176 CORAL-REEFS. 



which we know to be a line of recent elevation. I 

 may add, that Elizabeth Island, in the southern part 

 of the Low Archipelago, which seems to have had the 

 same kind of origin as the Fais, lies near Pitcairn 

 Island, the only one in this part of the ocean which 

 is high, and at the same time not surrounded by an 

 encircling barrier-reef. 



On the absence of active volcanoes in the areas of subsidence, 

 and on their frequent presence in the areas of elevation, — 

 Before making some concluding remarks on the relations of 

 the spaces coloured blue and red, it will be convenient to 

 consider the position on our map of the volcanoes histori- 

 cally known to have been in action. It is impossible not 

 to be struck, first with the absence of volcanoes in the 

 great areas of subsidence tinted pale and dark blue, — 

 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 ; and, secondly, with the coincidence of 

 the principal volcanic chains with the parts coloured red, 

 which indicates the presence of fringing-reefs ; and, as we 

 have just seen, the presence in most cases of upraised 

 organic remains of a modern date. I may here remark that 

 the reefs were all coloured before the volcanoes were added 

 to the map, or indeed before I knew of the existence of 

 several of them. 



The volcano in Torres Strait, at the northern point of 

 Australia, is that which lies nearest to a large subsiding 

 area, although situated 125 miles within the outer margin of 

 the actual barrier-reef. The Great Comoro Island, which 

 probably contains a volcano, is only twenty miles distant 

 from the barrier-reef of Mohila; Ambil volcano, in the 

 Philippines, is distant only a little more than sixty miles 



