in natural history, a sudden and violent convulsion of the earth, generally attended with strange noises under-ground or in the air; often destroying whole cities at once, throwing down rocks, altering the course of rivers, and producing the most terrible devastations.

Though there is hardly any country known in which shocks of an earthquake have not at some time or other been felt, yet there are some much more subject to them than others. It hath been observed, that northern countries in general are less subject to earthquakes than those situated near the equator, or in the southern latitudes; but this does not hold universally. The islands of Japan, which are situated pretty far north, are nevertheless exceedingly liable to these destructive phenomena. Islands, in general, are also more subject to earthquakes than continents; but neither does this hold without exceptions. Some particular parts of continents, and some particular islands, are more subject to them than others lying in the neighbourhood, and differing very little from them in external appearance. Thus, Portugal is more subject to earthquakes than Spain, and the latter much more than France; Mexico and Peru more than the other countries of America, and Jamaica more than the other Caribbee islands. Earthquakes are frequent, though not often violent, in Italy; but in Sicily they are often terribly destructive. Asia Minor has been remarkably subject to them from the remotest antiquity; and the city of Antioch in particular hath suffered more from earthquakes than any other in that country. The same phenomena are said also to occur very frequently in the north-eastern extremities of Asia, even in very high latitudes.

Though there are no phenomena in nature more calculated to impress the human mind with terror, and consequently to be well remembered and taken notice of, than earthquakes; yet the philosophy of them is but lately arrived at any degree of perfection; and even at this day, the history of earthquakes is very incomplete. The destruction occasioned by them engrosses the mind too much to admit of philosophical speculations at the time they happen; the same thing prevents the attentive consideration of the alterations that take place in the atmosphere after the earthquake is over, and which might probably throw some light on the causes which produced it; and the suddenness of its coming on prevents an exact attention to those slight appearances in the earth or air, which, if carefully observed, might serve as warnings to avoid the destruction.—From what observations have been made, however, the following phenomena may be deduced, and reckoned pretty certain.

1. Where there are any volcanoes or burning mountains, earthquakes may reasonably be expected more frequently than in other countries.

2. If the volcano hath been for a long time quiet, a violent earthquake is to be feared, &c. vice versa. But to this there are many exceptions.

3. Earthquakes are generally preceded by long droughts; but they do not always come on as soon as the drought ceases.

4. They are also preceded by electrical appearances in the air; such as the aurora borealis, falling flares, &c.; but this does not hold universally.

5. A short time before the shock, the sea swells up and makes a great noise; fountains are troubled, and send forth muddy water; and the beasts seem frightened, as if sensible of an approaching calamity.

6. The air at the time of the shock is generally calm and serene; but afterwards commonly becomes obscure and cloudy.

7. The 7. The shock comes on with a rumbling noise, sometimes like that of carriages; sometimes a rushing noise like wind, and sometimes explosions like the firing of cannon are heard. Sometimes the ground heaves perpendicularly upwards, and sometimes rolls from side to side. Sometimes the shock begins with a perpendicular heave, after which the other kind of motion commences. A single shock is but of very short duration, the longest scarcely lasting a minute; but they frequently succeed each other at short intervals for a considerable length of time.

8. During the shock, chasms are made in the earth; from which sometimes flames, but oftener great quantities of water, are discharged. Flame and smoke are also emitted from places of the earth where no chasms can be perceived. Sometimes these chasms are but small; but, in violent earthquakes, they are frequently so large, that whole cities sink down into them at once.

9. The water of the ocean is affected even more than the dry-land. The sea swells to a prodigious height; much more than we could suppose it raised by the mere elevation of its bottom by the shock. Sometimes it is divided to a considerable depth; and great quantities of air, flames, and smoke, are discharged from it. The like irregular agitations happen to the waters of ponds, lakes, and even rivers.

10. The shock is felt at sea as well as on land. Ships are affected by a sudden stroke, as if they had run aground or struck upon a rock.

11. The effects of earthquakes are not confined to one particular district or country, but often extend to very distant regions; though no earthquake has yet been known extensive enough to affect the whole globe at one time. In those places also where the shock is not felt on dry land, the irregular agitation of the waters above mentioned is perceived very remarkably.

