in the elastic crust of the globe, caused by the pressure of the liquid fire, vapor, and gases in its interior. Volcanoes are the chimneys of these internal fires, and when they get vent the earthquake always ceases. 2. It appears, from numerous observations, that the internal heat of the earth gradually increases as we descend below the surface, so that, at the depth of two hundred miles, the hardest substances must be in a state of fusion; but whether our globe is encompassed by a mere stratum of melted lava at that depth, or its whole interior is a ball of liquid fire seventy-six hundred miles in diameter, inclosed in a thin coating of solid matter, men of science are not agreed. 3. Some portions of the earth are much more subject to volcanoes and earthquakes than others. The range of the Andes, from Cape Horn to California, with a cross section embracing the Caribbean Sea, and extending westward quite across the Pacific Ocean, is one vast district of igneous action. A great volcanic chain, beginning at the northeastern extremity of Asia, follows the coast-line around Asia and Africa, and thence up to the Canaries and the Azores, while a broad belt extends over the Mediterranean and a large part of Central Asia. Northwardly the volcanic fires are developed in Iceland with tremendous force; and the recently discovered antarctic land is an igneous formation of the boldest structure, whence a volcano in high activity rises twelve thousand feet above the perpetual ice of those polar deserts, and within nineteen and a half degrees of the south pole. On an average, twenty volcanic eruptions take place annually in different parts of the world. 4. Volumes might be filled with accounts of the destructive effects of earthquakes and volcanoes. Whole cities, of which Herculaneum, Pompeii, and Stabiæ are examples, have been buried beneath the burning fire of liquid mountains. But where one city has been destroyed by lava, twenty have been shaken down by the rocking and heaving of earthquakes. Prominent on the list of the latter is the city of Antioch, in Asia Minor. 5. " 'Imagine," says Dr. Hitchcock, "the inhabitants of that great city, crowded with strangers on a festival occasion, suddenly arrested on a calm day by the earth heaving and rocking beneath their feet; and in a few moments two hundred and fifty thousand of them are buried by falling houses, or the earth opening and swallowing them up. Such was the scene which that city presented in the year 526; and several times before and since that period has the like calamity fallen upon it, and twenty, forty, and sixty thousand of its inhabitants have been destroyed at each time. In the year 17 after Christ, no less than thirteen cities of Asia Minor were in like manner overwhelmed in a single night. 6. "Think of the terrible destruction that came upon Lisbon in 1755. The sun had just dissipated the fog in a warm, calm morning, when suddenly the subterranean thundering and heaving began; and in six minutes the city was a heap of ruins, and sixty thousand of the inhabitants were numbered among the dead. Hundreds had crowded upon a new quay surrounded by vessels. In a moment the earth opened beneath them, and the wharf, the vessels, and the crowd went down into its bosom; the gulf closed, the sea rolled over the spot, and no vestige of wharf, vessels, or man ever floated to the surface." 7. One of the most singular effects produced, either by earthquakes or by the gradual pressure of the internal fires and gases, is the occasional raising of the earth's crust to a great extent. In South America, so late as the year 1822, an area of one hundred thousand square miles was raised several feet above its present level. In 1819 a strip in the delta of the Indus, fifty miles in length and less than twenty feet in width, was raised ten feet above the surrounding plain. Along the eastern coast of the Bay of Bengal, all the rocks and islands for a distance of one hundred miles have been gradually rising during the last hundred years, and in the central portion the elevation already attained is twenty-two feet. 8. Occasionally volcanic islands suddenly appear above the surface of the ocean; and when this is the case, or when an earthquake has its origin beneath the ocean's bed, an immense wave is sometimes driven upon the shore, overwhelming the inhabitants, and bearing their bodies to the ocean in its retreat. The earthquake which destroyed Lisbon in 1755 had its origin in the bed of the Atlantic, whence the shock extended over an area of about seven hundred thousand square miles, or a twelfth part of the circumference of the globe. 9. It was by an enormous wave, occasioned by an earthquake that had its origin in the bed of the Mediterranean, that the little maritime town of Scylla, on the coast of Naples, was destroyed in 1783. The waters passed with impetuosity over the shore of Scylla, and, in their retreat to the bosom of the deep, swept away four thousand human beings who had thought to find safety in the barrenness of the sands. This catastrophe is vividly portrayed in the following lines: 10. DESTRUCTION OF SCYLLA IN 1783. Calmly the night came down Where yesterday her thousands trode, Humbled in anguish now, The despot, midst his menial band, Ay, prince and peasant knelt in prayer, Again!