238 UTILIZATION OF MINUTE LIFE. 



tops, in the snow and in the ice, and sometimes in 

 the air we breathe. 



Ehrenberg found a few species of Infusoria in 

 the subterranean water of mines; he met with 

 several in some silver mines in Russia, at the depth 

 of fifty-six fathoms below the surface ; but he never 

 detected them in atmospheric water, such as dew- 

 drops.* The same author discovered that the 

 yel]ow dry fog which has been observed from time 

 to time advancing from the Cape Yerd Islands 

 towards the east, covering parts of North Africa, 

 Italy, and Central Europe, is composed of hosts of 

 silicious animalcule, carried away by the trade - 

 winds. This peculiar meteor has been often attri- 

 buted to the tails of comets which have passed near 

 the earth's orbit. f Similar animalculae have been 

 found in fixed or floating icebergs at 12 lat. from 

 the North Pole, while numerous forms of the same 

 group are seen in hot mineral springs. 



The invention of the microscope by Hans Jan- 



* This observation, made many years ago, agrees admirably 

 with the results of numerous researches lately made by Pouchet 

 of Rouen, who discovered no infusoria in snow that had recently 

 fallen, nor in the atmosphere. It has been held that the air 

 abounds with eggs of infusoria and seeds of microscopic plants ; 

 hut Pouchet denies this, upon the strength of many experiments 

 made in various parts of Europe. 



t See Humboldt's "Views of Nature," tome ii. ; also Kaemtz's 

 " Meteorology," and my work on " Phosphorescence," pp. 55-57, 

 regarding the nature of dry fogs. 



