Sea. Why it does not increase. 5 Theories of philosophers on this subject. 6 that the sea land. It may seem surprising that the sea, since it is continually receiving such an immense supply of water, does not visibly increase, and at last cover the whole earth. But our surprise will cease, if we consider that the rivers themselves are supplied from the sea, and that they do nothing more than carry back those waters which the ocean is continually lavishing on the earth. Dr Halley has demonstrated that the vapours raised from the sea and transported on land are sufficient to maintain all the rivers in the world. The simplicity of this great process is astonishing: the sea not only connects distant countries, and renders it easy to transport the commodities of one nation to another, but its waters rising in the air descend in showers, to fertilize the earth and nourish the vegetable kingdom, and collecting into rivers flow onwards, bringing fertility and wealth and commerce along with them, and again return to the sea to repeat the same round. Sea.. the sea. The Po, therefore, and the rivers which it receives, wa- who maintain the opposite theory, that the land is gra- The knowledge of this process of nature might, one would think, have convinced philosophers that the proportion between sea and land continued always nearly the same. Philosophers however have formed different theories about this as well as most other subjects, maintaining on the one hand that the sea is continually encroaching on the land, and on the other that the land is constantly gaining on the sea. Both sides have supported their theories by arguments, demonstrations, and incontrovertible facts! Arguments The height of the mountains, say the philosophers of those who support the encroachments of the sea, is continualwho afirm ly diminishing; exposed to the violence of every storm, isencroach- the hardest rocks must at last give way and tumble ing on the down. The rivers are continually sweeping along with them particles of earth which they deposit in the bot tom of the sea. Both the depth of the ocean then and the height of the dry land must be always decreasing; the waters therefore must, unless a part of them were annihilated, spread over a greater extent of surface in proportion as these causes operate. This reasoning, convincing as it is, might be confirmed by a great number of facts: it will be sufficient however to mention one or two. In the reign of Augustus the isle of Wight made a part of Britain, so that the English crossed over to it at low water with cart loads of tin; yet that island is at present separated from Britain by a channel half a mile wide. The Godwin sands on the eastern shore of England were formerly the fertile estate of Earl Godwin. Nor are the encroachments of the sea confined to Britain. In the bay of Baiæ near Naples there are remains of houses and streets still visible below the present level of the sea. The sea, therefore, is making continued encroachments upon the land; and the time will come, say they, when the waters will again cover the surface of the earth. Such are the arguments of those philosophers who maintain the continual encroachments of the sea. Those VOL. XIX. Part I. 8 examined. Such are the arguments advanced in support of both These artheories; for it is needless to mention a notion of Lin-guments næus that the whole earth was formerly covered with water except a single mountain. When fairly weigl ed, they amount to nothing more than this, that the sea has encroached upon the land in some places, and retired in others; a conclusion which we are very willing to allow. What was advanced by those philosophers who maintain that the sea is continually encroaching on the land, about the depth of the sea constantly diminishing, must remain a mere assertion, till they prove by experiments, either that this is really the case, or that nature has no way of restoring those particles of earth I earth which are washed down by the rivers. Nor have they any good reason to affirm that the height of the mountains is decreasing. Can a single uncontrovertible instance be produced of this? Are the Alps or the Apennines, or Taurus, or Caucasus, less lofty now than they were a thousand years ago? We mean not to deny that the rain actually washes down particles of earth from the mountains, nor to affirm that the hardest rocks are able to resist continual storms, nor that many mountains have suffered, and continue to suffer daily, from a thousand accidents. But the effects produced by all these causes are so trifling as to be altogether imperceptible (A). Nature has assiduously guarded against such accidents; she has formed the mountains of the most durable materials; and where they are covered with earth, she has bound it together by a thick and firm matting of grass, and thus secured it from the rains; and should accident deprive it of this covering, she takes care immediately to supply the defect. Even should the earth be swept away together with its covering, nature has