CLASSIFICATION. 



11 



haps assume a deeper interest, when he still more 

 closely examines their history. 



There are in Sweden certain extensive tracts of 

 country entirely composed of an exceedingly fine 

 earth, which, from its whiteness and from an idea 

 extensively prevalent, that it possesses nutritious 

 properties, has long been distinguished by the name 

 of Bergmehl, or " mountain meal." A little of this 

 earth, for long ages trodden under foot, submitted to 

 the modern microscope, has revealed itself to be 



FlG. 3. VEGETABLE FORMS OF MICROSCOPIC ORGANISMS. 



entirely resolvable into minute shells of exquisite 

 beauty and delicacy of sculpture. These shells, 

 being composed almost entirely of pure flint (silex), 

 are almost indestructible, and to a practised eye are 

 at once seen to have belonged to vegetable organisms 



