chapter 89, he speaks of other islands formed in the like manner; but

on this subject we have more clear and certain facts of later date.

On the 23d of May 1707, at the sun's rising, there was seen, at some little distance from the island of Therasia, or Santorini, something like a floating rock in the sea; some persons, to satisfy their curiosity, went towards it, and found it a shoal which had issued from the bottom of the sea; it increased under their feet, and they brought with them the pumice-stone and oysters, which the rock still had attached to its surface. There was a slight earthquake at Santorini two days before this shoal appeared: it increased considerably till the 14th of June, it was then half a mile round, and from 20 to 30 feet high; the earth was white, and a little argilaceous; after that the sea became more and more troubled; vapours arose which infected the island Santorini; and on the 16th of July several rocks were seen to issue at one time from the bottom of the sea, and unite into one solid body. This was accompanied with a dismal noise, which continued upwards of two months. Flames issued from the new island, which kept increasing in circumference and height, and the violent explosions frequently threw large stones to more than seven miles distance. The island Santorini itself was deemed among the ancients as a modern production, and in 726, 1427, and 1573, it increased in size, and small islands were formed near it.[AD] The same volcano, which in the time of Seneca formed the island of Santorini, in that of Pliny produced Hiera or Volcanella, and in our time the shoal above-mentioned.

[AD] See the Hist. of the Acad. 1708, page 23, &c.

On the 10th of October 1720, near the island Tercera, a very considerable fire arose out of the sea; some mariners were sent by the order of the governor to take a view of it, and who having come near it, perceived, on the 19th of the same month, an island which appeared only as fire and smoke, with a prodigious quantity of ashes thrown to a distance, as if caused by the force of a volcano, with a report like that of thunder. An earthquake happened at the same time, which was felt in the circumjacent places, and great quantities of pumice-stones were observed floating on the sea around the new island; pumice-stones indeed have sometimes been seen swimming in the midst of the high seas.[AE]

[AE] See Phil. Trans. Abridg. vol. VI. part ii. page 254.

The historian of the academy, anno 1721, says on this event, that after an earthquake in the island of St. Michael, one of the Azores, there appeared between this island and Tercera a torrent of fire, which gave birth to two new shoals; and the next year he gave the following detail:

"M. de l'Isle has informed the academy of many particulars concerning the new island among the Azores, which he received in a letter from M. de Montagnac, consul at Lisbon.

"Being in a vessel, which was moored the 18th of September 1721, before the fortress of the town of St. Michael, M. de Montagnac learnt the following account from the pilot:

"On the 7th of December 1720, at night, there was a great earthquake in Tercera and St. Michael, which are about 18 leagues apart, and between which a new island sprung up: it was remarked at the same time, that the point of the island of Peak, 30 leagues distant, and which before threw out fire, was sunk and emitted none; but the new island kept throwing out a constant thick smoke, and which I plainly perceived from the vessel I was in. The pilot assured us that he had gone round the island, rowing as near it as he conceived to be safe. On the south side he threw a line of sixty fathoms without finding any bottom; on the west side the water was greatly changed, appearing white, blue and green, and which extended two thirds of a league, where it seemed ready to boil. On the north-west, the part from which the smoke issued, he found, at 15 fathoms, a bottom of thick sand; he threw a stone in the sea, and where it fell the water seemed to boil and bubble with impetuosity; the bottom was so hot that it twice melted some grease fastened at the end of the sounding line. The pilot observed also on that side that smoke issued from a small lake bounded by a sand bank. This island is almost round and high enough to be perceived at the distance of seven or eight leagues in clear weather.

"It has since been learnt from a letter of M. Adrian, French consul in the island of St. Michael, dated March 1722, that the new island had considerably diminished, that it was almost level with the water, and there was every appearance it would not last long."

It is therefore by these, and a great number of other facts of a similar nature, very evident that inflammable matters are enclosed in the earth under the bottom of the sea, and that they sometimes cause violent explosions. The places where this happens might be termed marine volcanos, and which differ from common volcanos only by the shortness of the duration of their effects; for the fire having opened itself a passage, the water must penetrate therein and extinguish it. The elevation of new islands must consequently leave a void space which the water would shortly occupy, and this new earth, which is only composed of matters thrown out by the marine volcano, must resemble that of Monti di Cinere and other eminencies which terrestrial volcanos have formed. Now as the water rushes in, during the violence of the explosion, and fills the vacancies that it occasions, that is clearly the reason why these marine volcanos act less frequently than other volcanos, although the causes of both are the same.

These subterraneous, or sub-marine fires are doubtless the cause of all those ebullitions of the sea, which sailors have remarked in various places, and as well as of the water-spouts we have before mentioned; they likewise produce storms and earthquakes, which are not less felt on the sea than on the land. Islands formed by these sub-marine volcanos, are generally composed of pumice-stone, and calcined rocks, and produce, like those of the land, violent earthquakes and commotions.

Fires have been often observed on the surface of the water. Pliny tells us that the lake Thrasimenia appeared inflamed over all its surface. Agricola relates that when a stone was thrown into the lake Denstat, in Thuringia, it appeared, as it descended in the water, like a train of fire.

In short, the quantities of pumice-stones which travellers affirm are met with in many parts of the ocean, and the Mediterranean, prove there are volcanos at the bottom of the sea, similar to those we are acquainted with, and which differ not in the least from them, neither by the matters they cast out, nor by the violence of the explosion, but solely by the rarity and shortness of the duration of their effects. From hence we may fairly infer that the bottom of the sea in every respect resembles the surface of the earth.

We shall find many connections between land and sea volcanos; both are found at the summit of mountains. The islands of Azores and those of the Archipelago are only peaks of mountains, some of which rise above the water, and others are underneath. By the account of the new islands among the Azores we see that the part from whence the smoke issued was only 15 fathoms under water, which, compared with the common depth of the ocean, proves that even this part is the summit of a mountain; as much may be said of the new island near Santorini, which could not be any great depth, since oysters were found attached to the rocks which rose above the water. It appears also that marine-volcanos have, like those of the land, subterraneous communications, since the summit of the volcano of St. George, in the island Peak, sunk at the time the new island among the Azores arose. It must also be observed, that these new islands never appear but near the old ones, and that we have no example of new islands in the high seas; we must therefore look on them as a continuation of the adjacent islands; and when ancient islands have volcanos, it is not astonishing that the ground adjacent should contain matters proper to form them, and which inflame, either by fermentation alone, or by the action of subterraneous winds.

Islands produced by the action of fire and earthquakes are but few, but there are an infinite number produced by the mud, sand, and earth, which the rivers or the sea transport into different places. At the mouth of rivers earth and sand accumulate in such quantities as to form islands of a moderate extent. The sea, retiring from certain coasts, leaves the highest parts of the bottom naked, which forms so many new islands; so likewise the sea, by extending itself on certain shores, covers the lowest parts, and leaves the highest, which appear as so many islands; and thus it is we may account for there being so few islands in the open sea, and so many bordering on the continents.

Water and fire, whose natures appear so different and so contrary, produce many similar effects, independent of the particular productions of these two elements, some of which bear so striking a resemblance as to be mistaken for each other, as glass and crystal, natural and fictitious antimony, &c. There are in nature an infinity of great effects produced by them, which are scarcely to be distinguished. Water, as has been observed, has produced mountains and formed most islands, while others owe their origin to fire. There are likewise caverns, clefts, holes, gulphs, &c. some of which owe their origin to subterraneous fires, and others to waters.

Caverns are met with in mountains, and few or none in plains: there are many in the Archipelago, and in other islands, because they are in general only the tops of mountains: caverns are formed like precipices, by the sinking of rocks, or large abysses, by the action of the fire; for to make a cavern form a precipice or abyss, we need only suppose the tops of adjacent rocks had fallen together and formed an arch, which must often happen when their bottoms are shaken and dislodged by time or earthquakes. Caverns may be produced by the same causes which produce holes, the shaking and sinking of the earth, and which causes are the explosion of volcanos, the action of subterraneous vapours and earthquakes; for they occasion caverns, holes, and hollows of every kind by their shocks and commotion.

St. Patrick's cavern in Ireland is not so considerable as it is famous; it is the same with the Dog's Grotto in Italy; and that which throws out fire, in the mountain of Beniguazeval in the kingdom of Fez. In the county of Derby, in England, there is a very considerable cavern, much larger than the famous cavern of Beauman, near the Black Forest, in Brunswick. I have been informed by a person as respectable for his merit as his name, Lord Morton, that this large cavern, called the Devil's Hole, at first presents a very considerable opening, larger than any church door; that through this opening a rivulet flows; that in advancing the vault of the cavern becomes so low, that persons who are desirous of continuing their road are obliged to lie flat in a boat and be pushed through this narrow passage, where the water almost touches the roof; but after having passed this part of the vault, the arch rises to a considerable height, and continues so for some distance, when it sinks again so low as to touch the water, and where the cavern ends. The source of the rivulet which issues from it sometimes encreases considerably: it transports and heaps up a great quantity of sand in one part of the cavern, which is formed like a kind of alley, whose direction is different from that of the principal cavern.

In Carniola, near Potpechio, is a very spacious cavern, in which is a large lake. Near Adelsperg is a cavern, in which we may travel two German miles, and where very deep precipices are to be met with.[AF] There are also large caverns and beautiful grottos under the mountains of Mendip, in Wales; mines of lead are found near these caverns, and whole oaks at fifteen fathoms deep. In the county of Gloucester there is a very large cavern, called Pen Park-hole, at the bottom of which there is thirty fathoms water, and mines of lead are also found.

