GAUES IN THE SEA, 53 



Water converted into vapour is disburdened of its 

 salts ; air contained in water becomes richer in 

 oxygen. This gas plays a most important part in 

 oceanic phenomena. Without it no living thing could 

 exist in the sea. Except for it, even those beautiful 

 algae, whose long and brilliantly-coloured ribbons are 

 floated in undulating curves by the marine currents, 

 would no longer charm the eye. The whole race 

 of polypi would cease to construct their stony habi- 

 tations, which are so much admired by the lovers of 

 nature. 



The deeper we penetrate into the ocean the more 

 abundant are the gases. The increase of carbonic 

 acid gas with the increasing depth is especially re- 

 markable ; and hence the gaseous mixture found in 

 the deeper parts of the sea is less suitable for re- 

 spiration than that which is nearer the surface. It 

 is further to be observed that the renewal of gases 

 in deep water is effected with much less facility ; 

 and this may be regarded as one of the causes 

 which tend to prevent the existence of organised 

 beings at a great depth. As aerial plants and 

 animals are confined to the lower strata of the 

 atmosphere, so marine plants and animals are con- 

 demned to remain near the surface of the waters, com- 

 paratively speaking. Thus, the living beings which 

 flourish on our globe are confined to a very limited 



