PHYSICAL HISTORY AND GEOLOGY. 47 



The question as to what form of coral structure the BernfMi- 

 das actually are — what constitutes their fundament, and how 

 they were built to their existing level — still remains un- 

 answered, and possibly we. may never be able to answer. But 

 I have thought it worth while to introduce a discussion of the 

 general coral question (the chapter following), as it has a bear- 

 ing on the topic at issue. 