[AF] See Act. erud. Lips. anno. 1689, page 558.

The Devil's Hole, and other caverns, from whence issue large springs or rivulets, have plainly therefore been formed by the water, and their origin cannot be considered as the effects either of earthquakes or volcanos.

One of the most remarkable and largest caverns known is that of Antiparos, a description of which is given by M. de Tournefort. We enter a rustic cavern about thirty feet broad, divided by some natural pillars; between two of which, on the right, the ground is on a gentle slope, and then becomes more steep to the bottom, about twenty feet; this is the passage to the grotto, or internal cavern, which is very dark, and cannot be entered without stooping and the assistance of torches. We then descend an horrible precipice by the assistance of a rope, fastened at the entrance, into another still more frightful, the borders of which are very slippery, with dark abysses on the left. By the assistance of a ladder we pass a perpendicular rock, and then continue to go through places somewhat less dangerous: but when we think ourselves in a safe path, we are stopped short by a tremendous obstruction, and are obliged to crawl on our hands and knees, or slide on our back, the length of a large rock, and then descend by a ladder. When we are at the bottom of the ladder, we still have to stumble over pieces of rocks for some time, and then we reach the celebrated grotto. It is computed to be three hundred fathoms deep from the surface of the earth, appears to be forty fathoms high by fifty broad. It is filled with large beautiful stalactites of various forms, as well from the roof of the vault as on the bottom.[AG]

[AG] See the Voyage de Levant, page 188, and also Remarks in a Journey from Paris to Constantinople, which contains a copious description of this astonishing phenomenon.

In part of Greece called Livadia (the Achaia of the ancients) there is a large cavern in a mountain which was formerly famous for the oracles of Trophonius; it is between the lake Livadia and the adjacent sea; at the nearest part it is about forty miles; and there are forty subterraneous passages across the rock, through which the waters flow.[AH]

[AH] See Gordon's Geography, 1733, page 179.

In all countries which produce sulphur, volcanos, and earthquakes, there are caverns. The ground of most of the Archipelago islands is cavernous; the islands of the Indian ocean, principally that of the Malacca's, appear to be supported by vaults and cavities. The land Azores, the Canaries, the islands of Cape de Verd, and in general almost every small island, is in many parts hollow and cavernous; because these islands are, as we have observed, only points of mountains where considerable ebullitions are made, either by the action of volcanos, of the water, of frosts, or other injuries of the weather. In the Cordeliers, where there are many volcanos, and where earthquakes are frequent, there are also a great number of caverns.

The famous labyrinth of the island of Candia, is not the work of nature alone; M. de Tournefort assures us that it has evidently been greatly enlarged by men; and most likely this cavern is not the only one which has been augmented by human labour. Every day mines and quarries are digging, and when abandoned for a long time, it is not easy to discover whether they have been the productions of nature, or formed by the hands of men. We know of quarries of considerable extent; for example that of Maestricht, where it is said 50,000 men may conceal themselves, and which is supported by upwards of 1000 pillars, twenty-four feet high, and the earth and rock above is more than twenty-five fathoms thick.[AI]

[AI] See Abridg. Phil. Trans. vol. XI. page 461.

The salt mines in Poland form still greater excavations than the above. There are generally vast quarries near large towns. But we cannot proceed farther in particulars; besides, the labour of man, however great, will ever hold but a small place in the history of nature.

Volcanos and waters which produce caverns internally, form also external clefts, precipices, and abysses. At Cajeta, in Italy, there is a mountain which had formerly been separated by an earthquake, in a manner so as to appear as if the division was made by the hands of men. We have already spoken of the divisions in the island of Machian, of the abyss of mount Azarat, of the gap in the Cordeliers, and that of Thermopyle, &c. To these may be added, the gap in the mountain of Troglodytes, in Arabia, which nature only sketched out, and which Victor Amadeus caused to be finished. Water as well as subterraneous fires produce considerable sinking of the earth, fall of rocks, and overthrow mountains, of which we can give many examples.

"In the month of June 1714, a part of the mountain of Diableret, in Valois, fell suddenly, and some time after, the sky being serene, it appeared to have taken a conical figure. Fifty-three huts belonging to the boors were destroyed, together with several people and a great many cattle, covering a square league with the ruins it occasioned. A profound darkness was caused by the dust; the heaps of stones thrown together were above thirty perches in height, stopped the currents of the water, and formed new and very deep lakes. In all this there was not the least trace of bitumen, sulphur, lime, nor consequently any subterraneous fire, and apparently the base of this great rock was perished and reduced to dust.[AJ]"

[AJ] Histoire de l'Academie des Sciences, anno 1715, p. 4.

We have a remarkable example of these sinkings near Folkstone, in the county of Kent; the hills in its environs sunk gradually by an insensible motion, and without any earthquake. These hills internally are rocks and chalk, and by their sinking they have thrown into the sea rocks and earth which were adjacent to it. The relation of this fact may be seen in the Abridgment of the Philosophical Transactions, vol. VI. page 250.

In 1618, the town of Pleurs, in Valtelino, was buried under the rocks, at the bottom of which it was situated. In 1678, there was a great inundation in Gascony, caused by the sinking of some pieces of one of the Pyrennees, which forced the water to spring forth that was contained in the subterraneous caverns of those mountains. In 1680, there happened a still greater in Ireland, by the sinking of a mountain into caverns filled with water. We may easily conceive the cause of these effects. It is well known there are subterraneous waters in an infinity of places; these waters carry off by degrees the sand and earth over which they pass, consequently may in time destroy the bed of earth on which the mountain rests; and this bed of earth being more deficient on one side than on the other, the mountain of course must be overthrown; but if this base is worn every where alike, the mountain will sink and not be overthrown.

Having remarked on the sinkings and other changes on the earth, occasioned by what may be called the accidents of nature, we ought not to pass over the perpendicular clefts found throughout the strata of the earth: these clefts are perceptible not only in rocks and quarries of marble and stone, but also in clays and earths of every kind, which have never been removed. I call them perpendicular clefts, because, like the horizontal strata, they are oblique, by accident only. Woodward and Ray speak of these clefts, but in a confused manner; and they do not term them perpendicular clefts, because they thought they might be indifferently oblique or perpendicular. No author has explained the origin of them, although it is apparent that they have been produced, as we observed in a preceding article, by the dryness of the matters which compose horizontal beds. In whatsoever manner this drying happens, it must have produced perpendicular clefts; for the matters which compose the strata could not have diminished in size without splitting in a perpendicular direction to these strata. I comprehend under this name of perpendicular clefts all natural separations of rocks, as well as those which may have been occasioned by any convulsive accident. When some considerable motion happens to masses of rocks, these clefts are sometimes found obliquely placed, but this is because the mass is of itself oblique, and with a little attention it is always easy to discover that these clefts are in general perpendicular to the horizontal strata, particularly in quarries of marble, lime, stones, and all large chains of rocks.

Mountains internally are principally composed of stone and rocks in parallel beds: between the horizontal beds small strata of a softer matter than stone is found, and the perpendicular clefts are filled with sand, crystals, minerals, metals, &c. these last matters are of a more modern formation than the horizontal beds in which we find sea-shells. The rains have by degrees loosened the sand and the earth on the upper parts of mountains, and have left the stone and rocks entirely naked, in which we readily distinguish the horizontal strata and perpendicular clefts: in plains, on the contrary, the rain-water and flood having brought a considerable quantity of earth, sand, gravel, and other such matters, have formed a bed of tufa, soft and dissoluble stone, sand, gravel, and earth, mixed with vegetables. These beds contain no marine shells, or at least only fragments, which have been detached from mountains, with gravel and earth. We must carefully distinguish these new beds from the old, where almost always a great number of entire shells are found placed in their natural situation.

If we observe the order and internal disposition of matters in a mountain, composed, for example, of common stones, or calcinable lapidific matters, we generally find a bed of gravel under the vegetable earth, of the nature and colour of the stone which predominates in this ground; and under the gravel we meet with stone. When the mountain is divided by some trench, or deep cut, we easily distinguish all the strata of which it is composed. Each horizontal stratum is separated by a kind of joint, which is likewise horizontal, and their thickness generally increase in proportion as they lower from the summit of the mountain, and are all divided vertically by perpendicular clefts. In common, the first stratum which is met with under the gravel, and even the second, are only thinner than the beds which form the base of the mountain, but are so divided by perpendicular clefts, that pieces of any length are not to be seen: they perfectly resemble the cracks of ground which is very dry, but go not very far, gradually disappearing in proportion as they descend, and towards the bottom there are no great number but where they divide the strata in a more regular manner. These beds of stone are often many leagues in extent, without any interruption; we almost always meet with the same kind of stone in the opposite mountains, whether divided by a small neck or a valley; and the beds of stone disappear only in places where the mountain sinks and becomes level with some large plain. Sometimes, between the first stratum of vegetable earth and that of gravel, marl is found, which communicates its colour and other qualities to the other two: then the perpendicular clefts of the quarries which are beneath are filled with this marl, where it acquires an hardness in appearance equal to that of stone, but by exposing it to the air it crumbles, softens and becomes ductile.

