Sir H. H. Hoicorth — The Baltic — The Litorina Sea. 311 



V. — The Eecent Geological History of the Baltic. 

 Part I : The Litokina Sea. 



By Sir H. H. Howorth, F.R.S., F.G.S. 



rpHE recent history of the Baltic involves problems of great 

 X interest and importance, and promises to afford considerable 

 help in solving the mysteries of the later geological changes in 

 Western Europe. It is therefore vporth a closer study than has 

 been extended to it in tlais country. Perhaps I may be permitted 

 to condense in the Geological Magazine what has been written 

 about it in late years by the Scandinavian geologists, and to add 

 some inferences of my own. I am especially indebted to De Geers 

 and Munthe, the latter of whom has written quite an ideal monograph 

 on one section of the story in the Bulletin of the Geological 

 Institution of the University of Upsala, vol. ii.^ 



Thfe most conspicuous feature of the Baltic compared with other 

 seas directly communicating with the ocean, and in which it 

 resembles a lake, is the slight salinity of its water, while its upper 

 waters differ in this respect very sensibly from its lower ones. 



"In the Gulf of Bothnia, at the time when the river-flow is 

 greatest, the surface water is so little salt as to be quite drinkable, 

 its specific gravity being as low as 1-004. It is said to contain at 

 Christmas, when its fresh-water supplies are largely frozen, six 

 times as much salt as at Midsummer, showing that when the river 

 supply is at its lowest its place is taken by a reflux of salt water 



from the outside ocean At Kiel, if the direction of the 



prevalent winds in Autumn be such as to maintain a strong surface 

 out-current, and consequently a very strong inward under-current, 

 as happens in some years, the maximum of salinity will present 

 itself at that season, otherwise Meyer found that the specific gravity 

 of the water at Kiel ranges from about 1-0182 in Summer to 1'0142 

 in Winter, the latter showing about half the quantity of salt in sea 

 water." (Encyc. Brit., iii, 297, article Baltic.) 



The degree of salinity of the waters of the Baltic decreases very 

 much, as we should expect, as we leave the ocean and get nearer to 

 its inner recesses. The following is a useful table compiled by 

 Munthe from the best official sources, and showing the average 

 percentage of salt at different places in the Western Baltic going 

 eastwards. The figures are taken from actual observations. 



Darsser Ort 1-06 



GjedsorEev 1-01 



Lappegmnden 1-41 



Northern part of Oresund 1-25 



Copenhagen 1-21 



Drogden 1-08 



Lohme (Riigen) 0-81 



Christianso, N. of Bornholm 0-78 



Hela (West Prussia) ... 0-72 



Continuing the investigation further east, for which we have not 

 the same precision of testimony, Munthe, from considerations 



1 " Preliminary Eeport on the Physical Geography of the Litorina Sea," pp. 1-38. 



