366 NATURAL HISTORY. 
ing their original beauty, with the delicate tracery of 
their rich configuration, almost as sharp and clear as it 
was, perhaps, a thousand years ago.” 
637. The Tripoli, or rotten-stone of Bohemia, which, 
when ground, is used as a polishing powder, is full of 
flinty shells, which are so minute that forty thousand mil- 
lions are contained in a single cubic inch. Other in- 
stances, In great number, could be cited, from various 
quarters of the world, of large deposits of the remains of 
animalcules, in rocks, in earth, in peat-bogs, and in mud. 
Well does Lamarck say of these deposits, that “it is by 
means of the smallest objects that Nature every where 
produces her most remarkable and astonishing phenom- 
ena. Whatever she may seem to lose in point of volume 
in the production of living bodies, is amply made up by 
the number of individuals, which she multiplies with ad- 
mirable promptitude, to infinity. The remains of such 
minute animals have added much more to the mass of 
materials which compose the exterior of the crust of the 
globe than the bodies of Elephants, Hippopotami, and 
Whales.” In § 614 I spoke of the agency of coral ani- 
mals in building up portions of the earth by the forma- 
tion of their skeletons; but the agency of these animal- 
cules, by means of their remains, is vastly greater. 
638. The name Infusoria was given to animalcules be- 
cause they abound in infusions of decomposing vegetable 
or animal substances. By some, however, this term is 
confined to those animalcules which have cilia, by which 
they swim through water. An abundance of these can 
be obtained in warm weather from the surface of water 
in ponds, especially where there is a reddish or green 
tinge, or a slimy layer. In Fig. 277 you have a variety 
of these Infusoria. They move about very freely in the 
water by means of their cilia. ‘‘ These movements,” says 
Carpenter, ‘‘are extremely various in their character in 
different species ; and when a number of dissimilar forms 
are assembled in one drop of water, the spectacle is en- 