All these positions are verified by the accounts of those earthquakes which have been particularly described by witnesses of the best reputation. In 1692, an earthquake happened in Jamaica, attended with almost all the terrible circumstances above mentioned. In two minutes, it destroyed the town of Port Royal, at that time the capital of the island; and sunk the houses in a gulph 40 fathoms deep. It was attended with an hollow rumbling noise like that of thunder: the streets rose like the waves of the sea; first lifting up the houses, and then immediately throwing them down into deep pits. All the wells discharged their waters with the most violent agitation. The sea burst over its bounds, and deluged all that stood in its way. The fissures of the earth were in some places so great, that one of the streets appeared twice as broad as formerly. In many places it opened and closed again; and continued this agitation for some time. Of these openings, great numbers might be seen at once. In some of them, the people were swallowed up at once; in others, the earth caught them by the middle, and crushed them to death; while others, more fortunate, were swallowed up in one chasm, and thrown out alive by another. Other chasms were large enough to swallow up whole streets; and others, still more formidable, spouted up immense quantities of water, drowning such as the earthquake had spared. The whole was attended with stenches and offensive smells, the noise of falling mountains at a distance, &c.; and the sky, in a minute's time, was turned dull and reddish, like a glowing oven. Yet, as great a sufferer as Port-Royal was, more houses were left standing therein than on the whole island besides. Scarce a planting-house, or sugar-house, was left standing in all Jamaica. A great part of them were swallowed up, houses, people, trees, and all, in one gap: in lieu of which, afterwards appeared great pools of water; which, when dried up, left nothing but land, without any mark that ever tree or plant had grown thereon. The shock was so violent, that it threw people down on their knees or their faces as they were running about for shelter. Several houses were shuffled some yards out of their places, and yet continued standing. One Hopkins had his plantation removed half a mile from the place where it stood, without any considerable alteration. All the wells in the island, as well as those of Port-Royal, from one fathom to six or seven deep, threw their water out at the top with great violence. Above 12 miles from the sea, the earth gaped and spouted out, with a prodigious force, vast quantities of water into the air: yet the greatest violences were among the mountains and rocks; and it is a general opinion, that the nearer the mountains, the greater the shock; and that the cause thereof lay among them. Most of the rivers were stopped up for 24 hours by the falling of the mountains; till swelling up, they made themselves new tracks and channels; tearing up, in their passage, trees, &c. After the great shock, those people who escaped got on board ships in the harbour, where many continued above two months; the shocks all that time being so violent, and coming so thick, sometimes two or three in an hour, accompanied with frightful noises like a rolling wind, or a hollow rumbling thunder, with brimstone-blasts, that they durst not come ashore. The consequence of the earthquake was a general sickness, from the noisome vapours belched forth, which swept away above 3000 persons.

A still more terrible account, if possible, is that given by Kircher, of the earthquake which happened in Calabria in the year 1638. This instance is an exception to the second general position above laid down. In Italy, there had been an eruption of Mount Vesuvius five years before; and in Sicily there had been an eruption of Etna only two years before this earthquake. The event, however, plainly showed, that the cause of the earthquake, whatever it was, had a connection not only with Mount Etna, which lies in the neighbourhood, but also with the volcano of Stromboli, which is 60 miles distant. "On the 24th of March (says Kircher), we landed (in a small boat) from the harbour of Messina in Sicily, and arrived the same day at the promontory of Pelorus. Our destination was for the city of Euphemia in Calabria; but on account of the weather, we were obliged to continue three days at Pelorus. At length, wearied with the delay, we resolved to prosecute our voyage; and although the sea seemed more than usually agitated, yet we ventured forward. The gulph of Charybdis, which we approached, seemed whirled round in such a manner as to form a vast hollow, verging to a point in the centre. Proceeding onward, and turning my eyes to Mount Etna, I saw it cast forth large volumes of smoke, of moun- mountainous size, which entirely covered the island, and blotted out even the shores from my view. This, together with the dreadful noise, and the sulphurous stench, which was strongly perceived, filled me with apprehensions that some more dreadful calamity was impending. The sea itself seemed to wear a very unusual appearance; those who have seen a lake in a violent shower of rain all covered over with bubbles, will have some idea of its agitations. My surprize was still increased by the calmness and serenity of the weather; not a breeze, nor a cloud, which might be supposed to put all nature thus into motion. I therefore warned my companion, that an earthquake was approaching; and, after some time, making for the shore with all possible diligence, we landed at Tropaea. But we had scarce arrived at the Jesuits college in that city, when our ears were stunned with an horrid sound, resembling that of an infinite number of chariots driven fiercely forward, the wheels rattling and the thongs cracking. Soon after this, a most dreadful earthquake ensued; so that the whole track upon which we stood seemed to vibrate, as if we were in the scale of a balance that continued waving. This motion, however, soon grew more violent; and being no longer able to keep my legs, I was thrown prostrate upon the ground. After some time, finding that I remained unhurt amidst the general concussion, I resolved to venture for safety; and running as fast as I could, reached the shore. I did not search long here, till I found the boat in which I had landed, and my companions aloft. Leaving this seat of desolation, we prosecuted our voyage along the coast; and the next day came to Rovetta, where we landed, although the earth still continued in violent agitations. But we were scarce arrived at our inn, when we were once more obliged to return to our boat; and in about half an hour we saw the greatest part of the town, and the inn at which we had set up, dashed to the ground, and burying all its inhabitants beneath its ruins. Proceeding onward in our little vessel, we at length landed at Lopizium, a castle mid-way between Tropaea and Euphemia the city to which we were bound. Here, wherever I turned my eyes, nothing but scenes of ruin and horror appeared; towns and castles levelled to the ground; Stromboli, though at 60 miles distance, belching forth flames in an unusual manner, and with a noise which I could distinctly hear. But my attention was quickly turned from more remote to contiguous danger. The rumbling sound of an approaching earthquake, which by this time we were grown acquainted with, alarmed us for the consequences. It every moment seemed to grow louder, and to approach more near. The place on which we stood now began to shake most dreadfully; so that, being unable to stand, my companions and I caught hold of whatever shrub grew next us, and supported ourselves in that manner. After some time, the violent paroxysm ceasing, we again stood up, in order to prosecute our voyage to Euphemia, which lay within sight. In the mean time, while we were preparing for this purpose, I turned my eyes towards the city; but could see only a frightful dark cloud, that seemed to rest upon the place. This the more surprized us, as the weather was so very serene. We waited, therefore, till the cloud was passed away; then turning to look for the city, it was totally sunk; and nothing but a dismal and putrid lake was to be seen where it stood.

