between 
particular ports, as well as by the analysis of a large number 
of samples of surface water collected by officers of the same 
vessels. Surface observations of this kind have been found 
to yield valuable material when checked by the results of the 
more complete and exact data obtained on the special hydro- 
graphic cruises, and serve in many cases to bridge the gaps 
that would otherwise separate the hydrographic stations from 
one another. 
It has been recognised for some time that the North Sea 
is not a uniform mass of water, but a more or less imper- 
fect mixture of waters derivable from Atlantic, Arctic, 
and Baltic sources. The Atlantic current is twofold, one 
branch entering the North Sea by way of the English Channel, 
the other round the north of Scotland. There is a difference 
of temperature between these two streams, but both are 
warm and highly saline. The Baltic stream is largely fresh 
water. It attains its maximum volume during the spring 
months in consequence of the melting of the snows on the 
watersheds of northern Europe, and is then ice-cold ; in sum- 
mer, on the other hand, its waters becomes strongly heated. 
In consequence of its low specific gravity it Hows through the 
Cattegat and Skager-Rak as a surface stream overlying the 
salter waters in the depths. Water of Arctic origin covers 
