Yol. 57.] CLIMATE OF THE PLEISTOCENE EPOCH. 431 



The more humid conditions formerly existing- in Central Asia 

 (indicated by the greater extension of Lake Baikal), in Tibet, 

 Turkestan, the Han-Hai Basin, and elsewhere, may belong to some 

 stage or stages of the Glacial Period when the relative position of 

 the high- and low-pressure systems, different from that of the present 

 day, favoured the prevalence of moist winds over those regions. 

 These may conceivably have come from the Mediterranean, the Black 

 Sea, or the Caspian, the latter at one period covering a much larger 

 area than it now does. Moreover, the prevalent storm- tracks must 

 have been different during the Pleistocene Epoch from those of our 

 own era.^ As before stated, a considerable portion of the cyclonic dis- 

 turbances which approach the continent of Europe from the Atlantic 

 pass to the north or north-west of the British Isles, towards 

 Scandinavia.^ During the existence of an ice-sheet in those regions, 

 this course would not have been open to them ; so far as they 

 continued to travel eastward, they must have done so to the south 

 of the ice-clad region (figs. 21 & 22, pp. 458 & 460). Some of the 

 Atlantic storms do move that way now, but none of them penetrate 

 into Central Asia. 



In dealing with the post-Glacial Period, in his valuable work 

 on Prehistoric Europe, Prof. James Geikie calls attention to the 

 alternations of dry or humid, and of cold or mild climates, by 

 which it was characterized. That climatic changes occurred also 

 after the climax of the Great Ice Age need not surprise us. The 

 meteorological disturbances set up during that abnormal and 

 remarkable chapter in geological history may well have continued 

 to exert their influence during the post-Glacial Period. It would 

 not be possible, within the limits of such a paper as this, to attempt 

 to discuss these matters in detail, nor is the necessary information 

 available. It will be sufficient to call attention to the general 

 principle that anomalous weather in the past, even if 

 more or less permanent, may have been due to that 

 which causes temporary changes of a similar character 

 at present, namely, to a change of wind. Even if the 

 <}old of the Great Ice Age was due to some extra-telluric cause, it 

 seems hardly necessary to invoke such an origin for the various 

 changes of climate, some of them evidently local, which charac- 

 terize it, if some simpler explanation can be found. 



V. The Meteorological Conditions of the Pleistocene Epoch. 



I do not venture to express any opinion as to the cause of the 

 Glacial cold. There was a Glacial Period, and the refrigeration of 

 climate by which it was distinguished had been long coming on, 

 gradually, and apparently without intermission. There is no 



, ^ See further as to this, § VIII, p. 461. 



^ The low-pressure areas on statistical maps represent, to a considerable 

 extent, the prevalent track of cyclonic storms. 



