393 CAUSES OF CLIMATAL CHANGE 



as compared with the equatorial and with the Antarctic ; and 

 we might readily imagine other distributions that would give 

 very different results. But this is not an imaginary case, for 

 we can to some extent restore, on geological grounds, the 

 ancient geography of large regions, and can show that it has ^ 

 been very different from that prevailing at present. We 

 know also that, while the forms and positions of the great 

 continents have been fixed from a very early date, they have 

 experienced many great submergences and re-elevations, and 

 that these have occurred in somewhat regular sequence, as 

 evidenced by the cyclical alternations of organic limestones 

 and earthy sediments in the successive great geological periods, 

 each of which, as may be seen in any geological text book, 

 presents a dip of the continental plateaus, with subsequent 

 elevation, as if the land was subject to a series of regular 

 pulsations.^ 



Finally, the Lyellian theory tends to abate the tendency to 



imagine portentous and impossible climatal changes; and it 



• inclines geologists to give more attention to the connection 



of palaeo-geography with changes in the life history of the 



earth. 



References:— "Acadian Geology," ist ed., 1855 ; 4th ed., 1892. Ice- 

 bergs of Belle-Isle, and Glaciers of Mont Blanc, Canadian Naturalist^ 

 1865. "Notes on Pleistocene of Canada," Montreal, 1871. Papers 

 at various dates in the Canadian Naturalist and Canadian Record of 

 Science. "The Ice Age in Canada," Montreal, 1892. Canadian 

 Pleistocene, London Geological Magazine, March, 1883, Flora of 

 the Pleistocene, Dawson and Penhallow. Bulletin of Geological 

 Society of America, vol. i., 1890, p. 311. 



See "Acadian Geology" — Introduction to the Carboniferous System. 



