NATUEE AND OCCUEEENCE 5 



as, for example, by crushing a piece of soft white chalk 

 under water, and repeatedly washing the residue, 

 taking care that nothing but the fine milky fluid is 

 thrown away during the process of levigation. After 

 drying the residue, the powder thus obtained will 

 probably yield numerous specimens of Foraminifera. 

 That some chalks and limestones are largely com- 

 posed of foraminifera! shells we may see by examining 



Fig. 4. — From a Photojiicrograph of a Thin Section of Chalk 

 FROM MissENDEN, BUCKINGHAMSHIRE, x 36. Oriffinal. 



thin slices of these rocks from certain horizons. Fig. 

 4 is taken from a photomicrograph of a section of 

 the chalk-rock of Buckinghamshire ; in this zone the 

 Foraminifera are always abundant. The separated 

 microzoa often contain some handsome forms, as the 

 next illustration (fig. 5) will show. To be successful, 

 however, in extracting Foraminifera from the chalk, 

 it must be borne in mind that some strata are almost 