In most quarries the beds of stone formed on the summit of a mountain are soft, and those near the base are hard; the first is commonly white, of so fine a grain as scarcely to be perceived; it becomes more grained and harder in proportion as it descends, and the lowest stone is not only harder than that of the upper, but it is also closer, more compact and heavier its grain is fine and glossy, and often brittle, and breaks as clear as flint.

The interior part of a mountain is therefore composed of different beds of stone, the upper of which are of soft stone and the lower of hard, and much broader at the bottom than at the top; which indeed almost necessarily follows, for, as they become so much the harder as they descend, it may be fairly supposed that the currents and other motions of the water which have hollowed the vallies and given a shape to the turnings of a mountain, will have laterally worked on the matters of which the mountain is composed, and have worn them away in proportion as they were hard or soft. Now the upper strata being the softest, it will naturally have suffered the greatest diminution. This is one of the causes to which the inclination of mountains may be attributed, and this inclination will be still less steep in proportion as the earth and gravel have been washed away by the rain; and for these reasons it is, that hills and mountains composed of calcinable matters, have an inclination much less than those composed of live rock and flint in large masses; the last in general are of considerable heights and nearly perpendicular, because, in these masses of vitrifiable matters, the upper beds, as well as the lower, are of great hardness, and have alike resisted the action of the waters.

When on the top of a hill, whose summit is flat, and of a pretty large extent, we meet with hard stone directly under the stratum of vegetable earth, we must remark, that what appears to be the summit, is not so in fact, but only the continuation of some higher hill, whose upper strata are soft stone and the lower hard; and it is the prolongation of these last strata that we meet with again at the top of the first hill.

On the summit of mountains which are not surmounted by any considerable height it is generally only soft stone, and we must dig very deep to meet with hard. Banks of marble are never found but between these beds of hard stone, which are diversely coloured by the metallic earths which the rain introduces into the strata by filtration, and possibly in every country where there is stone, marble would be found if dug for to a sufficient depth; _Quoto enim loco non suum marmor invenitur?_ says Pliny. In fact it is a much more common stone than it is thought to be, and differs from other stones only by the fineness of its grain, which renders it more compact and susceptible of a brilliant polish; and from which quality it took its denomination from the ancients.

The perpendicular fissures and joints of quarries are often filled and incrusted with concretions, which are sometimes as transparent as crystal, of a regular figure, sometimes opaque: the water flows through the perpendicular clefts, and penetrates even the compact texture of the stone; the stones which are porous, imbibe so great a quantity of water, that the frost splits and divides them. The rain by filtrating through the beds of marle, stone, and marble, load themselves with every matter they can take up or dissolve. These waters at first run along the perpendicular clefts, afterwards penetrate the beds of stone, and deposit between the horizontal joints, as well as in the perpendicular clefts, the matters they have brought with them, and form these different congelations according to the nature of the matters they have deposited; for example, when the water filters through marle, chalk, or soft stone, the matters which they deposit are a very pure and fine marle, which generally enters in the perpendicular cleft of the rocks under the form of a porous, soft substance, commonly very white and light, which naturalists have called _Lac lunac_, or _Medulla Saxi_.

When these streams of water, loaded with lapidific matter, flow through the horizontal joints of soft stone or chalk, this matter attaches itself to the surface of the blocks of stone, and forms white, scaly, light, and spongy crust; which some authors have named _Mineral Agaric_, from its resemblance to Vegetable Agaric: but if the strata are of common hard stone, proper to make good lime, the filter being then more close, the water will issue from it loaded with lapidific matter, more pure and homogeneous, and whose molecules uniting more intimately, will form nearly concretions of the hardness of stone, with a little transparency, and we shall find on the surfaces of the blocks in these quarries, stony incrustations variously disposed, which entirely fill up the horizontal joints.

In grottos and cavities of rocks, which may be looked upon as the basons of perpendicular clefts, the diverted direction of the streams of water, give different forms to the concretion which result therefrom. They in general have the appearance of a cone attached to the top of the vault, although they may more properly be considered as hollow and white cylinders, formed by a concentrical surface; these congelations sometimes descend, by drops, to the bottom, and form pillars, and a thousand other figures, as uncouth and ridiculous as the names which naturalists have been pleased to give them, such as, _Stalactites_, _Stelegmites_, _Osleocollae_, &c.

When these concretic juices issue immediately from marble and hard stone, the lapidific matter conveyed by the water being rather dissolved than loosened, the small constituent parts take a regular figure, and form columns, terminated by triangular points, which are transparent and consist of oblique strata; this is called Spar, or Spall. It is generally transparent and colourless, but when the stone or marble, from whence it issues, contains metallic parts, this spar is as hard as stone; it dissolves, like stone, by acid spirits, and calcines with the same heat; therefore we cannot doubt that it is real stone, and perfectly homogeneous. It might even be said that it is a pure and elementary stone, under its proper and specific form.

Most naturalists nevertheless look on this matter as a direct substance, existing independent of stone; it is the lapidific or crystalline juice which, according to them, not only binds the parts of common stone, but even those of flint. This juice, say they, constantly augments the density of stones by reiterated filtrations, and at length converts them into real flint. When this juice is fixed in spar, it continues to receive still more pure juices, which increase its density and hardness, so that this matter successively becomes glass, then crystal, and at last a perfect diamond.

But if this is true, why, in whole provinces, does this crystalline juice form only stone, and in others nothing but flint? Will they say, that the two soils are not of a like age, and that this juice has not had time to circulate and complete the end of its natural action? This is not probable. Besides, from whence does this juice proceed? If it produces stone and flints, what is it that produces this juice? It is apparent that it has no existence independent of these matters, which of themselves can give to the water that penetrates them a petrifying quality, always relative to their native and specific character; insomuch that when it filtrates through stones it forms spar, and when it issues from flints, crystal: and there are as many different kinds of this juice, as matters from which they proceed. Experience perfectly agrees with this idea. The waters which filtrate through stone quarries, generally form soft and calcinable matters like the stones themselves; on the contrary, those which spring from rock and flint form hard and vitrifiable congelations, which have all the other properties of flint, as the first have all those of stone; so the waters which have penetrated the beds of mineral and metallic substances produce pyrites, marcasites, and grains.

We have observed, that we might divide all matters into two great classes, vitrifiable and calcinable; clay and flint, marle and stone, may be looked upon as the two extremes of each of these classes, the intervals of which are filled with an almost infinite variety of the mixt matters that have always one or other of these substances for their basis.

The substances of the first class can never acquire the nature and properties of the other. Stone will always be as remote from the nature of flint, as potters earth is from marle; no known agent will ever be capable of making them quit the combinations peculiar to their nature: the country which produces stone and marble will remain to do so as certainly as those wherein there is only flint and granate will never have either stone or marble.

If we observe the order and distribution of matters in a hill composed of vitrifiable matters, we shall commonly find, under the first bed of vegetable earth, a bed of clay, a vitrifiable matter, analogous to flint, and which, as I have observed, is only a decomposed vitrifiable sand: this bed of argilaceous earth or sand answers to a bed of gravel met with in hills composed of calcinable matters: beneath which we meet with some beds of free-stone scarcely ever more than six inches thick, and divided into small pieces by perpendicular clefts. Under these beds are many others of the same matters, and also beds of vitrifiable sand, the free-stone becomes harder and its blocks encrease in size in proportion as we descend; underneath these we find a very hard matter which I have called live rock, or flint in large masses, which is so hard as to resist the file, graver, and acid spirits, more than vitrifiable sand, and even powdered glass, on which aqua-fortis seems to have some effect. If struck by another hard body it emits sparks, and exhales a very penetrating smell of sulphur. This massy flint, as I have termed it, is generally found with beds of clay, earth, coals, and vitrifiable sand, answers to the strata of hard stone and marbles, which serve as a base to hills composed of calcinable matters.

Water, by flowing through perpendicular clefts, and by penetrating the strata of these vitrifiable sands, clays, and earths, becomes impregnated with the fine and most homogeneous parts of these matters, and forms many different concretions, such as talcs, amianthus's, and various other substances produced by distillations through vitrifiable matters.

Flint, notwithstanding its hardness and density, has, like common marble and hard stone, its exudations, from whence stalactites of different kinds result, whose varieties of transparency, colours and configuration, are according to the nature of the flint which produces them, and the different metallic or heterogeneous matters which it contains. Rock crystal, all precious stones, white or coloured, and even diamonds, may be regarded as stalactites of this kind. Flints in small pieces, whose strata are generally concentric, are also stalactites, or parasitical stones; from flints of large dimensions, and most fine opaque stones, are only species of flint. Matters of a vitrifiable kind, as we have observed, do not produce so great a variety of concretions as those of the calcinable class; and these concretions, produced by flints, are almost all hard and precious stones; whereas those of the calcareous are only soft matters of no value.

Perpendicular clefts are found in rocks of flint, as well as in those of marble and hard stone; they are sometimes even larger there, which proves that matter is still dryer than stone: hills, whether of calcinable or vitrifiable matters, are supported by clay or vitrifiable sand; these are the common and general matters of which the globe is composed, and which I look on as the lightest parts, or the scoria of vitrified matter, with which it is internally filled; thus all mountains or plains have argilaceous earth or sand for their common foundation. For example, we see that in the pits at Amsterdam and Marly la Ville, vitrifiable sand was below every other stratum.

