Chapter Fifteen.Coral Insects and Coral Islands—Polynesia—Operations of the Coral Insect—Growth of Coral Reefs.Many of the large and beautiful islands that stud the Pacific Ocean, like emeralds in a field of blue, areartificial; that is to say, they were made by artists—they were actuallybuiltbyartisans!These artisans are the coral insects; and as they not only affect the face of the sea by raising large islands above it, but also, in consequence of their labours, assist in causing the circulation of the ocean, we think they are justly entitled to very special attention.The great archipelago called Polynesia covers an area of the Pacific nearly 5000 miles in length, and not far short of 2000 in breadth. Some of the islands of this group are of volcanic origin, and some are crystal; but by far the greater number are of coral formation—the work of those curious little insects, which are so small that they inhabit a dwelling sometimes little larger than a pin-point.The manner in which these islands are made is, to some extent, a matter of uncertainty. The most generally received opinion is, that the insects fasten round the summit of a submarine mountain, and build upwards until they reach the surface of the sea, where they die, and their labours cease. As, however, the sea is sometimes unfathomable close to those islands, it has been supposed that the submarine islands on which the corallines began to build have gradually subsided, and that, as they did so, the insects always built a little more, so as to keep the top of their structures on a level with the sea. Above the sea they cannot build. To be washed by the waves is essential to their existence.We do not think this a very satisfactory theory, because it supposes a prolonged subsiding of these islands, and then an unaccountably sudden stoppage. For although the corallines might continue to build during the whole time of subsidence, it were utterly impossible that the coralisland, with its luxuriant herbage, could be formed until that subsidence should have ceased. The manner in which the islands are formed makes this obvious.When the coral reef, as it is called, reaches the surface, it advances no further. Soon the action of the waves breaks off the branches of the upper portions of coral, which are tossed upon the reef, and pulverised into fine sand. This goes on increasing until the island rises a little above the waves.When this happens, birds alight there; sea-drift is carried thither; seeds are blown to it by the wind; and gradually a few green blades arise. From this little beginning it is easy to conceive the process by which at last a flourishing island springs up. At the same time, it is not easy to see how such islands could ever be formed on the supposition that the submarine rocks on which they were founded were perpetually subsiding.But be that as it may, we have no difficulty in understanding the fact that the coral insect does build those islands. It possesses the power of secreting the lime held in solution by sea water, and depositing the same on the rocks below the waves. The coral rock is the edifice of the coralline. The insect itself is a soft and very minute worm, which, when washed by the waves, thrusts its head out of its tiny little door, and spreading abroad its numerous feelers, so that it resembles a beautiful little star, moves these about as if enjoying itself—though, doubtless, it is actually engaged in the process of manufacturing its little atom of coral rock.It is extremely interesting to think of the immense power ofunionthus exhibited. Singly, those little creatures could not produce a sufficient result to attract the attention of any creature save such as chanced to come in direct and close contact with its little cell. United, they have formed vast islands, which have become the abode of man, and which, in the aggregate, form no inconsiderable portion of the globe.The consideration of this leads us to perceive that God has ordained that units cannot, separately, accomplish much; and that united effort, in order to be successful, requires the harmonious action of units. “A house divided against itself cannot stand.†The innumerable and eminently beautiful isles of the Pacific had never stood where they now stand if the curious, and separately insignificant, little architects that reared them had not wrought unitedly upon a fixed and systematic plan—each insect working its utmost from the hour of its birth until that of its death.There are various kinds of coral insects, which form varied species of coral rock. Some kinds of coral assume the form of rounded masses; some are like a branching shrub; others are in layers, or thin plates; and some are shaped like the human brain, from which they derive their name—brainstones. These different kinds differ also in colour, and thus present a beautiful appearance when seen at the bottom of clear and shallow water.In regard to the rate at which the corallines build their cells there is some diversity of opinion—some asserting that the process is imperceptible, while others state as positively that it is rapid. There can be no doubt that some localities and positions are more favourable to the growth of coral than others. Dr Allan, while at Madagascar, made several experiments to test this. He selected several masses of coral, each weighing about ten pounds, and of different species. These he placed three feet below the surface of the sea, and staked them in to prevent removal. In a little more than six