76 HIDDEN BEAUTIES OF NATURE 



Any one with a microscope will find the comparison 

 of the micro-fossils of the chalk with those of the 

 globigerina an interesting study. Samples of the 

 latter may be had from most slide-mounters. In the 

 examination of the chalk, one point must be observed, 

 which will prevent disappointment. It will be 

 necessary to select a piece of chalk from the top layer 

 of the cliff or bed, and to wash out the shells carefully 

 with water and a camels'-hair brush. The shells are 

 so small and so fragile, that it would be unreasonable 

 to expect good specimens at the base of the cliff, 

 where the pressure is so great, and where great 

 changes have been taking place in the character of 

 these lower or earlier deposits. 



A cubic inch of globigerina ooze contains about 

 one million shells ! This was proved long ago by 

 Ehrenberg. 



The lecturer's illustrations on the black-board, 

 designed in chalk, and the chalk dust that falls from 

 the duster, consist of fragments of tiny shells that 

 contained tiny creatures untold ages ago. 



If we take a bit of chalk, and with a razor we cut 

 off a thin slice, so thin that it appears somewhat 

 transparent, we shall be able to pass a light through 

 it under the microscope, when the tiny animal remains 

 will be distinctly visible. We can then photograph it 

 through the microscope, and make a lantern slide 

 which will, in large characters, exhibit every section 

 of the shells in situ. 



Although the globigerina creatures are so minute, 



