Between the tropics, when uninfluenced by any local circumstances, they flow from the east with the movement of the celestial bodies. In the northern temperate zone they flow from the south, and in the southern temperate zone from the north; that is in both from the equator, where the power of these bodies is most forcibly exerted on the waters. In the northern Frozen Ocean the tides are in general very weak, owing to its distance from the centre of the sidereal attraction, from the lands which surround it, and from the ices with which it is encumbered. Of the tides in the southern Frozen Ocean we have little or no knowledge. The irregularities of the bottom of the ocean, the position of coasts, their declivity under water, the different breadths of channels and straits, winds, currents, and other local' and temporary causes, destroy the regularity of tides, and, by varying the degree of friction of the waters, shorten or prolong the duration of the ebb and flood. In most places of the globe the tide flows twice in twenty-four hours, according to the principles of the sidereal attraction; there are, however, a number of exceptions, particularly among the Asiatic islands within the tropics, as well as on the coast of Van Diemen's Land, where there is but one tide of flood in twenty-four hours, and in those places the passage of the moon over the meridian usually makes high water.-Horsburgh. Ind. Direc. Thus among the scattered islands of the tropics the tides are regular, but the rise is inconsiderable; while on the oceanic coasts of Europe, and on the east coast of Asia, they are extremely strong, and subject to many irregularities. The highest tides yet observed are in the Gulf of St. Malo, on the coast of France, where the flood, driven back by the coast of England, accumulates and rises to the height of seven and eight fathoms. It is difficult to give credit to the accounts of the travellers who inform us that, in 1632, the is land of Formosa experienced a tide that passed over the chain of mountains that traverses the island!

Among pilots it is customary to reckon the time of high water by the point of the compass the moon bears on at that time, allowing three quarters of an hour for each point: thus in places where it is high water at noon, the tide is said to flow north and south, or twelve o'clock; if she bears south-east at high water, it is said to flow south-east and north-west, or nine o'clock; and if she bears south-west it is said to flow south-west and north-east, or three o'clock; and so on for every point of the moon's bearing. But this method of reckoning the time of high water by the compass is liable to great errors. Thus, for instance, it is said, the tide flows east and west, or six hours at Plymouth; but if it was thence understood that the moon is always east or west when it is high water there at full and change very dangerous consequences might result; for, when the moon has a high northern declination, it may happen that she will not bear due east till near eight o'clock in the morning at Plymouth, which will be about two hours after high water, and on the same day she will bear due west soon after four o'clock in the afternoon, or nearly two hours before high water. The best

rule would be to say it is high water so many hours after the moon nas passed the meridian. Currents are movements of the ocean produced by various causes, and may be divided into general and particular; the former, depending on fixed and general causes, always preserve the same direction and limits; while the latter, resulting from local and temporary ones, vary in both. Between the latitudes of 30°, in both hemispheres, a constant movement of the ocean is observed, which seems to convey its waters from east to west, or in a contrary direction to the rotation of the globe: by another movement the waters of the polar seas are conveyed towards the equator. The causes of these two general and constant currents are the heat of the sun and the rotation of the globe. See our article CURRENT.

The existence of contrary superior and inferior currents, supposed by Halley and denied by Buffon, is still doubtful. Those who admit these opposite currents assign as the possible causes the different densities of the waters at different depths, a great rapidity of movement towards the surface, and the cohesion of the molecules of fluids. In the Strait of Gibraltar, the Sound, and the channel of Constantinople, these contrary currents are asserted to exist. See GIBRALTAR.

When two opposite currents of equal force meet they form a spiral vortex, or whirlpool, of which the most celebrated are the Maelstrom, on the coast of Norway, and Euripus, in the Strait of Negropont. Charybdis, in the Strait of Messina, has also been described, both by the ancients and moderns, as a whirlpool, though it seems to be only a violent agitation of the waters at the surface by the meeting of the tides, and has no vortex. It was the phenomena of whirlpools that gave rise to the now exploded idea of abysses, which penetrating through vast masses of land formed subterranean communications between distant seas; such as between the sea of Norway and the Gulf of Bothnia by the Maelström, between the Persian Gulf and Caspian Sea, &c.

