124 
THEORY OF THE FORMATION 
Ch. V. 
vast number of islands, all of which are low. In the 
western part of the Caroline Archipelago, there is a 
space of 480 miles in length, and about 100 in breadth, 
thinly interspersed with low islands. Lastly, in the 
Indian Ocean, the archipelago of the Maldivas is 470 
miles in length, and 60 in breadth ; that of the Lac- 
cadives is 150 by 100 miles : as there is a low island 
between these two groups, they may be considered as 
one group of a thousand miles in length. To this 
may be added the Chagos group of low islands, 
situated 280 miles distant, in a line prolonged from 
the southern extremity of the Maldivas. This group, 
including the submerged banks, is 170 miles in length 
and 80 in breadth. So striking is the uniformity in 
direction of these three archipelagoes, all the islands 
of which are low, that Captain Moresby, in one of his 
papers, speaks of them as parts of one great chain 
nearly 1,500 miles long. I am, then, fully justified 
in repeating that immense spaces, both in the 
Pacific and Indian Oceans, are interspersed with 
islands, of which none rise above the height to which 
the waves and winds in an open sea can heap up 
matter. 
On what foundations, then, have these reefs and 
islets of coral been constructed ? A foundation must 
originally have been present beneath each atoll, at 
that limited depth which is indispensable for the 
first growth of the reef-building polypifers. A con- 
jecture will perhaps be hazarded, that the requisite 
bases may have been afforded by the accumulation of 