In 1693 an earthquake happened in Sicily, which may justly be accounted one of the most terrible of which we have any account. It shook the whole island; and not only that, but Naples and Malta shaked in Sicily in red in the shock. It was impossible for any body in this country to keep on their legs on the dancing earth; nay, those that lay on the ground were tossed from side to side as on a rolling billow; high walls leaped from their foundations several paces, &c. The mischief it did was amazing; almost all the buildings in the countries were thrown down. Fifty-four cities and towns, beside an incredible number of villages, were either destroyed or greatly damaged. We shall only instance the fate of Catania, one of the most famous, ancient, and flourishing cities in the kingdom; the residence of several monarchs, and an university. This once famous city had the greatest share in the tragedy. Father Anthon Serrovia, being on his way thither, and at the distance of a few miles, observed a black cloud like night hovering over the city; and there arose from the mouth of Montigibello great spires of flame, which spread all around. The sea all of a sudden began to roar and rise in billows; and there was a blow, as if all the artillery in the world had been at once discharged. The birds flew about astonished; the cattle in the fields ran crying, &c. His and his companions horses stopped short, trembling; so that they were forced to alight. They were no sooner off, but they were lifted from the ground above two palms; when casting his eyes towards Catania, he with amazement saw nothing but a thick cloud of dust in the air. This was the scene of their calamity; for of the magnificent Catania, there was not the least footstep to be seen. S. Bonajutus affirms us, that of 18000 inhabitants, 18000 perished therein.

The great earthquake, however, which happened on the 1st of November 1755, affords the clearest example of all the phenomena above mentioned; having been felt violently in many places both on land and at sea, and extended its effects to the waters in many other places where the shocks were not perceived. At Lisbon at Lisbon, in Portugal its effects were most severe. In 1750, there had been a sensible trembling of the earth felt in this city: for four years afterwards, there had been an excessive drought; insomuch that some springs, formerly very plentiful of water, were dried and totally lost. The predominant winds were north and north-east, accompanied with various, though very small, tremors of the earth. The year 1755 proved very wet and rainy; the summer cooler than usual; and for 40 days before the earthquake, the weather was clear, but not remarkably so. The last day of October, the sun was obscured, with a remarkable gloominess in the atmosphere. The first of November, early in the morning, a thick fog arose, which was soon dissipated by the heat of the sun; no wind was stirring; the sea was calm; and the weather as warm as in June or July in this country. At 35 minutes after nine, without the least warning, except a rumbling noise not unlike the artificial thunder in our theatres, a most dreadful earthquake shook, by short but quick vibrations, the foundations of all the city, so that many buildings instantly fell. Then, with a scarcely perceptible pause, the nature of the motion was... was changed, and the houses were tossed from side to side, with a motion like that of a waggon violently driven over rough stones. This second shock laid almost the whole city in ruins, with prodigious slaughter of the people. The earthquake lasted in all about six minutes. At the moment of its beginning, some persons on the river, near a mile from the city, heard their boat make a noise as if it had run aground, though they were then in deep water; and at the same time they saw the houses falling on both sides of the river. The bed of the river Tagus was in many places raised to its surface. Ships were driven from their anchors, and jolted together with great violence; nor did their masters know whether they were afloat or aground. A large new quay sunk to an unfathomable depth, with several hundreds of people who were upon it; nor was one of the dead bodies ever found. The bar was at first seen dry from shore to shore; but suddenly the sea came rolling in like a mountain; and about Belém Castle the water rose 50 feet almost in an instant. About noon there was another shock; when the walls of several houses that yet remained were seen to open from top to bottom more than a quarter of a yard, and afterwards closed again so exactly that scarce any mark of the injury was left.

At Colares: At Colares, about 20 miles from Lisbon, and two miles from the sea, on the last day of October, the weather was clear, and uncommonly warm for the season. About four o'clock in the afternoon there arose a fog, which came from the sea, and covered the valleys; a thing very unusual at that season of the year. Soon after, the wind changing to the east, the fog returned to the sea, collecting itself, and becoming exceeding thick. As the fog retired, the sea rose with a prodigious roaring. The first of November, the day broke with a serene sky, the wind continuing at east; but about nine o'clock the sun began to grow dim; and about half an hour after was heard a rumbling noise like that of chariots, which increased to such a degree, that it became equal to the explosions of the largest cannon. Immediately a shock of an earthquake was felt, which was quickly succeeded by a second and third; and at the same time several light flames of fire issued from the mountains, resembling the kindling of charcoal. In these three shocks, the walls of the buildings moved from east to west. In another situation, from whence the sea-coast could be discovered, there issued from one of the hills called the Fojo a great quantity of smoke, very thick, but not very black. This still increased with the fourth shock, and afterwards continued to issue in a greater or less degree. Just as the subterraneous rumblings were heard, the smoke was observed to burst forth at the Fojo; and the quantity of smoke was always proportioned to the noise. On visiting the place from whence the smoke was seen to arise, no signs of fire could be perceived near it.

