Physical Characteristics and Commerce of Coral

Coral is a submarine production secreted by animals forming one little tribe in the grand class of polypi.

The colour of coral follows numberless gradations, from an intense red to a complete white. Its commercial value varies enormously according to its colour, the rose tints being the most esteemed. Different varieties are named according to the precise shade of colour, as "ecume de sang," "rose," "fleur de sang," &c. One hundred shades of red coral are distinguished at Marseilles.

Until the eighteenth century it was believed that coral was a small tree living and developing itself under the sea. It was only in 1727 that a Frenchman, Peyssonnel, established its real nature, showing that the flowers of this tree were radiated animals, and that the coral was gradually formed by them.

Coral is fixed to the solid body which it rests upon by a kind of conical outspread foot. The nature of the support would seem to be a matter of indifference, so long as it is solid. The stems of coral are directed often in an opposite direction to those of plants, inasmuch as, being attached to the under side of rocks, they grow downwards.

The coral that is known in commerce presents itself in the form of little trees more or less branched; but in the living coral all the branches are covered with a sort of pale-coloured fleshy rind, glossy and polished, showing at its surface a great number of cells, each one of which incloses a polype. These very elegant little animals are what were taken for the flowers of coral.

Fig. 86 shows the polypi of the coral in different degrees of expansion.

It will be seen that their eight extended tentacules, pointed and incised along their edges, joined to the completely white colour of the animals themselves, present an ensemble which a century or two ago might well be taken for a flower.

Stripped of its coating, the coral shows a great number of parallel, longitudinal, and very often sinuous striae, stretching from one end to the other of the axis. Its texture is extremely compact, this being precisely that which permits it to take a perfect polish, and gives it a great part of its value. But this texture is not homogeneous; on the contrary, it is perfectly organized. To be convinced of this we have but to break or cut a branch of coral perpendicularly to the axis, and to submit the part left bare to the action of an acid. The different parts will be unequally attacked, and a radiated texture becomes at once apparent.

Coral exists probably in all the seas of warm and temperate regions, but the Mediterranean furnishes to commerce the greater part of this product.

To gather it there has been for a long time used a sort of dredge called salabre, formed of two pieces of wood or iron, disposed in the form of a St. Andrew's cross, upon the extremities of which nets are fastened to receive the coral detached by the reiterated blows of the instrument.

There are also, as in the search for pearls, divers who plunge to a considerable depth to gather this beautiful production. But already the modern appliances for exploring the sea-depths have been employed with complete success to the gathering of coral.

There enters into the composition of coral 88 to 100 parts carbonate of lime, a little magnesia, some traces of organic matter, and about 1 part to the 100 of oxide of iron.

Coral possesses a very interesting property, which, beyond doubt, contributed to elevate it to the exceptional rank that it has occupied in medicine, even to the nineteenth century. Certain persons cannot wear against their skin any objects of coral without discolouring them, and this phenomenon is general among all invalids. The ancients asserted that if a person wearing a necklace of coral was on the verge of an illness, the coral showed discoloration before the least consciousness was felt of the approaching malady.