of all the facts. But what of the lagoons and the immense areas of sea behind the fringing reefs? How could these be accounted for? It was these which first impressed Darwin with the idea of subsidence. They looked as if the land had sunk behind the reef, leaving a space into which the sea had entered, but in which no fresh reefs could grow. And here we learn the important lesson that an hypothesis may adequately account for actual facts, and yet nevertheless may not be true. A given agency may be competent to produce some given effect, and yet that effect may not be due to it, but to some other. Subsidence would or might account for the lagoons and for the protected seas, and yet it may not be subsidence which has actually produced them.

subsidences might be the true explanation | them with living organic matter capable of resisting the chemical affinities of the inorganic world. But when that energy became feeble, and when at last it ceased, the once powerful structure descended again to that lower level of the inorganic, and subject to all its laws. Then, what the ocean could not do by the violence of its waves, it was all potent to do by the corroding and dissolving power of its calmer lagoons. Ever eating, corroding, and dissolving the back waters of the orig inal fringing reef-the mere pools and channels left by the outrageous sea as it dashed upon the shore were ceaselessly at work, aided by the high temperature of exposure to blazing suns, and by the gases evolved from decaying organisms. Thus the enlarging area of these pools and channels spread out into wide lagoons, and Darwin's theory took into full account into still wider protected seas. They two of the great forces which prevail in needed no theory of subsidence to account nature, but it took no account of another, for their origin or for their growth. They which is comparatively inconspicuous in would present the same appearance in a its operations, and yet is not less powerful slowly rising, a stationary, or a slowly than the vital energies, and the mechanical sinking area. Their outside boundary energies, which move and build up mate- was ever marching further outward on rial. Darwin had thought much and submarine shoals and banks, and ever as deeply on both of these. He called on it advanced in that direction its rear ranks both to solve his problem. To the vital were melted and dissolved away. Their energy of the coral animals he rightly inner boundary- the shores of some ascribed the power of separating the lime island or of some continent might be from sea-water, and of laying it down steady and unmoved, or it might be even again in the marvellous structures of their rather rising instead of sinking. Still, calcareous homes. In an eloquent and unless this rising were such as to overtake powerful passage he describes the wonder- the advancing reef, the lagoon would grow, ful results which this energy achieves in and if the shores were steady, it would constructing breakwaters which repel and widen as fast as the face of the coral barresist the ocean along thousands of miles rier could advance. Perhaps, even if such of coast. On the subterranean forces a wonderful process had ever occurred which raise and depress the earth's crust to Darwin-even if he had grasped this he dwelt at least enough. But he did extraordinary example of the "give and not know, because the science of his day take" of nature of the balance of opposhad not then fully grasped, the great working forces and agencies which is of the performed by the mysterious power of very essence of its system, he would have chemical affinity, acting through the cog. been startled by the vast magnitude of nate conditions of aqueous solution. Just the operations which such an explanaas it did not occur to him that a coral reef tion demanded. In its incipient stages might advance steadily seaward by build- this process is not only easily conceiv ing ever fresh foundations on its own able, but it may be seen in a thousand fragments when broken and submerged, places and in a thousand stages of ador that the vigorous growth of the reefs to vancement. There are islands without windward was due to the more abundant number in which the fringing reef is still supply of food brought to the reef-building attached to the shore, but in which it is animals from that direction by oceanic being "pitted," holed, and worn into numcurrents, so did it never occur to him that berless pools on the inner surfaces, where it might melt away to the rear like salt or the coral is in large patches dead or dying, sugar, as the vital energy of the coral and where its less soluble ingredients are animals failed in the sheltered and com- being deposited in the form of coral sand. paratively stagnant water. It was that There are thousands of other cases where vital energy alone which not only built up the lagoon interval between the front of the living tubes and cells, but which filled the reef and the shores has been so far

*

Mr.

