1908] on the Figure and Constitution of the Earth. 05 



2000 fathoms over considerably more than half of the oceanic area, yet 

 the areas over which the depth exceeds 3000 fathoms amount in the 

 aggregate to only about 3 per cent, of the total surface, and these 

 areas, 40 or more in number, are scattered irregularly over the globe. 



Total area j 100 



More than 6000 feet above sea level ... 2 



Above sea level 28 



Below sea level 72 



More than 6,000 feet below sea level . . 57 



12,000 „ „ ... 43 



18,000 ,, 3 



In seeking to appreciate the general features of the shape of the earth 

 we may disregard these " deeps," just as we disregard mountains. 

 Except in certain deeps, the surface of the earth beneath the sea is 

 everywhere convex. The most important data for determining the 

 shape of the earth are the coast line and the contour lines at 1000 

 and 2000 fathoms depth. 



If on a map of the world we draw the contour line at 1000 

 fathoms depth, we find that the continents are not only widened on all 

 sides, but that, with the exception of the Antarctic continent, they 

 form a single continuous region of elevation. At this depth the 

 Antarctic regions become a continuous region of elevation nearly as 

 far north as the 60th parallel all round. The xerotic Ocean is reduced 

 to two enclosed patches of deep water, one to the north of G-reat 

 Britain, the other to the north of Russia and Siberia. South America 

 does not taper to the south, but spreads out to the south-east. The 

 ridge joining Xorthand South America is widened out across the West 

 Indies, and the Caribbean Sea and Gulf of Mexico are reduced to 

 a few enclosed patches of deep water. North America is joined on 

 the northern side to Europe and to Asia. The Mediterranean and 

 adjacent seas are represented by a few patches of deep water. Asia 

 is joined to Australia by way of Borneo and New Guinea, and Australia 

 extends southwards over Tasmania and south-eastwards over New 

 Zealand. If we proceed to draw the contour line at 2000 fathoms 

 depth we find that the continents are further widened, and such seas as 

 the Arctic Ocean, the Caribbean and the Mediterranean, almost entirely 

 disappear ; but the most important fact is that at this depth the 

 Antarctic continent is not detached, but is united both to South 

 America and to Australia. [Maps of the world in hemisplieres with 

 the contour lines at 1000 fathoms and 2000 fathoms depth were 

 shown by slides.] Such maps teach us that the continents are to be 

 regarded as one continuous region of elevation. If we neglect small 

 isolated areas of depression and elevation, we can draw between the 

 1000-fathoms line and the 2000-fathoms line a curve which divides 