If we set out from 63° of N. lat., on the east side of the old continent, and follow its coasts to beyond the equator, we find them presenting a series of vast basins and gulfs penetrating into the continent, and enclosed within chains of islands and banks, separated by narrow and winding channels. On the western side of the same continent we observe nothing similar. From the north cape of Lapland to the Cape of Good Hope the coast presents a continuity unbroken, except by the mouths of rivers, and by the entrances of the Baltic and Mediterranean seas; the formation of which are accounted for on different principles; and with respect to the British islands, which form a mere point in this space, their separation from the continent was probably produced by a sudden convulsion of the earth, rather than by the gradual action of the waters.

In following the eastern coasts of the new continent, from the latitude of 60° N. to within 10° of the equator, ruptures of the land and chains of islands and banks are presented to us similar to those we have observed on the east coasts of our own continent: thus Davis's Strait

and Hudson's Bay answer to the Sea of Tartary, the Gulf of St. Lawrence to the Sea of Japan, while the West India islands enclose the Gulf of Mexico and Caribbean Sea, as the Lieu-Kieu islands and the Malay Archipelago do the seas of Corea, of China, and of Sunda. No such appearances are observed on the western coast of America, which, with the exception of the gulf of California, from Cape Horn to Cape Prince of Wales, presents a rainpart of abrupt cliffs, immediately washed by the Grand Ocean. This broken state of the eastern coasts of the continents is ascribed by Buffon and other writers to the constant movement of the ocean from east to west; and this opinion is strengthened by the observation, that the coast of Asia is more broken than that of America, and that it ought to be so from the difference in the masses of waters of the two oceans, the Grand Ocean being at least three times broader than the Atlantic, consequently allowing them the same lengths, and supposing their depths in proportion to their different breadths, the former has nine times the solid contents of the latter, and therefore must, their velocities being equal, act with nine times the power on the body of land that opposes it. Moreover the greatest effect ought to be produced, near the equator, because it is there that the masses of the waters and the velocity of their constant movements are greatest; and accordingly it is between the tropics that the eastern coasts of both continents are most torn, and the greatest effect is manifested precisely where the breadth of the ocean is greatest, that is, in the Atlantic, between the parallels of 7° and 29° N. and in the Grand Ocean, on the entire space between the tropics; for it is at the equator itself that this ocean has the greatest breadth. The only difficulty in adopting the opinion of Buffon is, that the lapse of several centuries has scarcely rendered sensible the action of the sea on these coasts; but to this objection it may be replied that, the sea having washed away the lighter or less cohesive matter that primitively united the now detached lands to the continents, there remain only substances of so hard a nature that the efforts of the ocean against them are almost powerless. It is also to be observed, in support of this hypothesis, that the coast of South America within the tropic, which is exposed to the continual action of the equatorial winds and currents, is lined by a chain of rocky banks which protect it from their violence, while the opposite coast of Africa is bordered by a beach of fine sand.

But, though the changes produced by the sea on the coasts since the period of history are insignificant in a great general point of view, they are nevertheless sufficient to demand particular notice. The sea forms new lands by the sand, shells, marine plants, and mud of rivers which it deposits on the margins of the shores, and also by retiring from some parts, in consequence of having encroached on others. The coasts of the Mediterranean have both gained and lost, so that it is probable the one compensates the other. The port of Alexandria, on the coast of Egypt, grows every day shoaler; and Damietta, the walls of which were washed by the sea in the

thirteenth century, is at present considerably inland. These alterations, however, seem to be produced rather by the sand blown from the desert, than by matters thrown up by the sea; and to compensate them Lake Menzaleh appears to have been formed, either by an irruption of the sea, or by a branch of the Nile, whose channel has been neglected. Some of the ancients supposed that a great gulf once penetrated into Egypt as far as Thebes, by which the isle of Pharos was separated a day's navigation from the Terra Firma; but the existence of this gulf is unsupported by any historical or natural proof, and, with the few trifling alterations we have noticed, the coast of Egypt at this day answers to the earliest description by Herodotus.

