THE OCEAN UNEXPLORED AND UNEXPLORABLE 247 



Helena, Tristan d'Acunha, and G-ough Islands soar 

 into the upper air. Possibly at some period of the 

 wondrous early history of our globe this great ridge 

 was above water, dividing the South Atlantic sheer 

 in two, with such effect upon the climate of that 

 ancient world as we can now hardly imagine; but 

 owing to our utter inability to penetrate the mysteries 

 of those inscrutable depths, we have no means of 

 knowing whether this was so or not. We may, how- 

 ever, reasoning from the known to the unknown, feel 

 fairly certain that there is but little difference really 

 between the land above and the land below the sea, 

 except in those attributes which the former has gained 

 from its contact with the atmosphere and sunlight. 



Among the most potent forces at work in the 

 depths of the sea must be the volcanic upheavals, 

 some of which having taken place near land have 

 given evidence of their terrible effects. Arguing from 

 our knowledge of the fact that the deeper we go down 

 from the Earth's surface the nearer we approach to 

 the incandescent core of our world, it would seem only 

 reasonable to suppose that at a depth of about ten 

 times that of the deepest mine ever bored by man 

 there must be but a comparatively thin skin between 

 the sea-bed and molten conditions. Consequently, 

 where in the course of the planet's cooling that skin 

 cracks, and the astounding mass of water at the freezing 

 point rushes in upon that glowing reservoir, the up- 

 heaval caused by the sudden conversion of so many 

 millions of tons of water into steam would be sufficient, 

 one would think, to rend off whole continents from the 

 submerged surface, and to change its whole contour 

 in a way which we dry land-dwellers can only dimly 