In most naked rocks it is observable that the sides of the perpendicular clefts, whether broad or narrow, correspond as exactly as those of a piece of slit wood. In the large quarries in Arabia, which are almost composed of granate, these perpendicular separations are very frequent; and although some are twenty or thirty yards wide, yet the ridges exactly correspond and leave a deep cavity between them.[AK] It is very common to find in perpendicular clefts shells broken in half, and each piece remaining fastened to the stone on the opposite side; which proves these shells were placed in the solid stratum, and before the cleft was made.[AL]

[AK] See Shaw's Travels, vol. II. p. 83.

[AL] See Woodward, page 198.

In some matters the perpendicular clefts are very wide, as in the quarries quoted by Shaw, which perhaps is the reason that they are not so frequently met with. In the quarries of flint and granate, the stone may be cut out in very large pieces without the smallest inconveniency, as the obelisks and pillars seen at Rome, which are upwards of sixty, eighty, an hundred, or one hundred and fifty feet long. It appears that these large pillars were raised from the quarry, and that they are to be had of any required thickness, as well as some species of free-stone. There are other matters where these perpendicular strata are very narrow; as in clay, marl, and chalk, and they are wider in marble and most hard stones. Some are imperceptible from being filled with a matter nearly similar to that of the stone itself, which nevertheless breaks off the continuity of the stone, and are what the workmen call hairs. I have often remarked that in marble and stone these hairs cross the blocks entirely, and differ from particular clefts only because their separation is not complete; these kind of clefts are filled with a transparent matter, which is a true spar. There are a great number of considerable clefts in the quarries of free-stone; this proceeds from these rocks often resting on less solid bases than marble or calcinable stones, which generally rest on clay. There are many places where free-stone is not to be met with in large masses; and in most quarries where it is good it lies in the form of cubes and parallel pipedes placed on each other in a very irregular manner, as in the hills of Fontainbleau, which at a distance appear to be the ruins of ancient buildings. This irregular disposition proceeds from the base of these hills being composed of sand, which permits the rocks to sink one on the other, particularly in places that formerly have been worked, which has occasioned a great number of clefts and intervals between the blocks; and we may observe, in every country where sand and free-stone abound, that there are many pieces of rock and large stones in the middle of plains and vallies; whereas in a country consisting chiefly of marble and hard stone, these scattered pieces, which have rolled from the hills and mountains, are very scarce, which proceeds only from the different solidity of the base on which these stones rest, and from the extent of the banks of marble and calcinable stone, which is more considerable than that of free-stone.

ARTICLE XVIII.

OF THE EFFECTS OF RAIN--OF MARSHES, SUBTERRANEOUS WOOD, AND WATER.

We have already observed that rains, and the currents of water they produce, continually detach from the heights of mountains sand, earth, gravel, &c. which they carry into plains, from whence the rivers convey a part of them into the sea. Plains therefore are successively filled, and by degrees raised higher, while mountains daily diminish. Joseph Blancanus relates various facts on this subject, which were of public notoriety in his time, and which prove that mountains have been considerably lowered. In the county of Derby, in England, the steeple of the village Craich was not visible in 1572 from a certain mountain, on account of the height of another which intervened; in eighty or an hundred years after, not only this steeple but every part of the church became visible from that very spot. Dr. Plot gives a similar example of a mountain between Sibbertoft and Ashby, in Northamptonshire. The rain waters not only carry with them the lightest parts of the mountains, as earth, gravel, and small stones, but even undermine and roll down large rocks, which considerably diminish the height of them. The mountains of Wales are very steep and high, and the fragments of these rocks are to be seen in large pieces at their feet, which as well as all fragments of rocks met with in vallies are the works of frosts and water. It is not mountains of sand and earth alone which the rain causes to sink, for they attack the hardest rocks, and carry with them large fragments into the vallies. In a valley in Nant-phrancon, in 1685, a part of a large rock, which rested on a narrow base, having been undermined by the waters, fell and broke in many pieces, the largest of which, in descending, tore up a considerable trench in the plain, and crossed a small river on the other side of which it stopped. It is to similar accidents we must attribute the origin of all the large stones found adjacent to the mountains. We must recollect, as before observed, that these large stones, scattered abroad, are more common in countries whose mountains are composed of sand and free-stone, than in those where their composition is marble and clay, because sand is a less solid foundation than clay.

To give an idea of the quantity of earth which the rain detaches from mountains and carries into the vallies, we shall quote a circumstance related by Dr. Plot; he says, in his Natural History of Staffordshire, that 18 feet deep in the earth a great number of pieces of money had been found, coined in the reign of Edward IV. two hundred years before his time, from which he concludes that the ground which is marshy has increased above a foot in eleven years, or an inch and a twelfth every year. A similar observation occurs with respect to some trees buried seventeen feet deep from the surface under which medals of Julius Cæsar were found; so the earth, brought from the top of mountains by the waters, considerably increases the elevation of the ground of plains.

This gravel, sand, and earth which the waters from mountains convey into plains form strata, which must not be confounded with the ancient and original strata of the globe. In the former class must be placed those of soft stone, gravel, and sand, the grains of which are washed and rounded; to these may be added, the strata of stones which are formed by a kind of incrustation; neither of which owe their origin to the motion or sediments of the sea. In these strata of soft and imperfect stones are found an infinity of vegetables, leaves, land and river shells, and small bones of terrestrial animals, but never sea shells, or other marine productions; which evidently proves, together with their want of solidity, that these strata are formed on the surface of the dry land; and that they are more modern than those of marble and other stones which contain shells, and were originally formed by the sea. All these modern stones appear to be hard and solid when they are first hewn out, but when, exposed to the weather, the air and rain presently dissolve them; their substance is so different from true stone, that when reduced into minute parts, to make sand of them, they are converted into a kind of earth or clay. Stalactites, and other stony concretions, which Tournefort took for vegetated marble, are not real stones, no more than those formed by the incrustations. We have already shewn that tufa is not of ancient formation, and must not be ranked in the class of stones. Tufa is an imperfect matter, differing from stone or earth, but which derives its origin from both by the means of rain water, as incrustations derive theirs from the deposit of the water of certain springs; therefore the strata of these matters are not ancient, nor been formed like the rest, by the sediments of the sea. The strata of turf are also modern, and have been produced by the successive assemblage of leaves and other perishable vegetables, and which are only preserved by a bitumous earth. Among these modern strata we never meet with any marine production; but, on the contrary, many vegetables, bones of land animals, and land and river shells, as may be seen in the meadows, near Ashby, in the county of Northampton, where a great number of snail shells, plants, herbs, and many river shells are found all in good preservation, some feet deep in the earth, but not a single marine shell among them.[AM]

[AM] See Philosophical Trans. Abridg. XI. page 271.

These new strata have been formed by the water which runs on the surface of the earth, often changing situation and dispersing on every side. Part of these waters penetrate internally and flow across the clefts of rocks and stones; and the reason we meet with no water in high lands, no more than on the tops of hills, is, because all elevations are generally composed of stone and rocks, therefore to find water we must dig through the rock till we come to clay, or firm earth, on which these rocks stand, and we shall not meet with any water until the stone is pierced to the bottom: therefore, when the thickness of the rock, which must be pierced, is very considerable, as in lofty mountains, where they are often upwards of 1000 feet in height, it is impossible to dig to their base, and of course to have any water. There are even large parts of land where there is not any water, as in Arabia Petrea, which is a desert where no rain ever falls, where the scorching sand covers the whole surface of the earth, where there is scarcely any vegetable soil, where the few plants found are sickly, and where springs and wells are so very scarce that only five are reckoned between Cairo and Mount Sinai, and the water of them is salt and bitter.

When the waters on the surface cannot find vent to flow they form marshes and fens. The most famous marshes in Europe are those of Muscovy, at the source of the Tanais; and those of Savolaxia and Enasak, in Finland; there are also some in Holland, Westphalia, and other low countries: in Asia are the marshes of the Euphrates, of Tartary, and of the Palus Meotis; nevertheless there are fewer of them in Asia and Africa than in Europe but America may be said to be but one continued marsh throughout all its plains, which is a greater proof of the modern date of the country, and of the small number of inhabitants than of their want of industry.

There are very great bogs in England, especially near the sea in Lincolnshire, which has lost much ground on one side and gained it on the other. In the ancient ground a great number of trees are found buried below the new ground, which has been deposited there by the water. The same also are met with in Scotland, particularly at the mouth of the river Ness. Near Bruges, in Flanders, in digging to the depth of 40 or 50 feet, a great quantity of trees were found, as close to each other as in a forest: the trunks, branches, and leaves, were so well preserved that the different kinds were easily distinguished. About 500 years since, the land where these trees were found was covered by the sea, and before that time there is no trace or tradition that it ever existed; nevertheless it must have been so, when these trees stood and vegetated; therefore this ground, which formerly was covered with wood, has been overwhelmed by the sea, the waters of which has, by degrees, deposited there between 40 and 50 feet of earth upon the former surface, and then retired. A number of subterraneous trees have been also found at Youle, in Yorkshire, 12 miles below the town, near the river Humber; there are some large enough for building; and it is said, perhaps improperly, that this wood is as durable as oak. The people cut them into long thin slips, and sell them in the neighbouring towns, where they are used for lighting of pipes. All these trees appear broken, and the trunks are separated from the roots as if they had suffered the violence of a hurricane, or an inundation. This wood greatly resembles willow, it has the same smell when burnt, and makes charcoal exactly like it.[AN] In the Isle of Man there is a marsh six miles long by three broad, it is called Curragh; subterraneous trees, like willows, are found there, and although they are 18 or 20 feet high, they are, nevertheless, firm on their roots.[AO] Trees are met with in almost every morass, bog, and marsh, in Somerset, Chester, Lancaster, and Stafford. There are some places where trees are found under the earth, which have been cut, sawed, squared, and worked by the labour of man; and even wedges and saws have likewise been found by them. Between Birmingham and Bromley, in the county of Lincoln, there are lofty hills of fine light sand, which the rain and wind sweep away, leaving uncovered the roots of large willow trees, on which the impression of the axe is exceedingly plain. These hills, without doubt, have been formed like downs, by the accumulation of sand, which the waters of the sea has brought there and deposited at different periods. A great number of these subterraneous trees are also found in the marshy lands of Holland, Friesland, and near Groningen, from whence the turfs which they burn are dug.