On the coast of Syria the island of Tyre has been united to the continent, and on the west coast of Asia Minor the inhabitants of Miletus and Ephesus have several times been obliged to change the sites of their towns to follow the sea which receded from them. The valley through which the Meander now serpentizes was evidently once a gulf, its soil consisting of the depositions of the sea and river. On the west coast of Greece many islets have been joined to the main, while the celebrated peninsula of Leucadia has become an island. In the Adriatic the sea has encroached on the coasts of Dalmatia and Istria, and retired from those of Italy, so that the greater part of ancient Lombardy has been formed by the combined depositions of the sea and the Po. Ravenna, which formerly had an excellent port, and was surrounded by lakes and salt marshes, is now three miles from the sea, in the midst of gardens and meadows; Aquileia was also formerly on the margin of the sea, and finally the lagoons of Venice are daily filling up.

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From the Mediterranean coasts of France and Spain the sea has retired in several places and gained on none; thus much new land has been formed at the mouths of the Rhone; and Aigues Mortes, which in the thirteenth century was a sea-port, is now five miles inland. Miquelon and Psalmodi were islands in 815, though now two leagues from the sea, and the vineyards of Agde were covered by the sea only a century past. The coasts of Valencia and Catalonia have also considerably gained from the sea, and the port of Barcelona is fast filling up. this series of facts it would appear that the coasts of the Mediterranean have gained more than they have lost; but it must be considered that, with the exception of Egypt, we are unacquainted with the relative ancient and modern state of the coast of Africa: and besides a number of celebrated ports preserve the same depths as in the time of the ancients, such are Marseilles, Genoa, Syracuse, Navarin, &c.; hence there seems to be no sufficient reason to suppose a diminution of the waters of the Mediterranean.

The waters of the Atlantic by their depositions have formed the bases of the landes, or sandy downs that border the coast of France from Bayonne to Bordeaux, and by which several ancient bays have been filled up. The marshes of la Vendée have also been left by the sea. the English Channel the bay on the coast of France, in which is Mount St. Michael, grow

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shoaler, while near Dol the sea is again encroaching on the lands from which it had formerly retired. The sea has encroached on some of the coasts of England and retreated from others; thus the Goodwin Sands are generally thought to have been formed by an irruption of the sea in 1100, while in later times several of the best harbours between the Thames and Beachy-head have been filled up. On the coast of Lincoln the sea seems to have alternately formed new lande and submerged them.

On the coast of Holland the most remarkable alterations and vicissitudes have been produced by the sea. In the earliest history of this country it is described as composed of immense marshes, alternately inundated by the sea and rivers; the first threw up sand on the shores, and the latter deposited mud on their banks, and thus elevated spots were formed, round which human industry raised embankments, thought capable of resisting the utmost fury of the ocean. The country, however, still remained intersected by lakes and rivers, which silently undermined these new formed lands, and the sea in high tides rushing up the rivers produced terrible inundations. Before 1250 the Zuyder Zee was a lake of middling size, which communicated with the British Sea by the river Vlie; in that year an irruption of the sea gave it its present form and extent. Until 1300 the gulf of the Dollart was a rich plain; and, in 1421, a united inundation of the sea and rivers formed the Biesboch, by submerging seventy-two villages with 100,000 souls.

The coasts of Holstein and Sleswick have alternately lost and gained by the action of the sea. In 1240 the territory of North Friezeland had an extent of fifteen leagues east and west, and consisted of rich pastures and corn lands. An irruption of the sea destroyed this smiling appearance, swallowing up a considerable portion of the territory, and, detaching the rest from the continent, formed the island of Nordstrand, which at the commencement of the fifteenth century had still an extent of six to eight leagues, and was celebrated for its fertility and population. The sea still continuing to encroach on it, dikes were thrown up to arrest its progress, and the inhabitants, to the number of 8000, thought themselves in perfect safety. In 1643, however, the sea penetrated by more than forty breaches in the dikes, swept away 1000 habitations and 6000 persons, and of the island left but two fragments above water and several submerged banks; even these small remains have been attacked by the merciless element, the dikes being considerably damaged in 1791 and 1793. On the other hand, the sea deposits on the shores of the mainland of these provinces a fat mud, which forms new lards, that by their great fertility in a few years repay the considerable expense of embanking them. All the west and north coasts of Jutland appear to owe their formation to the sea, which by throwing up sand has made a connected coast of what was formerly probably chain of islands. It is at least certain, that several gulfs, which, according to the annals of the north, afforded retreats to the Scandinavian pirates, have been thus filled up. The alterations

