464 ME, T. W. HAKMEK ON THE [Aug. I9OI, 



Ploods of great violence must also have been prevalent in 

 jSTorthern Italy and elsewhere in Southern Europe during the 

 Miocene Epoch. I noticed, during a recent visit, in the coarse 

 Miocene conglomerates (Aquitano) of the Superga, an enormous 

 vs^aterworn block, measuring at least 12 x 6 feet. In Prof. Sacco's 

 opinion, the Miocene Epoch was characterized by alternations of 

 periods of tranquillity and of great fioods. Some meteorological 

 explanation of these recurring atmospheric disturbances may 

 hereafter be found. 



Referring now to the prevalent storm-tracks of North-western 

 Europe during its period of maximum glaciation, the fact that the 

 accumulation of ice was greater in the Baltic region than in Norway 

 indicates that the cyclonic disturbances from the Atlantic, by which 

 the necessary humidity was supplied, did not cross the latter 

 country, else precipitation would have been greater on the Nor- 

 wegian highlands than in Sweden, as it is at present.^ Moisture 

 must therefore have reached Scandinavia from the south-west, 

 possibly as shown in figs. 21 & 22 (pp. 458 & 460), the cyclones 

 moving towards the Baltic along the region lying between the 

 mer de glace of Great Britain and that of Switzerland. This 

 view supports, I think, that suggested on p. 457, that during the 

 maximum glaciation of Europe the Icelando-Scandin avian channel 

 was closed, an anticyclone then existing prevalently in that region, 

 by which the passage of cyclones from the North Atlantic to the 

 North Cape was more or less barred. 



IX. A Possible Explai^ation of the Seculae Mot-ements op the 

 . Ice-Sheets, and oe the Polae Anticyclone, dueing the 

 Pleistocene Epoch. 



It will be less difficult, I fear, to show that glacial periods in one 

 hemisphere may have coincided with milder conditions in the other, 

 than to offer a satisfactory explanation of the way in which such 

 changes of climate may have been brought about. As Huxley 

 once observed, however, there are two kinds of difficulty : that 

 of which we cannot at once find the solution, and that which 

 knocks us down altogether ; and our present difficulty is of the 

 first class. Moreover, if the theory now proposed is rejected, we 

 are confronted by what seems to me the still greater difficulty of 

 accepting the opposite view. 



The present meteorological condition of the temperate regions of 

 the Northern Hemisphere is that of unstable equilibrium, charac- 

 terized by never-ceasing change. We observe and register the 

 daily and seasonal movements of the isobaric curves to which the 

 variations of the weather are due, but we cannot trace the ultimate 



^ The average annual rainfall on the western coast of Norway is very heavy, 

 amounting at Bergen to 73 inches. In Sweden it is low : 21 inches, for 

 example, at Upsala. See Bartholomew's 'Atlas of Meteorology ' p. 20. 



