more we know of its structure and of the shapes? Extreme cases of any peculiar nature of its builder. But let the growth phenomenon are always those which most of corals in seas of a certain depth and attract attention, and sometimes they are temperature be assumed and passed over, the cases which most readily suggest as we do assume and pass over a thousand an explanation. Ring-shaped islands of other things with which we are familiar. such moderate dimensions that the whole The puzzle here is why it should grow in of them can be taken in by the eye, supply the form of a linear barrier along a coast, such cases. There are atoll islands where and yet not touching it, but at a distance ships can enter, through some break in the more or less great — sometimes very great ring, into the inner circle. They find them

-and always leaving between it and the selves in a perfect harbor, in a sheltered land an enclosed and protected space of lake which no wave can ever enter, yet deep water, which, once they have found an enough and wide enough to hold all the entrance through the reef, ships can navi- navies of the world. Round about on every gate for hundreds of miles. Why should side there are the dazzling beaches which this same curious phenomenon be re-are composed of coral sand, and crowning peated on a smaller scale throughout the these there is the peaceful cocoanut palm, thousands of islands and islets which dot and a lower jungle of dense tropical vegethe immense surfaces of the Pacific? Why tation. On landing and exploring the should these islands so often be the centre woods and shores nothing can be seen but of a double ring first a ring of calm and coral. The whole island is a ring of this as it were inland water, then a ring of purely marine product; with the exception coral reef fronting the outer sea, and of an occasional fragment of pumice-stone, lastly the ocean, depths out of which the which having been floated over the sea coral reef rises like a wall? Why should from some distant volcanic eruption, like this curious arrangement repeat itself in that of Krakatoa, here disintegrates and every variety of form over thousands of furnishes clay, the most essential-element miles until we come to that extreme case of a soil. But reason tells us that there when there is no island at all except the must be something else underground, howouter ring of the coral reef and an inner ever deeply buried. When the corals first pool or lake of shallower water which is began to grow, they must have found some thus secluded from the ocean, with noth- rock to build upon, and the shape of these ing to break its surface — shining with a walls must be the shape which was thus calm, splendid, and luminous green, set determined. One suggestion is obvious. off against the deep purple blues of the Elsewhere all over the globe there is only surrounding sea? For effects so uniform one physical cause which determines or so analogous, repeated and multiplied rocky matter into such ring-like forms as over an area so immense, there must be these, and which determines also an some physical cause as peculiar as its included space of depth more or less effects. Moreover, this cause must be profound. This physical cause is the one affecting not merely or only the pecul- eruptive action of volcanic force. When iarities of the animal which builds up the anchored in the central lagoon of a coral coral, but some cause affecting also the atoll, are we not simply anchored in the solid rocks and crust of the earth. The crater of an extinct volcano - its walls coral animals must build on some foun- represented by the corals which have dation. They must begin by attaching grown upon it, its crater represented by themselves to something solid. Every the harbor in which our ship is lying? coral ef, therefore, whatever be its form | The vegetation is not difficult to account - every line of barrier reef however long for. The coral grows until it reaches the - every ring however small or however surface. It is known to flourish best in wide, must indicate some corresponding foaming breakers. These, although conarrangement of subjacent rock. What fronted and in the main resisted by the cause can have arranged the rocky foun. wondrous tubes and cells, are able here dations of the coral in such curious and there in violent storms to break off


[ocr errors]

ient guano.

the weaker or overhanging portions of the of coral which build up reefs, so far from coral and dash them in fragments upon the wanting the shelter of a lagoon, are unable top of the reef. Often the waves are to live within it. They can only live and loaded with battering-rams in the shape thrive fronting the open ocean, and in the of immense quantities of drift timber. highly aerated foam of its resisted billows. These bring with them innumerable seeds Moreover, on this view, many species of and hard nuts able to retain their vitality distinct genera and families are supposed whilst traversing leagues of ocean. Such instinctively to combine for one end; and seeds again find lodgment among the of such a combination Darwin declares broken corals, and among the decaying "not a single instance can be found in the pumice. Under tropical heat and mois- whole of nature.” This is rather a sweepture, they soon spring to life. The ing assertion. In the sense in which moment a palm-tree rears its fronds, it is Darwin meant it, and in the case to which visited by birds - especially by fruit-eat. he applied it, the assertion is probably, if ing pigeons bringing with them other not certainly, true. The


of analyseeds, which are deposited with conven- sis, however, if employed upon it, would

