Yol. 57-] CLIMATE OF THE PLEISTOCENE EPOCH. 463 



During the maximam glaeiation of Europe, storms may have 

 passed in winter from Japan to Kamtchatka, across Behring Sea, 

 while others traversed North America ; but those which crossed the 

 Atlantic towards Europe must have more often than at present 

 taken a south-easterly course (fig. 21, p. 458). In this way, as we 

 have seen, a humid climate may have been caused in the Sahara. 



The great extension of the Swiss glaciers during the Pleistocene 

 Epoch shows that a considerable amount of moisture must have 

 reached them from the ocean, some doubtless from the west. 

 Cyclonic storms, possibly of small diameter, travelling eastward 

 from the Atlantic, as suggested in fig. 22 (p. 460), may have then 

 occurred in South-western Europe from time to time. 



The climate of the region north of the Swiss massif was colder 

 at this period than that to the south of it, the former having been 

 more or less under the influence of the anticyoJonic winds pro- 

 ceeding from the ice-sheet of ISTorthern Europe. While ice was 

 accumulating from age to age in the north, and the great glacier of 

 the E,hone Valley was piling uj) its moraine against the flanks of the 

 Jura, the sun's heat on the southern slopes of the ice-clad mountains 

 during summer, and the rains which may have there fallen, pro- 

 duced floods of incredible violence, which have covered the low- 

 lands of Piedmont and Lomhardy, from the foot of the Alps to the 

 Adriatic, with a thick and continuous sheet of diluvial gravel and 

 mud.^ It is only when standing on the tower of the Cathedral at 

 Milan, or on the summit of the Superga, near Turin, looking across 

 the great plain towards the distant mountains rising abruptly from 

 it, that one can realize the strength and volume of the torrents 

 which must have issued from the Alpine valleys at this epoch. 



The Pleistocene deposits of ISTorthern Italy here mentioned are 

 believed by Italian geologists^ to belong to the Saharien zone of 

 Meyer, that is, to a period contemporaneous with the humid 

 condition of the desert region of Northern Africa, and of the great 

 extension of the Swiss glaciers. This view harmonizes with the 

 meteorological conditions suggested in iigs. 21 & 22 (pp. 458 & 460). 



To the same period has been referred part of the vast sheet 

 of coarse detritus, often containing blocks of large size, which 

 extends northward from the foot of the Pyrenees to the Garonne, 

 and thence to Bordeaux, and also the gravels of the Rhone delta 

 and of the valley of the Var,^ as well as the enormous sheet of 

 gravel which covers the plains of Hungary. The inundations by 

 which these deposits were caused can only have occurred during 

 the prevalence of atmospheric disturbances of far greater intensity 

 than those of our own era. 



''- On the contrary, the snow-line descends much lower on the southern than 

 on the northern slopes of the Himalayas, moist winds reaching that region 

 from the former quarter only. 



2 For much interesting information as to the Pleistocene deposits of 

 Southern Europe I am indebted to my good friends, M. G. F. Dolltus, of 

 Paris, and Prof. Sacco, of Turin. 



^ As to the latter, see Chamhrun de Rosemont's ' Etudes Geol. sur le Var & lo 

 Khone ' Nice, 1873, The former have been described by many observers. 