still such resources left as frequently restore things to their former state. Many kinds of moss, one would be tempted to think, have been created for this very purpose they take root and flourish almost upon the bare rock, and furnish as they decay a sufficient bed for several of the hardy Alpine plants. These perish in their turn, and others succeed them. The roots of the plants bind fast the earth as it accumulates, more plants spring up and spread wider, till by degrees the whole surface is covered with a firm coat of grass. As the sea covers so great a portion of the globe, we should, no doubt, by exploring its bottom, discover a vast number of interesting particulars. Unfortunately in the greater part of the ocean this has hitherto been impossible. Part, however, has been examined; and the discoveries which this examination has produced may enable us to form some idea at least of the whole. The bottom of the sea, as might have been conjectured indeed before hand, bears a great resemblance to the surface of the dry land, being, like it, full of plains, rocks, caverns and mountains; some of which are abrupt and almost perpendicular, while others rise with a gentle deelivity, and sometimes tower above the water and form islands. Neither do the materials differ which compose the bottom of the sea and the basis of the dry land. If we dig to a considerable depth in any part of the earth, we uniformly meet with rock; the same thing holds in the sea. The strata, too, are of the same kind, disposed in the same manner, and form indeed but one whole. The same kind of mineral and bituminous substances are also found interspersed with these strata; and it is to them probably that the sea is indebted for its bitter taste. Över these natural and original strata an artificial bed has pretty generally been formed, composed of different materials in different places. It consists frequently of muddy tartareous substances firmly cemented Sea. together, sometimes of shells or coral reduced to powder, and near the mouths of rivers it is generally composed of fine sand or gravel. The bottom of the sea resembles the land likewise in another particular: many fresh springs and even rivers rise out of it, which, displacing the salt water, render the lower part of the sea wherever they abound quite fresh. An instance of this kind occurs near Goa on the western coast of Indostan*, and another + in the Mediterranean sea not far* Boyle de from Marseilles. These facts occasioned a notion, which Fundo Malater experiments have exploded, that the sea beyond a certain depth was always fresh. ris. + Marsigli Histoire Physique de Substances of a very beautiful appearance are frequently brought up by the sounding line from the bot-la Mer, tom of the sea. The plummet is hollowed below, and partie 1. this cavity filled with tallow, to which some of the substances adhere which form the bed of the ocean. These are generally sand, gravel, or mud; but they are sometimes of the brightest scarlet, vermilion, purple, and yellow; and sometimes, though less frequently, they are blue, green, or white. These colours are owing to a kind of jelly which envelopes the substances, and vanish entirely as soon as this jelly dries. At times, however, they assume the appearance of tartareous crusts, and are then so permanent, that they can be received into white wax melted and poured round them, and perhaps by proper care might be converted into valuable paints. ΙΟ Sea-water is really, as any one may convince himself Colour of by pouring it into a glass, as clear and transparent as the sea. river water. The various appearances therefore which it assumes are owing to accidental causes, and not to any change in the water itself. The depth, or the materials which compose the bottom of the sea, occasions it to assume different colours in different places. The Arabian gulf, for instance, is said to be red from the colour of the sands which form its bed. The appearance of the sea is affected too by the winds and the sun, while the clouds that pass over it communicate all their various and fleeting colours. When the sun shines it is green; when the sun gleams through a fog it is yellow; near the north pole it appears black; while in the torrid zone its colour is often brown. Sometimes the sea assumes a luminous appearance. See LIGHT, Vol. XII. page 2. : II The sea contains the greatest quantity of salt in the Saltness of torrid zone, where otherwise from the excessive heat the sea it would be in danger of putrefaction as we advance northward this quantity diminishes, till at the pole it nearly vanishes altogether. Under the line Lucas found that the sea contained a seventh part of solid contents, consisting chiefly of sea-salt. At Harwich he found it yieldedth of sea-salt. At Carlscroon in Sweden it contains th part (B), and on the coast of Greenland a great deal less. This deficiency of salt near the poles probably contributes a good deal towards the prodigi ous (A) M. Geusanne pretends that the Pyrenean mountains become an