222 THE BERMUDA ISLANDS. 



narrow ditches, the walls of which on both the inner and outer 

 sides were very abrupt, rising at an inclination of about 80. 

 One of these ditches, reaching in its bottom to 1200 feet, has a 

 depth, measured by the height of the outer wall,- of upwards of 

 350 feet. 



The facts of this island, so far as they go, are distinctly in 

 favor of the subsidence theory, and they have been properly 

 estimated by Prof. Bonney (Nature, May 23, 1889). Mr. Guppy, 

 on the other hand (Nature, May 16, 1889), sees in Captain 

 Maclear's sections evidences favoring Murray's views! How 

 they favor these views is not stated, nor do I believe that it 

 would be easy to find an} confirmation in them of the theory 

 of organic upgrowth. Of course it can be assumed that out- 

 ward growth on an extended talus might (under special condi- 

 tions) produce such a steep slope, but this is far from proving 

 that the condition did in fact exist. Further, we should still 

 be compelled to prove that any such large talus can form (and 

 I believe Prof. Dana has well argued that it cannot readily 

 form), and that even if formed, there is that (vast) outward 

 growth upon it which has been assumed by Murray and 

 Guppy. As regards his own special views of the formation of 

 barrier-reefs, etc., Mr. Guppy finds full confirmation in the 

 "ditches" which were located on the slopes of Masamarhu, for 

 he thus expresses himself: " The ' ditches ' shown in these sec- 

 tions I look upon as indicating the formation of barrier-reefs 

 at considerable depths, and as giving remarkable support to 

 my views on the origin of these reefs" (Nature, May 16, 1889). 

 Mr. Guppy has, indeed, pointed out (in a very unsatisfactory 

 manner) that reef-building corals 'may thrive at depths of 50 

 or 60 fathoms (300-360 feet), and that barrier-reefs and atolls 

 may begin to build up frorn 'these depths (answering the diffi- 

 culty with regard to the deep lagoons and channels); but now 

 we are suddenly called upon to assume that they build up from 

 of a depth of 200 fathoms (1200 feet) ! Surely the most doubt- 

 ful cannot readily object to a theory which is so elastic as that 

 of coral upgrowth. 