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produced by the action of the waters on the coasts of the Baltic since the memory of history seem to compensate each other, and to be principally produced by currents.

On the eastern shores of the old continent we know that the sea retires from the east shore of the bay of Bengal and encroaches on the west, where it has washed away almost the whole of the ancient city of Mahabilipur, some of the ruins of which, called by the English the seven pagodas, are still to be seen between Madras and Sadras. The sea has also encroached on the Malabar coast, where a part of the old city of Calicut is now under water. The whole coasts of the Red Sea, according to Niehbur, indicate the retreat of the waters. On a great part of the coasts of Cochin-China and Tonquin are observed proofs of the recent retreat of the sea, while on some parts it has encroached, and obliged the inhabitants to remove their villages inland.

The changes operated on the coasts of the new continent are little known to us; the new lands formed at the mouths of the Mississippi and Oronoka owe their origin to the alluvion of these rivers. On the western coast the sea is said to gain on the land, and captain Vancouver observed appearances which indicated a considerable encroachment on the north-west coast.

We are now brought to the consideration of a question which has long divided the most celebrated naturalists:- Are the waters of the ocean diminishing?' Celsius, a learned Swede, towards the middle of the last century, revived the opinion held by some of the ancients, respecting the gradual desiccation of the ocean, and published a memoir in which he supported the diminution of the waters from the first existence of our continents, and the continuance of that diminution, which, from observations made on the coasts of the Baltic, he estimated at fifty-four inches in every 100 years. This hypothesis was favored by many learned naturalists of the north, among whom Linnæus stood foremost, and on it founded a theory of the earth; but it at the same time met with great opposition, and even the states of Sweden took a part in the dispute, the clergy anathematising it as contrary to holy writ, and the citizens uniting with them, while the nobles and peasants more wisely remained neutral.

The arguments in favor of the diminution are founded on the shells and other remains of sea animals met with on the highest mountains, the filling up of ancient ports and straits, and the anchors and remains of vessels found far from the sea, and at considerable heights above its present level.

The opposers reply that the two first of these facts ought to be referred to two very different periods; for that the remains of sea animals belong to an age anterior to the formation of the present continents, and consequently prior to the existence of the present ocean, while the changes produced by the sea on the coasts have generally been effected since the memory of history. With respect to the anchors and vessels they explain the fact by supposing them to be the monuments of inland navigations on lakes and rivers which no longer exist, or of the universal deluge, pre

vious to which there existed other continents inhabited by men, and which disappeared in the grand catastrophe that brought our present continents out of the waters; hence, say they, it is presumable that the antediluvians navigated over our present lands, and threw out their anchors on our mountains, which were then shoals covered by the ocean. It is further observed by the opposer sof the diminution, that the experience of twenty centuries, handed down to us by historical record, proves that the ocean with respect to its total volume is perfectly stationary, the diminution by evaporation being exactly compensated by the supplies it receives from rains, rivers, &c. To this it may be replied, that the loss of the sea by evaporation, being compensated only by these supplies, whatever tends to decrease them must necessarily produce an absolute diminution of the ocean; but, as the mountains decrease in height by the action of the elements, the vapors they arrest, and the condensation of which produces rains and rivers, must also be diminished. But what then, it may be asked, becomes of the water thus withdrawn from the ocean? Is it absorbed by volcanoes or by vegetables, or does it rise in vapors to other spheres? These are questions which it is not given to science to resolve, nor are they the only insolvable ones on the subject of the immense ocean, the probable cradle of the universe, and of which it may possibly be also the grave.

