206 DIATOMACEJE. PART n. 



fossil deposits in various parts of the globe, containing 

 species which have long ceased to exist, and others that 

 are identical with those still alive even in their most 

 minute and delicate engravings. The polishing slate of 

 Bilin in Bohemia, which occurs in beds 14 feet thick, and 

 the Tripoli and Phonolite stones on the Rhine consist 

 entirely of the silicious coats of diatoms, while the city 

 of Richmond in Virginia stands upon a marine deposit 

 of the debris of diatoms 1 3 feet thick, and of unknown 

 extent. Near the Mediterranean, very extensive strata, 

 consisting almost entirely of marine Diatomacese, alter- 

 nate with calcareous strata chiefly formed of Forami- 

 nifera, the latter being a race of microscopic mollusca. 

 The fossil Dia/fcomaceae at Oran in Algeria are particu- 

 larly perfect and beautiful. In many of these deposits 

 existing species are found. 



The trade winds bring over large quantities of dust 

 mixed with diatoms, which sinks through the upper into 

 the lower current, blowing over America, and at last 

 falls in Europe. Professor Ehrenberg found that this 

 dust contained chiefly true American species, many of 

 which were identical with forms existing at the bottom 

 of the Antarctic Ocean, where an area of 4,800 square 

 miles was discovered by Sir James Ross skirting the 

 volcanic coast of Victoria Land, consisting of the re- 

 mains of these microscopic plants, which have deposited 

 their silicious valves at death for countless generations, 

 producing geological changes of enormous magnitude ; 

 while a still greater area of sea-bed in the North 

 Atlantic is the perpetual grave-yard of myriads of 

 microscopic mollusca. Thus the Supreme Being, whose 

 power is stupendously manifested in the motions of the 

 celestial bodies, creates generations of infinitesimal 

 creatures, adorns them with exquisite beauty, and makes 

 them His agents to form future continents. 



The Confervacese are a numerous tribe of pretty little 



