480 THE CHEMISTRY OP CREATION. 



the danger of being driven ashore by the long 

 and heavy swell of the Pacific. They are sup- 

 posed to grow without attachment to any rock, 

 carried about by the waters which bear them 

 and supply them with all necessary to their 

 existence. In the tropics, where the waters 

 are singularly pure and pellucid, and the light 

 very powerful, it is often a splendid spectacle to 

 look down over the ship's side, and contemplate 

 the beautiful vegetation adorning the sea-bed. 



But there exists a limit to the vegetation of 

 the sea, beyond which it is unable to pass. The 

 dark bottom of the ocean is a water desert, un- 

 enlivened with a single species of plant. Thou- 

 sands of miles in area of the bed of the waters 

 are thus waste and barren. Professor Forbes, 

 in his dredging researches in the JEgean Sea, 

 found no plants below 100 fathoms. A more 

 singular part of their history is, that they are 

 distributed in zones, at various depths and de- 

 grees of removal ' from light and warmth. The 

 first zone is the space included between high- 

 and low- water marks : this zone, on the British 

 coast, does not descend deeper than 30 fathoms. 

 It is occupied by distinct species of sea-weeds. 

 The second zone on our coast, beginning at 

 low-water mark, extends below it to a depth of 

 from 7 to 15 fathoms. This also has its peculiar 

 vegetable inhabitants. The great sea-tangle 