Murray's new explanation of the struc-
ture and origin of coral reefs and islands
was communicated to the Royal Society of
Edinburgh in 1880, and supported with
such a weight of facts and such a close
texture of reasoning that no serious reply
has ever been attempted. At the same
time the reluctance to admit such an error
in the great idol of the scientific world,
the necessity of suddenly disbelieving all
that had been believed and repeated in
every form, for upwards of forty years
of cancelling what had been taught to the
young of more than a whole generation
has led to a slow and sulky acquiescence,
rather than to that joy which every true
votary of science ought to feel in the dis-
covery of a new truth and not less-
the exposure of a long-accepted error.
Darwin himself had lived to hear of the
new solution, and with that splendid can-
dor which was eminent in him, his mind,
though now grown old in his own early
convictions, was at least ready to entertain
it, and to confess that serious doubts had
been awakened as to the truth of his fa
mous theory.

widened that it is taking the form of a the naturalists of the Challenger expedibarrier, as distinguished from a fringing tion, a man whose enthusiasm for science, reef, and where the lagoon can be navi- whose sagacity and candor of mind, are gated by small boats. But when we come not inferior to those of Darwin, and whose to the larger atolls, and the great seas literary ability is testified by the splenincluded between a barrier reef and its did volumes of reports now in course of related shores, the mind may well be stag-publication under his editorial care. gered by the enormous quantity of matter which it is suggested has been dissolved, removed, and washed away. The breadth of the sheltered seas between barrier reefs and the shore is measured in some cases not by yards or hundreds of yards, not by miles but by tens of miles, and this breadth is carried on in linear directions, not for hundreds of miles, but for thousands. And yet there is one familiar idea in geology which might have helped Darwin, as it is much needed to help us even now, to conceive it. It is the old doctrine of the science, long ago formulated by Hutton, that the work of erosion and of denudation must be equal to the work of deposition. Rocks have been formed out of the ruins of older rocks, and those older rocks must have been worn down and carried off to an equivalent amount. So it is here, with another kind of erosion and another kind of deposition. The coral-building animals can only get their materials from the sea, and the sea can only get its materials by dissolving it from calcareous rocks of some kind. The dead corals are among its greatest quarries. The inconceivable and immeasurable quantities which have been dissolved out of the lagoons and sheltered seas of the Pacific and of the Indian Ocean, are not greater than the immeasurable quantities which are again used up in the vast new reefs of growing coral, and in the calcareous covering of an inconceivable number of other marine animals.

Here then was a generalization as magnificent as that of Darwin's theory. It might not present a conception so imposing as that of a whole continent gradually subsiding, of its long coasts marked by barrier reefs, of its various hills and irreg. ularities of surface marked by islands of corresponding size, and finally of the atolls which are the buoys indicating where its highest peaks finally disappeared beneath the sea. But, on the other hand, the new explanation was more like the analogies of nature - more closely correlated with the wealth of her resources, with those curious reciprocities of service which all her agencies render to each other, and which indicate so strongly the ultimate unity of her designs. This grand explanation we owe to Mr. John Murray, one of

in

If, however, Mr. John Murray has not been cheered by the acclamations which greeted his illustrious predecessor, if the weight of a great accepted authority and of preconceived impressions has kept down the admiration which ought ever to reward the happy suggestions of laborious research, he has had at least the great satisfaction of observing the silence of any effective criticism. But more than this-he is now having the still greater satisfaction of receiving corroborative support from the observations of others. His own series of facts as ascertained during the voyage of the Challenger constituted an array of evidence tolerably conclusive. But since he read his paper in Edinburgh, an island has been discovered in the Solomon group by another naturalist, Dr. Guppy,t which lifts into the light and air a complete record of the series of operations beneath the waters of the Pacific to which Mr. Murray ascribes the origin of countless other islands, islets, and atolls. Here the barrier reef and the atoll have

