should assume. In the Museum at Liverpool, among the specimens of coral, there is a branching piece of coral which is a calcareous crystal, formed in the evaporating house of the salt-works of the King of Prussia."

So, in regard to sea-shells, instead of saying that the animals secrete the calcareous coverings which they inhabit, he thinks that they emit or secrete a gluten, to which the calcareous particles adhere, and thus form the shell. Let there be a chemical precipitation of the minute calcareous particles floating in sea-water by any means, and there might be formed a reef; agreeably to the experiment, in which the passing of a stream of electric fluid through water having calcareous and silicious particles in solution, produces stones.

The lightning of tropical regions, and the electric fluid engendered by sub-marine and other volcanoes which abound in the South Seas, may thus produce an effect adequate to the formation of those wonderful and invaluable structures. This is a much more rational theory to account for the existence of the immense coral reefs and coral islands of the Pacific, than that alluded to above, which supposes them wholly the work of saxigenous polypes or lithophytes.

The so-called saxigenous, or rock-making polype, builds upon the reefs, and cements his singular treeimitating structures to them; but this agency, we cannot but think, is altogether inadequate to the formation of immense islands. The more solid and compact texture of the coral rock, often stratified, would also lead

PROCESS OF CONSTRUCTING A CORAL REEF. 181

one to ascribe to it a different origin from the corals, whose exact and beautiful cellular structure evinces an animal agency as plainly as the honeycomb of a beehive.

It is therefore quite unnecessary to suppose the calcareous coral rocks either secreted by insects, or the exuviæ of the insects, or the dead bodies of the insects themselves; but they are simply carbonate of lime precipitated from the sea-water which holds its particles in solution, mixed and cemented together with broken shells and pieces of corals. The coral, properly so called, (that which is to be seen in museums and cabinets,) is what is built upon this rock as a foundation, by the coral insect.

These observations made on corals as seen in the beds where they grow, at the Sandwich Islands, and recorded on the spot, have induced me to compare the results thus obtained with what has been written on this subject by certain late authors.

In a recent article from the North British Review, by Sir David Brewster, he says:—“Our readers, no doubt, are aware that the coral rocks which form islands and reefs hundreds of miles in extent, are built by small animals, called polypus, that secrete, from the lower portion of their body, a large quantity of carbonate of lime; which, when diffused around the body, and deposited between the folds of its abdominal coats, constitutes a cell, or polypidom, or polypary, into the hollow of which the animal can retire. The solid thus formed is called a coral, which represents exactly the animal itself.

"These stony cells are sometimes single and cupped; sometimes ramifying like a tree, and sometimes grouped like a cauliflower, or imitating the human brain. The calcareous cells which they build remain fixed to the rock in which they began their labors, after the animals themselves are dead. A new set of workmen take their places, and add another story to the rising edifice. The same process goes on from generation to generation, until the wall reaches the surface of the ocean, where it necessarily terminates.

"These industrious laborers act as scavengers of the lowest class; perpetually employed in cleansing the waters of the sea from impurities which escape even the smallest crustacea; in the same manner as the insect tribes, in their various stages, are destined to find their food by devouring impurities caused by dead animals and vegetable matter in the land.

"Were we to unite into one mass the immense coral reefs, three hundred miles long, and the numberless coral islands, some of which are forty and fifty miles in diameter; and if we add to this all the coralline limestone, and the other formations, whether calcareous or silicious, that are the works of insect labor, we should have an accumulation of solid matter which would compose a planet or a satellite-at least one of the smaller planets, between Mars and Jupiter. And if such a planet could be so constructed, may we not conceive that the solid materials of a whole system of worlds might have been formed by the tiny, but long-continued labors of beings that are invisible !"

VIEWS OF SIR DAVID BREWSTER.

183

Now here is a mixture of fancy and fact, which a single personal inspection of a coral reef by the learned theorizer would have very considerably modified. He would become satisfied, I think, that the great reef itself, as it appears at the Sandwich Islands, so far from being the work of insect labor alone, is the basis which Nature herself lays, in the way before referred to, by the precipitation of carbonate of lime, through electrical agency, from sea-water, for the coral insect to build upon, and garnish with his beautiful structures. This basis, it is true, is increased from time to time by the decay of the coral fabrics, but it is never reared by them alone from the depths of the sea.

Coral was generally deemed a vegetable substance until the year 1720, when M. de Peyronnel, of Marseilles, commenced and continued for thirty years a series of observations, by which he ascertained the coral to be the production of a living animal of the polypi tribe. The general name of zoophytes, or plant-animals, has since been applied to these marine insects, though sometimes called lithophytes, or stone-plants. They occur most frequently in the tropical seas, and decrease in number and variety as we approach the poles.

"The various species of these animals (says Dr. Milner, Gallery of Nature, p. 381) appear to be furnished with minute glands, secreting gluten, which, upon exudation, convert the carbonate of lime in the ocean, and other earthy matters, into a fixed and concrete substance, twisted and fashioned in every variety of shape.

The formation of coral is one of those chemical processes in the great laboratory of nature, which the skill of man has not enabled him either to imitate or to comprehend; but the fact is clear, that large masses of solid rock are formed by those diminutive living agents, sea-workers, toiling and spinning to the music of the waves, whose constructions are capable of resisting the tremendous power of ocean, when most agitated by winds and tempests, and ultimately become a secure habitation for man himself."

The coral substance appears to bear the same relation to the insect, as the shell of a snail or of an oyster does to either of those animals, without which they cannot long exist; and it is upon the death of the animalcules that their separate structures become firmly knit together by some mysterious cement, and serve as the basis for the erections of fresh races, which, as they die off, increase the growth of the firm and solid fabric.

"Millions of millions thus, from age to age,
With simplest skill, and toil unweariable,
No moment and no movement unimproved,
Line laid on line, on terrace terrace spread,

To swell the heightening, brightening, gradual mound,

By marvellous structure climbing towards the day.

Each wrought alone, yet all together wrought,

Unconscious, not unworthy instruments,.

By which a hand invisible was raising

A new creation in the secret deep.

Omnipotence wrought in them, with them, by them;
Hence, what Omnipotence alone could do,

Worms did."

Captain Flinders, while surveying the coasts of New