months they were found to have risen nearly to the surface, and to have attached themselves to the solid rock.There is also a case mentioned of a ship in the Persian Gulf which, in the course of twenty months, had her copper encased with living coral to the thickness of two feet.On the other hand, it is asserted, and we doubt not with equal truth, that many reefs do not seem to increase in size in the course of many years.When a coral reef has reached the surface, the formation of an island instantly begins; but it necessarily takes a long time ere this island becomes habitable by man. Among the first plants that raise their heads to the sea-breeze is the graceful cocoa-nut palm. This tree is exceedingly hardy, and is found growing on reefs which are so low that at a distance the trees seem to be standing on the surface of the water. Indeed many of them spring out of the pure white sand, and their roots are washed perpetually by the salt spray. Nevertheless, the fruit of such trees is sweet and good.Coral islands of the kind we have just described seldom rise more than a few feet above the level of the sea; but most of them are clothed with luxuriant vegetation.We might easily fill a volume on the subject of the ocean’s inhabitants, small and great; but we think the few to which we have made reference is sufficient for the purpose of showing that one set of creatures accounts for that strange luminosity of the ocean which is seen at times in all marine parts of the globe, while another set accounts not only for the sudden appearance of coral islands in the sea where no such islands existed in days of old, but also, partly, for that circulation of the waters of the ocean which is absolutely necessary to the wellbeing of all the creatures on this earth.There are other animals in the sea, besides medusae, which assist in giving luminosity to its waters; and there are other insects, besides corallines, which extract its lime, destroy its equilibrium, and assist in causing its perpetual motion; but the two species which we have described are the best types of the respective classes to which they belong.
Many of the large and beautiful islands that stud the Pacific Ocean, like emeralds in a field of blue, areartificial; that is to say, they were made by artists—they were actuallybuiltbyartisans!
These artisans are the coral insects; and as they not only affect the face of the sea by raising large islands above it, but also, in consequence of their labours, assist in causing the circulation of the ocean, we think they are justly entitled to very special attention.
The great archipelago called Polynesia covers an area of the Pacific nearly 5000 miles in length, and not far short of 2000 in breadth. Some of the islands of this group are of volcanic origin, and some are crystal; but by far the greater number are of coral formation—the work of those curious little insects, which are so small that they inhabit a dwelling sometimes little larger than a pin-point.
The manner in which these islands are made is, to some extent, a matter of uncertainty. The most generally received opinion is, that the insects fasten round the summit of a submarine mountain, and build upwards until they reach the surface of the sea, where they die, and their labours cease. As, however, the sea is sometimes unfathomable close to those islands, it has been supposed that the submarine islands on which the corallines began to build have gradually subsided, and that, as they did so, the insects always built a little more, so as to keep the top of their structures on a level with the sea. Above the sea they cannot build. To be washed by the waves is essential to their existence.
We do not think this a very satisfactory theory, because it supposes a prolonged subsiding of these islands, and then an unaccountably sudden stoppage. For although the corallines might continue to build during the whole time of subsidence, it were utterly impossible that the coralisland, with its luxuriant herbage, could be formed until that subsidence should have ceased. The manner in which the islands are formed makes this obvious.
When the coral reef, as it is called, reaches the surface, it advances no further. Soon the action of the waves breaks off the branches of the upper portions of coral, which are tossed upon the reef, and pulverised into fine sand. This goes on increasing until the island rises a little above the waves.
When this happens, birds alight there; sea-drift is carried thither; seeds are blown to it by the wind; and gradually a few green blades arise. From this little beginning it is easy to conceive the process by which at last a flourishing island springs up. At the same time, it is not easy to see how such islands could ever be formed on the supposition that the submarine rocks on which they were founded were perpetually subsiding.
But be that as it may, we have no difficulty in understanding the fact that the coral insect does build those islands. It possesses the power of secreting the lime held in solution by sea water, and depositing the same on the rocks below the waves. The coral rock is the edifice of the coralline. The insect itself is a soft and very minute worm, which, when washed by the waves, thrusts its head out of its tiny little door, and spreading abroad its numerous feelers, so that it resembles a beautiful little star, moves these about as if enjoying itself—though, doubtless, it is actually engaged in the process of manufacturing its little atom of coral rock.
