Ocean's Story; or, Triumphs of Thirty Centuries / Maritime Adventures, Achievements, Explorations, Discoveries and Inventions; and of the Rise and Progress of Ship-Building and Ocean Navigation, from the Ark to the Iron Steamships

by Frank B. Goodrich

The specific gravity of sea water is greater than that of fresh. This comes from the various matters which it holds in solution. This difference varies with different seas; with the quantity of matters held in solution; with the amount of evaporation; the size and number of rivers flowing into the various seas; the ice melting into them; the currents, and various other causes. The average quantity of salts held in solution in sea water is estimated at 34.40 parts in 1,000, and this average is the same in all seas. The quantity of common salt held in solution is always a little more than three-quarters (75.786) of the total mineral matter held in solution. The salt of the sea averages, if the water is evaporated, about two inches to every fathom; so that, were the ocean dried up, a layer of salt about two hundred and thirty feet thick would remain on the bottom, or the whole salt of the sea would measure more than a thousand millions of cubic miles. This vast quantity of salt in the sea explains how the enormous beds of rock salt were formed, when the lands now exposed were covered by the waters.

Beside the oxygen and hydrogen which constitute its waters, the sea contains chlorine, nitrogen, carbon, bromine, iodine, fluorine, sulphur, phosphorus, silicon, sodium, potassium, boron, aluminium, magnesium, calcium, strontium, barium. From the various sea-weeds most of these substances can be obtained. Copper, lead, zinc, cobalt, nickel and manganese have also been found in their ashes. Iron has also been obtained from sea water, and a trace of silver also is often deposited by the magnetic current established between the sheeting of ships and the salt water. Though only a trace is thus found, yet it has been estimated that the whole waters of the ocean contain in solution two million tons of silver. In the boilers of ocean steamships, which use sea water, arsenic has also been found.

Sea water also retains dissolved air better than fresh water, and the bulk of this in ocean water is generally greater by a third than that found in river water. It varies from a fifth to a thirtieth, and gradually increases from the surface to a depth of about three hundred and twenty-five to three hundred and eighty fathoms. The uniformity in the constitution of the waters of the sea is chiefly caused by the action of the waves, which finally mix and mingle the waters into a homogeneous mass. The waves of the sea are caused chiefly by the action of the wind, and the effect continues even after the wind has ceased. One of the grandest spectacles at sea is offered by the regular movement of the waves in perfectly calm weather, when not a breath of air stirs the sails. During to the Autumnal calm under the Tropic of Cancer, these waves appear with astonishing regularity at intervals of two hundred to three hundred yards, sweep under the ship, and as far as the eye can reach, are seen advancing and passing away, as regularly as the furrows in a field. Such waves are caused by the regularity of the trade winds. The height of the waves is not the same in all seas. It is greater where the basin is deeper in proportion to the surface, and also as the water is fresher and yields easier to the impulses of the wind.

The height of waves has been variously measured. Some observers have claimed to see them over one hundred feet high, but from twenty to fifty feet is about the average of observations on the Atlantic. The breadth of a wave is calculated as fifteen times its height. Thus, a wave four feet high is sixty feet broad. The inclination of the sides of the waves varies however with the force of the wind, and with the strength of the secondary vibrations in the water, which may interfere with the primary ones. The speed of the waves is only apparent like the motion in a length of cloth shaken up and down. Floating objects do not change their relative positions, but slowly, except in rising and falling with the wave. The real movement of the sea is that of a drifting current, which is slowly formed under the action of the wind, and this is not rapid, but slow. The astronomer Airey says that every wave 100 feet wide, traversing a sea 164 fathoms in average depth, has a velocity of nearly 2,100 feet a second, or about fifteen and one-half miles an hour; a wave 674 feet, moving over a sea 1,640 fathoms deep, travels more than 69 feet a second, or nearly fifty miles an hour, and this last calculation may be taken as the average speed of storm waves in great seas. As, therefore, we can calculate the velocity of waves from their width and the known depth of the sea, we can calculate the depth of the sea from the known size and velocity of the waves. By this method the depth of the Pacific between Japan and California has been calculated from the size and speed of an earthquake wave, which was set in motion by an eruption in Japan. The accuracy of the calculation was afterward established by actual soundings.

It was formerly supposed that the disturbance of the waves did not penetrate the depth of the water, below four or six fathoms, but this has been found, on further observation, erroneous. Sand and mud have been brought up from a depth of a hundred fathoms below the surface, and experiments have shown that waves have a vertical influence 350 times their height. Thus a wave a foot high influences the bottom at a depth of 50 fathoms, and a billow of the ocean 33 feet high is felt below at a distance of 1 3/43/4 miles. At these great depths the action of the wave is perhaps imaginary, but to this reason we can ascribe the heavy swells which are often so dangerous. A hidden rock, far below the surface, arrests some moving wave and causes an eddy, which, rising to the surface, produces the "ground swells" which suddenly rise in the neighborhood of submarine banks and endanger ships. This cause also explains the tide races, which, coming from the depths of the ocean, advance suddenly upon the beaches, destroying all that opposes them. It is this cause which makes the position of light-houses upon certain reefs so dangerous. The Bell Rock house, on the Scottish coast, stands 112 feet above the rock, and yet it is often covered with the waves and foam, even after the tempest has ceased to rage. Such light-houses are often washed away; as that at Minot's Ledge, on the coast of Massachusetts, has often been. In consequence the modern method of building these structures differs from that formerly in use. The custom was to build them of solid masonry, hoping to make them strong enough to resist the waves. Now they are generally built of iron lattice open work, making the bars as slender as is consistent with the proper strength, so as to offer the least resisting surface to the rushing water. This open frame work is raised up high enough, if possible, to place the house and lantern above the reach of the body of the wave.

