Vol. 57.] THE CLIMATE OF THE PLETSTOCENE EPOCH. 405 



28. The Ineltjence of the Winds ujwn Climate during the 

 Pleistocene Epoch : a PALiEOMETEOEOLoaiCAL Explanation 

 of SOME Geolo&ical Peoblems.^ By Frederic William 

 Harmer, Esq., F.G.S. (Eead May 8th, 1901.) 



Contents. 



Page 



I. Introductory 405 



II. The Humid Conditions of the Sahara during the Pleistocene 



Epoch 420 



III. The Former Existence of the Mammoth on the Shores of the 



Polar Sea 422 



IV. The Former Existence of Great Lakes in the Basin of Nevada 



and in Central Asia 429 



V. The Meteorological Conditions of the Pleistocene Epoch 431 



VI. The Meteorological Conditions during the Maximum Grlaciation 



of North America ' 445 



VII. The Meteorological Conditions during the Maximum Glaciation 



of Europe and of the British Isles 455 



VIII. The Prevalent Storm-Tracks of the Pleistocene Epoch 461 



IX. A Possible Explanation of the Secular Movements of the 

 Ice-Sheets, and of the Polar Anticyclone, during the Pleisto- 

 cene Epoch 464 



X. Summary 469 



XI. Appendix 472 



I. Introductory. 



The progress of meteorological science during recent years has 

 given us much information as to the causes of the constant, and to 

 a superficial observer the apparently capricious, changes of weather 

 which obtain over certain portions of the earths surface. We 

 understand now, not only why, in Great Britain for example, one 

 day is dry or cold, and the next rainy or warm ; but also why the 

 general character of the seasons often differs so widely from the 

 normal, the climate of spring being experienced at one time in 

 January, and the conditions of winter in May or June, The 

 scientific meteorologist, equally with the unlettered peasant, still 

 looks, however, to the vane on the church-tower for his first expla- 

 nation of anomalous weather, though the meteorologist shows us that 

 the direction of the winds is due to the relative position, and to the 

 form and alignment, of areas of high and low barometric pressure. 

 The winds must necessarily blow, as is well known, in a direction 

 more or less parallel to the isobaric lines, moving iu the Northern 

 Hemisphere outward from, and round the centre of, an anticyclone 

 in the direction of the hands of a watch, and towards and round a 

 cyclone in the opposite direction. To use the old formula (Buys 

 Ballot's law), 'if you stand with your back to the wind, you have 

 the higher barometer on your right hand.' 



^ The views expressed in this paper were laid before the Bradford Meeting 

 of the British Association in September, 1900; see Geol. Mag. 19U0, p. 565. 



