CHEMISTRY OF THE TIDES. 457 



as distinguishable from that of the wave and 

 ripple, must first occupy our consideration. 

 Let us ascend the hillock hard by, and thence 

 take a chemical view of the interesting phe- 

 nomena of the sea-shore. 



In considering the tidal chemistries as distin- 

 guished from those of the wave, we have chiefly 

 to inquire into the probable effects of a periodic 

 flux and reflux of sea-water upon the objects 

 exposed to its influence. This phenomenon 

 exerts an influence upon the inorganic consti- 

 tuents of the shore, and also upon the various 

 inhabitants of the sea, vegetable and animal, 

 lying within the line of low-water, or ebb of 

 the tide. On almost all sea-coasts, and parti- 

 cularly on such a one as that we are contem- 

 plating, where a river brings down constant 

 supplies of material from a rich alluvial soil 

 inland, there exists a certain amount of organic 

 vegetable and animal matters, which, as is com- 

 mon with all such matters, is extremely prone 

 to decomposition, and is here placed in circum- 

 stances peculiarly favourable to it. The ebb 

 of the tide exposes such matters to the full 

 influence of the air, leaving them sufficiently 

 moist to forward the changes which immediately 

 commence in organic matter so exposed. A pro- 

 cess of putrefactive decomposition is set up, the 

 gaseous elements of the air unite with the solid 