These in turn take root and limit and curtail it much. We cannot live. Each new accession to the incipient indeed suppose that any of the lower ani. forest attracts more and more numerous mals, even those much higher than the winged messengers from interminable coral-builders, have any consciousness of archipelagoes until the result is attained the ends or purposes which they or their which so excites our admiration and our work subserve in the great plan of nature. wonder, in the atoll islands of the Pacific. But Darwin has himself shown us, in later All this is simple. But here as elsewhere years, how all their toil is co-operant to it is the first step that costs. Are all ends, and how not only different species atolls nothing more than the cup-like rings and families, but creatures belonging to of volcanic vents? And if they are, can different kingdoms, work together most a like explanation be given for the barrier directly, however unconsciously, to rereefs which lie off continental coasts, and sults on which their common life and where the crater-like lagoon of an atoll is propagation absolutely depend. In the represented only by a vast linear expanse case before us, however, this second obof included and protected sea ?

jection of Darwin is superfluous. The Here were problems eminently attrac- first was in itself conclusive. If the tive to such a mind as that of Darwin. reef-building corals cannot live in a laVast in the regions they affect, complicated goon, or in a protected sea, it is needless in the results which are presented, most to argue further against a theory which beautiful and most valuable to man in the credits them with working on a plan to products which are concerned, the facts insure not their own life and well-being, do nevertheless suggest some physical but their own destruction. cause which would be simple if only it But next, Darwin had to encounter the could be discovered. All his faculties theory that atoll islands were built upon were set to work. Analysis must begin extinct volcanoes, and represented nothevery work of reason. Its function is to ing but the walls and craters of these destroy — to pull to pieces. Darwin had well-known structures. This he encounto deal with some theories already formed. Stered not with a sweeping assertion, but With some of these he had no difficulty. with a sweeping survey of the vast Pacific. " The earlier voyagers fancied that the Had those who believed in this theory coral-building animals instinctively built ever considered how vast that island-bearup these great circles to afford themselves ing ocean was, and how enormous its protection in the inner parts.” To this supposed craters must have been ? It Darwin's answer was complete. So far was all very well to apply some known is this explanation from being true, that it cause to effects comparable in magnitude is founded on an assumption which is the to its effects elsewhere. The smaller reverse of the truth. These massive kinds , atolls might possibly represent volcanic craters. But what of the larger ? And commanded a wide space of sea, looked what of the grouping? Could any vol. down upon an atoll with its curious ring canic region of the terrestrial globe show of walled-in water, calm, green, and gleamsuch and so many craters as could corre- ing in the middle of the oceanic depths of spond at all to the coral islands ? One blue, Did it not look as if there had once group of them occupies an irregular square been an island in the middle? Did it not five hundred miles long by two hundred look as if the coral ring had been built and forty broad. Another group is eight up upon the rocky foundation of its former hundred and forty miles in one direction, shores? Did it not look as if, somehow, and four hundred and twenty miles in this island had been removed, and the another. Between these two groups there encircling reef had been left alone? Someare other smaller groups, making a linear how! This could not satisfy Darwin. space of more than four thousand miles of How could such an island be removed ? ocean in which not a single island rises Its once fringing and encircling reef would above the level of true atolls — that is to have protected it from the devouring sea. say, the level up to which the surf can Did it not look as if it had simply sunk? break and heap up the coral masses, and Subsidence ! Was not tliis the whole to which the winds can drift the result- secret? The idea took firm hold upon ing sands. Some atolls seem to have his mind. The more he thought of it, the been again partially submerged —“half. more closely it seemed to fit into all the drowned atolls as they were called by facts. The coral fringing reef of the Captain Moresby. One of these is of island would not subside along with its enormous size – ninety nautical miles supporting rocks, if that subsidence took along one axis, and seventy miles along place slowly, because the coral animals another. No such volcanic craters or would build their wall upwards as fast as mountains exist anywhere else in our their original foundation was sinking world. We should have to go to the air- downwards. And was there not a perfect less and waterless moon, with its vast series of islands in every stage of the vents and cinder-heaps, to meet with any suggested operation? There were islands thing to be compared either in size or in with coral reefs still attached to their distribution. And then, the linear barrier original foundations, islands with fringing reefs lying off continental coasts and the reefs adhering to them all round, and leave coasts of the great islands are essentially ing no lagoons. There were others where the same in character as the encircling the foundations had sunk a little, but not reefs round the smaller islands. They very much, leaving only shallow and narcannot possibly represent the walls of row spaces of lagoon water between the craters, nor can the long and broad shel. island and the barrier reef. Others there tered seas inside them represent by any were again where the same process had possibility the cup-like hoilows of volcanic gone further, and wide and deep lagoons vents.

