INFUSORIAL ANIMALCULES. 63 



this class are loricatcd, and the other half illoricated. Of 

 the former, the most curious discovery, of late, is that by 

 M. Fischer, of the siliceous or glass-like covering of 

 many species, who, although the creatures to which they 

 belong may have been dead for thousands of years, yet 

 these remains inform us of the local conditions of the soil 

 at the time they existed. 



These shell-like coverings are often found in large 

 masses, covering many miles of the earth's surface, and 

 occur, when indurated and mixed with argillaceous and 

 other earths, in the form of siliceous slate-rocks, &c. 

 These remains of the primeval inhabitants of our globe 

 are records in the pages of history, penned by Infinite 

 Truth, unbiassed by ignorance or prejudice, and form 

 some of the first fruits of the effective application of 

 achromatic glasses to our microscopes. 



Some of these shell-like coverings have been preserved 

 without any admixture of other matters, and form masses 

 of delicate white powder {Berg-Mehl), with which the 

 cupidity of man, in situations where it can be procured, as 

 Lapland, has induced him to adulterate the material which 

 is so truly said to constitute the staff of life. 



The antiquarian has also brought the microscope to 

 bear in his researches, and by the discovery of the exist- 

 ence of these shelly remains in various ancient articles of 

 pottery, and the remains of similar species in the clay in 

 the vicinity in which they occur, has proved that they 

 were made on the spot, and not imported from the higher 

 civilized nations of that day, as had been previously 

 supposed. 