[AN] See Philosophical Transactions, No. 228.

[AO] See Ray's Discourses, page 232.

In the earth are found trees of almost every kind, as willows, oaks, firs, aspins, beach, yew, ash, hawthorn, &c. In the fens of Lincoln, along the river Ouse, and in Hatfield-Chace, in the county of York, these trees are as straight as we see them in a forest. The oaks are very hard and used in buildings; they are said to last a long time, but which I must doubt, as all trees that are dug out of the earth, at least all those which I have seen, whether oak or others, lose, in drying, all the solidity, which they appeared to have at first. The ash is tender, and soon crumbles to dust. There are many trees which have clearly been shaped and sawed by men, and the hatchets, sometimes found near them, resemble, in form, the knives anciently used in sacrifices. Besides trees, nuts, acorns, &c. are met with in great quantities, in many other fenny parts of England and Ireland, as well as the morasses of France, Sweden, Savoy, and Italy.[AP]

[AP] See Transactions Philosophical Abridg. Vol. IV, page 218, &c.

In the city of Modena, and four miles round, whatever part of the earth is dug, to the depth of sixty-three feet, and then bored five more with an auger, the water springs out with such great force, that the well is filled instantly; and this water continues always the same, neither diminishing nor increasing by rain nor draught. What is more remarkable in this ground, when we reach the depth of fourteen feet, we find the ruins of an ancient town, as paved streets, houses, different pieces of mosaic work, &c. After this is a very solid ground, which appears to have never been stirred; yet below it we find a moist earth mixed with vegetables; and at twenty-six feet entire trees, as filberds with nuts thereon, and a great quantity of branches and leaves. At twenty-eight feet is a stratum of chalk mixed with shells, and this bed is eleven feet in thickness; after this we again meet with vegetables; and so on alternatively to the depth of sixty-three, feet, when there is a bed of sand mixed with gravel and shells, like those formed on the coasts of the Italian sea; these successive beds are always met with in the same order, wheresoever it has been dug, and very often the auger meets with large trunks of trees, which the workmen bore through with much labour. Bones of animals, coals, flint, and pieces of iron are also found. Ramazzini, who relates these circumstances, thinks that the gulph of Venice formerly extended beyond Modena, and, that by the sediments of rivers in the course of time, assisted perhaps by the inundations of the sea, this ground has been formed.

I shall no longer dwell on the varieties in the formation of modern strata, it suffices to have shewn that they have been produced by no other causes than the running and stagnate waters, which are upon the surface of the earth, and that they are neither so hard nor solid as the ancient strata which are formed under the waters of the sea.

ARTICLE XIX.

OF THE CHANGES OF LAND INTO SEA AND SEA INTO LAND.

By what has been said in the Articles I, VII, VIII, and IX, it appears that great and general changes have happened to the terrestrial globe; and it is as certain, from what we have related in other articles, that the surface of the earth has undergone particular alterations. Although the order, or succession, of these particular alterations is not perfectly known, yet we are acquainted with the principal causes; we can even distinguish their different effects; and if we could collect all the facts, which Natural and Civil History furnishes on the subject of the revolutions which have happened to the surface of the earth, we do not doubt but that the Theory of the Earth which we have, laid down would receive additional support.

One of the principal causes of these alterations is the motion of the sea; a motion it has endured from the earliest ages; for since the sun, moon, earth, waters, air, &c. have existed from the time of the creation, the effects of the tides, the motion of the sea from east to west, as well as that of the winds and currents, must have been felt for the same space; and if even we should suppose the axis of the globe had formerly another inclination, and that the continents, as well as the sea, had another disposition, it does not destroy the motion of flux and reflux, nor alter the cause and effects of the winds: it is sufficient that the immense quantity of waters, which fill the vast space of the sea, is found in some part on the globe of the earth, for wherever they had been collected they would have still been subject to the same motions, and produced similar effects.

When it was once supposed that our continent was formerly the bottom of the sea, there was soon no doubt remaining thereon. The devastations of the sea, which are every where to be met with; the horizontal situation of the strata of the earth; and the correspondence of hills and mountains, appear as so many convincing proofs; for by examining the plains, vallies, and hills, we clearly perceive that the surface of the earth has been formed by the waters. It is equally evident, when we look into the interior parts of the earth, that those stones which contain sea-shells, have been formed by the sediments of the waters, since the shells are found filled with the same matter as that which surrounds them; and lastly, by reflecting on the corresponding angles of opposite hills, we cannot doubt that their directions are the works of the currents of the sea. It is true, that since the earth has been left uncovered, the original form of the surface has been constantly changing; the mountains have diminished in height; the plains have been elevated; the angles of hills become more obtuse; many matters washed away by floods, or rivers, have taken a round shape; beds of gravel, soft stone, &c. have been formed; but the essential matter is still remaining, the ancient form is still apparent, and I am persuaded that all the world may be convinced by their own inspection of what has been advanced on this subject; and whoever attends to the observations and proofs I have given, will not doubt, the earth was formerly covered by the waters of the sea, and that it is the currents of the sea which have given to the surface of the earth, the form we at present perceive.

The principal motion of the sea is, as we have already observed, from east to west. It also appears that the sea has gained above 500 leagues of ground on the eastern coasts of both the old and new continents; for the proofs of which we refer to those given in Article XI. and shall only add thereto, that all straits which join two seas, are directed from east to west; the straits of Magellan, Frobisher, of Hudson, of Ceylon, and those of the seas of Corea and Kamtschatka have all this direction, and appear to have been formed by the currents of the waters, which being impelled from east to west, opened these passages in the same direction, and in which they preserve a more considerable motion than in any other; for in these straits there are high and violent tides, whereas in those situated on the western coasts, like that of Gibraltar, Sund, &c. the motion of the tides is almost insensible.

The inequalities of the bottom of the sea change the direction of the water's motion; they have been successively produced by the sediments of the water, and by matters transported by the tides or other motions; for we do not consider the motion of the tides as the sole cause of those inequalities, but only as the principal and first, because it is the most constant and acts without interruption; the action of the winds is another cause; the action of which beginning at the surface, extends to considerable depths, as is plain from the matters that are loosened and thrown up by a storm from the bottom of the sea, and which never happens but in tempestuous weather.

We have already mentioned that between the tropics, and even some degrees beyond them, an east wind continually blows; this wind, which contributes to the general motion of the sea from east to west, is as ancient as the flux and reflux, since it depends on the rarefaction of the air, produced by the heat of the sun. Here then are two united causes of motion, the greatest of which is near the equator. The first, the tides which are more sensibly felt in southern latitudes: and the second, the east wind which blows continually in the same climates. These two causes have concurred, ever since the formation of the globe, to produce a motion in the waters from east to west, and to agitate them more in that part of the globe than in all the rest. It is for this reason that the greatest inequalities of the surface of the globe are found between the tropics. The part of Africa, comprehended between these two circles, is only a group of mountains whose different chains extend for the most part from east to west, as is evident from the direction of the great rivers of this part of the world; it is the same with those parts of Asia and America which are comprised between the tropics.

From the combination of the general motion of the sea from east to west, with the flux and reflux of the currents, and the winds, an infinite number of different effects has resulted, both on the bottom of the sea, and on the coasts. Varenius says, it is very probable that the gulphs and straits have been formed by the reiterated efforts of the ocean against the land; that the Mediterranean sea, the gulphs of Arabia, Bengal, and Cambay, have been formed by the eruption of the waters, as well as the straits between Sicily and Italy, between Ceylon and India, between Greece and Euboea, and that it is the same with respect to the straits of the Manillas, Magellan, &c. that one proof of these eruptions, and that the sea has forsaken different lands is, that but few islands are to be met with in the great seas, and never a great number of islands close to each other; that in the immense space occupied by the Pacific sea, not above two or three small islands are to be found towards the middle of it; that in the vast Atlantic ocean, between Africa and the Brazils, we only find the small islands of St. Helena and Ascension; but that all islands are near the great continents, as those of the Archipelago, near the continents of Europe and Asia, the Canaries, near Africa, all the islands of the Indian sea, near the eastern coast of Asia; the Antille islands, close to that of America, and that only the Azores lie at any great distance in the sea between Europe and America.