At Oporto: At Oporto (near the mouth of the river Douro), the earthquake began about 40 minutes past nine. The sky was very serene; when a dreadful hollow noise like thunder, or the rattling of coaches at a distance, was heard, and almost at the same instant the earth began to shake. In the space of a minute or two, the river rose and fell five or six feet, and continued to do so for four hours. It ran up at first with so much violence, that it broke a ship's hawser. In some parts the river opened, and seemed to discharge vast quantities of air; and the agitation in the sea was so great about a league beyond the bar, that air was supposed to have been discharged there also.

St Ube's, a sea-port town about 20 miles south of Lisbon, was entirely swallowed up by the repeated shocks and the vast surf of the sea. Huge pieces of rock were detached at the same time from the promontory at the west end of the town, which consists of a chain of mountains containing fine Jasper of different colours.

The same earthquake was felt all over Spain, except at Ayamonte in Catalonia, Arragon, and Valencia.—At Ayamonte (near where the Guadiana falls into the Bay of Cadiz), a little before 10 o'clock on the first of November, the earthquake was felt; having been immediately preceded by a hollow rushing noise. Here the shocks continued for 14 or 15 minutes, damaged almost all the buildings, throwing down some, and leaving others irreparably shattered. In little more than half an hour after, the sea and river, with all the canals, overflowed their banks with great violence, laying under water all the coasts of the islands adjacent to the city and its neighbourhood, and flowing into the very streets. The water came on in vast black mountains, white with foam at the top, and demolished more than one half of a tower at the bar named De Canula. In the adjacent strands every thing was irrecoverably lost; for all that was overflowed sunk, and the beach became a sea, without the least resemblance of what it was before. Many persons perished; for although they got aboard some vessels, yet part of these foundered; and others being forced out to sea, the unhappy passengers were so terrified, that they threw themselves overboard. The day was serene, and not a breath of wind stirring.

At Cadiz, some minutes after nine in the morning, the earthquake began, and lasted about five minutes. The water of the cisterns under ground washed backwards and forwards, so that a great froth arose. At ten minutes after eleven, a wave was seen coming from the sea, at eight miles distance, at least 60 feet higher than usual. It dashed against the west part of the town, which is very rocky. Though these rocks broke a good deal of its force, it at last came upon the city walls, beat in the breasting-work, and carried pieces of the building of eight or ten ton weight to the distance of 40 or 50 yards.—When the wave was gone, some parts that are deep at low water, were left quite dry; for the water returned with the same violence with which it came. At half an hour after 11 came a second wave; and after that four other remarkable ones; the first at ten minutes before twelve; the second, half an hour before one; the third, ten minutes after two; and the fourth, ten minutes before two. Similar waves, but smaller, and gradually lessening, continued with uncertain intervals till the evening.

At Gibraltar, the earthquake was not felt till after 12. It began with a tremulous motion of the earth, which lasted about half a minute. Then followed a violent shock; after that, a trembling of the earth for five or six seconds; then another shock not so violent as the first, which went off gradually as it began. The whole lasted about two minutes. Some of the guns on the battery were seen to rise, others to sink, the earth having an undulating motion. Most people were seized with giddiness and sickness, and some fell down; others... were stupified; and many that were walking or riding felt no motion in the earth, but were sick. The sea rose five feet every fifteen minutes; and then fell low, that boats and all the small craft near the shore were left aground, as were also numbers of small fish. The flux and reflux lasted till next morning, having decreased gradually from two in the afternoon.

At Madrid, Malaga, etc.

At Madrid the earthquake came on at the same time as at Gibraltar, and lasted about six minutes. At first every body thought they were seized with a swimming in their heads; and afterwards, that the houses were falling. It was not felt in coaches, nor by those who walked on foot, except very slightly; and no accident happened, except that two lads were killed by the fall of a stone-crofs from the porch of a church.

Malaga (a sea-port on the Mediterranean) felt a violent shock; the bells rung in the steeples; the water of a well overflowed, and as suddenly retired.

Saint Lucar (at the mouth of the Guadalquivir) was violently shocked, and the sea broke in and did a great deal of mischief.

At Seville (16 leagues above the mouth of the Guadalquivir) several houses were shaken down; the famous tower of the cathedral called La Giralda opened in the four sides; and the waters were so violently agitated, that all the vessels in the river were driven ashore.

In Africa, the earthquake was felt almost as severely as it had been in Europe. Great part of the town of Algiers was destroyed. At Arzila (a town in the kingdom of Fez), about ten in the morning, the sea suddenly rose with such impetuosity, that it lifted up a vessel in the bay, and dropped it with such force on the land, that it was broke to pieces; and a boat was found two musket-shot within land from the sea. At Fez and Mequinez, great numbers of houses fell down, and a multitude of people were buried in the ruins.

