] 02 APPENDIX. 



country, is one of the most interesting discoveries of 

 modern Geology*. 



The peat-bogs and swamps, both of modern and an- 

 cient date, often contain masses of a white, marly, 

 siliceous paste, wholly made up of the shells of Infu- 

 soria. Such is the white earthy substance found in the 

 peat-bogs of Ireland, Yorkshire, &c. The polishing- 

 slate of Bilin, in Prussia, forms a series of strata four- 

 teen feet thick, and is entirely composed of the siliceous 

 shields of Infusoria, of such extreme minuteness, that a 

 cubic inch of the stone contains forty-one thousand mil- 

 lions of distinct organisms ! 



In Virginia there are extensive beds of siliceous 

 marls, that are largely composed of the durable shields 

 of various kinds of marine animalcules. When a 

 few grains of this earth are properly prepared for 

 the microscope, numerous species of the most ex- 

 quisite forms are visible: in fact, the merest stain 

 left by the evaporation of a drop of water in which 

 some of the marl has been mixed, teems with beau- 

 tiful infusorial structures. This aggregation of the 

 fossil remains of beings, so minute, as to be invisible 

 to the naked eye, forms strata several yards in thick- 



* This subject is treated at length in my " Medals of Creation," 

 chap. vii. 



