i8 4 THE POPULAR SCIENCE MONTHLY. 



it, " Life is life which generates" and generation implies an energy to 

 which all other energy in a living cell yields homage. 



In thus measuring the energy which cells exert, it seems to me we 

 lay our finger on the very pulse of the living world ; we feel the push 

 of its ceaseless stream, and in the impact of the latest wave catch the 

 full force of that primal impulse in which life's history on earth began. 



GEOLOGY OF THE ATLANTIC OCEAN* 



By Sir WILLIAM DAWSON, 



PRINCIPAL OF M C GILL COLLEGE, MONTREAL. 

 II. 



THUS far our discussion has been limited almost entirely to physic- 

 al causes and effects. If we now turn to the life-history of the 

 Atlantic, we are met at the threshold with the question of climate, not 

 as a thing fixed and immutable, but as changing from age to age in 

 harmony with geographical mutations, and producing long cosmic 

 summers and winters of alternate warmth and refrigeration. We can 

 scarcely doubt that the close connection of the Atlantic and Arctic 

 Oceans is one factor in those remarkable vicissitudes of climate ex- 

 perienced by the former, and in which the Pacific area has also shared 

 in connection with the Antarctic Sea. No geological facts are indeed 

 at first sight more strange and inexplicable than the changes of cli- 

 mate in the Atlantic area, even in comparatively modern periods. We 

 know that in the early Tertiary perpetual summer reigned as far north 

 as the middle of Greenland, and that in the Pleistocene the Arctic 

 cold advanced until an almost perennial winter prevailed half-way to 

 the equator. 



It is no wonder that nearly every cause available in the heavens 

 and the earth has been invoked to account for these astounding facts. 

 It will, I hope, meet with the approval of your veteran glaciologist, 

 Dr. Crosskey, if, neglecting most of these theoretical views, I venture 

 to invite your attention in connection with this question chiefly to 

 the old Lyellian doctrine of the modification of climate by geograph- 

 ical changes. Let us, at least, consider how much these are able to 

 account for. The ocean is a great equalizer of extremes of tempera- 

 ture. It does this by its great capacity for heat and by its cooling 

 and heating power when passing from the solid into the liquid and 

 gaseous states, and the reverse. It also acts by its mobility, its cur- 

 rents serving to convey heat to great distances or to cool the air by 

 the movement of cold, icy waters. The land, on the other hand, cools 

 or warms rapidly, and can transmit its influence to a distance only 



* From the inaugural address of the President of the British Association for the 

 Advancement of Science, delivered at Birmingham, England, September 1, 1S86. 





