SLOPE OF THE SHORE. 247 



shod. The surface is, towever, traversed by numerous channels 

 running in all directions, without any arrangement, and fre- 

 quently ending in a deep hole. Nor are there here, as on the 

 western side, true passages ; for though the outer reef is cut 

 through in a few places, these channels nowhere lead to a, 

 navigable deep water canal. Hence the natives, when going 

 out to sea, never follow these rifts in the reef, but steer across 

 in a straight line for the outer edge of the reef, where they 

 seek a spot low enough to allow them at high tide to float 

 across the raised wall of the reef by skilfully availing them- 

 selves of the high surf dashing over it. 



The structure of the reef, as we see, is here essentially dis- 

 similar to what we ought to expect on the hypothesis of subsi- 

 dence. However, this deviation from the normal conditions 

 may be explained in the way actually attempted by Darwin — 

 by the assximption that on the more precipitous east coast the 

 reef necessarily comes nearer to the shore, and that consequently 

 so deep a channel would not be formed as has been the case on 

 the western side. A very successful passage across the eastern 

 reef out into the open sea, however, provides me with an argu- 

 ment against this hypothesis, of which I have already made 

 use in a former small communication on this subject, which has, 

 however, remained unnoticed by both Darwin and Dana. It was 

 on the occasion of my passage to Kriangle. After crossing the reef 

 early in the day, at about nine in the morning, I occupied 

 myself for several hours till the afternoon on the outer edge 

 of the eastern reef, being favoured by most beautiful weather. 

 My investigations yielded a result which at that time I thought 

 very unsatisfactory ; I saw plainly that the reef certainly does 

 not fall abruptly into the sea, as it ought according to theory, 

 but that its slope, on the contrary, is quite gradual. I could 

 push some thousand paces straight away fi'om the reef seawards 

 without losing sight of the bottom ; the separate blocks of coral 

 lying there were plainly distinguishable in their various forms. 

 The sea was almost still, but in a great ocean it is never free 

 from that slow swaying motion known as a 'swell.' This 

 exhibited perfectly the phenomena observable on all shelving 

 coasts ; i.e. the upward wave rises more and more strongly a.s 