It is extremely interesting to think of the immense power ofunionthus exhibited. Singly, those little creatures could not produce a sufficient result to attract the attention of any creature save such as chanced to come in direct and close contact with its little cell. United, they have formed vast islands, which have become the abode of man, and which, in the aggregate, form no inconsiderable portion of the globe.
The consideration of this leads us to perceive that God has ordained that units cannot, separately, accomplish much; and that united effort, in order to be successful, requires the harmonious action of units. “A house divided against itself cannot stand.†The innumerable and eminently beautiful isles of the Pacific had never stood where they now stand if the curious, and separately insignificant, little architects that reared them had not wrought unitedly upon a fixed and systematic plan—each insect working its utmost from the hour of its birth until that of its death.
There are various kinds of coral insects, which form varied species of coral rock. Some kinds of coral assume the form of rounded masses; some are like a branching shrub; others are in layers, or thin plates; and some are shaped like the human brain, from which they derive their name—brainstones. These different kinds differ also in colour, and thus present a beautiful appearance when seen at the bottom of clear and shallow water.
In regard to the rate at which the corallines build their cells there is some diversity of opinion—some asserting that the process is imperceptible, while others state as positively that it is rapid. There can be no doubt that some localities and positions are more favourable to the growth of coral than others. Dr Allan, while at Madagascar, made several experiments to test this. He selected several masses of coral, each weighing about ten pounds, and of different species. These he placed three feet below the surface of the sea, and staked them in to prevent removal. In a little more than six months they were found to have risen nearly to the surface, and to have attached themselves to the solid rock.
There is also a case mentioned of a ship in the Persian Gulf which, in the course of twenty months, had her copper encased with living coral to the thickness of two feet.
On the other hand, it is asserted, and we doubt not with equal truth, that many reefs do not seem to increase in size in the course of many years.
When a coral reef has reached the surface, the formation of an island instantly begins; but it necessarily takes a long time ere this island becomes habitable by man. Among the first plants that raise their heads to the sea-breeze is the graceful cocoa-nut palm. This tree is exceedingly hardy, and is found growing on reefs which are so low that at a distance the trees seem to be standing on the surface of the water. Indeed many of them spring out of the pure white sand, and their roots are washed perpetually by the salt spray. Nevertheless, the fruit of such trees is sweet and good.
Coral islands of the kind we have just described seldom rise more than a few feet above the level of the sea; but most of them are clothed with luxuriant vegetation.
We might easily fill a volume on the subject of the ocean’s inhabitants, small and great; but we think the few to which we have made reference is sufficient for the purpose of showing that one set of creatures accounts for that strange luminosity of the ocean which is seen at times in all marine parts of the globe, while another set accounts not only for the sudden appearance of coral islands in the sea where no such islands existed in days of old, but also, partly, for that circulation of the waters of the ocean which is absolutely necessary to the wellbeing of all the creatures on this earth.
There are other animals in the sea, besides medusae, which assist in giving luminosity to its waters; and there are other insects, besides corallines, which extract its lime, destroy its equilibrium, and assist in causing its perpetual motion; but the two species which we have described are the best types of the respective classes to which they belong.
