CORAL REEFS. APPENDIX. 215 



feet in diameter; whilst the largest masses that I found in the 

 wash of the breakers at the outer edge of the reef, which be- 

 longed to species of Coeloria and Micandrina, measured only 5 

 feet across" (p. 890). Surely, with such evidence before us it 

 cannot reasonably be supposed that there could be such an 

 extermination from the outer slope, if reef-building corals 

 really thrive at these depths, as Mr. Guppy would lead us to 

 suppose. 



With regard to the formation of the deep lagoons and chan- 

 nels and the actual thickness of the coral-made rock, Mr. 

 Guppy's own views seem to be in conflict. The author ap- 

 parently inclines to the views of Murray and his followers 

 that these deep bodies of water are after-formations, and that 

 they have been produced through steady removals of material. 

 As factors in this removal he cites the action of carbonated 

 waters ("solution theory") and the various forms of organic 

 degradation (pp. 893-97). 



But no instance is cited where any considerable depth of 

 water has been brought about in this way ; it is merely the as- 

 sumed hypothesis of possibility. On the other hand, we are 

 positively informed (pp. 878-79) that the lagoon of the Oima 

 atoll (which measures nearly two miles in its longest diameter), 

 with a depth of some 20 fathoms, is filling up through the ac- 

 cumulation of sand ! And this condition exists in an atoll 

 which has seemingly experienced no "upheaval since the 

 commencement of its growth." 



The same condition prevails in the case of the Keeling atoll, 

 where, as Mr. Guppy informs us, " the lagoon is rapidly filling 

 up with sand and coral " (Nature, Jan. 3, 1889). The facts are 

 thus clearly opposed to the theory that is assumed. 



One of the points that have been specially insisted upon by 

 the opponents of the subsidence theory as being destructive of 

 that theory is the supposed thinness of the coral-made rock, 

 and much stress has been laid upon the researches of Guppy in 

 the Solomon Islands. This subject has been considered in the 

 chapter dealing with the " Coral-Reef Problem," but a few adU 