At Morocco, by the falling down of a great number of houses, many people lost their lives; and about eight leagues from the city the earth opened and swallowed up a village with all the inhabitants, who were known by the name of the Sons of Bejumba, to the number of about 8000 or 10,000 persons, together with all their cattle, &c.; and, soon after, the earth closed again in the same manner as before.

At Salle, a great deal of damage was done. Near a third part of the houses were overthrown; the waters rushed into the city with great rapidity, and left behind them great quantities of fish.

At Tangier, the earthquake began at ten in the morning, and lasted 10 or 12 minutes. The sea came up to the walls (a thing never heard of before); and went down immediately with the same rapidity with which it arose, leaving a great quantity of fish behind it. These commotions were repeated 18 times, and lasted till six in the evening.

At Tetuan, the earthquake began at the same time it did at Tangier, but lasted only seven or eight minutes. There were three shocks so extremely violent, that it was feared the whole city would be destroyed.

In the city of Funchal, in the island of Madeira, a shock of this earthquake was first perceived at 38 minutes past nine in the morning. It was preceded by a rumbling noise in the air, like that of empty carriages passing hastily over a stone pavement. The observer felt the floor immediately to move with a tremulous motion, vibrating very quickly. The shock continued more than a minute; during which space, the vibrations, though continual, were weakened and increased in force twice very sensibly. The increase after the first remission of the shock was the most intense. The noise in the air accompanied the shock during the whole of its continuance, and lasted some seconds after the motion of the earth had ceased; dying away like a peal of distant thunder rolling through the air. At three quarters past eleven, the sea, which was quite calm, it being a fine day, and no wind stirring, retired suddenly some paces; then rising with a great swell without the least noise, and as suddenly advancing, overflowed the shore, and entered the city. It rose 15 feet perpendicular above the high-water mark, although the tide, which flows there seven feet, was then at half ebb. The water immediately receded; and after having fluctuated four or five times between high and low water mark, it subsided, and the sea remained calm as before. In the northern part of the island the inundation was more violent, the sea there retiring above 100 paces at first, and suddenly returning, overflowed the shore, forcing open doors, breaking down the walls of several magazines and storehouses, leaving great quantities of fish ashore and in the streets of the village of Machico. All this was the effect of one rising of the sea, for it never afterwards flowed high enough to reach the high-water mark. It continued, however, to fluctuate here much longer before it subsided than at Funchal; and in some places farther to the westward, it was hardly, if at all, perceptible.

These were the phenomena with which this remarkable earthquake was attended in those places where it was violent. The effects of it, however, reached to an immense distance; and were perceived chiefly by the agitations of the waters, or some slight motion of the earth. The utmost boundaries of this earthquake to the south are unknown; the barbarity of the African nations rendering it impossible to procure any intelligence from them, except where the effects were dreadful. On the north, however, we are assured, that it reached as far as Norway and Sweden. In the former, it in Norway, the waters of several rivers and lakes were violently agitated. In the latter, shocks were felt in several Swedish provinces, and all the rivers and lakes were strongly agitated, especially in Dalecarlia. The river Dalälven suddenly overflowed its banks, and as suddenly retired. At the same time a lake at the distance of a league from it, and which had no manner of communication with it, bubbled up with great violence. At Falun, a town in Dalecarlia, several strong shocks were felt.

In many places of Germany the effects of the earthquake were very perceptible. Throughout the duchy of Holstein, the waters were violently agitated, particularly those of the Elbe and Trave. In Brandenburg, the water of a lake called Liepzig, ebbed and flowed six times in half an hour, with a dreadful noise, the weather being then perfectly calm. The same agitation was observed in the waters of the lakes called Mühlberg and Neusiedl; but at this last place they also emitted an intolerable stench.

In Holland, the agitations were more remarkable. In Holland, At Alphen on the Rhine between Leyden and Woerden, in the afternoon of the first of November, the waters were agitated to such a violent degree, that buoys were broken from their chains, large vessels snapped their cables, smaller ones were thrown out of the water upon the land, and others lying on land were set afloat. At Amsterdam, about eleven in the forenoon, the air being perfectly calm, the waters were suddenly agitated in their canals, so that several boats broke loose; chandeliers were observed to vibrate in the churches; but no motion of the earth, or concussion of any building, was observed. At Haarlem, in the forenoon, for near four minutes together, not only the water in the rivers, canals, &c. but also all kinds of fluids in smaller quantities, as in coolers, tubs, backs, &c. were surprizingly agitated, and dashed over the sides, though no motion was perceptible in the vessels themselves. In these small quantities also the fluid apparently ascended prior to its turbulent motion; and in many places, even the rivers and canals rose 12 inches perpendicular. At Leyden, between half an hour after 10 and 11 in the forenoon, the waters rose suddenly in some of the canals, and made several very sensible undulations, so that the boats were strongly agitated. The same motion was perceived in the water of the backs of two brew-houses.

Round the island of Corsica, the sea was violently agitated, and most of the rivers of the island overflowed their banks.—In the city of Milan in Italy, and throughout that district, shocks were felt. At Turin in Savoy, there was felt a very violent shock.

