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HISTORICAL GEOLOGY 



Tertiary waters. "The microscopic plants which form siliceous 

 shells, called Diatoms, make extensive deposits in some places 

 (Fig. 190). One stratum near Richmond, Virginia, is 30 feet thick 

 and is man} r miles in extent; another, near Monterey, California, 

 is 50 feet thick, and the material is as w T hite and fine as chalk, 

 which it resembles in appearance; another, near Bilin in Bohemia, 



Fig. 191 

 A well-preserved fossil Palm, Thrimax eocenica, from the Eocene of Georgia. 

 (After Berry, U. S. Geological Survey, Prof. Paper 84.) 



is 14 feet thick. . . . Ehrenberg has calculated that a cubic inch 

 of the fine earthy rock contains about forty-one thousand millions 

 of organisms. Such accumulations of Diatoms are made both in 

 fresh waters and salt, and in those of the ocean at all depths." 1 

 During the earlier Tertiary, as we have learned, the climate of 

 Europe and the northern United States was warm temperate to 

 even subtropical and there flourished such trees as Palms (Fig. 

 1 J. D. Dana: Text-book of Geology, 5th ed., pp. 391-393. 