inch lower every ten years. But even according to his own calculation, it would require a million of years to level these mountains with the plain, though they continued to decrease at the same rate; and philosophers tell us that this rate is constantly diminishing! (B) This gradual diminution of saltness from the equator to the pole is not, however, without particular exceptions. The Mediterranean sea contains of sea-salt, which is less than the German sca contains. Sea. Sea. a very violent tempest, rise two feet higher. It is affirmed by Pliny, and several other ancient writers, that oil calms the waves of the sea; and that divers were ac- 14 stilled by customed to carry some of it for that purpose in their oil. mouths. This account was always considered by the moderns as a fable, and treated with such contempt, that they did not even deign to put it to the test of experiment, till Dr Franklin accidentally discovered its truth. Happening in 1757 to be in the middle of a large fleet, he observed that the water round one or two vessels was quite calm and smooth, while everywhere else it was very much agitated by the winds. He ap. plied to the captain for an explanation of this phenomenon, who replied, that the cooks, he supposed, bad thrown their greasy water out at the scupper-holes, and by that means oiled the sides of the vessels in question. This answer did not satisfy the Doctor at first; but recollecting what Pliny had said on the subject, he resolved at least to make the experiment. He did so accordingly in 1762, and found that oil actually calmed the waves of the sea. He repeated the experiment upon a pond at Clapham: the oil spread itself with great rapidity upon the surface, but did not produce the desired effect, because, having been thrown in upon the side opposite to the wind, it was immediately driven to the edge of the water. But upon throwing in a like quantity upon the other side of the lake, it calmed in an instant several yards of surface and gradually spreading, rendered all that part of the lake, to the extent of at least half an acre, as smooth as glass. The curious effect produced by this liquid may be accounted for by the repulsion which exists between oil and water, and between oil and air, which prevents all immediate contact, all rubbing of the one upon the other. ous quantities of ice which are met with in these seas; for salt water requires a much greater degree of cold to freeze it than fresh water. It was this circumstance, probably, together with its constant motion, which induced the ancients to believe that the sea never froze. Even among the moderns it has been a generally received opinion, that sea-ice is originally formed in rivers. Buffon has made the great quantities of ice with which the South sea abounds an argument for the existence of a continent near the Antarctic pole. But it is now well known that great quantities of ice are formed at a distance from land. Sea-ice is of two kinds; field ice, which extends along the shore, and is only two or three feet thick; and mountain ice, which abounds in the middle of the ocean. The size of these mountains is sometimes prodigious. The sea-ice is always fresh, and has been often of great use to navigators. The weight of sea-water is to that of river-water as 73 to 70; that is, a cubic foot of sea-water weighs 73lb. while the same quantity of river-water weighs only 70lb.; but this proportion varies in different places. It is worthy of our attention, too, that the water at the surface of the sea contains less salt than near the bottom; the difference indeed is inconsiderable, but still it is something. The Compte de Marsigli found the same quantity of water, when taken from the bottom of the Mediterranean, to weigh one ounce three pennyweights 51 grains; whereas from the surface it weighed only one ounce three pennyweights 49 grains. He repeated the experiment frequently with nearly the same result. TemperaThe sea, with respect to temperature, may be divided ture of the into two regions: The first begins at the surface of the water, and descends as far as the influence of the sun's rays; the second reaches from thence to the bottom of the sea. In summer the lower region is considerably Boyle de colder than the upper: but it is probable that during Temperie Regionum winter the very reverse takes place; at least the Compte Submarina- de Marsigli found it so repeatedly in the Mediterranean. This naturally results from the situation of the water near the bottom of the sea. Uninfluenced by the changes in the atmosphere, it retains always nearly the same degree of temperature: and this is considerably above congelation; for the lower region of the sea, at least in the temperate parts of the world, was never known to Phil Trans. freeze. Captain Ellis let down a sea-gage (see GAGE) for 1751, in latitude 25° 12′ north, and longitude 25° 13' west, to take the degrees of temperature and saltness of the sea at different depths. It descended 5346 feet, which is a mile and eleven fathoms. He found the sea salter and colder in proportion to its depth till the gage had descended 3900 feet, when the mercury in the thermometer came up at 53; but the water never grew colder, though he let down the gage 2446 feet lower. At the surface the thermometer stood at 84. 