34 THE MICROSCOPE. 



foundations of the earth, and in laying the floors 

 of the ocean, and in building up the walls of the 

 everlasting hills ! And if the works of these 

 minute labourers are so much more extensive, 

 so, as Professor Owen remarks, " they will be 

 infinitely more durable than the proudest mau- 

 solea by which Egyptian kings endeavoured to 

 perpetuate the memory of their existence." l 



As the earth receives much of its bulk from 

 this source, so hence also it derives much of its 

 fertility at the present hour. Vast masses of the 

 richest mud that lines the banks of our rivers, 

 and forms the beds of our seas, consist of infu- 

 soria, partly living, partly dead. The waters of 

 the Nile, e.g., are proverbially the wealth of 

 Egypt. It was generally supposed that the de- 

 gradation of rocks, and the decay of vegetable 

 remains, rendered the waters of the Nile thus 

 enriching. But the Microscope, in the hands of 

 Ehrenberg, has brought to light the strange fact 

 that this river owes its most fertilizing proper- 

 ties to the minute infusorial earths contained in 

 its water. For it is found that when the flood 

 of the Nile subsides, it leaves behind accumu- 



1 Owen's Compar. Anat. vol. i. pp. 40, 41. 



