xxiv DEPARTMEXT OF THE NATAL 8ERTIGE 



the cold intermediate layer. Even in the first half of August, however, considerable 

 areas on the banks in the gulf of St. Lawrence were found to 'be covered with water 

 colder than 0° C. 



As will be seen from these brief remarks, we had now succeeded in procuring a 

 material which enabled us to measure the thickness of the various water layers by sec- 

 tions taken transversely to their direction of movement, and this in the shortest pos- 

 sible time. We had furthermore been able to repeat such investigations at a later 

 period. This furnished us with the basis for a theoretical treatment of the material, 

 and an analysis of the influence exerted by the various factors; the earth's rotation, 

 melting of the ice, specific gravity, temperature, etc. In Mr. Bjerkan's 'paper, the 

 reader will find all the precise data concerning the values for salinity, temperature, 

 and density. And Mr. Sandstrom has endeavoured, on a wide scale, to give a thorough 

 analysis of the causes conducive to the circulation of the water as a whole, and its 

 dynamics generally. This is, as iar as my experience goes, the most thorough treat- 

 ment of these questions which has yet appeared. 



We are now brought face to face with a great number of most interesting problems 

 for future hydrographical investigations. 



In the first place, it would be well to ascertain what fluctuations may occur from 

 the conditions found to prevail in 1915. What variation can take place, for instance, 

 in the amount of fresh water discharged by the St. Lawrence river, in the Gaspe cur- 

 rent, in the interchange of water between the gulf of St. Lawrence and the area out- 

 side, in the great cold intermediate water layer, in the Labrador current, and in the 

 distance of the warm ocean water from the costal banks? All these questions will 

 naturally be of the highest importance in th& study of biological problems, chiefly, per- 

 haps, the varying distribution of the cold water layers. A particularly interesting 

 feature is the remarkable wedge of the very coldest salt water off the Continental 

 Shelf (Acadia station 12). Can this current penetrate still further southward in the 

 spring, and can this be the great cause of the death of multitudes of fish, occasionally 

 observed in the sea off the east coast of America ? Bearing in mind the state of things 

 in the North-European waters, as revealed more especially by the Swedish investiga- 

 tions, there is good reason to believe that the fluctuatiions in the Canadian waters will 

 likewise prove to be of very considerable extent. 



Sandstroom's investigations revealed various possibilities for a further comprehen- 

 sion of hydrodynamics in the sea. I would here more particularly call attention to his 

 suggestions as to the study of submarine waves, where fresher layers encounter the 

 mighty wall of the saltest Atlantic water, or in the intermediate layers in the gulf of 

 St. Lawrence, or in the current movements of the deeper layers, as, for instance, those 

 in the Laurentiian channel. 



PLANKTON' INVESTIGATIONS. 



The scientific, and particularly the quantitative study of plankton in the sea has 

 long been a subject of discussion giving rise to widely divergent views. Hensen and 

 his followers have emphatically maintaied that only quantitative investigations could 

 lead to results of any scientific value, and that the methods developed by Hensen him- 

 self afforded satisfactory means of ascertaining the quantitative occurrence not only 

 of separate species, but also of the total plankton in a column of water corresponding 

 to the range filtered by the Hensen net from bottom to surface. Other investigators, 

 again, were indisposed to bind themselves to such methods of research, or to accept the 

 given formula'tion of the problem. It has been pointed out, for instance, that the 

 method in .question was not altogether satisfactory in itself, as the nets did not by any 

 means take the entire plankton content— i.e., all the forms represented— in the column 

 of water through which they were drawn. And it has also been demonstrated beyond 

 (luestion that many forms passed .through the nets, while the larger ones managed to 

 avoid them. Moreover, it has been maintained that both the term " plankton," and the 