12 A 215 13 The sea motions. Motion cecasioned by the wind, The sea has three kinds of motion: 1. The first is Las three that undulation which is occasioned by the wind. This motion is entirely confined to the surface; the bottom even during the most violent storms remains perfectly calm. Mr Boyle bas remarked, from the testimony of several divers, that the sea is affected by the winds only to the depth of six feet. It would follow from this, that the height of the waves above the surface does not exceed six feet; and that this holds in the Mediterranean at least, we are informed by the Compte de Marsigli, though he also sometimes observed them, during wards the west rents. Cur IS 2. The second kind of motion is that continual ten- Motion todency which the whole water in the sea has towards the west. It is greater near the equator than about the poles; and indeed cannot be said to take place at all in the northern hemisphere beyond the tropic. It begins on the west side of America, where it is moderate : hence that part of the ocean has been called Pacific. As the waters advance westward their motion is accelerated; so that, after having traversed the globe, they strike with great violence on the eastern shore of America. Being stopped by that continent, they turn northward, and run with considerable impetuosity in the gulf of Mexico; from thence they proceed along the coast of North America, till they come to the south side of the great bank at Newfoundland, when they turn off, and run down through the Western Isles. This current is called the Gulf Stream. It was first accurately described by Dr Franklin, who remarked also, that the water in it having been originally heated in the torid zone, cools so gradually in its passage northward, that even the latitude might be found in any part of the stream by means of a thermometer.➖➖ This motion of the sea westward has never been explained: it seems to have some connection with the trade-winds and the diurnal revolution of the earth on its axis. 16 the tide. 3. The third and most remarkable motion of the sea Motion ocis the tide, which is a regular swell of the ocean once casioned by every 12 hours, owing, as Newton has demonstrated, to the attraction of the moon. In the middle of the sea the tide seldom rises higher than one or two feet, I 2 but Sca. SEA-Crow, Mire-Crow, or Pewit. See LARUS, ORNITHOLOGY Index. but on the coast it frequently reaches the height of 45 feet, and in some places even more. The tide generally rises higher in the evening than in the morning on the coast of Britain this holds in winter, but in summer the morning tides are highest. In some seas it is said that there are no tides. This cannot be owing to their being surrounded by land, because there is a tide in the lakes of North America. For an explanation of these and other phenomena we refer to the article TIDE. SEA-Air, that part of the atmosphere which is above the sea. Sea-air has been found salubrious and remarkably beneficial in some distempers. This may be owing to its containing a greater portion of oxigenous gas or vital air, and being less impregnated with noxious vapours than the land. Dr Ingenhousz made several experiments to ascertain the salubrity of sea-air. By mixing equal measures of common air and nitrous air, he found that at Gravesend, they occupied about 1.04, or one measure and of a measure: whereas on sea, about three miles from the mouth of the Thames, two measures of air (one of common and one of nitrous air) occupied from 0.91 to 0.94. He attempted a similar experiment on the middle of the channel between the English coast and Ostend; but the motion of the ship rendered it impracticable. He found that in rainy and windy weather the sea-air contained a smaller quantity of vital air than when the weather was calm. On the sea-shore at Ostend it occupied from 94% to 97; at Bruges he found it at 105; and at Antwerp 109. Dr Ingenhousz thus conPhil. Trans. cludes his paper: 1780, P. 354. It appears, from these experiments, that the air at sea and close to it is in general purer and fitter for animal life than the air on the land, though it seems to be subject to the same inconstancy in its degree of purity with that of the land; so that we may now with more confidence send our patients, labouring under consump tive disorders, to the sea, or at least to places situated close to the sea, which have no marshes in their neighbourhood. It seems also probable, that the air will be found in general much purer far from the land than near the shore, the former being never subject to be mixed with land air. Dr Damman, an eminent physician and professor royal of midwifery at Ghent, told Dr Ingenhousz, that when he was formerly a practitioner at Ostend, during seven years, he