The wonders of the world

by John Loraine Abbott

The shallowness and narrowness of many parts of the sea, give rise also to a peculiarity in the tides of some parts of the world: for in many places, in the British seas in particular, the greatest swell of the tide is not while the moon is in its meridian hight, and directly over the place, but some time after it has declined thence. The sea, in this case, being obstructed, pursues the moon with what dispatch it can, but does not arrive with all its waters, until after the moon has ceased to operate. Lastly, from this shallowness of the sea, and from its being obstructed by shoals and straits, it happens that the Mediterranean, the Baltic and the Black sea, have not any sensible tides, to raise or depress them in a considerable degree.

Among the phenomena of the tides, one of the most singular is the bore, peculiar to several rivers: it is ascribed to the waters, which were before expansive, being suddenly pent up, and confined within a narrow space. This bore or impetuous rush of waters, accompanies the first flowing of the tide in the Ferret, in Somersetshire, and in the Seine, in France. It is also one of the peculiarities of the Severn, the most rapid river in England.

One of the greatest known tides is that of the Bristol channel, which sometimes flows upward of forty feet. At the mouth of the river Indus, the water rises thirty feet. The tides also are remarkably high on the coasts of Malay, in the straits of Sunda, in the Red sea, at the mouth of the river St. Lawrence, along the coasts of China and Japan, at Panama, and in the gulf of Bengal. The most remarkable tides, however, are those at Batsha, in the kingdom of Tonquin, in twenty degrees, fifty minutes, north latitude. In that port, the sea ebbs and flows once only in twenty-four hours, while in all other places there are two tides within that space. What is still more extraordinary, twice in each month, when the moon is near the equinoctial, there is not any tide, the water being for some time quite stagnant. These, with other anomalies of the tides there, Sir Isaac Newton, with peculiar sagacity, ascertained to arise from the concurrence of two tides, one from the South sea, and the other from the Indian ocean. Of each of these two tides there come successively two every day; two at one time greater, and two at another which are less. The time between the arrival of the two greater was considered by him as high tide; that between the two less, as ebb. In short, with these simple facts in his possession, that great mathematician solved every appearance, and so established his theory as to silence every opposer.

Besides the common and periodical tides, a variety of local currents are met with in different seas, on different parts of the ocean, and for the greater part at an inconsiderable distance from land. They have been usually ascribed to particular winds; but their origin is not easy to trace, as they have been occasionally found beneath the surface of the water, running in a contrary direction to the stratum above, and can not, therefore, have been owing to winds or monsoons. These particular currents have been ascribed to the immense masses of polar ice, which produce a greater degree of cold in the under than in the upper stratum of waters; and it has been suspected that there is an under-current of cold water flowing perpetually from the poles toward the equator, even where the water above flows toward the poles. The great disparity of temperature which is frequently found in deep and superficial soundings of the same space of water, is thus accounted for.

The most extraordinary current of this kind, is that of the gulf of Florida, usually called the Gulf stream, which sets along the coast of North America to the northward and eastward, and flows with an uninterrupted rapidity. It is ascribed to the trade-winds, which, blowing from the eastern quarter into the great Mexican gulf, cause there an accumulation above the common level of the sea. The water, therefore, constantly runs out by the channel where it finds least resistance, that is, through the gulf of Florida, with such force as to continue a distinct stream to a very great distance. A proof of its having thus originated is, that the water in the Gulf stream has been found to have retained a great portion of the heat it had acquired in the torrid zone.

A very singular upper current often prevails to the westward of Scilly, and is highly dangerous to ships which approach the British channel. Currents of this description are, however more frequently met with about the straits of Gibraltar, and near the West India islands, the coasts of which are so subject to counter-tides, or extraordinary currents, that it is often dangerous for boats to land. They proceed to the westward, along the coasts of Yucatan and Mexico, and running round into the gulf, return into the great ocean by the straits of Bahama, along the coasts of Florida, in order to pursue, in the north, the course ordained them by the great Author of nature. In this course the waters run with an extraordinary rapidity, passing on, however, by a motion so even and imperceptible, that their speed is not realized by the spectator. But against the shores and coasts of the various islands in their way, their progress becomes very manifest, and even dangerous, interrupting the navigation, and rendering it hardly possible to stem them in their course.

In addition to these regular currents, there are others, called counter-tides, which are observable on the sea-coasts and shores. In places where these flow, the sea rolls and dashes in an extraordinary manner, becoming furious without any apparent cause, and without being moved by any wind. The waves rise and open very high, breaking on the shore with such violence, that it is impossible for vessels to land. These counter-tides have been, by some, ascribed to the pressure of the heavy black wind-clouds which are occasionally seen to hang over an island, or over the sea where they occur, though it is far more probable that in every case they are caused by under-currents and hidden shoals, by which the ordinary currents are checked and broken so as to cause the effects described.

Somewhat similar to these, at least in its hidden cause, is the celebrated Maelstrom on the coast of Norway, a view of which is given in the cut. This is caused by the tides, in their violent passage between the Loffoden islands; and its terrors, though at all times great, are sometimes greatly increased by the winds. The roar of the sea, when the Maelstrom is in full action, is said to be terrific. It is stated that not only ships, but even whales, have been sucked into this vortex, and killed by being dashed against the hidden rocks. The following description, though imaginary, gives a correct idea of the destruction of a ship in this whirlpool.

THE MAELSTROM.