Yol. 57.] CLIMATE OF THE PLEISTOCENE EPOCH. 433 



a third in British Columbia ; that in Europe the ice lay thickest 

 in the Baltic area, crossing the Scandinavian watershed towards 

 Xorwa)', with independent centres of dispersal in the British Isles, 

 in Switzerland, and in other mountain-regions ; and further, that 

 the ice travelled outward from these centres to a considerable 

 distance in both hemispheres/ 



The direction in which the ice-streams travelled may have varied 

 from time to time, but the centres of dispersion were possibly always 

 more or less the same ; and this, from a meteorological point of view, 

 is important, since it is upon the position of the centres of the anti- 

 cy clonic or cyclonic systems that the direction of the winds largely 

 depends. 



It seems satisfactorily proved, moreover, that the ice-sheets were 

 for a time melted back more than once, if they did not altogether dis- 

 appear,^ and that climatic conditions comparatively genial prevailed 

 during the ice-age, locally at least, both in North America and in 

 Europe. 



As the form and extension of the ice-sheets varied from time to 

 time, the position of the continental anticyclones would vary also ; 

 but so far as the centres of the latter remained the same, their general 

 relation to the low-pressure systems of the Atlantic and the Pacific 

 during the cold periods would be unaltered. 



For the purpose of my argument, I propose to take those stages 

 at which, in the eastern and western continents, the ice-sheets are 

 supposed to have attained their greatest development, adopting the 

 views expressed by Prof. James Geikie ^ ; and I shall endeavour to 

 trace out what may possibly have been, under such circumstances, 

 the meteorological conditions of the period or periods in question. 



It has often been urged that the existence of great ice-sheets 

 must have been accompanied by excessive precipitation. It is clear, 

 of course, that no ice could accumulate, except in regions visited 

 from time to time by oceanic winds. The amount of precipitated 

 moisture necessary to produce permanent glaciation may not, how- 

 ever, have been so great as has been sometimes supposed. When 

 in summer, heavy and sudden downfall takes place, or when in 

 winter, rain is continuous for many days, the streams are flooded, 

 and the greater part of the water which falls is quickly carried out 

 to sea.'' On the other hand, when the temperature drops below the 



^ The outward travel of the ice-sheets may have been partly due, as Mr. G-. 

 W. Lamplugh points out, to the accumulation of snow falling on them, other- 

 wise than at the great ice-centres, Geol. Mag. 1901, p. 142. 



^ Prof. Chambei4in considers (Geikie's ' Great Ice Age' 3rd ed. 1894, p. 769) 

 that the character of the fauna and flora of the Interglacial deposits of Toronto, 

 first described by my friend, Dr. G. J. Hinde, F.R.S., in Canad. Journ. vol. xv 

 (1877) p. 388, points to the existence of milder climatic conditions than those 

 of the present day in the same region, 



•^ ' Great Ice Age ' 3rd ed. (1894) pi. is facing p. 437, & pi. xiv facing p. 724. 



* The loss of water, in this way, from the great ice-sheets would have been, 

 on the contrary, comparatively small. 



