iU 



EXTINCTION OV SPECIES. 



[CiL XLII, 



Nature 



animals 



lation of a certain portion of the habitable sea and land 

 would, even in a few years^ be considerable, so great is the 

 instability of the earth's surface. 



Whenever 



sediment 





materially to diminish 



its depth, the aquatic animals and plants which delight in 

 deep water are expelled : the tract, however, is not allowed 

 to remain useless; but is soon peopled by species which 

 require more light and heat, and thrive where the water is 

 shallow. Every addition 

 ment of the delta of a ri 



made 



species 



•formed 



permitted to lie unoccupied, being instantly covered with 

 terrestrial vegetation. The ocean devours continuous lines 

 of sea-coasts, and precipitates forests or rich pasture land 

 into the waves ; but this space is not lost to the animate 

 creation ; for shells and sea-weeds soon adhere to the new- 

 made cliffs, and numerous fish people the channel which the 

 current has scooped out for itself. No sooner has a volcanic 

 island been thrown up than some lichens begin to grow upon 

 it, and it is sometimes clothed with verdure while smoke and 

 ashes are still occasionally thrown from the crater. The 

 cocoa, pandanus, and mangrove take root upon the coral reef 

 before it has fairly risen above the waves. The burning stream 

 of lava that descends from Etna rolls through the stately 

 forest, and converts to ashes every tree and herb which stands 

 in its way ; but the black strip of land thus desolated is covered 



a 



time 



as luxuriant as those which the fiery torrent swept away. 



Every flood and landslip, every wave which a hurricane or 

 earthquake throws upon the shore, every stream of lava or 

 shower of A'-olcanic dust and ashes which buries a country far 

 and wide to the depth of many feet, every advance of the 

 sand-flood, every conversion of salt water into fresh, when 

 rivers alter their main channel of discharge, every permanent 

 variation in the rise or fall of tides in an estuary— tliese and 



countless other causes displace, in 



the course of a few 



centuries, certain plants 



animals from stations which 



1 