In Switzerland, many rivers turned suddenly muddy without rain. The lake of Neufchatel swelled to the height of near two feet above its natural level for the space of a few hours. An agitation was also perceived in the waters of the lake of Zurich.

At the island of Antigua, there was such a sea without the bar as had not been known in the memory of man; and after it, all the water at the wharfs, which used to be six feet deep, was not two inches.—At Barbadoes, about two in the afternoon, the sea ebbed and flowed in a surprising manner. It ran over the wharfs and streets into the houses, and continued thus ebbing and flowing till ten at night.

The agitation of the waters was perceived in great numbers of places in Great Britain and Ireland.—Accounts of the most remarkable of them follow. At Barlborough in Derbyshire, between 11 and 12 in the forenoon, in a boat-house on the west side of a large body of water called Pibley Dam, supposed to cover at least 30 acres of land, was heard a surprising and terrible noise; a large swell of water came in a current from the south, and rose two feet on the sloped dam-head at the north end of the water. It then subsided; but returned again immediately, though with less violence. The water was thus agitated for three quarters of an hour; but the current grew every time weaker and weaker, till at last it entirely ceased.

At Busbridge in Surrey, at half an hour after ten in the morning, the weather being remarkably still, without the least wind, in a canal near 700 feet long and 58 feet broad, with a small spring constantly running through it, a very unusual noise was heard at the east end, and the water there observed to be in great agitation. It raised itself in a heap or ridge in the middle; and this heap extended lengthwise about 30 yards, rising between two or three feet above the usual level. After this, the ridge heeled or vibrated towards the north side of the canal with great force, and flowed above eight feet over the grass walk on that side. On its return back into the canal, it again ridged in the middle, and then heeled with yet greater force to the south side, and flowed over its grass walk. During this latter motion, the bottom on the north side was left dry for several feet. This appearance lasted for about a quarter of an hour, after which the water became smooth and quiet as before. During the whole time, the sand at the bottom was thrown up and mixed with the water; and there was a continual noise like that of water turning a mill.

At Cobham in Surrey, between 10 and 11 o'clock, a person was watering a horse at a pond fed by springs. Whilst the animal was drinking, the water suddenly ran away from him, and moved towards the south with such swiftness, that the bottom of the pond was left bare. It returned again with such impetuosity, that the man leaped backwards to secure himself from its sudden approach. The ducks were alarmed at the first agitation, and instantly flew all out of the pond.

At Dunstall in Suffolk, the water of a pond rose gradually for several minutes in the form of a pyramid, and fell down like a water-spout. Other ponds in the neighbourhood had a smooth flux and reflux from one end to the other.

Near the city of Durham, about half an hour after ten, a gardener was alarmed by a sudden rushing noise from a pond, as if the head of the pond had been broken down: when casting his eye on the water, he saw it gradually rise up, without any fluctuating motion, till it reached a grate which stood some inches higher than the common water level. After this it subsided, and then swelled again; thus continuing to rise and fall during the space of six or seven minutes, making four or five returns in the space of one minute. The pond was about 40 yards long and 10 broad.

At Earfy Court, Berks, about 11 o'clock, as a gardener was standing by a fish pond, he felt a violent trembling of the earth, which lasted about a minute. Immediately after, he observed a motion of the water from the south to the north end of the pond, leaving the bottom at the south end altogether dry for about six feet. It then returned, and flowed at the south end, rising three feet up the slope bank; and immediately after returned to the north bank, rising there also about three feet. In the time between the flux and reflux, the water swelled up in the middle of the pond, collected in a ridge about 20 inches higher than the level on each side, and boiled like a pot. This agitation from south to north lasted about four minutes.

At Eaton-bridge, Kent, in a pond about an acre in size, a dead calm, and no wind stirring, some persons heard a noise, and imagining something had been tumbling in, ran to see what was the matter. On their arrival at the pond, to their surprise they saw the water open in the middle, so that they could see a pool a good way down, almost to the bottom. The water in the mean time dashed up over a bank two feet high, and perpendicular to the pond. This was repeated several times with a great noise. At Eyam-bridge, Derbyshire (in the Peak), the overseer of the lead-mines sitting in his writing-room about 11 o'clock, felt a sudden shock, which very sensibly raised him up in his chair, and caused several pieces of plaster to drop from the sides of the room. The roof was so violently shaken, that he imagined the engine shaft had been falling in. Upon this he immediately ran to see what was the matter, but found everything in perfect safety.—At this time two miners were employed in carting, or drawing along the drifts of the mines, the ore and other materials to be raised up at the shafts. The drift in which they were working was about 120 yards deep, and the space from one end to the other 50 yards or upwards. The miner at the end of the drift had just loaded his cart, and was drawing it along; but he was suddenly surprised by a shock, which so terrified him, that he immediately quitted his employment, and ran to the west end of the drift to his partner, who was no less terrified than himself. They durst not attempt to climb the shaft, lest that should be running in upon them; but while they were consulting what means they should take for their safety, they were surprised by a second shock more violent than the first; which frightened them so much, that they both ran precipitately to the other end of the drift. They then went down to another miner who worked about 12 yards below them. He told them that the violence of the second shock had been so great, that it caused the rocks to grind upon one another. His account was interrupted by a third shock, which, after an interval of four or five minutes, was succeeded by a fourth; and, about the same space of time after, by a fifth; none of which were so violent as the second. They heard, after every shock, a loud rumbling in the bowels of the earth, which continued about half a minute, gradually decreasing, or seeming to remove to a greater distance.

