FORMATION OF CORAL REEFS. 149 



figuration of our globe, as the sinking of lands 

 beneath the ocean, or the gradual rising of con 

 tinents and islands above it, — or the wearing of 

 great river-beds, or the filling of extensive water- 

 basins, till marshes first and then dry land suc- 

 ceeded to inland seas, — or the slow growth of 

 coral reefs, those wonderful sea-walls raised by 

 the little ocean-architects whose own bodies fur- 

 nish both the building-stones and the cement 

 that binds them together, and who have worked 

 so busily during the long centuries, that there 

 are extensive countries, mountain-chains, islands, 

 and long lines of coast consisting solely of their 

 remains, — or the countless forests that must 

 have grown up, flourished, died, and decayed, 

 to fill the storehouses of coal that feed the fires 

 of the human race to-day, — if we consider all 

 these records of the past, the intellect fails to 

 grasp a chronology for which our experience 

 furnishes no data, and the time that lies behind 

 us seems as much an eternity to our conception 

 as the unknown future that stretches indefinitely 

 before us. 



The physical as well as the human history of 

 the world has its mythical age, lying dim and 

 vague in the morning mists of creation, like that 

 of the heroes and demigods in the early tra- 

 ditions of man, defying all our ordinary dates 

 and measures. But if the succession of periods 