The inhabitants of Ceylon say, that their island was separated from the peninsula of India by an eruption of the ocean; and this popular tradition is very probable. It is also imagined the island of Sumatra has been separated from the continent, and the great number of shoals and sand banks are a strong proof of it. The Malabars assert, that the Maldivian islands formed a part of the continent of India, and in general it may be reasonably supposed that all the eastern islands have been divided from the continents by eruptions of the ocean.[AQ]

[AQ] See Varenius Geography, page 203, 217, and 220.

There is an appearance that formerly the island of Great Britain was part of the continent, and that England was joined to France; the similarity of the stones on the two coasts, and the narrowness of this strait seem plainly to indicate it. By supposing, says Dr. Wallis, "that England formerly communicated with France, by an isthmus between Dover and Calais, it must follow that the sea would be carried against both sides of it with great violence by the tides twice in every twenty-four hours, the German ocean, which is between England and Holland, striking of it on the eastern side, and that of France on the west, would be sufficient in time to wear away so narrow a neck of land, as we have supposed. The tides acting with great violence, not only against this isthmus but also against the coasts of France and England, must have washed away a great quantity of sand, earth, and clay, from every part against which the sea was forced: but, being stopt in its course, it would not deposite, as might be supposed, their sediments against this isthmus, but transported them into the great plain that now forms Romney Marsh, which is eight miles long by four broad; for whosoever has seen this plain, cannot doubt but that it was formerly covered with the sea, as it would be still overflowed by spring tides if it was not for the Dikes of Dimchurch."

The German sea must have acted in the same manner against this isthmus, and the coasts of England and Flanders would convey its sediments into Holland and Zealand, the ground of which, though formerly covered with water, is now forty feet above. On the coast of England, the German sea must have filled up that large valley, where the river Stour actually flows for more than 20 miles, beginning at Sandwich, passing Canterbury, Chatham, Chilham as far as Ashford. At this place the ground is much higher than it was formerly, since at Chatham the bones of an hippopotamus were found seventeen feet deep in the earth, together with anchors and marine shells.

It is very probable the sea may form new land, by bringing and depositing, at particular places, sand, earth, mud, &c. for in the island of Orkney, which is adjacent to Romney Marsh, there was a tract of low land continually in danger of being inundated by the river Rother; but in less than 60 years this ground has been considerably elevated by quantities of earth and mud being brought thither every tide, and the channel through which it enters, in less than fifty years has deepened so much as to admit of the reception of large vessels, whereas at that time it was a ford over which people might pass.

In this manner, the sand bank was formed which extends obliquely from the coast of Norfolk to that of Zealand. This bank forms that part where the tides of the German and French sea meet, since the isthmus has been broken, and where the earth and sand are deposited which are washed away from the coasts; nor is it by any means improbable but that in the course of time this bank may become an isthmus.[AR]

[AR] See Abridgment of Philosophical Transactions, vol. II. page 227.

There is a great appearance, says Ray, that the island of Great Britain was formerly joined to France, and formed part of that continent: but it is not known whether its separation was caused by an earthquake, an eruption of the ocean, or by the labour of man; but that this island formed part of the continent is evident, from the rocks and coasts of both being of the same nature, composed of the same matters, and exactly of the same height; the length of the rocks, along these coasts, are also nearly the same, about six miles on either side. The little breadth of the channel, which in this part is not more than twenty-four English miles, and its shallowness, comparatively with the neighbouring sea, is another reason to suppose that England has been divided from France by accident. We may add to these proofs, that there were formerly wolves and bears in this island; it is not to be presumed that they could swim over, nor that men transported such destructive animals; for in general we find the noxious animals of the continent in the adjacent islands, and never in those which are separated from them by a great distance; as the Spaniards remarked when they landed in America.[AS]

[AS] See Ray's Discourses, page 208.

In the reign of Henry I. King of England, a great inundation happened by an eruption of the sea in part of Flanders. In 1446 by a like eruption 10,000 persons were drowned in the territory of Dordrecht, and more than 100,000 round Dullart, Friezeland, and in Zealand. In these last two provinces upwards of 300 villages were overflowed; the tops of their towers and steeples are still to be seen rising out of the water.

From the coasts of France, England, Holland and Germany, the sea has retreated in many parts. Hubert Thomas relates, in his description of Liege, that the sea formerly surrounded the walls of the city of Tongres, which is now more than 35 leagues distant from it; this he proves by many eligible reasons, and, among others, he says; that in his time the iron rings, to which the ships were moored, were to be seen remaining in the walls. We may likewise look on as lands deserted by the sea, the fens of Lincoln in England, Provence in France, and which has also very considerably retreated from the mouth of the Rhone since the year 1665. In Italy a considerable tract of land has been gained at the mouth of the Arno; and Ravenna, formerly a sea-port, is no longer a maritime town. Holland appears to be an entire new country, where the surface of the earth is almost on a level with the sea, although the land is considerably elevated by the daily deposit of mud and earth from the Rhine, Maese, &c. for it was formerly computed that the ground of Holland was, in many places, 50 feet lower than the bottom of the sea.

It is asserted, that in the year 860, a furious tempest drove on the coast so great a quantity of sand that it shut up the mouth of the Rhine, near the Cat, and that this river inundated the whole country, tore up trees and houses, and, at last, emptied itself into the channel of the Maese. In 1421 another inundation separated the town of Dordrecht from the main land, submerged 72 villages, many castles, and drowned 100,000 souls, beside a great number of cattle. The dyke of Yssel was broken in 1638 by the ice brought down by the Rhine, which, having shut up the passage of the water, made an opening of some fathoms, and a great part of the province was overflowed before the breach could be repaired. In 1682 there was a similar inundation in the province of Zealand, which destroyed upwards of 30 villages, and drowned a considerable number of people and cattle, from their being surprised by the waters in the night. It was a fortunate circumstance for Holland that a south wind opposed the inroad of the sea, for it was so greatly swelled that the water was 18 feet higher than the highest ground of the province.[AT]

[AT] See the Historical Voyages of Europe, vol V. page 70.

At Hithe, in the county of Kent, the harbour has filled up in defiance of every expence and precaution that was made to prevent it. A surprising number of sea-shells, &c. are met with for several miles round, which were formerly heaped together, and which are now covered by earth, and are beautiful meadows. On the other side the sea has gained in several places, as for instance, the Goodwin Sands, which was an estate belonging to an Earl of that name, but at present is no more than sand covered by the waters of the sea: thus the sea in many places gains on the land and loses in others, according to the different situation of the coasts, and other circumstances.[AU]

[AU] See Abridg. Philosophical Trans. vol. IV. p. 234.

On Mount Stella, in Portugal, is a lake in which the wrecks of ships have been found, notwithstanding this mountain is more than 12 leagues from the sea.[AV] Sabinius, in his Commentaries on Ovid's Metamorphoses, says, that in the year 1460 a ship, with its anchors, was found in a mine of the Alps.

[AV] See Gordon's Geography, page 149.

It is not in Europe alone we meet with these vicissitudes of land into sea and sea into land; other parts of the world might furnish more remarkable, and in a greater number, if investigated with precision.

Calecut was formerly a famous city and the capital of a kingdom of that name; at present it is only a trifling town, meanly built, and but thinly inhabited: the sea, which for a century has gained greatly on this coast, has overflowed the greatest part of the old city, with a beautiful fortress of stone which was therein. Vessels at present moor on their ruins, and the port is filled with a great number of shoals, and on which ships are frequently wrecked.[AW]

[AW] See Letters Edifiantes Recueil 11. page 187.

The province of Jucatan, a peninsula in the gulph of Mexico, was formerly a part of the sea. This neck of ground extends 100 leagues in length, and is not more than 25 leagues at its greatest breadth. The air is perfectly hot and moist. Although there are neither rivulets nor rivers throughout so long a space, the water is every where so nigh the surface as to furnish plenty; and, by opening the earth, so great a number of shells are found as to leave no doubt that this great extent may be regarded as a place which formerly was part of the sea.

The inhabitants of Malabar pretend that formerly the Maldivian islands were attached to the Indian continent, and that the violence of the sea has divided them from it. The number of these islands is so great, and some of the channels, which separate them, are so narrow, that the boltsprits of vessels which pass them tear off the leaves of the trees on each side, and in some places an active man, by holding by the branch of a tree, may leap into another island.[AX]

[AX] See the Dutch Travels to the East-Indies, page 274.

The cocoa-trees, which are at the bottom of the sea, is a proof that the Maldivians were formerly part of the continent: cocoa-nuts are often detached from them and thrown on the shore by a storm.

It is imagined that the island of Ceylon was formerly united to the continent, and that the currents, which are extremely rapid in many parts of India, have divided that as well as Rammanakoil, and many other islands.[AY] However, it is certain that the island of Ceylon has lost 30 or 40 leagues of ground towards the north-west side, which the sea has gained.

[AY] See the Dutch Travels to the East-Indies, vol. II. p. 486.

It appears that the sea has recently forsaken a great part of the projecting lands and islands of America. We have just observed, that the ground of Jucatan is filled with shells. It is the same with the low lands of Martinico and the other Antille islands. The inhabitants have termed the earth below the surface lime, because they make their lime with these shells, considerable banks of which are found immediately under the vegetable earth. In the new voyages to the islands of America it is said, "lime, which is found in the land of Guadaloupe, when the earth is turned up, is of the same kind as that drawn out of the sea, the reason of which is difficult to be assigned. Might it not be possible, that all the extent of ground, which composes this island, was, in former times, only a high ground filled with lime-plants, which having grown and filled the void spaces that were occupied by the water, have raised up the ground, obliged the water to retire, and leave all the superficies dry? This conjecture, as extraordinary as at first it may appear, has, nevertheless, nothing impossible in it; and if the people who reside there were to dig in different parts of the earth they would discover what the real soil is, and by that means destroy or strengthen my conjecture."

