currents is not invariable, but is much accelerated or retarded by the prevalence of hard gales, the navigator sailing with or against them has to take this element into the account, in order to be sure of his place. In proceeding from the American coast to Bermuda, Captain Hall found that an unusual increase in the rate of the gulf stream had carried him so far beyond his mark, that when from his reckoning, the weather having prevented observations for the longitude, he supposed himself about forty miles on the western side of the island, and was therefore beating to the eastward, he was actually about the same distance on the eastern side, and had to sail westward to gain his port. By not making due allowance for the force of the current that sweeps round the Cape of Good Hope from the Pacific, navigators proceeding to India have often fancied themselves east of the Cape when they have been still west, and have been driven ashore on the African coast, which, according to their reckoning, lay behind them. A similar cause has led to many a disastrous shipwreck on the Senegal coast, upon which a branch current from the gulf stream rushes, and upon the savage shores of the Great Desert, it has been the fate of many a gallant crew, either to perish of hunger or to be sold into slavery. A more accurate acquaintance with oceanic regions, and the accomplished nautical education of commanders, have diminished such accidents in recent times. Still, besides the great sea-streams, there are an immense number of offsets from them, some of which are only occasional currents, and others have not been noticed, which may deceive the most skilful commander, and hurry his vessel ashore, when his reckoning gives him a considerable distance from it. This misfortune happened to the fine frigate the Challenger, in the year 1835, which struck upon the south coast of Chili, owing to the action of an unusual and unexpected current, against which it was impossible to guard. At eight o'clock in the evening there was a careful examination of the ship's place upon the charts. At nine, the weather was hazy, the wind moderate, the water smooth, the stars occasionally appearing overhead, and an expected moon at midnight promised a fine and quiet night to the crew. At a quarter to ten the breakers were seen, and immediately the ship dashed upon the rocks along the beach, became a complete wreck, the officers and men reaching the shore with difficulty.

The existence of under-currents, running in a direction opposite to the flow of the surface stratum, has been surmised in various places, but chiefly owing to circumstances

which may be differently explained. It has been mentioned, that the Black Sea pours its surplus waters, through the Bosphorus and the Hellespont, into the Grecian Archipelago. The current here flows at the rate of from two to four miles an hour, and is occasionally so strong that ships experience great difficulty in making way against it. The exploit of Leander and Byron, who swam across the Hellespont, conquering the power of the stream, has acquired celebrity. This is one of the sites where it has been imagined that there is an under-current flowing upwards from the Archipelago to the Black Sea. The saltness of the water of the latter, which is only one-seventh less than that of the Atlantic, and fully one-tenth more than that of the Baltic, has suggested this idea. While receiving an immense influx of fresh water from numerous large rivers, and having a constant outflow, this degree of saltness is certainly a singular problem; and it has been thought difficult to account for it, otherwise than by supposing an under-current communicating the saltness of the Archipelago to the Euxine. But salt prevails extensively in the countries along its north and north-eastern shores, a considerable portion of which, finding its way to the sea, may be the true cause of its waters being so largely impregnated by it. The physical condition of the Mediterranean has also been deemed inexplicable, except upon a similar supposition. While a perpetual stream flows into it from the Black Sea through the channels named, there is another from the Atlantic through the Straits of Gibraltar; and to account for the disposal of the quantity of water flowing inward, a submarine current, flowing outward at the Straits, has been maintained by many philosophers. The following circumstance has been considered to be confirmative of this opinion. M. Du L'Aigle, the commander of a privateer called the Phoenix, of Marseilles, gave chace to a Dutch merchant ship, near Ceuta Point, and came up with her in the middle of the Straits, between Tariffa and Tangier, and gave her a broadside which directly sunk the

vessel. A few days after, the sunk ship, with its cargo of brandy and oil, arose on the shore near Tangier, which is at least four leagues to the westward of the place where she sunk, and directly against the strength of the current from the Atlantic. Besides, however, this current, there are two lateral currents in the Straits, one on the European and the other on the African side, which alternately flow outward and inward with the tide; and the drifting of the vessel to the rear of the spot in the main stream where she sank might be occasioned by one of these lateral currents, at that time flowing out of the

Straits. With reference to the immense body of water which is constantly pouring into the Mediterranean from the Atlantic, there is no necessity to have recourse to an undercurrent conveying it back into the ocean to account for its disposal; for a considerable portion may be returned there by the lateral currents, while an enormous evaporation expends the rest. We have no evidence whatever of the existence of such a phenomenon as the superior and inferior stratum of the same volume of water flowing in opposite directions. Ray long ago remarked: "I do not understand how waters can run backward and forward in the same channel at the same time. For, there being but one declivity, this is as much as to affirm that a heavy body should ascend. It is a crossing of proverbs, ǎv оraμwv, making rivers ascend to their fountains, affirming that to be done which all the world hath hitherto looked upon as absurd and impossible."