had been established between the reef These theories being disposed of, the and the subsiding island. Then there was work of synthesis began in Darwin's mind. every variety and degree of the results He sorted and arranged all the facts, such which must follow from such a process, as he knew them to be in some cases, until we come to the last stage of all, such as he assumed them to be in other when the island had wholly sunk, and Above all

, like “stout Cortez and nothing remained but the surviving reef his men,” from their peak in Darien, "he a true atoll — with its simple ring of stared at the Pacific." The actual seeing coral and its central pool of protected of any great natural phenomenon is often water. Then further it could not but occur fruitful. It may not be true in a literal to Darwin that the objection which was sense that, as Wordsworth tells us, “Na- fatal to the volcano theory was no diffiture never did betray the heart that loved culty in the way of his new conception; her.” But it is true that sometimes she on the contrary, it was in strict accordance discloses her secrets to an earnest and with that conception. The vast linear inquiring gaze. Sometimes things actu- reefs lying off straight and continental ally are what they look to be. Outwardly coasts, which could not possibly represent they are what their image on the retina volcanoes, were completely explained by directly paints them; and in their history a vast area of subsiding lands. The reefs and causes they may be what that image were linear because the shores on which suggests not less directly to the intellect they had begun to grow had been linear and the imagination. So Darwin, one day, also. The immense areas of sheltered standing on a mountain from which he sea, from twenty to seventy miles in


breadth, which often lie between the bar- | even a few hundred miles in length, with their rier reefs and the existing shores, for ex. many summits rising within a few feet of a ample, of Australia and New Guinea, were given level, and not one pinnacle above it? explained by the comparatively shallow If then the foundations, whence the atollcontours of land which had gradually sub- building corals sprang, were not formed of sided and had left these great spaces be- sediment, and if they were not listed up to the tween the original fringing reef and the subsided into it; and this at once solves the

required level, they must of necessity have existing shores. The more Darwin pon- difficulty. For as mountain after mountain, dered, the more satisfied he became that and island after island, slowly sank beneath he had found the clue. The cardinal facts the water, fresh bases would be successively were carefully collated and compared. afforded for the growth of the corals. First there was the fact that the reef. So certain was Darwin of these conclu. building, corals could not live at any sions that he adds, in a most unwonted greater

depth than from twenty to thirty tone of confidence : fathoms. Secondly there was the fact that they cannot live in water charged other manner how it is possible that numerous

I venture to defy any one to explain in any with sediment, or in any water protected islands should be distributed throughout vast from the free currents, the free winds, areas — all the islands being low, all being and the dashing waves of the open and built of corals, absolutely requiring a foundauncontaminated sea -- that vast covering tion within a limited depth from the surface. * of water which in the southern hemi. sphere is world-wide and world-embracing; autumn of 1836, and Darwin landed in

The voyage of the Beagle ended in the Thirdly there was the fact that the coral reefs rise suddenly like a wall out of England on the 2nd of October. He prooceanic depths, soundings of a thousand coral islands of the Pacific, and in May,

ceeded to put into shape his views on the fathoms and more being constantly found close up to the barrier reefs. Fourthly lic in a paper read before the Geological

1837, they were communicated to the pubthere is the fact that on the inner șide, Society of London. His theory took the next the island or the continent which scientific world by storm. It was well they enclose or protect, the lagoon or the calculated so to do. There was an attracsheltered area is often very deep close to tive grandeur in the conception of some the reef, not indeed affording oceanic soundings, but nevertheless soundings of great continent sinking slowly, slowly,

into the vast bed of the southern ocean, twenty to thirty fathoms. All these facts having all its hills and pinnacles gradually are indisputably true. Taking them to covered by coral reefs as in succession gether, the conclusions or inferences to they sank down to the proper depth, until which they point may well seem inevita: at last only its pinnacles remained as the ble. Let us hear how Darwin himself basis of atolls, and these remained, like puts them in the short summary of his buoys upon a wreck, only to mark where theory which is given in the latest edition of his journal :

some mountain peak had been finally sub

merged. Besides the grandeur and simFrom the fact of the reef-building corals not plicity of this conception, it fitted well living at great depths, it is absolutely certain into the Lyellian doctrine of the “bit by that throughout these vast areas, wherever bit” operation of all geological causes there is now an atoll, a foundation must have a doctrine which had then already begun originally existed within a depth of from twenty to establish its later wide popularity. to thirty fathoms from the surface. It is im- Lyell had published the first edition of probable in the highest degree that broad, his famous “ Principles" in January, 1830 lofty, isolated, steep-sided banks of sediment,

that is to say, almost two years before arranged in groups and lines hundreds of the Beagle sailed. He had adopted the leagues in length, could have been deposited volcanic

theory of the origin of the coral in the central and profoundest parts of the Pacific and Indian Oceans, at an immense islands; and it'is remarkable that he had distance from any continent, and where the nevertheless suggested the idea, although water is perfectly limpid. It is equally im- in a wholly different connection, that the probable that the elevatory forces should have Pacific presented in all probability an uplifted throughout the above vast areas innu- area of subsidence. Darwin most probamerable great rocky banks within twenty to bly had this suggestion in his mind when thirty fathoms, or one hundred and twenty to he used it and adopted it for an argument one hundred and eighty feet, of the surface of which its author had never entertained. the sea, and not one single point above that level; for where on the whole face of the

