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Part III. — Seventh Annual Report 



A reference to the values for D given in Table IV. column IX. will show 

 that almost all the samples collected at Stations I. to XXIV. in the early part 

 of the cruise along the east coast of Scotland, and off the Orkney and 

 Shetland Islands, had practically the same composition as the waters found 

 in the Moray Firth in the summer of 1883. The values for D ranging 

 between 14611 and 14543 in seventeen out of the twenty bottom and 

 surface samples. The three exceptions are the bottom water near the Isle of 

 May at the mouth of the Firth of Forth (Station IV.), and the bottom 

 waters from between the Sutors at the entrance of the Cromarty Firth 

 (Stations XIIL and XIV.) — the values for D in these samples being 

 14714, 1*4735, and 14705 respectively. But on crossing over from 

 Shetland to Norway, the ' Jackal ' passed through a great tract of water 

 the composition of which both at -surface and bottom was the same as 

 that found in the Moray Firth in the summer of 1886. The value for 

 D belonging to the six samples collected at Stations XXV., XXVI., 

 and XXVII. range from 14759 to 1-4710. 



On neariug the coast of Norway, the composition of the sea water 

 reverted to that found generally off the Scottish coast, but as the Baltic 

 was approached the character of the water again changed. In the Sound, 

 Stations XXXVI. and XXXVII., and in the Baltic, Stations XXXVIII., 

 XXXIX., and XL., the values for D again approximate to 14710. The 

 samples collected during the homeward passage at Stations XLIII. 

 and XLIV., which are situated in the southern part of the northern 

 area of the North Sea, that is, to the north of the Dogger Bank, all 

 correspond in composition to those found at Stations XXV., XXVI., and 

 XXVII., more than 200 miles further north. 



The water corresponding to that found in the Moray Firth in the summer 

 of 1886, if we look away for the moment from the samples collected in or 

 near the Baltic, is seen to have occupied, broadly speaking, a central 

 position, while the waters corresponding to that found in the Moray 

 Firth in the summer of 1883 were apparently confined to a comparatively 

 narrow strip along the coast. 



It must not, however, be supposed that this is due to any influence of 

 land or of rivers draining the land. The result obtained with the Moray 

 Firth samples collected in 1883 and 1886 are proof to the contrary. 

 Further, as already stated, the influence of the land waters would, 

 necessarily tend to raise the value for D, and not to lower it. Any 

 addition to sea water of salts containing a less proportion of chlorine, or 

 what is much the same thing, a less proportion of common salt, must 

 necessarily raise the value for D. Now the salts derived from the drainage 

 of the land uniformly contain a much smaller proportion of common salt 

 than that found in sea water. Moreover the effect of such admixture of 

 sea water with land water is really very small. I have come to the 

 conclusion that the presence of land water in sea water may be better 

 traced, apart from the lowering of the specific gravity produced thereby, 

 by the determination of the alkalinity of the sea water, that is to say, by 

 the determination of the amount of bases present in combination with 

 carbonic acid. 