Currents pursuing an inverse course sometimes meet and conflict; and when this occurs in narrow channels, it renders their passage troublesome and dangerous to the mariner. When two currents, thus meeting together, are nearly of equal force, they often cause eddies or whirlpools, of which the Maelstrom, off the coast of Norway, is a remarkable example. Its influence is felt for more than nine miles, and its power is such, that vessels drawn into its grasp have been unable to extricate themselves, and have perished in its vortex. In a storm, the roar of the contending waters is heard through a wide area upon the surface of the deep. Charybdis, in the straits of Messina, is another instance, so famed in antiquity, with its companion Scylla, for offering perils to the ancient navigators. Homer pourtrays Scylla as a rock so lofty that its summit is continually cloudcapt, and so steep, smooth, and slippery, that no mortal could scale its height, though the capabilities of his physical frame for the ascent were largely multiplied :

Though borne by twenty feet, though arm'd with twenty hands.
Smooth as the polish of the mirror rise

The slippery sides, and shoot into the skies."

The Greek poet, and Virgil after him, personify this rock as a sea monster, lurking in the darkness of a vast cavern, surrounded by ravenous, barking mastiffs, together with wolves, increasing the horror of the scene:—

"Here Scylla bellows from her dire abodes,
Tremendous pest! abhorr'd by man and gods!
Hideous her voice, and with less terrors roar
The whelps of lions in the midnight hour."

Not less terrible is the description of Charybdis, represented by Homer as a companion monster, three times in a day drinking up the water, and three times vomiting it forth:

"Beneath Charybdis holds her boisterous reign

'Midst roaring whirlpools, and absorbs the main ;
Thrice in her gulfs the boiling seas subside,

Thrice in dire thunder she refunds the tide."

This language of poetical fable and exaggeration rests upon a stratum of truth. In the Straits of Messina -the site of Scylla on the Calabrian shore, and of Charybdis by the

opposite coast of Sicily-there are numerous and variable currents. The centre of the channel is occupied by a stream, which runs alternately north and south, six hours each way, at the rate of from two to five miles an hour. On each side there is a counter or returning stream, running at a varying distance from the beach, and numerous eddies or whirlpools are formed by the contact of the lateral and central currents. In rough weather, when a high wind is blowing in the direction of the main stream, it becomes sufficiently powerful to stop the course of the lateral currents, but the collision gives rise to strong whirls in the water, which are sent off to each shore. It is easy to conceive, that to the inexpert mariners of ancient times, such a navigation would be alarming in dark, rainy, blustering nights, and would often involve the wreck of their feeble craft, disasters upon which the poets seized, and magnified the causes beyond the reality. At the same time, it is not improbable, that the physical paroxyms to which the adjacent districts have been subject, may have so altered the bottom of the straits, either by elevation or depression, as to have really diminished the danger of the passage. During the great Calabrian earthquake, the quay of Messina sank fourteen inches, vast masses of sea-cliff on the coast of the straits fell down, and one such mass, detached from Mount Jaci beside the rock of Scylla, rolled by night to the margin of the Mediterranean, which immediately rose with a wave twenty feet high.

