404 THE INHABITANTS OP THE SEA. 



stitute the leading features in the structure of the soil. Under 

 the whole city of Kichmond, in Virginia, and far beyond its 

 limits, over an area of unknown extent, they form a stratum of 

 eighteen feet in thickness, and similar deposits are found to 

 alternate in the neighbourhood of the Mediterranean with 

 calcareous strata chiefly composed of Foraminifera. At first 

 eight it may seem a gross exaggeration to attribute so vast an 

 agency to beings individually so minute, but when we recollect 

 how quickly they multiply by division, and how their activity 

 dates from the first dawn of organic creation, their architectural 

 powers no longer seem incredible. In forty-eight hours a single 

 diatom may multiply to 8,000,000, and in four days to 

 140,000,000,000,000, when the silicious coverings of its enor- 

 mous progeny will already suffice to fill up a space of two cubic 

 feet. 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. In no case is the 

 power of numbers more forcibly exemplified, for where can we 

 find results more vast, proceeding from the infinite multiplica- 

 tion of the smallest individuals, than that whole tracts of country 

 should literally be built up of the skeletons of Foraminifera and 

 Diatomacese ? 



Hooded Merganser. 