Proc. Roy. Soc. Edin., vol. x., pp. 505-18. ↑ Surgeon of H.M.S. Lark. Trans. Roy. Soc. Edin., June, 1885.

been elevated from their bed, and all their | wall began to grow must have been prefoundations have been shown. Those viously elevated to the requisite level, foundations are not solid rock, but are just what Darwin assumed they could never be, deep-sea deposits. These had been originally, of course, laid down in more or less oceanic depths. But elevation, not depression, had begun the work. The deep deposit had ceased to be deep, because the crust of the earth, on which it lay, had been bulged upwards by subterranean force. The deep bottom had become a shoal, rising to the required distance from the surface level of the sea. The moment it reached the thirty or the twenty fathom depth, the reef-building corals seized upon it as their restingplace, and began to grow. Possibly some process of induration may have affected the deposit before it reached this point. Probably it was consolidated or indurated by the luxuriant growth of myriads of deep-sea creatures at depths greater than thirty fathoms.

It has recently been discovered by another naturalist of the Challenger school that there may be a special explanation of this part of the operation. It is found that shoals have the immediate effect of converting the tidal wave of deeper water into a current. This current sweeps off the looser deposits covering the shoal. Deep-sea corals then settle upon it. These may, and often do, build up their walls to a great height, and if this height reaches the zone of the true reef-building species, a firm basis is at once provided for their operations. Shoals have lately been discovered off the African coasts of the Atlantic, which in tropical seas would probably have become coral islands. This may or may not have been often the case in the Pacific. But it does not affect the question, except in so far as it may justify Darwin's conception that reef corals cannot grow on "loose deposits." They may have ceased to be so soft and loose as they are when resting in the quiet depths of the thousand-fathoms sea. This induration may be part or an accompaniment of the process of elevation, but whether it be so or not the process is equally one of elevation and not of subsidence. In the island described by Dr. Guppy the foundations of the reef-building corals are seen resting directly on the remains of the pelagic fauna, and both theories equally assume and assert the uncontested fact that these foundations when the coral

On Oceanic Shoals discovered by the S.S. Dacia, by J. Y Buchanan, F.R.S. E. Proc. Roy. Soc. Edin., Oct., 1883.

that, namely, of from one hundred and eighty to one hundred and twenty feet below the surface of the ocean. Mr. John Murray's explanation is fully confirmed that the coral reefs often begin on shoals ; that these shoals are due to elevations of the sea bottom; that the reef when once established can and does grow seaward upon its own fragments broken and submerged; that these form a " talus "capable of indefinite advance until the furthest limit of the shoal is reached; that the rearward ranks of the coral animals die as they are left behind in the hot and shallow waters of the lagoon; that their calcareous skeletons are then attacked by the solvent action of the water, are eaten away and carried off to form the materials of new reefs and the shells of countless other creatures. These have likewise been confirmed by the investigations of Mr. Alexander Agassiz in the West Indies. Often in the Pacific, as in all other regions of the earth, the elevating forces rest for ages, having done all the work which on some particular area they have got to do. The shoals remain shoals only covered with the walls and battlements of coral. This is the case which accounts for countless islands never exceeding a certain height. On the other hand, and otherwhere, the elevating forces, after a rest, resume their operation, lift up these coral walls and battlements wholly out of the sea, and make other islands by the thousand which become the delight of man; whilst in yet another class of cases the elevations open out into volcanoes, and constitute great areas of land which are among the most fertile regions of the habitable globe. But everywhere and always the ubiquitous coral animals fix on every shoal and on every shore, whether old or new, and resume the wonderful cycle of operations in whch they are a subordinate but a powerful agent.