A variety of plants are nourished by the ocean to which are given the general denomination of fuoi, and which are vulgarly known by the names of sea and rock weeds. Some species adhere to the rocks close to the bottom, while others rise from these rocks to the surface, over which they spread for considerable spaces; such is the fucus giganteus observed by captain Cook in the Great Southern Ocean, near Terra del Fuego and Kerguelen's Land, which rising from a rocky bottom, twenty-four fathoms deep, spreads over the sea in such a manner that its whole length is estimated at sixty fathoms, though the thickness is not greater than that of a man's thumb. In the North Atlantic is a space extending between the latitudes of 20° and 40°, and between the longitudes of 25° and 40° W., which is at all seasons covered with a species of weed (fucus natans) of a beautiful green color, whence the early Dutch navigators gave to this space of the ocean the name of Kroos Zee, Sea of Duckweed, and the Portuguese that of Mer de Sargaço. It was formerly generally believed that this weed was torn from the Florida Reefs, and conveyed by the gulf stream to where it is met with, and hence it received the name of gulf weed: an accurate examination has however shown this idea to be unfounded, and leads to the inference that it propagates in the sea, and vegetates floating. Navigators have been led from isolated facts to consider the meeting patches of rock-weed at sea as a sign of the vicinity of land; this however is by no means a certain indication, such weeds being frequently met with at some hundreds of leagues from any land, and out of soundings.

It seems probable that the different regions of the ocean have their peculiar animals confined to

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them by the temperature of the waters and their own species of food To commence with the lowest class, or zoophites, they are in great measure so little known, and so difficult to class, that we cannot say if each region exclusively possesses such or such a species. The varieties of corals, called madrepores, millepores, tubepores, &c., seem to exist in a state of vitality only in the tropical regions, and there we find them forming what may be justly named coral seas; such are the South Pacific Ocean, the region between the coast of Malabar and the island of Madagascar and the West Indian seas. various species of mollusca also appear to be confined to their respective regions, those of the torrid zone not being met with beyond the lowest limits of the temperate. The abysses of the ocean contain monsters of this class, of which we have still but a very imperfect knowledge. Polypuses and hydras, several yards long, have been observed in the English Channel and in the strait of Messina; nor is it unlikely that the famous sea snake of the Norwegian seas is an immense animal of the same class. There is also reason to suppose that the depths of the sea are inhabited by testaceous molluscæ, which are never seen on the shores; such appear to be the cornes d'ammon and other species found in a petrified state in the bowels of the earth, and of which none have been hitherto met with on the shores, or fished up from the bottom of the sea.

The want of industry in fishes renders it probable also that each region has its peculiar species, which never quit it: thus the various species of the cod (gadus), the herring, and the mackarel, are only found in the northern seas; while the dolphins, albicores, bonetas, &c., are confined to the tropics, or a little beyond them, where they wage an unmerciful war against the flying fish, which is also confined to the torrid region. Cetaceous and oceanic amphibious animals being under the necessity of frequently respiring the atmospheric air, it is probable that their various species are confined to certain climates; thus the black whale of the Northern Frozen Ocean seldom appears in the temperate zone; while the spermaceti whale, which affords ambergris, is scarcely ever seen out of the tropical seas. The seals of the southern seas also differ from those of the north; and the great sea lion of Kamtschatka from that of Greenland.

Each grand maritime division of the globe has also its particular species of birds; the albatross and several of the petrel tribe, the penguin, &c., are only met with in the temperate or frozen zones, while the man of war and tropic bird never quit the equatorial regions.

A few words as to the dominion of the ocean may be excused from us as Englishmen.

England has long claimed the empire of the Channel, and even of all the three seas, encompassing the British isles. It is in consequence of this claim that children born in these seas are declared natural Englishmen, as much as if born on English ground. The justice of this pretension is strenuously argued between Grotius and Selden.

The open sea in its own nature cannot be exclusively possessed, as no one is able to settle