There are some lands which are sometimes covered with water and sometimes uncovered, as many islands in Norway, Scotland, Maldivias, the gulph of Cambaya, &c. The Baltic has, by little and little, gained a great part of Pomerania, and covered and destroyed the famous port of Vineta. So likewise the sea of Norway has projected into the continent, and formed many small islands. The German sea has projected into Holland near Cat, insomuch that the ruins of an ancient citadel of the Romans, which was formerly on the coast, are now very far in the sea. The marshy grounds in the Isle of Ely, in England, and those in Provence, in France, are, on the contrary, as we have observed, land which the sea has abandoned. Downs have been formed by the sea-winds, which have thrown and accumulated earth, sand, shells, &c. on the shore. For example, on the western coast of France, Spain, and Africa, durable and violent westerly winds reign, which impel the waters towards the shore with great impetuosity, and on which coasts downs are very frequent. In the like manner the easterly winds, when they remain any long time, so strongly drive the waters from the coasts of Syria and Phoenicia that the chain of rocks, which are covered with water during the westerly winds, are left quite dry. Thus downs are never composed of stone, or marble, like mountains formed in the bottom of the sea, because they have not been long enough under the water. In our discourse on minerals we shall shew that the sea possesses the power of petrifaction, and that the stones formed in the earth are quite different from those formed in the sea.

When I had just finished my Theory of the Earth, which I composed in 1744, I received from Mons. Barrere, his dissertation on the origin of figured stones, and I was pleased to find myself of the same opinion with this able naturalist, on the subject of the formation of downs, and the time the water remained on the earth which we inhabit; he recounts many alterations which have happened to the sea coasts: "_Aiguis-mortes_, which is now more than a league and a half from the sea, was a port in the time of St. Louis: Psalmodi was an island in 815, and at present it is inland two leagues from the sea. It is the same with respect to Maguelone. The greatest part of the vineyards of Agde, was forty years ago covered by the sea: and in Spain the sea has considerably retreated within a short space of time from Blancs, Badalona, the mouth of the river Vobregat, Cape Tortosa, along the coasts of Valentia, &c.

"The sea may form hills and mountains in many different manners; first, by the transportations of earth, sand, and shells, from one place to another; secondly, by depositing sediments, consisting of small particles detached from the coasts and bottom, and which it might have transported from a considerable distance; and lastly, by sand, mud, and other articles, which the sea winds often drive against coasts, downs and hills may be produced, which the water forsaking, by degrees, become parts of the continent." The downs of Flanders and Holland are of this kind, being only hills composed of sand and shells, which the sea winds have driven towards the land. Mons. Barrere quotes another example which merits a place in this work. "The sea, by its motion, detaches from its bottom an infinity of plants, shells, slime, and sand, which the waves and winds continually drive towards the shore. Now, all these different operations must continually form new strata, elevate the beds of earth, gradually raising downs and hills, retrenching the bounds of the ocean, and by that means extending the lands on the continents."

"It is visible that new strata have been successively formed by the same reiterated motion of the waters from the deposition of sediments and other constant causes from time immemorial; of which I find strong proofs in the different beds of fossils, shells, and other marine productions found in Roussillon near the village of Naffiac, about seven or eight leagues from the sea; these beds of shells which are inclined from the west to the east, and in different angles, are separated from each other by banks of sand and earth, are sometimes from one and a half to two or three feet in thickness. They appear as if sprinkled with salt in dry weather, and form together hillocks from twenty-five to thirty fathoms in height: now a long chain of hills of such an height can only be formed gradually, and at different successions of time. Such might be the effect of an universal deluge, which must have disturbed all nature; but which could not have given a regular form to these different beds of fossil shells, but would have jumbled them together without any order or regularity."

On this subject I am perfectly of the same opinion as M. Barrere, excepting as to the formation of mountains, which I cannot agree ought to be entirely attributed to the causes which occasion the ocean to gain upon the land on some parts, and lose it upon others. As I am, on the contrary, of opinion, I could produce many convincing arguments to prove that most of the eminencies seen on the surface of the earth have been actually formed in the sea itself. First, because they have a correspondence of saillant and returning angles, which necessarily implies the cause we have assigned, that is, the motion of the currents. Secondly, because downs and hills, which are formed by the materials that the sea brings on its shores, are not composed of marble and hard stone, like common hills; the shells also in the former are generally only fossils, whereas in the latter, the petrifaction is compleat; besides the beds of earth are not so horizontal in downs as in the hills composed of marble and hard stone, but are more or less inclined, as in the hills of Naffiac, whereas in the hills and mountains, formed under the water by the sediment of the sea, the strata are always parallel, and very often horizontal, and the shells and other marble are entirely petrified. I have no doubt of proving that marble and other calcinable matters, which are almost all composed of madrepores, astroites, and shells, have acquired their hardness and perfection at the bottom of the sea; on the contrary, gravel, soft stones, incrustations, stalactites, &c. which are also calcinable and found in the earth, and formed since our continent has been discovered, cannot acquire this degree of hardness and petrifaction which marble or hard stones have.

In the history of the French Academy for 1708, may be seen the observations of Saulmon, on the subject of the galets found in many places. These galets are round and flat flints very smooth, and which are cast on the shores by the sea. At Bayeux, and at Prutel, which are a league from the sea, we find them in digging wells or pits. The mountains of Bonneuil, Broie, and Quesny, which are eighteen leagues from the sea, are all covered with galets; they are also found in the valley of Clermont in Beauvois. M. Saulmon likewise relates, that a hole, 16 feet deep, was bored horizontally into the beach of Tresport, which is soft earth, and that it entirely disappeared in 30 years: so that if the sea always encroaches alike, it would gain half a league in 12,000 years.

The motions of the sea are therefore the principal causes of the alterations which have happened, and which daily happen on the surface of the globe. But there are many, other causes, which, though less considerable, contribute to those changes. Running waters, rivers, streams, the melting of snow, torrents, frosts, &c. have occasioned many changes; the rains have diminished the height of mountains; rivers and rivulets have raised plains, and stopped up the sea at their mouths; the melting of snow, and torrents, have dug hollows in vallies; and the frosts have split rocks and separated them from their former stations. We might quote an infinity of examples on the alterations these causes have occasioned. Varenius says, that rivers convey into the sea great quantities of earth, which they deposit at a greater or less distance from the coasts, according to the rapidity of their currents; these earths fall to the bottom of the sea, and, at first, form those small banks which daily encrease, become shoals, and, at last, form islands, which are fertile and inhabitable. This is the manner in which the islands of the Nile are formed, as well as those of St. Laurence, the Isle of Landa, situate on the coast of Africa, near the mouth of the river Coanza, the island of Norway, &c.[AZ] To these may be added the island of Trong Ming, at China, which has been gradually formed by the earth that the river Nankin has brought and deposited it at its mouth. This island is more than 20 leagues long by five or six broad.[BA]

[AZ] See Varenni Geograph. page 214.

[BA] See Letters Edifiantes, Recueil xi. page 234.

The Po, Trento, Athesis, and other rivers of Italy, bring with them great quantities of earths into the lakes of Venice, especially during the time of inundations, which, in course of time, must fill them up. In many places they are now dry at low water, and, excepting the canals, which are kept up at a great expence, have no depth of water.

At the mouths of the Nile, the Ganges, the Indus, the Plata, the Nankin, and of many other rivers, the earth and sand deposited form considerable banks. Loubere, in his Voyage to Siam, says, that the banks of sand and earth daily increase at the mouths of the great rivers of Asia, insomuch that the navigation of them becomes every day more difficult, and will one day be impassable. The same remark may be made of the large rivers of Europe, and particularly of the Wolga, which has more than 70 mouths in the Caspian sea, and of the Danube, which has seven in the Black sea, &c.

As it seldom rains in Egypt the regular inundations of the Nile proceed from the torrents which fall therein from Ethiopa. These annually bring with them great quantities of mud, which they not only deposit on the land of Egypt but even throw to a considerable distance in the sea, and thus lay the foundation of a new land, which, in the course of time, arises therefrom; for, by sounding with the lead, we find, at more than 20 leagues distance from the coast, the mud of the Nile at the bottom of the sea, and which is every year increasing. Lower Egypt, where[BB] Dela at present stands, was formerly a gulph of the sea. Homer tells us that the island of Pharos was 24 hours voyage from Egypt, and at present it is almost contiguous to it. The soil of Egypt has not the same depth of good ground throughout its extent, it lessens as we approach the sea. Near the borders of the Nile there is sometimes near thirty feet depth of good earth, whereas at the extremity of the inundation there is scarcely more than seven inches.[BC] The town of Damietta, at present more than 10 miles from the sea, in 1243 was a sea-port. The town of Fooah, which, 300 years ago, was situate at the mouth of the Canopic, a branch of the Nile, is now more than seven leagues from it. Within 40 years the sea has retreated half a league from before Rosetta and Idern.

[BB] See Diodorus de Suc, lib. 3. Aristotle, lib. 1. of Meteors, h. xiv. Herodotus, f. 4, 5, &c.