Chapter Sixteen.Volcanic Islands—Opinions of the Ancients—“Atlantisâ€â€”Instance of the Formation of a Volcanic Island—Conclusion.In the last chapter we described the manner in which a certain class of islands in the South Seas are formed; in the present we will make a few observations on another class, which have sprung up from the bottom of the sea, as if by magic, under the irresistible influence of fire.There are volcanoes in the sea, as well as on the land; and these volcanoes have in former times up-heaved huge masses of land so as to form large islands, while in other cases they have caused islands formerly in existence to subside and disappear.In the writings of the ancients we find reference made to an island which, if it ever did exist, now exists no longer. It was situated opposite the Straits of Gibraltar, was nearly two hundred miles in length, and was called “Atlantisâ€â€”hence the name of the Atlantic Ocean. Many believe, and with some reason, we think, that this island was not altogether a myth, although much that is said of it is undoubtedly fabulous.Plato tells us that it was a large island in the Western Ocean, situated before or opposite to the Straits of Gades; and that out of this island there was an easy passage into some others which lay near a large continent, exceeding in bigness all Europe and Asia. So far Plato may have told the truth, and from this passage it is conjectured that the existence of the continent of America was known to the ancients. But he goes on, immediately after, to draw upon his imagination, and to tell us that Neptune settled on this island, and that his posterity dwelt there for a period of nine thousand years in the midst of fertility and abundance. But, not content with their ample possessions and prolific soil, they went over to Africa and Europe, and even penetrated into Asia, bent on conquest.Passing from this mixture of probable truth and undoubted fable, Plato then asserts that the island of Atlantis finally sank and disappeared. This may or may not be true, but there is more reason for our crediting the statement than many people would suppose. Certain it is that no such island exists at the present time, but it is believed by some that the Azores, which are volcanic in their formation, are the summits of the mountain ranges of the Atlantis of the ancients.But the best evidence we have of the possible existence of such an island is the fact that in modern times an island has beenseento rise out of the sea, and, after a time, to disappear, under the influence of volcanic action.This remarkable event is related by Captain Tillard, an officer of the British Navy, who saw it on the 12th of June 1811, when approaching the island of St. Michael. On this occasion smoke was seen to rise from the surface of the sea, and, soon after, showers of cinders to burst forth. We cannot do better than give the captain’s own words, as follows:“Imagine an immense body of smoke rising from the sea, the surface of which was marked by the silvery rippling of the waves. In a quiescent state it had the appearance of a circular cloud revolving on the water, like a horizontal wheel, in various and irregular involutions, expanding itself gradually on the lee side; when, suddenly, a column of the blackest cinders, ashes, and stones, would shoot up in the form of a spire, at an angle of from ten to twenty degrees from a perpendicular line, the angle of inclination being universally to windward. This was rapidly succeeded by a second, third, and fourth shower, each acquiring greater velocity, and overtopping the other, till they had attained an altitude as much above the level of our eye as the sea was below it.“As the impetus with which the several columns were severally propelled diminished, and their ascending motion had nearly ceased, they broke into various branches resembling a group of pines. These again formed themselves into festoons of white feathery smoke, in the most fanciful manner imaginable, intermixed with the finest particles of falling ashes; which at one time assumed the appearance of innumerable plumes of black and white ostrich feathers surmounting each other; at another, that of the light wavy branches of a weeping willow.“During these bursts the most vivid flashes of lightning continually issued from the densest part of the volcano; and the cloud of smoke now ascending to an altitude much above the highest point to which the ashes were projected, rolled off in large masses of fleecy clouds, gradually expanding themselves before the wind, in a direction nearly horizontal, and drawing up to them a quantity of water-spouts, which formed a most beautiful and striking addition to the general appearance of the scene.â€Such is the description given of this submarine volcano in action; and the crater which was thrown up at the time was about twenty feet above the level of the sea. As Captain Tillard could not, however, delay his voyage to make further observations at that time, the action that subsequently took place is not known; but its results were seen shortly afterwards.In about three weeks after the date of his passing the spot, Captain Tillard returned to it and found an island of about a mile in circumference, with a height of between two and three hundred feet at its highest point. There was no violent eruption going on, although the craters still emitted smoke. He therefore landed, and, on reaching the largest crater, found it to be full of boiling water, which overflowed and found its way to the ocean in a river of about six yards in width. This island, however, was not a permanent addition to the world’s archipelago. It sank into the ocean again, and disappeared in October of the same year in which it rose.In commencing this little book we set out with the intention of rambling hither and thither, among things that relate to the sea, without regard to order. We have carried out our intention; and now, at the close of our task, find that the more we listen to the Ocean’s Voice, the more we find its tale to be interminable, though the reverse of uninteresting.In these rambles we have sought to treat chiefly of those scientific facts relating to the sea and the atmospheric ocean, which are not so frequently made the subject of books for the young, as are