"I first," says the Abbé Spallanzani, “proceeded in a small boat to Scylla. This is a lofty rock which rises almost perpendicularly from the sea, on the shore of Calabria, and beyond which is the small city of the same name. Though there was scarcely any wind, I began to hear, two miles before I came to the rock, a murmur and a noise, like a confused barking of dogs, and on a nearer approach readily discovered the cause. This rock in its lower part contains a number of caverns; one of the largest of which is called by the people there, Dragara. The waves, when in the least agitated, rushing into these caverns, break, dash, throw up frothy bubbles, and thus occasion these various and multiplied sounds. Such is the situation and appearance of Scylla: let us now consider the danger it occasions to mariners. Though the tide is almost imperceptible in the open parts of the Mediterranean, it is very strong in the Strait of Messina, in consequence of the narrowness of the channel, and it is regulated, as in other places, by the periodical elevations and depressions of the water. Where the flow or current is accompanied by a wind blowing the same way, vessels have nothing to fear; since they either do not enter the Strait, both the wind and the stream opposing them, but cast anchor at the entrance; or, if both are favourable, they enter on full sail, and pass through with such rapidity that they seem to fly over the water, But when the current runs from south to north, and the north wind blows hard at the same time, the ship, which expected easily to pass the Strait with the wind in its stern, on its entering the channel is resisted by the opposite current, and, impelled by two forces in contrary directions, is at length dashed on the rock of Scylla, or driven on the neighbouring sands; unless the pilot shall apply for the succour necessary to his preservation. For to give assistance in case of such accidents, four and twenty of the strongest, boldest, and most experienced sailors, well acquainted with the place, are stationed night and day along the shore of Messina, who, at the report of guns fired as signals of distress from any vessel, hasten to its assistance, and tow it with one of their light boats."

The site of Charybdis is defined by Strabo, "in the strait, a little before we reach the city" Messina. It is off the entrance of the harbour, distant about 6047 yards from Scylla, according to the measurement of Captain Smyth, and about 700 feet from the shore, upon a promontory of which a lighthouse warns the sailor by night of the spot. The classical name is no longer its local title, but Kalofaro, from raλos and papos, the "beautiful tower," alluding to the lighthouse. It is not a vortex of the ordinary kind,

endangering vessels by suction, but rather a tumultuous movement of the water, which circulates in several quick eddies, varying with the force and direction of the winds and currents. When the wind and the current oppose each other, the Kalofaro becomes a scene of extensive and violent agitation, and will wheel round even ships of war upon its surface; but there is no appearance of an absorbing gulf answering to the ancient imagination, though smaller vessels are exposed to the peril of being driven ashore, or destroyed by the waves beating over them. In order to avoid the danger arising from Charybdis, the mariners of former times went as near as possible to the coast of Calabria, and sometimes went too near, provoking the dangers arising from Scylla; and hence the proverb still applied to those who, in attempting to escape one evil, encounter another:

:

Incidat in Scyllam, cupiens vitare Charybdim.
"Who flies Charybdis. upon Scylla strikes."

Brydone, after referring to the accounts given of it by the classical writers, remarks: "It certainly is not now so formidable, and very probably the violent motion, continued for so many ages, has by degrees worn smooth the rugged rocks and jutting shelves that may have intercepted and confined the waters. The breadth of the straits, too, in this place, I make no doubt, is considerably enlarged. Indeed, from the nature of things, it must be so; the perpetual friction occasioned by the current must wear away the bank on each side, and enlarge the bed of the water."

Of all the oceanic movements exhibited in the form of waves, tides, and currents, of which a summary notice has been given, the latter are the most influential in affecting the displacement of its waters. The tides alternately elevate and let down the surface, rather than produce an actual stream, except along shore, and in confined channels; for when we speak of the motion of a tide-wave, and of its rate of advance, we do not mean a shifting of the water from place to place, but the progressive elevation of its surface stratum. The influence of the winds in creating waves is very circumscribed in forcing the sea to change its situation, except where they are strong and permanent; and it is the upper stratum that they chiefly affect. It may here be mentioned that during a recent circumnavigation of the globe by the French ship Venus, the highest wave that struck her on the voyage was 75 metres, or 23 feet; and the longest wave, met with to the south of New Holland, was three times the length of the frigate, 150 metres, or 492 feet. Currents, on the contrary, involve extensive areas of the ocean; extend in many instances to the bottom of the sea, and transfer its waters from one hemisphere to another— from the Pacific to the Atlantic, and to the Pacific again, in perpetual revolution—from the congelation of polar regions to the heat of the equatorial. Owing to the joint influence of winds, tides, and currents, there is no part of the ocean, for any long interval, in a state of rest—an obviously benign arrangement of Providence; for if it became for any length of time a vast stagnant pool, its waters, charged with an immense amount of decomposing animal and vegetable matter, notwithstanding their saltness, would soon become fœtid, would give off noxious exhalations, infect the whole atmosphere, and reduce the world to an uninhabitable desert. It has been wisely ordained, therefore, that the physical condition of this enormous mass of water should answer to the apostrophe"Roll on, thou deep and dark blue ocean, roll!”

BB