866 NATUEAL HISTOET. 



ing their onginal 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- 



fstances, 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. 



