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Part III. — Fifteenth Annual Report 



XIII.— THE CURRENTS OF THE NORTH SEA, AND THEIR 

 RELATION TO FISHERIES. By Dr T. Wemyss Fulton, 

 F.R.S.E., Scientific Superintendent (Plates X., 



CONTENTS. 



I. Introduction ...... 



II. The Direction and Rate of the Currents — 



1. The Course of the Drifters .... 



Shetland — Orkney Area .... 

 The Moray Firth Area .... 

 The East Coast of Scotland 

 The English Coast and the Continent 

 Between the Isle of May and the Naze of Norway 

 Retween the Isle of May and Hamburg 

 Between the English and Dutch Coasts 



2. Seasonal Variations ..... 



3. The Cause of the Movement of the Surface Water . 



The Prevailing or Effective Winds 

 The Tidal Streams .... 



4. Reversal of the Normal Current 



5. The Rate and Depth of the Current . 

 III. The Relation of the Current to Fisheries 



I. INTRODUCTION. 



In recent years the attention of a number of investigators has been 

 directed to the hydrography of the North Sea, and several inquiries and 

 series of observations have been made with the object of determining its 

 principal physical conditions at different seasons and in successive years, 

 with especial relation to the movements of its waters. The most important 

 investigations on the subject have been made by the eminent Swedish 

 scientists, Professor Otto Pettersson and Dr Ekman, who have succeeded 

 in throwing a great deal of light on the physical changes which take place 

 in the Kattegat, Skagerrak, and adjoining areas ; and apparently in 

 correlating them with the herring and mackerel fisheries. At their initia- 

 tive approximately simultaneous observations were carried on in 1893 

 and 1894 by Danish and Swedish vessels in the Kattegat and Skagerak 

 by H.M.S. 1 Jackal' in the Faroe-Shetland Channel, and in other parts 

 of the North Sea by Norwegian and German vessels ; and several pre- 

 liminary reports embodying and discussing the observations have been 

 published. 



The method adopted in these hyclrographic researches consists essen- 

 tially in the determination of the salinity and temperature of the water at 

 various depths in different localities, and, as far as possible, at the same 

 time, so as to obtain a simultaneous record of the conditions over the whole 

 area. The waters which enter the North Sea and may circulate within it 

 come from two great sources, the ocean on the one hand and the Baltic and 

 fresh-water rivers on the other ; and, since these waters differ in salinity 

 and temperature according to their source, it is possible, by com- 

 paring the temperature and salinity observations, to trace the course 

 and extent of their movements. For this purpose it is obviously 

 necessary to have both simultaneous observations over a wide area, 

 and a series of such observations in different seasons and in successive 

 years. The final results of the work already accomplished have not yet 

 been published, but Mr H. N. Dickson is now engaged in preparing 

 synoptic charts. 



Another method of tracing the movement of the water is by a study of 



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