The force of the water in such positions is prodigious. Stephenson calculated that the sea dashed against the Bell Rock light-house with a force of 17 tons for every square yard. At breakwaters in exposed situations the sea has been known to seize blocks of stone weighing tons, and hurl them as a child would pebbles. At Cherbourg, in France, the heaviest cannon have been displaced; and at Barra Head, in the Hebrides, Stephenson states that a block of stone weighing 43 tons was driven by the breakers about two yards. At Plymouth, England, a vessel weighing 200 tons was thrown up on the top of the dike, and left there uninjured. At Dunkirk it has been found that from the dash of the breakers the ground trembles for more than a mile from the shore. Results of this kind, to which our attention is specially directed, since they affect man's work, show us what must be the effect produced by the sea, in constantly eating away the shore; altering the coast lines; changing continents, and building them up elsewhere; and suggest how much greater than what we see must have been the effects of the sea upon the land during the countless ages in which it has been at work.

The currents in the ocean, which constitute the real motion of its waters, are very important in the study of the influence of the sea upon the land. By these the circulation of the waters of the globe is carried on. The warm water of the equatorial regions seeking the poles, and a counter movement from the poles to the equator, is established. By their means a constant mingling of the waters on the face of the whole earth is maintained, and the wonderful similarity of its different portions, in their composition, appearance, and the substances held in solution, is produced. The chief causes of this grand circulation are found in the heat of the sun and in the rotation of the earth upon its axis. By the evaporation of the waters in the tropics the surface of that portion of the ocean is estimated to be lowered more than fourteen feet yearly. By this means not only is the atmosphere provided with its store of vapor, to be dispensed in rain upon the land, and thus returned again to the sea, but this lowering of the surface of the ocean, in one part, leads to the currents flowing from the others to restore the equilibrium. The same cause leading also to the circulation of the atmosphere, produces the trade winds, which aid in producing the currents in the ocean.

Now that by study and observation mankind have arrived at the conception of the form of the earth, at its general features, and can, in idea, grasp it as a whole, the opportunity is prepared for the methodical study of its parts, and their relation to each other; and this is the subject which for the first time in the history of mankind is offered to the physical geographer, with the certainty that none of his observations can be lost, but that they all are important, and can each be referred to its proper place. Another movement of the ocean is the tides. To the ancients, unacquainted with the form of the earth, its position in space, or its relations with the other bodies of the solar system, the tides were naturally inexplicable. It has been possible, only in modern times to attempt their explanation. Kepler first indicated the course to be followed; and Descartes and Newton each gave a theory; the first that of the pressure of the waters; the last, that of the attraction of the sun and moon upon the waters. This last theory is the one generally accepted, since it has been found satisfactory in most respects; yet it still has its opponents. Now, however, that the telegraph has been discovered, and a means thus afforded for instantaneous communication between observers at distant points, it has become possible to organize a simultaneous observation of the tides at various places, and eventually this will be done, so that the theory that the tides are caused by the attraction of the sun and moon will be entirely proved or rejected according as it will be found consistent with the facts observed.

In this connection an interesting instance of the different manner in which the ancients regarded natural phenomena, from that in which the moderns regard the same occurrences, is found in the fear the ancients had of the two monsters Scylla and Charybdis, which were the fabled guardians of the Straits of Messina. At present there are no straits in the Mediterranean more frequented than those of Messina. By the soundings which have been made there, these monsters had been effectually destroyed, and the whirlpools are known to be produced by the ebb and flow of the tide, causing a greater flow of water than can be accommodated by the narrow channel. The width of the channel is hardly two miles, and at low tide it has often been crossed on horseback, by swimming. The rising tide tends toward the north, from the Ionian to the Tyrrhenian sea, and the falling tide in the opposite direction. There is a strife between these currents, and on their confines eddies are formed which ships avoid, but there is no danger unless the wind blows strongly against the tide.

Besides the influence of the currents and the tides of the ocean in altering the configuration of the land, the sea is the home of innumerable forms of animal life, which are constantly laboring in the same direction. It has been truly said, that a beef bone, thrown overboard by a sailor on a ship, may form the nucleus of a new continent. The entire chalk cliffs of England were formed from the minute shells deposited by the small animals which secreted them. At their death these fell to the bottom, and thus slowly through the ages the deposit was formed. The recent deep sea dredgings have shown the sea, at all depths, is full of animal life; and as the steady fall of snow-flakes in a winter's storm, piled up by currents of wind, form the drifts, or falling quietly, cover the ground uniformly, so the sea is full of the minute shells, which, carried by currents, form banks, or, falling evenly, prepare the plains which in the future will appear, in some upheaval, to form new continents.