148 THE AQUAEIAN NATURALIST. 



The prodigious extent of the combined and uninter- 

 mitting labours of these little world-architects must 

 be witnessed in order to be adequately conceived. 

 They have built up a barrier-reef along the shores of 

 New Caledonia for a length of four hundred miles, 

 and another which runs along the north-east coast of 

 Australia 1000 miles in extent. Now, assuming this 

 latter to be only a quarter of a mile in breadth and 

 150 feet deep, here is a mound compared with which 

 the walls of Babylon, the great wall of China, or the 

 Pyramids of Egypt are but children's toys ; and built 

 too amidst the waves of ocean and in defiance of its 

 storms, which sweep away the solid works of man. 



" The geologist," says Professor Owen, " in con- 

 templating these stupendous operations, appreciates 

 the conditions and powers by which were deposited in 

 ancient times, and under other atmospheric influences 

 than now characterize our climate, those downs of 

 chalk which give fertility to the south coast, and many 

 other parts of our native island. The remains of corals 

 in these masses, though allied in their general nature, 

 are specifically distinct from the living polyps which 

 are now actively engaged in forming similar fertile 

 deposits on the undulating and half-submerged crust 

 of the earth washed by the Indian and Pacific Oceans. 

 Again, those masses of limestone rocks which form a 

 large part of the older secondary formations, give evi- 

 dence by their organic remains that they too are due 

 to the labours of polyps, the species of which perished 

 before those that formed the cretaceous strata were 

 created. As the polyps of the secondary epochs have 

 been superseded by the Porites, Millepora, Madre- 



