CORAL REEFS. APPENDIX. 213 



Between thriving at depths of 50-60 fathoms and the finding 

 of an obscure impression at 31 fathoms there is surely a vast 

 difference. But Mr. Guppy himself informs us (" Coral Sound- 

 ings in the Solomon Islands," Ann. Mag. Nat. Hist., June, 1884), 

 that in Selwyn Bay, on the west side of Ugi Island, the depth 

 at which coral thrives is between 20 and 25 fathoms (p. 461) ; 

 in Port Mary, Santa Anna, the limit is placed at 20-30 fathoms, 

 although the deepest recognizable impression (of an Astraan) 

 was obtained from only 17 fathoms (p. 461) ; off Onua the 

 "lower limit at which coral thrives" is about 20 fathoms (p. 

 463) ; while off the northwest coast of Balftlai Island, Bougain- 

 ville Straits, "a depth of 15 fathoms apparently represented 

 the lowest limit of the zone of-corals " (p. 463). 



Mr. Guppy's own observations are, therefore, practically 

 confirmatory of the observations of nearly all other investiga- 

 tors who had preceded him. In fact, if we except the impres- 

 sion obtained at 31 fathoms, they are seemingly absolutely 

 confirmatory ; moreover, the impression may have been that 

 of a dead coral. 



Dana well remarks (" Corals and Coral Islands," 1872, p. 

 118) that "soundings with reference to this subject are liable 

 to be incorrectly reported by persons who have not particularly 

 studied living zoophytes. It is of the utmost importance, in 

 order that an observation supposed to prove the occurrence of 

 living coral should be of any value, that fragments should be 

 brought up for examination, in order that it may be unequiv- 

 ocally determined whether the corals are living or not. Dead 

 corals may make impressions on a lead as perfectly as living 

 ones." 



It is on this slender basis, if it is a basis at all, that Mr. 

 Guppy constructs his theory for the formation of barrier-reefs 

 (which inclose deep channels) and his explanation of the deep 

 lagoons of atolls. Prof. Bonney has, it appears to me, well an- 

 swered that "till Mr. Guppy can produce cases of growing reefs 

 at depths well exceeding 25 fathoms, isolated instances of the 

 occurrence, at such depths, of living corals which are among 