* Journal,

P: 468, globe can we find a single chain of mountains, + Lyell's Principles, Ith edition, p. 595.

However this may be, it must have pre- | the obviously inclining balance has been pared the greatest living teacher of geol- looked at askance many times. But deogy to adopt the new explanation which spite all averted looks I apprehend that it turned his own hint to such wonderful has settled to its place forever, and Daraccount. And adopt it he did, accordingly. win's theory of the coral islands must be The theory of the young naturalist was relegated to the category of those many hailed with acclamation. It was a mag- hypotheses which have indeed helped nificent generalization. It was soon al science for a time by, promoting and promost universally accepted with admiration voking further investigation, but which in and delight. It passed into all popular themselves have now finally “kicked the treatises, and ever since for the space of beam.” nearly half a century it has maintained its But this great lesson will be poorly unquestioned place as one of the great learnt unless we read and study it in triumphs of reasoning and research. Al- detail. What was the flaw in Darwin's though its illustrious author has since reasoning, apparently so close and coeclipsed this earliest performance by the- gent? Was it in the facts, or was it in ories and generalizations still more attrac- the inferences ? His facts in the main tive and much further reaching, I have were right; only it has been found that heard eminent men declare that, if he had they fitted into another explanation better done nothing else, his solution of the great than into his. It was true that the corals problem of the coral islands of the Pacific could only grow in a shallow sea, not would have sufficed to place him on the deeper than from twenty to thirty fathoms. unsubmergeable peaks of science, crowned It was true that they needed some founwith an immortal name.

dation provided for them at the required And now comes the great lesson. After depth. It was true that this foundation an interval of more than five-and-thirty must be in the pure and open sea, with its years the voyage of the Beagle has been limpid water, its free currents, and its followed by the voyage of the Challenger, dashing waves. It was true that they could furnished with all the newest appliances not flourish or live in lagoons or in chan. of science, and manned by a scientific nels, however wide, if they were secluded staff more than competent to turn them and protected from oceanic waves. One to the best account. And what is one error, apparently a small one, crept into of the many results which have been Darwin's array of facts. The basis or added to our knowledge of nature — to foundation on which corals can grow, if it our estimate of the true character and his satisfied other conditions, need not be tory of the globe we live on? It is that solid rock. It might be deep-sea deposits Darwin's theory is a dream. It is not if these were raised or elevated near only unsound, but it is in many respects enough the surface. Darwin did not know directly the reverse of truth. With all his this, for it is one of his assumptions that conscientiousness, with all his caution, coral “cannot adhere to a loose bottom." * with all his powers of observation, Dar- The Challenger observations show that win in this matter fell into errors as pro- thousands of deep-sea corals and of other found as the abysses of the Pacific. All lime-secreting animals flourish on deepthe acclamations with which it was re- sea deposits at depths much greater than ceived were as the shouts of an ignorant those at which true reef-building species mob. It is well to know that the plebis- are found. The dead remains of these cites of science may be as dangerous and deeper-living animals, as well as the dead as hollow as those of politics. The over- shells of pelagic species that fall from the throw of Darwin's speculation is only surface waters, build up submarine elevabeginning to be known. It has been tions towards the sea-level. Again, the whispered for some time. The cherished reef-building coral will grow upon its own dogma has been dropping very slowly out débris — rising, as men, morally and spirof sight. Can it be possible that Darwin itually, are said by the poet to do, "on was wrong? Must we indeed give up all stepping-stones of their dead selves to that we have been accepting and teaching higher things.” This small error told for for more than a generation? Reluctantly, much ; for if coral could grow on deep-sea almost sulkily, and with a grudging silence deposits when lifted up, and if it could also as far as public discussion is concerned, grow seaward, when once established, the ugly possibility has been contemplated upon its own dead and sunken masses, then as too disagreeable to be much talked submarine elevations and not submarine about. The evidence, old and new, has been weighed and weighed again, and

• Journal, ed. 1853, p. 477.

« ElőzőTovább »