found the people there remarkably healthy; that nothing was rarer there than to see a patient labouring under a consumption or asthma, a malignant, putrid, or spotted fever; that the disease to which they are the most subject, is a regular intermittent fever in autumn, when sudden transitions from hot to cold weather happen. People are in general very healthy at Gibraltar, though there are very few trees near that place; which Dr Ingenhousz thinks is owing to the purity of the air arising from the neighbourhood of the sea. Most small islands are very healthy. SEA, Dead. See ASPHALTITES. SEA-Devil. See LOPHIUS, ICHTHYOLOGY Index. SEA-Dragon, a monster of a very singular nature. In the Gentleman's Magazine for the year 1749, we have the account of a sea-dragon which was said to be taken between Orford and Southwould, on the coast of Suffolk, and afterwards carried round the country as a curiosty by the fishermen who caught it. "Its head and tail (says the writer) resemble those of an alligator; it has two large fins, which serve it both to swim and to fly; and though they were so dried that I could not extend them, yet they appear, by the folds, to be shaped like those which painters have given to dragons and other winged monsters that serve as supporters to coats of arms. Its body is covered with impenetrable scales; its legs have two joints, and its feet are hoofed like those of an ass: it has five rows of very white and sharp teeth in each jaw, and is in length about fourfeet, though it was longer when alive, it having shrunk as it became dry. "It was caught in a net with mackerel; and being dragged on shore, was knocked down with a stretcher or boat-hook. The net being opened, it suddenly sprung up, and flew above 50 yards: the man who first seized it had several of his fingers bitten off; and the wound mortifying, he died. It afterwards fastened on the man's arm who shows it, and lacerated it so much, that the muscles are shrunk, and the hand and fingers distorted; the wound is not yet healed, and is thought to be incurable. It is said by some to have been described by naturalists under the name of the Seadragon." We must add to the account now given of the monster called a sca-dragon, that we think it extremely probable that the animal was nothing more than a distorted or overgrown individual of some of the well known species of fish. SEA-Gage. See Sea-GAGE, SEA-Hare. See LAPLYSIA, HELMINTHOLOGY In dex. SEA-Horse, in Ichthyology, the English name of the Hippocampus. See SYNGNATHUS, ICHTHYOLOGY Index. SEA-Lemon. See DORIS, HELMINTHOLOGY Index. SEA-Lion. See PHOCA, MAMMALIA Index. SEA-Mall, or SEA-Mew. See LARUS, ORNITHOLOGY Index. SEA-Man. See MERMAID. SEA-Marks. The erection of beacons, light-houses,, and sea-marks, is a branch of the royal PREROGATIVE. By 8 Eliz. 13. the corporation of the Trinity-house are empowered to set up any beacons or sea-marks wherever they shall think them necessary; and if the owner of the land or any other person shall destroy them, or take down any steeple, tree, or other known sea-mark, he shall forfeit 100l. sterling; or, in case of inability to pay it, he shall be ipso fucto outlawed. SEA-Needle, Gar-fish. See Esox, ICHTHYOLOGY Sea Sea scales; the skin was uneven and wrinkled, and the lower part was formed like a snake. The body of this monster is said to be as thick as a hogshead; his skin is variegated like a tortoise shell; and his excrement, which floats upon the surface of the water, is corrosive." Notwithstanding the belief of Guthrie, and the testimony which he produces, we cannot help doubting of the existence of the sea-serpent. Its bulk is said to be so disproportionate to all the known animals of our globe, that it requires more than ordinary evidence to render it credible but the evidence which is offered is so very feeble and unsatisfactory, that no man of sound judgment would think it sufficient to establish the truth. of an extraordinary fact. divided these into three classes. 1. The first class, according to their arrangement, contained the algae, the fuci, the sea-mosses, or confervas, and the different species of sponges. 2. The second contained substances of a hard texture, like stone or horn, which seem to have been of the same nature with what we call zoophyta, with this difference, that we refer sponges to this class and not to the first. The third class is the same with our lithphyta, comprehending corals, madrepora, &c. It is now well known that the genera belonging to the second and third of these classes, and even some referred to the first, are not vegetables, but animals, or the productions of animals. See CORALLINA, MADREPORA, SPONGIA, Sea-plants, then, properly speaking, belong to the class of cryptogamia, and the order of algæ; and, according to Bomare, are all comprehended under the genus of fucus. We may also add several species of the ulva and conferva and the sargazo. The fuci and marine ulvæ are immersed in the sea, are sessile, and without root. The marine confervæ are either sessile or floating. The