66 SELECTED ESSAYS FROM LAY SERMONS 



with any magnifying power that may be thought desirable. 

 A thin slice of the fur of a kettle might be made in the same 

 way. If it were examined microscopically, it would show 

 itself to be a more or less distinctly laminated mineral sub- 

 stance, and nothing more. 



But the slice of chalk presents a totally different appear- 

 ance when placed under the microscope. The general mass 

 of it is made up of very minute granules; but, imbedded 

 in this matrix, are innumerable bodies, some smaller and 

 some larger, but, on a rough average, not more than a hun- 

 dredth of an inch in diameter, having a well-defined shape 

 and structure. A cubic inch of some specimens of chalk 

 may contain hundreds of thousands of these bodies, com- 

 pacted together with incalculable millions of the granules. 



The examination of a transparent slice gives a good notion 

 of the manner in which the components of the chalk are 

 arranged, and of their relative proportions. But, by rubbing 

 up some chalk with a brush in water and then pouring off 

 the milky fluid, so as to obtain sediments of different degrees 

 of fineness, the granules and the minute rounded bodies may 

 be pretty well separated from one another, and submitted 

 to microscopic examination, either as opaque or as trans- 

 parent objects. By combining the views obtained in these 

 various methods, each of the rounded bodies may be proved 

 to be a beautifully-constructed calcareous fabric, made up 

 of a number of chambers, communicating freely with one 

 another. The chambered bodies are of various forms. 

 One of the commonest is something like a badly-grown 

 raspberry, being formed of a number of nearly globular 

 chambers of different sizes congregated together. It is 

 called Globigerina, and some specimens of chalk consist of 

 little else than GlobigerincB and granules. Let us fix our at- 

 tention upon the Globigerina. It is the spoor of the game 



