8 REPORT — 1886. 



of the Pacific and Antarctic Oceans is dotted with islands — like a shallow 

 pool with stones rising above its surface — as if its general depth were 

 small in comparison with its area. He might also notice that a mass or 

 belt of land surrounds each pole, and that the northern ring sends off 

 to the southward three vast tongues of land and of mountain chains, 

 terminating respectively in South America, South Africa, and Australia, 

 towards which feebler and insular processes are given off by the Ant- 

 arctic continental mass. This, as some geographers have observed,' 

 gives a rudely three-ribbed aspect to the earth, though two of the three 

 ribs are crowded together and form the Europ-asian mass or double con- 

 tinent, while the third is isolated in the single continent of America. He 

 might also observe that the northern girdle is cut across, po that the 

 Atlantic opens by a wide space into the Arctic Sea, while the Pacific is 

 contracted toward the north, but confluent with the Antarctic Ocean. The 

 Atlantic is also relatively deeper and less cumbered with islands than the 

 Pacific, which has the higher ridges near its shores, constituting what 

 some visitors to the Pacific coast of America have not inaptly called the 

 * back of the world,' while the wider slopes face the narrower ocean, into 

 which for this reason the greater part of the drainage of the land is 

 poured.2 The Pacific and Atlantic, though both depressions or flattenings 

 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. 



If our imaginary observer had the means of knowing anything 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 

 be led to believe that the Atlantic, though comparatively narrow, is an 

 older feature of the earth's surface, while the Pacific belongs to more 

 modern times. But he would note in connection 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 

 extending southwards from it constitute the most ancient and permanent 

 elevations of the earth's crust, though now greatly surpassed by moun- 

 tains of more recent age nearer the equator. Before leaving this general 

 survey we may make one further remark. An observer looking at the 

 earth from without would notice that the margins of the Atlantic and 

 the main lines of direction of its mountain chains are north-east and 

 south-west, and north-west and south-east, as if some early causes had 



' Dana, Manual of Geology, introductory part. Green, Vesti-ges of a Molten Globe, 

 has summed up these facts. 



^ Mr. Mellard Reade, in two Presidential addresses before the Geological Society 

 of Liverpool, has well illustrated this point and its geological consequence. 



