100 THE HARMONIES OP NATURE. 



no wonder then that, during the course of ages, these micro- 

 scopic plants have been able to form prodigious strata wherever 

 circumstances favoured their propagation. 



Under the whole city of Kichmond in Virginia, and far 

 beyond its limits, over an area of unknown extent, they consti- 

 tute a stratum of eighteen feet in thickness ; and similar depo- 

 sits are found in the Island of Mauritius, in the province of Oran 

 in Algeria, in Bermuda, in the heaths of Luneburg in Hanover, 

 and numberless other localities, so that there is scarce a coun- 

 try on earth where their fossil remains have not left the traces 

 of their history in broad geological features. Nor are they of 

 less importance in the great household of living creation. In 

 the Antarctic Ocean, where there is a marked deficiency of 

 higher forms of vegetation, they supply the chief food of the 

 minor aquatic animals, which in their turn serve as prey to the 

 fishes and Cetaceans. And not only in the vast deserts of the 

 Polar Seas, but wherever they abundantly germ forth, under 

 the stones of mountain-streams or in shallow pools, or in 

 road-side ditches, they afford nourishment to an amazing multi- 

 tude of small creatures. It is not useless that their propagation 

 is so rapid, since enormous losses have constantly to be repaired, 

 and not in vain that they abound in the most inhospitable seas, 

 where but for them no sea bird would flap its wings and no dol- 

 phin dart through the desert waters. 