the wild and daring deeds of man upon the surface of the mighty deep.It is not sufficient that man should become acquainted with the doings of his fellows on the sea. This is but one branch of general knowledge, and a very secondary one compared with that infinitely higher branch which treats of the workings of the Almighty in the ocean; workings which render it what it is—not merely a means of commercial enterprise for man and a home for fish, but also a great purifier and revivifier of the earth and sweetener of the atmosphere. God is the great first cause of all that is and that operates in the universe. It were an act of presumption to inquire into what we may term the first acts of the Almighty’s power. But there is no presumption—on the contrary there is propriety, as well as the highest gratification of which the human mind is capable—in penetrating through the paths of knowledge up to that first series of second causes which circle like a glory round the fountain-head. We may not put the question, “How did God create all things out of nothing?†but, all things having been created, it is quite legitimate to inquire how the circles of their manifold operations are carried on, and in what respect the things that be do affect each other.No book that has of late years issued from the press treats more eloquently and interestingly of such subjects of inquiry than that admirable work of Captain Maury of the United States Navy, entitled “The Physical Geography of the Sea.†Much of the substance of what we have written has been culled from the pages of that fascinating volume. But we have merely plucked one or two leaves, as it were, and presented them to our readers in the hope that they may be tempted by their fragrance to pluck the flower. The mysteries of the atmospheric and aqueous oceans are here treated of fully, yet so agreeably, that one is frequently apt to fancy one is perusing the pages of romance.In our own little book we have been compelled to skim lightly, and, in many places, to pass over subjects of great interest.As for other subjects connected with the sea, of which we may not treat, they are innumerable. Of the sea-weeds that clothe the bottom of the deep with the rich profusion and glowing colours of the gardens of earth—of the myriads of animalcules (besides those we have mentioned) that disport in its waters and fill the abyss with life and lambent fire—of the great whales and other huge creatures that revel in its depths and lash its waters in their terrible might—of these and a host of kindred subjects, our space forbids our saying more than that the Voice of Ocean has much to tell us in regard to them, and in regard to the provident care of their beneficent Creator.
In the last chapter we described the manner in which a certain class of islands in the South Seas are formed; in the present we will make a few observations on another class, which have sprung up from the bottom of the sea, as if by magic, under the irresistible influence of fire.
There are volcanoes in the sea, as well as on the land; and these volcanoes have in former times up-heaved huge masses of land so as to form large islands, while in other cases they have caused islands formerly in existence to subside and disappear.
In the writings of the ancients we find reference made to an island which, if it ever did exist, now exists no longer. It was situated opposite the Straits of Gibraltar, was nearly two hundred miles in length, and was called “Atlantisâ€â€”hence the name of the Atlantic Ocean. Many believe, and with some reason, we think, that this island was not altogether a myth, although much that is said of it is undoubtedly fabulous.
Plato tells us that it was a large island in the Western Ocean, situated before or opposite to the Straits of Gades; and that out of this island there was an easy passage into some others which lay near a large continent, exceeding in bigness all Europe and Asia. So far Plato may have told the truth, and from this passage it is conjectured that the existence of the continent of America was known to the ancients. But he goes on, immediately after, to draw upon his imagination, and to tell us that Neptune settled on this island, and that his posterity dwelt there for a period of nine thousand years in the midst of fertility and abundance. But, not content with their ample possessions and prolific soil, they went over to Africa and Europe, and even penetrated into Asia, bent on conquest.
Passing from this mixture of probable truth and undoubted fable, Plato then asserts that the island of Atlantis finally sank and disappeared. This may or may not be true, but there is more reason for our crediting the statement than many people would suppose. Certain it is that no such island exists at the present time, but it is believed by some that the Azores, which are volcanic in their formation, are the summits of the mountain ranges of the Atlantis of the ancients.
But the best evidence we have of the possible existence of such an island is the fact that in modern times an island has beenseento rise out of the sea, and, after a time, to disappear, under the influence of volcanic action.
This remarkable event is related by Captain Tillard, an officer of the British Navy, who saw it on the 12th of June 1811, when approaching the island of St. Michael. On this occasion smoke was seen to rise from the surface of the sea, and, soon after, showers of cinders to burst forth. We cannot do better than give the captain’s own words, as follows:
“Imagine an immense body of smoke rising from the sea, the surface of which was marked by the silvery rippling of the waves. In a quiescent state it had the appearance of a circular cloud revolving on the water, like a horizontal wheel, in various and irregular involutions, expanding itself gradually on the lee side; when, suddenly, a column of the blackest cinders, ashes, and stones, would shoot up in the form of a spire, at an angle of from ten to twenty degrees from a perpendicular line, the angle of inclination being universally to windward. This was rapidly succeeded by a second, third, and fourth shower, each acquiring greater velocity, and overtopping the other, till they had attained an altitude as much above the level of our eye as the sea was below it.