At Shireburn castle, Oxfordshire, at a little after ten in the morning, a very strange motion was observed in the water of a moat which encompasses the house. There was a pretty thick fog, not a breath of air, and the surface of the water all over the moat as smooth as a looking-glass, except at one corner, where it flowed into the shore, and retired again successively, in a surprising manner. In what manner it began to move is uncertain, as nobody observed the beginning of its motion. The flux and reflux, when seen, were quite regular. Every flood began gently; its velocity increased by degrees, when at last it rushed in with great impetuosity, till it had attained its full height. Having remained for a little time stationary, it then retired, ebbing gently at first, but afterwards sinking away with great swiftness. At every flux, the whole body of water seemed to be violently thrown against the bank; but neither during the time of the flux nor that of the reflux, did there appear even the least wrinkle of a wave on the other parts of the moat. Lord Viscount Parker, who had observed this motion, being desirous to know whether it was universal over the moat, sent a person to the other corner of it, at the same time that he himself stood about 25 yards from him, to examine whether the water moved there or not. He could perceive no motion there, or hardly any; but another, who went to the north-east corner of the moat, diagonally opposite to his lordship, found it as considerable there as where he was. His lordship imagining, that in all probability the water at the corner diagonally opposite to where he was would sink as that by him rose, he ordered the person to signify by calling out, when the water by him began to sink, and when to rise. This he did; but, to his lordship's great surprize, immediately after the water began to rise at his own end, he heard his voice calling that it began to rise with him also; and in the same manner he heard that it was sinking at his end, soon after he perceived it to sink by himself. A pond just below was agitated in a similar manner; but the risings and sinkings of it happened at different times from those at the pond where lord Parker stood.

At White Rock in Glamorganshire, about two hours ebb of the tide, and near three quarters after six in the evening, a vast quantity of water rushed up with a prodigious noise; floated two large vessels, the least of them above 200 tons; broke their moorings, drove them across the river, and had like to have overflown them. The whole rise and fall of this extraordinary body of water did not last above ten minutes, nor was it felt in any other part of the river, so that it seemed to have gushed out of the earth at that place.

At Loch Lomond in Scotland, about half an hour after nine in the morning, all of a sudden, without the least gust of wind, the water rose against its banks with great rapidity, but immediately subsided, till it was as low in appearance as any body then present had ever seen it in the greatest summer-drought. Instantly it returned towards the shore, and in five minutes time rose again as high as before. The agitation continued at the same rate till 15 minutes after ten the same morning; taking five minutes to rise, and as many to subside. From 15 minutes after 10 till 11, the height of every rise came somewhat short of that immediately preceding, taking five minutes to flow, and as many to ebb, till the water was entirely settled. The greatest perpendicular height of this swell was two feet four inches. A still more remarkable phenomenon attending the earthquake in this lake was, that a large stone lying at some distance from shore, but in such shallow water that it could easily be seen, was forced out of its place in the lake upon dry land, leaving a deep furrow in the ground all along the way in which it had moved.

In Loch Nefs, about half an hour after nine, a very great agitation was observed in the water. About ten the river Oich, which runs on the north side of Fort Augustus, into the head of the loch, was observed to swell very much, and run upwards from the loch with a pretty high wave, about two or three feet higher than the ordinary surface. The motion of the wave was against the wind, and it proceeded rapidly for about 200 yards up the river. It then broke on a shallow, and flowed three or four feet on the banks, after which it returned gently to the loch. It continued ebbing and flowing in this manner for about an hour, without any such remarkable waves as the first; but about 11 o'clock, a wave higher than any of the rest came up, and broke with so much force on the low ground on the north side of the river, that it run upon the grass upwards of 30 feet from the river's bank.

At Kinfaus, between two and three in the afternoon, in Ireland, the weather being very calm, and the tide near full, a large large body of water suddenly poured into the harbour with such rapidity, that it broke the cables of two floops, each moored with two anchors, and of several boats lying between Sicily and the town. But just at the time that a great deal of mischief was apprehended by all the vessels running foul of each other, an eddy whirled them round several times, and then hurried them back again with the same rapidity as before. This was several times repeated; and while the current rushed up at one side of the harbour, it poured down with equal violence at the other. A vessel that lay all this time in the pool did not seem to be any ways affected by it; nor was the violence of the currents much perceived in the deeper parts of the harbour, but raged with most violence on the flats. The bottom of the harbour, which is muddy, was much altered; the mud being washed from some places, and deposited in others. The perpendicular rise of the water at one quay was measured, and found to be five feet and an half; and is said to have been much higher at another, where it overflowed, and poured into the market-place with such rapidity, that some people who were on the quay immediately ran off, and yet could not prevent themselves from being overtaken and immersed knee-deep in the water. The agitations extended several miles up the river; but, as in the harbour, were most perceived in the shallowest places. The successive risings and fallings of the water continued about ten minutes, and then the tide returned to its natural course. Between six and seven in the evening, the water rose again, though not with so great violence as before, and it continued to ebb and flow alternately till three in the morning. The waters did not rise gradually at first; but, with a hollow and horrid noise, rushed in like a deluge, rising six or seven feet in a minute, and as suddenly subsiding. They were as thick as puddle, very black, and stank intolerably.—From different accounts it appeared, that the water was affected in a similar manner all along the coast to the westward of Kinsale.

