The Coral Sea, from the number of coral reefs and sunken islands, with which it abounds; it includes a region of many miles in extent, the whole of which is studded with numberless reefs, rocks, islands, and columns of coral, continually joining and advancing towards each other.  All navigators who have visited these seas, state that no charts or maps are of any service after a few years, owing to the number of fresh rocks and reefs which are continually rising to the surface.  The wonderful instinct of these animals leads them to continue working without ceasing, until their labors are finished, or their lives extinct.

     Reef, a chain or line of rocks lying near the surface of
     the water.

     Extinct, at an end, dead.

What are the names of the principal islands of Coral formation?

The New Hebrides, the Friendly Isles, the Navigator’s Isles, the Society Islands, the Marquesas, the Gambier group, and others.  These groups are separated from each other by channels or seas, wider than those which divide the individual islands which form the respective groups; but all these waters abound with shoals and minor islets, which point out the existence of a common base, and show that the work by which they will afterwards be united above the level of the sea is continually going forward.

     Shoals, shallows; places where the water is of little
     depth.

     Minor, less, smaller than others.

     Existence, being.

What is a singular characteristic of the Coral Islands?

On all of them a plentiful supply of sweet and fresh water may be obtained by digging three or four feet into the coral; and even within one yard of high-water mark such a supply is to be found.  They are mostly covered with a deep rich soil, and well wooded with trees and evergreens of different kinds.  These islands vary in extent, as well as in the degree of finish to which they have arrived; some of the largest being about 30 miles in diameter, and the smallest something less than a mile;—­all of various shapes, and all formed of living coral.

     Diameter, a straight line through the middle of a circle.

Is Coral put to any use by man?

White Coral, which is nowhere so abundant as about the shores of Ceylon, and others of the neighboring Indian coasts, is employed as lime by the inhabitants of that part of the world, for building houses, &c., by burning it after the manner of our lime.  This coral lies in vast banks, which are uncovered at low water.  Coral, particularly the beautiful red sort, is likewise made into various ornaments, as necklaces, &c.

Of what is our Lime composed?

Of a useful earth, which absorbs moisture and carbonic acid, and exists as limestone, or in marble and chalk, which, when burnt, become lime:  in its native state it is called carbonate of lime, and is burnt to disengage the carbonic acid; when made into a paste, with one part water and three parts lime,[13] and mixed with some other mineral or metallic substances, it forms plastic cements and mortars; and afterwards, imbibing carbonic acid from the atmosphere, it becomes again carbonate of lime, as hard as at first; and hence its use in building.