12 INTRODUCTION. 



different minds, and there are several cases in which diffe- 

 rent views are held with regard to a certain area having 

 been above or below water during a certain period. In 

 such cases I have carefully examined the different views 

 which have been taken by those who have written on the 

 subject, before selecting that which appeared to be the 

 most probable interpretation of the facts. 



