1856.] CONTINENTAL EXTENSION. 75 



across the ocean to the Azores, and further north right across. 

 In short, we must suppose probably, half the present ocean 

 was land within the period of living organisms. The Globe 

 within this period must have had a quite different aspect. 

 Now the only way to test this, that I can see, is to consider 

 whether the continents have undergone within this same pe- 

 riod such wonderful permutations. In all North and South 

 and Central America, we have both recent and miocene (or 

 eocene) shells, quite distinct on the opposite sides, and hence 

 I cannot doubt that fundamentally America has held its place 

 since at least, the miocene period. In Africa almost all the 

 living shells are distinct on the opposite sides of the inter- 

 tropical regions, short as the distance is compared to the range 

 of marine mollusca, in uninterrupted seas ; hence I infer that 

 Africa has existed since our present species were created. 

 Even the isthmus of Suez and the Aralo-Caspian basin have 

 had a great antiquity. So I imagine, from the tertiary depos- 

 its, has India. In Australia the great fauna of extinct mar- 

 supials shows that before the present mammals appeared, 

 Australia was a separate continent. I do not for one second 

 doubt that very large portions of all these continents have 

 undergone great changes of level within this period, but yet I 

 conclude that fundamentally they stood as barriers in the sea, 

 where they now stand ; and therefore I should require the 

 weightiest evidence to make me believe in such immense 

 changes within the period of living organisms in our oceans, 

 where, moreover, from the great depths, the changes must 

 have been vaster in a vertical sense. 



Secondly. Submerge our present continents, leaving a few 

 mountain peaks as islands, and what will the character of the 

 islands be ? Consider that the Pyrenees, Sierra Nevada, 

 Apennines, Alps, Carpathians, are non-volcanic, Etna and 

 Caucasus, volcanic. In Asia, Altai and Himalaya, I believe 

 non-volcanic. In North Africa the non-volcanic, as I imagine, 

 Alps of Abyssinia and of the Atlas. In South Africa, the 



