470 Part III.— Seventh Annual Report 



different chemical composition to that of the water coming from the north, 

 and is characterised according to my determinations by a value for D 

 about 1-4556. It was found during the cruise of the 'Jackal' lying off 

 the East Coast of Scotland, and stretching northward as far as Balta 

 Sound in North Unst, the farthest point to the north visited by the 'Jackal' 

 during the cruise. It was also traced as a narrow band lying immediately 

 off the coast of Norway. The water forming this band may be assumed 

 to have entered the North Sea by the English Channel, with a degree of 

 probability approaching to certainty. The observations made during the 

 ' Pommerania' Expedition as to the direction of the currents, the tempera- 

 ture, and the specific gravity of the different waters in the North Sea, 

 confirmed by the observations of a similar character made during the 

 short cruise of the ' Jackal ' and taken along with the apparently identical 

 composition of this water with that flowing in from the Atlantic round 

 the North of Scotland, appear to me to lead to this and no other 

 conclusion. 



A third though less important contribution to the waters of the North 

 Sea is the outflow from the Baltic, which also flows northward along the 

 Norwegian coast. It is characterised by its low specific gravity, its high 

 temperature in summer, and its high alkalinity. 



The cold dense water coming from the north occupies in general a some- 

 what central position in the North Sea. The explanation of its having been 

 found at the surface, and not under a superficial layer of surface Atlantic 

 water, may be in a great measure ascribed to the action of the wind. 

 The North Sea, with the exception of the comparatively narrow outlets 

 into the English Channel and into the Baltic, is bounded on three sides 

 by land, and is open to the north. When the wind therefore blows over 

 the surface of the North Sea, from any point of the compass with a 

 touch of south in it, it will tend to blow out the surface Atlantic water 

 and bring in the cold water from the north along the bottom. The 

 advance southwards of this cold water, as is well known, is arrested by 

 the Dogger Bank, to the north of which therefore it will probably be 

 frequently found at or near the surface, as was the case during the recent 

 cruise of the 'Jackal.' 



The conclusions thus briefly summarised have an important bearing on 

 the problems connected with oceanic circulation, and oceanography 

 generally. I have been led by them to examine the data regarding the 

 relation between chlorine and density in sea water, published in the 

 reports of previous scientific expeditions. In a preliminary note recently 

 read before the Royal Society of Edinburgh, I have endeavoured, I believe 

 with some success, to trace similar relationships and differences between 

 the great number of samples collected during the ' Challenger ' Expedition, 

 the densities of which were determined by Mr. J. Y. Buchanan, and the 

 chlorines by Prof. Dittmar. In this connection I would like to record my 

 sense of indebtedness to Prof. Dittmar's great work on the Composition of 

 Ocean Water constituting Part I. of the volume on the Chemistry and 

 Physics of the ' Challenger ' Expedition. Whatever the value of my results 

 may be, they are in a very great measure due to the fact that I have been 

 able to follow up, as it were, the lines of research therein laid down. 



It would go beyond the scope of this report to discuss any of the inter- 

 esting questions connected with oceanic circulation, which appear to me 

 to be materially affected by the conclusions which I have been able to 

 draw. I may however point out that, unless I am altogether mistaken, 

 it will be possible to trace some at least of the great ocean currents. 

 If in future expeditions a number of small samples of sea water be 

 collected from various positions and depths, and carefully preserved in 



