116 



Lieut. Nelson on the Geology of the Bermudas. 



the ends of the nearly straight and tubular roots, about one-fifth of an inch 

 in diameter^ which diverge into the ground as so many radii. Now in 

 the supposed organics, in the inside of the cup, although smooth, I never 

 could detect these ends of the radicles ; and there is too much irregularity to 

 allow me to join in the received opinion without hesitation ; though nothing 

 like any other description of palm relics has been yet discovered. 



Reefs. 



The notices relative to these structures, which I at first intended for this 

 paper, have so exceeded it in bulk, that they are reserved for a separate 

 essay. I merely remark that there are two distinct kinds ; those formed by 

 Serpula, and those by Zoophytes of all descriptions, which construct calca- 

 reous skeletons. 



Figs. 11, 12, and 13, exhibit such plans, sections, and views as will suffice 

 to illustrate their leading peculiarities, especially one that is common to both 

 varieties, that of forming a belt round any obstacle which offers a rallying 

 point; whether such centre be the head of a rock, or the base of a mountain. 



Fig. 1 1 . Plan of a Coral Reef forming around a sandbank. 



Fig. 12. Section of a small isolated Coral Reef. 



