278 DISTRIBUTION OF CORAL-REEFS, 



through the occasional accidents of their existence, 

 to their death and final obliteration. 



In my volume on " Coral Formations" I have 

 published a map, in which I have coloured all the 

 atolls dark-blue, the barrier-reels pale-blue, and 

 the fringing-reefs red. These latter reefs have 

 been formed whilst the land has been stationary, 

 or, as appears from the frequeiit presence of up 

 raised organic remains, whilst it has been slowly 

 rising : atolls and barrier-reefs, on the other hand, 

 have grown up during the directly opposite move- 

 ment of subsidence, which movement must have 

 been very gradual, and in the case of atolls so vast 

 in amount as to have buried every mountain-sum- 

 mit over wide ocean-spaces. Now in this map 

 we see that the reefs tinted pale and dark blue, 

 which have been produced by the same order of 

 movement, as a general rule, manifestly stand near 

 each other. Again, we see that the areas with the 

 two blue tints are of wide extent, and that they lie 

 separate from extensive lines of coast coloured red, 

 both of which circumstances might naturally have 

 been inferred, on the theory of the nature of the 

 reefs having been govei'ned by the nature of the 

 earth's movement. It deserves notice, that in more 

 than one instance Avhere single red and blue circles 

 approach near each other, I can show that there 

 have been oscillations of level ; for, in such cases, 

 the red or fringed circles consist of atolls, original- 

 ly, by our theory, fonned during subsidence, but 

 subsequently upheaved ; and, on the other hand, 

 some of the pale-blue or encircled islands are com- 

 posed of coral-rock, which must have been uplifted 

 to its present height before that subsidence took 

 place, during which the existing barrier-reefs grew 

 upwards. 



