184 DISTRIBUTION OF CORAL-REEFS. Ch. VI. 



On the absence of active Volcanos in the areas of 

 subsidence, and on their frequent presence in the areas 

 of elevation.* — The absence of active volcanos through- 

 out the great areas of subsidence on our map, as 

 shown by the pale and dark blue tints, — namely, in 

 the central parts of the Indian Ocean, in the China 

 Sea, in the sea between the barriers of Australia and 

 New Caledonia, in the Caroline, Marshall, Gilbert, and 

 Low Archipelagoes, — is a very striking fact. So is the 

 presence of active volcanic vents and chains on or near 

 many of the shores coloured red on our map, and which 

 are fringed with reefs ; for, as we have just seen, these 

 fringed coasts have been recently upheaved in a large 

 number of cases. Active volcanos likewise coincide with 

 proofs of recent elevation on or near several other 

 long lines of coast within the limits of our map, 

 where there are no reefs of living corals, and which 

 consequently are not coloured red. It must be here 

 remarked with regard to the proofs of both subsidence 

 and elevation, that I do not judge by the absence or 

 presence or nature of the coral-reefs round the volcanos 

 themselves ; for, as Dana repeatedly insists, the corals 

 may have been there destroyed or injured by the heat 

 or exhalations. Nor have I taken into account the 

 presence of upraised organic remains on the flanks of 

 the volcanos themselves. I judge from the position of 



1 It may be well here to state that all the reefs on the map were 

 coloured either red or blue before the vermilion spots and streaks, 

 showing the position of the active volcanos and volcanic chains, were 

 added ; and indeed before I knew of the existence of several of them. 



