558 Sir H. H. Howorth — Geological History of the Baltic. 



According to the evidence, as we have seen, the breach in the 

 Baltic bridge took place after the kitchen midden time and during 

 the succeeding period of the Neolithic age. That is a terminus a quo 

 from which we may roughly calculate the time that has elapsed. 

 Von Baer, who was the first, I believe, to make such a calculation, 

 put the date of the breach at 5,000 years ago. He based his 

 calculation, however, on the uncertain element of the rate at which 

 the Baltic lands were supposed to be now rising. 



Dr. Brogger, in his book on the Mollusca of the Christiania Fiord, 

 bases his calculation on the archaeological evidence, and puts it at 

 8,000 years ago. 



If we take the mean of these two calculations, say 6,600 years, 

 we shall perhaps roughly approximate to a tentative date since 

 which salt water has been flowing into the Baltic basin, and 

 introducing partially marine conditions there, while the fresh 

 water has been flowing out in a large stream into the Cattegat 

 and destroying the oysters and associated shells there, initiating 

 the Litorina sea on the one side and pushing back the Tapes sea 

 on the other. This double action of the catastrophe seems plain 

 from the evidence, and I therefore cannot agree with De Geer and 

 Brogger when they equate the Tapes and Oyster period in the 

 southern Cattegat with the Litorina stage of the Baltic, instead 

 of with the Ancylus stage. The Litorina time was, in fact, the 

 inception of the present condition of things in the Baltic, as the 

 contemporaneous withdrawal of the Tapes fauna initiated the present 

 condition of things in the Cattegat. 



The next question is to ascertain what climatic changes we can 

 predicate in Scandinavia during the interval bounded by the begin- 

 nings of the Litorina time and the close of the Tapes time on the 

 one hand and the present day on the other. First let us look at the 

 question from an a priori view. 



Ekholm, in a paper in Ymer, Heft iv, p. 377 £f., translated in the 

 27th volume of the Quart. Journ. of the Meteorological Society, 

 No. 117, January, 1901, has argued that about 8,000 years ago the 

 Summer temperature in Mid Sweden would be enhanced to an 

 extent of 2 degrees Centigrade, due to the fact that the inclination of 

 the ecliptic would then be at its minimum, and further that since 

 that date it has been growing slightly more severe. 



In the first two chapters of my new book, " Ice or Water," 

 I have given an elaborate analysis of the astronomical conditions 

 affecting climate, and notably of changes affecting the inclination 

 of the ecliptic, showing that the problem is a good deal more 

 intricate than has been generally thought, and that it has to be 

 qualified by many conditions. I do not, however, propose to raise 

 any issue with Ekholm on the matter, and he is mathematically 

 approximately right. 



Brogger has, as we have seen, tried to equate the archaeological 

 evidence with the theory of Ekholm by giving a higher value to the 

 length of time during which the second stage of the Neolithic age 

 persisted than I have here tentatively given. I am not constrained 