[BC] See Shaw's Travels, vol. II. page 185, and 186.

The great rivers of America, and even those which have been but lately discovered, have suffered great alterations at their mouths. Charlevoix, speaking of the river Mississipi, says, that at its mouth, below New Orleans, the country forms a point of land which does not appear to be very ancient, for by digging but a little into the earth water is met with; besides, the quantity of small islands which have recently been formed at all the mouths of this river, leaves no doubt of this neck of land being formed after the same manner. It appears certain, says he, that when M. de la Salle went down the Mississipi, to the sea, the mouth of this river was not as it is at this present time.

"The nearer we approach towards the sea, adds he, the more it becomes perceptible, the bar has scarcely any water in most of the small outlets which the river has opened, and which have multiplied so greatly from the trees that are carried along with the currents, one of which stopt in a part where it is shallow, will entangle hundreds. I have seen, continues he, 200 leagues from New Orleans, collections of trees, one of which would have filled all the timber-yards of Paris. Nothing can set them free; the mud which the river brings down serves to cement, and, by degrees, covers them. Each inundation leaves a new stratum, and, after 10 years, shrubs and vegetables grow thereon: after this manner most points and islands are formed, which so often change the course of rivers."[BD]

[BD] See Charlevoix Travels, vol. II. page 440.

Nevertheless all the changes which rivers cause are very slow, and become not considerable till after a long series of years: but quick and sudden changes have happened by inundations and earthquakes. The ancient Egyptian priests, 600 years before the birth of Christ, asserted, according to the Timæus of Plato, that there was a great island near Hercules Pillars; called _Atlantis_, which was larger than Lybia and Asia taken together; and that this island was buried under the waters of the ocean after a great earthquake. "Traditur Atheniensis civitas restitisse olim innumeris hostium copiis quæ, ex Atlantico mari profectæ, prope cunctam Europam Asiamque obsederunt; tunc enim fretum illud navigabile habens in ore et quasi vestibulo ejus insulam quam Herculis columnas cognominant; ferturque insula illa Lybiâ simul et Asiâ Major fuisse, per quam ad alias proximas insulas patebat aditus, atque ex insulis ad omnem continentem è conspectu jacentem vero mari vicinam: sed intrà os ipsum portes augusto sinu traditur, pelagus illud verum mare, terra quoque illa verè erat continens, &c. Post hæc ingenti terræ motu jugique diei unius et noctis illuvione factum est, ut terra dehiscens omnis illos bellicosos absorberet, et Atlantis insula sub vasto gurgite mergeretur." _Plato in Timæus._ This ancient tradition is not absolutely contrary to all probability. The earths which were absorbed by the waters are perhaps those which join Ireland to the Azores, and those to the continent of America; for in Ireland there are the same fossils, shells, and marine productions as in America, some of which are different from any found in other parts of Europe,

Eusebius relates two testimonies on the subject of deluges: one of which is Melo, who says that the plains of Syria had formerly been laid under water; the other is Abydenus, who says, that in the time of King Sisithrus there was a great deluge, which had been predicted by Saturnus, Plutarch _De Solestia Animalium_. Ovid, and other mythologists, speak of the deluge of Deucalion, which, according to them, was in Thessaly, about 700 years from the universal deluge. It is also asserted that there had been one more ancient in Attica, in the time of Ogiges, about 230 years before that of Deucalion.

In the year 1095 there was a deluge in Syria, which drowned a number of people.[BE] In 1164 there was so considerable a one in Friezeland, that all maritime coasts were covered, and several thousands of the inhabitants drowned.[BF] In 1218 there was another inundation which destroyed near an hundred thousand people. There are a multitude of other examples of great inundations, like that of 1604 in England, and many more.

[BE] See Alsted. Chron. chap. 25.

[BF] See Krank, Lib. 5, cap. 4.

A third cause of the change on the surface of the globe, are impetuous winds. They not only form downs and hills on the sea shores, but they often stop and choak up rivers, and change their directions; they tear up cultivated land, destroy trees, overthrow edifices, and cover entire countries with sand. We have an example of these inundations of sand on the coasts of Britany in France: the history of the Royal Academy at Paris, anno 1722, makes mention of it in the following terms.

"In the environs of St. Paul de Leon, in Lower Britany, there is a quarter near the sea, which before the year 1666, was inhabited; but is so no longer, by reason of a sand which covers it to the height of more than twenty feet, and which gains ground every year. Reckoning from that time it has proceeded upwards of six leagues into the country, and is now not more than about half a league from St. Paul, so that according to all appearance that town must soon be deserted. The tops of some steeples and chimnies are still seen peeping out of this sea of sand; the inhabitants of the interred villages have always had sufficient time to quit their houses in safety.

"An east or north wind increases this calamity, by raising up a sand of a very fine nature, which sweeps it away in such great quantities, and with such velocity, that M. Deslandes, to whom the academy are indebted for this observation, when walking in that country during an east wind, was obliged, from time to time, to wipe it off his hat and cloaths they were so loaded with sand, and felt so heavy. Besides, when this wind is violent, it throws this sand over a small arm of the sea into Roscof, a small port much frequented by foreign vessels; the sand collects in their streets to the height of two feet, and the inhabitants are obliged to have it carted away. There are many ferruginous particles in this sand, which are easily discovered by a magnet.

"The coast which furnishes this sand extends from St. Paul as far as Plouefoat, somewhat more than four leagues. The disposition of the place is such that only the east or the north-east wind can convey the sand over the lands. It is easy to be conceived how the sand, conveyed and accumulated by the wind in one part, can again be taken up by the same wind and carried farther, and that the sand can thus advance into and cover the country while the mine which furnishes it continues unexhausted; for without this the sand, by advancing, would always diminish in height, and would cease its destructive ravages. Now it is but too possible that the sea throws up or deposits new sand in the place from whence the wind raises it up, and therefore the dreadful effects may long continue.

"The disaster is but of modern date, possibly the shoal which furnishes it has not yet a sufficient quantity to lift itself above the surface of the sea, or perhaps the sea has but just left it uncovered. There has been some alteration on the coast, and the sea at present reaches, at high water, half a league beyond certain rocks that formerly it never passed.

"This unhappy province justifies what the ancient and modern travellers relate concerning the tempests of sand in the deserts of Arabia, in which cities and armies have been enveloped and destroyed."

Mr. Shaw tells us that the ports of Laodicea, Jebila, Tortosa, Rowada, Tripoli, Tyre, Acra, and Jaffa, are all filled up with sand brought thither by the great waves which beat on that side of the Mediterranean when the west wind blows impetuously.[BG]

[BG] See Shaw's Travels, vol. II.

It is useless to give a greater number of examples of the alterations that have happened on the surface of the globe. Fire, air, and water, produce continual changes, which become very considerable by time. It is not from general causes alone, whose effects are periodical and regular, that the sea successively takes the place of the earth, and forsakes its own dominions. There are a number of particular causes which contribute to these mutations, such as earthquakes, inundations, sinking of mountains, &c. Thus the most solid thing, at least to our conception, like the rest of nature, undergoes continual and perpetual vicissitudes.

CONCLUSION

OF THE

_THEORY OF THE EARTH_.

By the proofs we have given in Articles VII. and VIII. it appears certain that the whole of the present dry land was formerly covered by the sea. It appears also as certain, from Article XII. that the flux and reflux, and other motions of the ocean, continually detach, from the side and the bottom of the sea, shells and matters of every kind, some part of which are deposited in other places in form of sediments, and which are the origin of the parallel and horizontal strata every where to be met with. We have proved in Article IX. that the inequalities of the globe have been caused by the motion of the sea, and that mountains have been produced by the successive masses and heapings of the sediments we have just described. It is evident by Article XIII. that the currents, which at first followed the direction of these inequalities, afterwards gave to them all the figure which they at present preserve; that is, that alternate correspondence of the saliant angles always opposed to the returning angles. It appears likewise by Articles VIII. and XVIII. that the greatest part of the matters which the sea has detached from its sides and bottom were, when deposited as sediments, in form of a fine impalpable powder, which perfectly filled the cavities of the shells, whether it was of the same nature or only analogous to that with which they were composed. It is certain, from Article XVII. that the horizontal strata which have been produced by the accumulation of sediments, and which at first were in a soft state, acquired hardness in proportion as they became dry, and that this drying has produced perpendicular clefts, which cross the horizontal strata.

It is impossible to doubt, after perusing the facts in the Articles X. XI. XIV. XV. XVI. XVII. XVIII. and XIX. that an infinite number of revolutions, particular changes and alterations, have happened on the surface of the globe, as well from the natural motion of the waters of the sea as by the effects of rain, frost, running waters, winds, subterraneous fires, earthquakes, inundations, &c. and that consequently the sea has alternately changed places with the earth, especially in the earliest times after the creation, when the terrestrial matters were much softer than they are at present. It must nevertheless be acknowledged, that we can but very, imperfectly judge of the succession of natural revolutions; that we can still less judge of the cause of accidents, changes, and alterations; that the defect of historical monuments deprives us of the knowledge of particular facts, and experience and time is deficient to us. We do not pay any consideration that, though the time of our existence is very limited, nature proceeds in her regular course. We would condense into our momentary existence the transactions of ages past and to come, without reflecting that this instant of time, nay even human life itself, is only a single fact in the history of the acts of the Almighty.

HISTORY OF ANIMALS.