CHAPTER IL. 
ON CORAL FORMATIONS. 
Corat reefs and islands partake sufficiently of the mysterious, both 
from their magnitude, position, and fancied origin, to have excited 
much curious inquiry. The question is often heard, How have these 
island structures been raised from the ocean’s depths; through what 
means have the reefs, like bulwarks of rock, risen to the surface, to 
serve as a barrier to the shores of the basaltic islands, and a break- 
water for their harbours? Moreover, with greater earnestness, the 
navigator asks whether new reefs are not yearly adding to the intri- 
cacies of tropical seas, obstructing old channels, and rendering useless 
former charts. Curiosity as well as interest thus prompts to a thorough 
study of this subject, in order that we may trace out the modes of 
growth and accumulation from the first development of the zoophyte, 
and discover those laws which preside over the forms and distribution 
of coral formations. 
Coral islands also merit special attention, on account of their pro- 
ductions, their extent and number, the various forms and beauty of 
the coral zoophytes, and the singular features of the emerging land. 
The submarine garden grows slowly towards the surface, and as it 
increases, the waves contribute towards forming and consolidating the 
structure, and finally aid in covering the new islet with soil, and sup- 
plying it with vegetation. Such is the brief history. In this way, as 
we shall more particularly explain, vast seas have been studded with 
islands; two hundred may now be counted over an area of ten millions 
of square miles in the Pacific, where otherwise there would have been 
less than twenty. 
Reef formations are exciting much attention for the part they have 
taken in forming many of the rock strata of our globe. They have 
not always been confined as now to the equatorial regions; but early 
in the earth’s history, extended far towards either pole. Reef-rocks 
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