THE HISTORY OF THE NORTH ATLANTIC 59 



tenings of the earth, are, as we shall find, different in age, 

 character, and conditions; and the Atlantic, though the smaller, 

 is the older, and, from the geological point of view, in some 

 respects, the more important of the two ; while, by virtue of its 

 lower borders and gentler slope, it is, though the smaller basin, 

 the recipient of the greater rivers, and of a proportionately 

 great amount of the drainage of the land. 1 



If our imaginary observer had the means of knowing any- 

 thing of the rock formations of the continents, he would notice 

 that those bounding the North Atlantic are, in general, of 

 great age some belonging to the Laurentian system. On the 

 other hand, he would see that many of the mountain ranges 

 along the Pacific are comparatively new, and that modern 

 igneous action occurs in connection with them. Thus he 

 might see in the Atlantic, though comparatively narrow, a 

 more ancient feature of the earth's surface ; while the Pacific 

 belongs to more modern times. But he would note, in con- 

 nection with this, that the oldest rocks of the great continental 

 masses are mostly toward their northern ends ; and that the 

 borders of the northern ring of land, and certain ridges en- 

 tending southward from it, constitute the most ancient and 

 permanent elevations of the earth's crust, though now greatly 

 surpassed by mountains of more recent age nearer the equator, 

 so that the continents of the northern hemisphere seem to 

 have grown progressively from north to south. 



If the attention of our observer were directed to more 

 modern processes, he might notice that while the antarctic 

 continent freely discharges its burden of ice to the ocean north 

 of it, the arctic ice has fewer outlets, and that it mainly dis- 

 charges itself through the North Atlantic, where also the great 

 mass of Greenland stands as a huge condenser and cooler, 



* Mr. Mellard Reade, in two Presidential addresses before the Geo- 

 logical Society of Liverpool, has illustrated this point and its geological 

 consequences. 



