CORAL. By this designation we gene rally understand that substance of which a variety of ornaments are made, consi dering it as a concrete substance, and sup posing it to be a marine plant. This a as the opinion entertained for centuries, from the time even of Pliny to the beginning of the seventeenth century, when various circumstances gave rise to doubts as to the formation of coral. Monsieur de Peyssottnel of Marseilles observed, that the ramifications were inhabited by a nu merous tribe of insects ; and that what ap peared to be the flowers of the coral, and which receded into small apertures on its being withdrawn from the salt water, were those insects, which, on re-immer sion, again protruded themselves. Added to this, the softness of the terminations of all the points, and their being filled with a milky fluid, gives just reason to con clude, that nature has not been deficient in providing these insects with both the means of forming their abodes, and with the means of subsistence. What that sub sistence may be, or to what purpose, or how the milky fluid is formed, naturalists have not yet discovered. It should seemthat the main channels in the principal branches are gradually formed, and that the lateral ramifications are produced by the expul sion of supernumeraries in the family, which attach themselves to the exterior, and form new galleries. This is the more probable, because pieces of coral, broken off from the main branches, in a fewdays are found to be again cemented to such parts as they may happen to light upon. By this we may also infer, that a state of rest is necessary to the existence of the coral insect, and that it has very powerful means of attaching itself to rocks, &c. Coral is generally found covered with a rugged incrustation, and on being left to dry in the sun, soon appears discoloured, and emits a very foetid smell, arising from the corruption of the polypi, or insects, that have died for want of their natural element, and of food. The incrustation being decoriated, the coral presents it self; mostly of a beautiful blood red co lour; some are white, and a few pieces are black. The latter is much valued, but the red only is used in medicine as an astrin gent. Vegetable distilled oils dissolve co
ral; the red kind yields, by distillation in a retort, a volatile vitreous spirit, that ef fervesces with acids, turns syrup of violets green, and causes the solution of corro sive sublimate to assume a milky appear ance. Calcined in a gentle heat it be comes white, and it imparts to all the menstrtta a red colour, which itself gra dually loses. The white coral is little va lued, and is generally made into lime of the finest quality, where it grows in abun dance between high and low water mark. Fisheries for red and black coral are esta blished in many parts of the world, prin cipally in the Levant, in the Red Sea, Peruvian Gulf; Chinese Seas, and among many of the numerous clusters of islands in the Eastern and Pacific Oceans. The largest, brightest, and heaviest, is account ed the best. The women of Asia wear necklaces and bracelets made of one or more rows of red coral ; there called moongalt. Although obtained in their own quarter of the world, the heads are very dear ; those of about the size of a large marrow-fat pea being usually sold for four or five rupees per tolah of half an ounce ; which is equal to sixteen or twenty pounds sterling for a pound avoirdupois. The na tives of Hindostan have a mode o_f imitat ing coral by means of the butts of large conch-shells, which they colour very art fully. Coral is sometimes found in a fos sil state, but invariably of a white or yel lowish colour ; these, from some remain ing red spots in their interior, appear to have been formerly entirely of that co lour, but to have lost it by absorption, or by the action of acids : and the colour of coral is by no means fixed : if u pound of red coral (the Isis nobilis of Linnaeus) be boiled in a strong syrup, in which a pound of wax is mixed, both being previously dissolved in spirits of wine, the whole co louring matter of the coral may be extract ed. Artificial coral is made of leviga ted cinnabar, or of minium ; but these are easily detected : they will not ef fervesce with acids, nor do they affind an alkaline' earth, as real coral invariably does.