Sect. II. 
HATE OF GKOWTH. 
97 
creased in dimensions during the last half century, and 
from the comparison of old charts with recent surveys, 
probably not during the last two hundred years. 
These, and other similar facts, have so strongly im- 
pressed many with the belief of the extreme slowness 
of the growth of corals, that they have even doubted 
the possibility of islands in the great oceans having 
been formed by their agency. Others again, who have 
not been overwhelmed by this difficulty, have ad- 
mitted that it would require thousands, and tens of 
thousands of years, to form a mass even of incon- 
siderable thickness : but the subject has not, I believe, 
been viewed in the proper light. 
That masses of considerable thickness have been 
formed by the growth of coral, may be inferred with 
certainty from the following facts. In the deep 
lagoons of Peros Banhos and of the Great Chagos 
bank, there are, as already described, small steep- 
sided knolls covered with living coral. There are 
similar knolls in the southern Maldiva atolls, some of 
which, as Captain Moresby assures me, are less than 
a hundred yards in diameter, and rise to the surface 
from a depth of between 250 and 300 feet. Con- 
sidering their number, form, and position, it would be 
preposterous to suppose that they are based on pin- 
nacles of rock, or on isolated cones of sediment. As 
no kind of living coral grows above the height of a 
few feet, we are compelled to suppose that these knolls 
have been formed by the successive growth and death 