“As the impetus with which the several columns were severally propelled diminished, and their ascending motion had nearly ceased, they broke into various branches resembling a group of pines. These again formed themselves into festoons of white feathery smoke, in the most fanciful manner imaginable, intermixed with the finest particles of falling ashes; which at one time assumed the appearance of innumerable plumes of black and white ostrich feathers surmounting each other; at another, that of the light wavy branches of a weeping willow.
“During these bursts the most vivid flashes of lightning continually issued from the densest part of the volcano; and the cloud of smoke now ascending to an altitude much above the highest point to which the ashes were projected, rolled off in large masses of fleecy clouds, gradually expanding themselves before the wind, in a direction nearly horizontal, and drawing up to them a quantity of water-spouts, which formed a most beautiful and striking addition to the general appearance of the scene.â€
Such is the description given of this submarine volcano in action; and the crater which was thrown up at the time was about twenty feet above the level of the sea. As Captain Tillard could not, however, delay his voyage to make further observations at that time, the action that subsequently took place is not known; but its results were seen shortly afterwards.
In about three weeks after the date of his passing the spot, Captain Tillard returned to it and found an island of about a mile in circumference, with a height of between two and three hundred feet at its highest point. There was no violent eruption going on, although the craters still emitted smoke. He therefore landed, and, on reaching the largest crater, found it to be full of boiling water, which overflowed and found its way to the ocean in a river of about six yards in width. This island, however, was not a permanent addition to the world’s archipelago. It sank into the ocean again, and disappeared in October of the same year in which it rose.
In commencing this little book we set out with the intention of rambling hither and thither, among things that relate to the sea, without regard to order. We have carried out our intention; and now, at the close of our task, find that the more we listen to the Ocean’s Voice, the more we find its tale to be interminable, though the reverse of uninteresting.
In these rambles we have sought to treat chiefly of those scientific facts relating to the sea and the atmospheric ocean, which are not so frequently made the subject of books for the young, as are the wild and daring deeds of man upon the surface of the mighty deep.
It is not sufficient that man should become acquainted with the doings of his fellows on the sea. This is but one branch of general knowledge, and a very secondary one compared with that infinitely higher branch which treats of the workings of the Almighty in the ocean; workings which render it what it is—not merely a means of commercial enterprise for man and a home for fish, but also a great purifier and revivifier of the earth and sweetener of the atmosphere. God is the great first cause of all that is and that operates in the universe. It were an act of presumption to inquire into what we may term the first acts of the Almighty’s power. But there is no presumption—on the contrary there is propriety, as well as the highest gratification of which the human mind is capable—in penetrating through the paths of knowledge up to that first series of second causes which circle like a glory round the fountain-head. We may not put the question, “How did God create all things out of nothing?†but, all things having been created, it is quite legitimate to inquire how the circles of their manifold operations are carried on, and in what respect the things that be do affect each other.
No book that has of late years issued from the press treats more eloquently and interestingly of such subjects of inquiry than that admirable work of Captain Maury of the United States Navy, entitled “The Physical Geography of the Sea.†Much of the substance of what we have written has been culled from the pages of that fascinating volume. But we have merely plucked one or two leaves, as it were, and presented them to our readers in the hope that they may be tempted by their fragrance to pluck the flower. The mysteries of the atmospheric and aqueous oceans are here treated of fully, yet so agreeably, that one is frequently apt to fancy one is perusing the pages of romance.
In our own little book we have been compelled to skim lightly, and, in many places, to pass over subjects of great interest.
As for other subjects connected with the sea, of which we may not treat, they are innumerable. Of the sea-weeds that clothe the bottom of the deep with the rich profusion and glowing colours of the gardens of earth—of the myriads of animalcules (besides those we have mentioned) that disport in its waters and fill the abyss with life and lambent fire—of the great whales and other huge creatures that revel in its depths and lash its waters in their terrible might—of these and a host of kindred subjects, our space forbids our saying more than that the Voice of Ocean has much to tell us in regard to them, and in regard to the provident care of their beneficent Creator.
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