sargazo grows beyond soundings. As some species of the fucus, when dried and preserved, are extremely beautiful, the curious, and especially those who prosecute the study of botany, must be anxious to know the best method of preserving them, without destroying their colour and beauty. The following method is recommended by M. Mauduyt. Take Ia sheet of paper, or rather of pasteboard, and cover it with varnish on both sides; and having rowed in a boat to the rock where the fucus abounds, plunge your varnished paper into the water, and, detaching the fucus, receive it upon the paper. Agitate the paper gently in the water, that the plants may be properly spread over it; and lift them up together softly out of the water: then fix down with pins the strong stalks, that they may not be displaced, and leave the plant lying upon the varnished paper to dry in the open air. When it is fully dry, the different parts will retain their position, and the plant may be preserved within the leaves of a book. To free it from the slime and salt which adhere to it, wash it gently in fresh water, after being removed from the rock on which it grew. SEA-Serpent, a monstrous creature, said to inhabit the northern seas about Greenland and the coasts of Norway. The following marvellous account of this monster is given by Guthrie. "In 1756, one of them was shot by a master of a ship: its head resembled that of a horse; the mouth was large and black, as were the eyes, a white mane hanging from its neck: it floated on the surface of the water, and held its head at least two feet out of the sea between the head and neck were seven or eight folds, which were very thick; and the length of this snake was more than 100 yards, some say fathoms. They have a remarkable aversion to the smell of castor; for which reason, ship, boat, and bark masters provide themselves with quantities of that drug, to prevent being overset, the serpent's olfactory nerves being remarkably exquisite. The particularities related of this animal would be incredible, were they not attested upon oath. Egede, a very reputable author, says, that on the 6th day of July 1734, a large and frightful sea-monster raised itself so high out of the water, that its head reached above the main-top-mast of the ship; that it had a long sharp snout, broad paws, and spouted water like swhale; that the body seemed to be covered with Attempts have lately been made to revive the opi nion of the existence of mermaids and sea-serpents. An individual of the latter it is supposed, was some time ago thrown on shore in Orkney. Part of the skeleton is said to be in the museum of the University of Ediuburgh, and another part is in the possession of Mr Home of London, who thinks that it may have belonged to an individual of some of the whale tribe, perhaps a monster of that tribe; but according to others it is to be considered as constituting a distinct genus. We cannot. avoid observing, that this point must remain unsettled till other species of this new genus have been discovered, or at least till an entire individual have been described by an experienced naturalist. SEA-Sickness, a disorder incident to most persons on their first going to sea, occasioned by the agitation of the vessel. This disorder has not been much treated of, although it is very irksome and distressing to the patient during its continuance. It has, however, been found beneficial in asthmatic and pulmonary complaints, and the instances in which it has proved fatal, are ex tremely rare. The sea-sickness appears to be a spasmodic affection of the stomach, occasioned by the alternate pressure and recess of its contents against its lower internal surface, according as the rise and fall of the ship oppose the action of gravity. The seas in which the attacks of this disorder are accompanied with the greatest violence, are those where the waves have an uninterrupted freedom of action; and of consequence bays, gulfs and channels, may be navigated with less inconvenience, as the waves, meeting with more frequent resistance, the vessel does not experience that gentle uniform vacillation which induces sickness, and renders the head giddy. A person feels less inconvenience from the disorder in a small vessel on the wide ocean, on which the slightest motion of the waves makes a strong impression. He is also less exposed to it in a very large vessel deeply laden, as the waves, in this case, scarcely affect the vessel. It is in ships of an ordinary size, and which carry but a light cargo, that the passenger suffers most from the sea-sickness. The sooner it takes place after embarkation, the continuance of it becomes the more probable. It does not always cease immediately on landing, but in some cases continues for a considerable time. Many methods of preventing, or at least of mitigating this disorder, have been recommended, of which the most efficacious appear to be the following. 1. Not to go on board immediately after eating, and not to eat, when on board, any large quantity at a time. Sea. |