TIDES. 



43 



many pages, and require many diagrams. Suffice 

 it to say, that the grand exciting cause of the 

 tides is the force called attraction, or gravitation ; 

 the moon being the chief among the many agents 

 through which it acts. It matters not whether 

 the water is salt or fresh, whether as an ocean it 

 fills the bed of the Atlantic, or as a drop of dew 

 trembles on a violet leaf. The tide-force still 

 acts on it, and tides there are, although we are 

 incapable of perceiving them. It is the same 

 with the upper sea, namely, the atmospheric air 

 of our earth. In the aerial ocean there are waves, 

 whirlpools, calms, and storms, although our eyes 

 are too dull to perceive them, and can only be 

 made aware of their existence by seeing their 

 effects. 



Twice in every day of twenty- four hours the 

 water advances and recedes, and thus at least 

 one opportunity is given daily for the observer 

 to follow the retiring waves, and to discover some 

 small portion of the wonders of the sea. Some 

 of its living and breathing inhabitants have been 

 mentioned in the preceding chapter, and in the 

 following pages will be briefly described some 

 few of its vegetative inhabitants, that breathe 

 not, but yet live. 



If we walk on the sea-shore, vast masses of 