In a recent article in this review I had occasion to refer to the curious power which is sometimes exercised on behalf of certain accepted opinions, or of some reputed prophet, in establishing a sort of reign of terror in their own behalf, sometimes in philosophy, sometimes in politics, sometimes in science. This observation was received as I expected it to be - by those who being themselves subject to this kind of terror are wholly unconble illustration of this phenomenon that scious of the subjection. It is a remarkaMr. John Murray was strongly advised

against the publication of his views in gradually "altering its form," so that derogation of Darwin's long-accepted the-entangled granules gradually changed ory of the coral islands, and was actually their relative positions.' The naturalinduced to delay it for two years. Yet the late Sir Wyville Thomson, who was at the head of the naturalists of the Challenger expedition, was himself convinced by Mr. Murray's reasoning, and the short but clear abstract of it in the second volume of the "Narrative of the Voyage" has since had the assent of all his colleagues.*

ists of the Challenger began their voyage in the full bathybian faith. But the sturdy mind of Mr. John Murray kept its balance all the more easily since he never could himself find or see any trace of this pelagic protoplasm when the dredges of the Challenger came fresh from bathysmal bottoms. Again and again he looked for it, but never could he discover it. It always hailed from home. The bottles sent there were reported to yield it in abundance, but somehow it seemed to be hatched in them. The laboratory in Jermyn Street was its unfailing source, and the great observer there was its only sponsor. The ocean never yielded it until it had been bottled. At last, one day on board the Challenger an accident revealed the mystery. One of Mr. Murray's assistants poured a large quantity of spirits of wine into a bottle containing some pure sea-water, when lo! the wonderful protoplasm bathybius appeared. It was the chemical precipitate of sulphate of lime produced by the mixture of alcohol and sea-water. This was bathos indeed. On this announcement bathybius disappeared from science, reading us, in more senses than one, a great lesson on "precipitation." †

Nor is this the only case, though it is the most important, in which Mr. Murray has had strength to be a great iconoclast. Along with the earlier specimens of deepsea deposits sent home by naturalists during the first soundings in connection with the Atlantic telegraph cable, there was very often a sort of enveloping slimy mucus in the containing bottles which arrested the attention and excited the curiosity of the specialists to whom they were consigned. It was structureless to all microscopic examination. But so is all the protoplasmic matter of which the lowest animals are formed. Could it be a widely diffused medium of this protoplasmic material, not yet specialized or individualized into organic forms, nor itself yet in a condition to build up inorganic skeletons for a habitation? Here was a grand idea. It would be well to find missing links; but it would be better to find the This is a case in which a ridiculous primordial pabulum out of which all living error and a ridiculous credulity were the things had come. The ultra-Darwinian direct results of theoretical preconcepenthusiasts were enchanted. Haeckel tions. Bathybius was accepted because clapped his hands and shouted out Eureka of its supposed harmony with Darwin's loudly. Even the cautious and discriminating mind of Professor Huxley was caught by this new and grand generalization of the "physical basis of life." It was announced by him to the British Association in 1868. Dr. Will. Carpenter took up the chorus. He spoke of "a living expanse of protoplasmic substance," penetrating with its living substance the "whole mass of the oceanic mud.f A fine new Greek name was devised for this mother slime, and it was christened bathybius," from the consecrated deeps in which it lay. The conception ran like wildfire through the popular literature of science, and here again there was something like a coming plebiscite in its favor. Expectant imagination soon played its part. Wonderful movements were seen in this mysterious slime. It became an "irregular network," and it could be seen

speculations. It is needless to say that Darwin's own theory of the coral islands has no special connection with his later hypotheses of evolution. Both his theory and the theory of Mr. Murray equally involve the development of changes through the action and interaction of the old agencies of vital, chemical, and mechanical change. Nevertheless the disproof of a theory which was so imposing, and had been so long accepted, does read to us the most important lessons. It teaches us that neither the beauty, nor the imposing character, nor the apparent suffi ciency of an explanation may be any proof whatever of its truth. And if this be taught us even of explanations which concern results purely physical, comparatively simple, and comparatively definite, how much more is this lesson impressed upon us when, concerning far deeper and

* The Depths of the Sea, 2nd ed. London, 1874, pp.