LIGHT AND SEA-PLANTS. 491 



fectly clean and bare. We are apt also to forget 

 that in all the domains of nature organized 

 beings are fitted to the stations they occupy, 

 and exactly perform the duties required of 

 them. The sea-weed, low though it is in the 

 order of vegetable creation, and insignificant as 

 it appears in our eyes, is beautifully adapted to 

 the place of its abode, and amid many apparent 

 disadvantages faithfully executes its chemical 

 task of decomposing carbonic acid and evolving 

 oxygen. 



As in the air, so in the water of the sea also, 

 ammonia may be detected. It is probably, as 

 in the former case, the source of the chief por- 

 tion of the nitrogen contained in such plants. 

 It originates in the death and decomposition 

 of the marine animals. Phosphates, earthy 

 and alkaline carbonates, are also present in sea- 

 water, and are found in the ashes of marine 

 plants, which is sufficient to show that they 

 are necessary to them. 



The marine vegetation acts a part with refer- 

 ence to the preservation of the constancy of 

 composition in sea-water not less beautiful and 

 interesting than the decomposition of carbonic 

 acid by plants growing in the air. The sea is not 

 less exposed to the risk of deterioration than 

 the air. The sources of its 'gaseous deteriora- 

 tions and their remedies have just been noticed. 



