404 THE INHABITANTS OF THE SEA. 
stitute the leading features in the structure of the soil. Under 
the whole city of Richmond, 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 
sight 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. 
