74 HIDDEN BEAUTIES OF NATURE 



that when this 'ooze' is examined under the micro- 

 scope, it is found to consist mainly of the shells, or 

 fragments of shells, of extremely minute creatures, 

 known as globigerina. Myriads of these, and kindred 

 tiny organisms, live on almost every square yard of 

 the surface of this ocean. Vast numbers live a foot 

 or two below the surface, and even the floor of the 

 ocean is peopled with them. 



The shells, though exceedingly small, are elegant, 

 especially so when tenanted. They are also perforated, 

 so that the jelly-like speck may protrude a multitude 

 of feelers which interlace and form a meshwork 

 arrangement for catching and bringing in food. 

 Owing to these perforations, the shells of these and of 

 other creatures are classed as Foraminifera. 



The creatures die, and their shells descend to the 

 floor below, where they form layer upon layer of 

 chalky matter. We have as yet no means of knowing 

 how deep this North Atlantic bed is now, nor of the 

 time that has elapsed since this particular stratum 

 was commenced. 



We are able, however, with the aid of the microscope, 

 to throw light on another problem, namely the form- 

 ation of the chalk of our cliffs ; and although there 

 may elapse some considerable time before we can say 

 with positive certainty that the chalk of Europe and 

 Asia was deposited on the floor of some vast ocean 

 similar to the globigerina formation of the Atlantic, 

 yet we seem to have one of the several keys required 

 to unlock this geological secret. 