-as at the morn, The earthquake rolled its car; Up rose the kneelers then, As the wave's rush was heard: Was broken by no word. But closer still the mother press'd One long, wild shriek went up, As bow'd to drink death's bitter cup And man's strong wail, and woman's cry, On swept the whelming sea; The mountains felt its shock, As the long cry of agony Thrill'd through their towers of rock; The death-wail of the sufferers bore. The morning sun shed forth Its light upon the scene, Where tower and palace strewed the earth With wrecks of what had been; But of the thousands who were gone, No trace was left-no vestige shown.-Anonymous. LESSON XIV. THE OCEAN: ITS MORAL GRANDEUR. "THE sea! the sea! the open sea! It runneth the earth's wide regions round; 1. There are two widely different aspects in which the ocean may be viewed. It may be regarded as an object of moral grandeur-"the symbol of a drear Immensity"-a Voice that sometimes "6 speaketh in thunders" to awe the world; a Power, terrible in its wrath, but lovely in repose; or it may be viewed as the great highway of commerce, and as a vast store-house of wealth: the laws which govern its tides, its waves, and its currents may be presented as objects of scientific regard, and the mysteries of its depths as *The Prince of Scylla perished with his vassals. opening some of the most interesting departments in natural history. But it is only when we unite, in our contemplation, these various aspects, that we begin to have any adequate idea of the real interest and importance of this, the grandest division of our globe. 2. The first impression made by a view of the ocean is doubtless that of vastness, illimitable-inappreciable; while the thoughts which its mighty waters teach are those of Eternity, Eternity, and Power." Such thoughts are forcibly expressed in the following lines addressed to 66 THE OCEAN. Oh thou vast ocean! ever sounding sea! Thou thing that windest round the solid world At once, and on thy heavily-laden breast Fleets come and go, and things that have no life Or motion, yet are moved and met in strife. The earth hath naught of this: no chance nor change Ruffles its surface, and no spirits dare Give answer to the tempest-waken air; But o'er its wastes the weakly tenants range Thou only, terrible ocean, hast a power, A will, a voice, and in thy wrathful hour, A fearful and magnificent beauty shrouds Thy broad green forehead. If thy waves be driven How quickly dost thou thy great strength unbind, And stretch thine arms, and war at once with Heaven! Thou trackless and immeasurable main ! On thee no record ever lived again To meet the hand that writ it: line nor lead Hath ever fathomed thy profoundest deeps, Where haply the huge monster swells and sleeps, King of his watery limit, who, 'tis said, Can move the mighty ocean into storm Oh, wonderful thou art, great element, And fearful in thy spleeny humors bent, Marking the sunlight at the evening hour, "Eternity, Eternity, and Power."-BRYAN W. PROCTOR. LESSON XV.- -THE OCEAN: ITS PHYSICAL ASPECTS. 1. THE bed of the ocean, like dry land, is diversified by plains and mountains, table-lands and valleys, sometimes barren, sometimes covered with marine vegetation, and teeming with life. Its plateaus and depressions have been ascertained by the sounding-line, and are mapped out in profile as a part of our geographical knowledge. Its average depth is believed to be about equal to the height of the land, the lowest valleys of the ocean's bed corresponding with the summits of the loftiest mountains. 2. The ocean is continually receiving the spoils of the land, washed down by numerous rivers, and deposited as sand and mud, or held in solution in its waters. These causes tend to diminish its depth and increase its superficial extent. There are, however, causes in operation which counteract these agencies. It is clearly shown by geologists that processes of elevation and subsidence are continually taking place in different parts of the globe. 3. The waters of the ocean contain about three and a half per cent. of saline matter; but, owing to the melting of snow and ice in the polar regions, and the volumes of fresh water poured in by rivers, the degree of saltness diminishes toward the poles, and also near the shores. The temperature of the ocean, though varying in different latitudes, is more uniform than that of the land; its color, generally of a deep bluishgreen, is varied in particular localities by the myriads of animalcules and vegetable substances which float on its surface, and also, in shallow places, by the color of the bed on which it rests. In some parts of the tropical seas the waters are remarkably clear, like an immense vase of crystal; and one may look downward unmeasured fathoms beneath the vessel's keel, but still find no boundary: the sight is lost in one uniform transparent blueness. The calm midnight ocean" of the tropics has been beautifully described in the following lines: 4. "6 It is the midnight hour-the beauteous sea, Calm as the cloudless heaven, the heaven discloses, Far down within the watery sky reposes. As if the ocean's heart were stirr'd With inward life, a sound is heard, Like that of dreamer murmuring in his sleep; 'Tis partly the billow, and partly the air That lies like a garment floating fair Above the happy deep.-JOHN WILSON. |