Xll 



INTRODUCTION. 



of this East Yorkshire formation with Wealden rocks of North- 

 West Germany, England, and North France is expressed in 

 tabular form as follows * : 



FOUR ZONES OF SPEETON CLAY. 



In another recent work, "Text Book of Comparative Geology," 

 by Kayser (translated and edited by Lake), we find this extremely 



WEALDEN. 



simple table in which the term Wealden is used in the wider sense. 2 



Having thus defined the term Wealden as employed by some of 



the most recent writers, and stated the sense in which it is used 



1 Arg. Speeton, pp. 200-201. 



2 p. 288. 