In France, shocks were perceived in several places; as at Bayonne, Bordeaux, and Lyons. Commotions of the waters also were observed at Angoulême, Bleville, Havre de Grace, &c. but not attended with the remarkable circumstances above mentioned.

These are the most striking phenomena with which the earthquake of Nov. 1, 1755 was attended on the surface of the earth. Those which happened below ground cannot be known but by the changes observed in springs, &c. which were in many places very remarkable.—At Colares, on the afternoon of the 31st of October, the water of a fountain was greatly decreased: on the morning of the first of November it ran very muddy; and, after the earthquake, returned to its usual state both as to quantity and clearness. On the hills, numbers of rocks were split; and there were several rents in the ground, but none considerable. In some places where formerly there had been no water, springs burst forth, which continued to run.—Some of the largest mountains in Portugal were impetuously shaken as if they were from their foundation; most of them opened at their summits, split and rent in a wonderful manner, and huge masses of them were thrown down into the subjacent valleys.—From the rock called Pedra de Alvidar, near the hill Fojo, a kind of parapet was broken off, which was thrown up from its foundation in the sea.—At Varge, on the river Macaas, at the time of the earthquake, many springs of water burst forth, some spouted to the height of 18 or 20 feet, throwing up sand of various colours, which remained on the ground. A mountainous point, seven or eight leagues from St Ube's, cleft asunder, and threw off several vast masses of rock.—In Barbary, a large hill was rent in two; the two halves fell different ways, and buried two large towns. In another place, a mountain burst open, and a stream issued from it as red as blood. At Tangier, all the fountains were dried up, so that there was no water to be had till night.—A very remarkable change was observed on the medicinal waters of Toplitz, a village in Bohemia famous for its baths. These waters were discovered in the year 762; from which time the principal spring of them had constantly thrown out hot water in the same quantity, and of the same quality. On the morning of the earthquake, between 11 and 12 in the forenoon, the principal spring cast forth such a quantity of water, that in the space of half an hour all the baths ran over. About half an hour before this great increase of the water, the spring flowed turbid and muddy; then having stopped entirely for a minute, it broke forth again with prodigious violence, driving before it a considerable quantity of reddish ochre. After this it became clear, and flowed as pure as before. It still continues to do so; but the water is in greater quantity, and hotter, than before the earthquake. At Angoulême in France, a subterraneous noise like thunder was heard; and presently after the earth opened, and discharged a torrent of water mixed with red sand. Most of the springs in the neighbourhood sunk in such a manner, that for some time they were thought to be quite dry. In Britain, no considerable alteration was observed in the earth, except that, near the lead mine above mentioned in Derbyshire, a cleft was observed about a foot deep, six inches wide, and 150 yards in length.

At sea, the shocks of this earthquake were felt most violently. Off St Lucar, the captain of the Nancy the earth-frigate felt his ship so violently shaken, that he thought she had struck the ground; but, on heaving the lead, found he was in a great depth of water. Captain Clark from Denia, in N. Lat. 36° 24', between nine and ten in the morning, had his ship shaken and strained as if she had struck upon a rock, so that the seams of the deck opened, and the compass was overturned in the binnacle. The master of a vessel bound to the American islands, being in N. Lat. 25°, W. Long. 40°, and writing in his cabin, heard a violent noise, as he imagined, in the steerage; and while he was asking what the matter was, the ship was put into a strange agitation, and seemed as if she had been suddenly jerked up and suspended by a rope fastened to the mast-head. He immediately started up with great terror and astonishment; and looking out at the cabin-window, saw land, as he took it to be, at the distance of about a mile. But, coming upon the deck, the land was no more to be seen, but he perceived a violent current across the ship's way to the leeward. In about a minute, this current returned with great impetuosity, and at a league's distance he saw three craggy-pointed rocks throwing up water of various colours resembling fire. This phenomenon, in about two minutes, ended in a black cloud, which ascended very heavily. After it had risen above the horizon, no rocks were to be seen; though the cloud, still ascending, was long visible, the weather being extremely clear.—Between nine and ten in the morning, another ship, 40 leagues west of St Vincent, was so strongly agitated, that the anchors, which were lashed, bounced up, and the men were thrown a foot and a half perpendicularly up from the deck. Immediately after this, the ship sunk in the water as low as the main chains. The lead showed a great depth of water, and the line was tinged of a yellow colour and smelt of sulphur. The shock lasted about ten minutes, but they felt smaller ones for the space of 24 hours.

Such were the phenomena of this very remarkable and destructive earthquake, which extended over a tract of at least four millions of square miles. The earthquakes, however, which in the year 1783 ruined a great part of Italy and Sicily, tho' much more confined in their extent, seem to have been not at all inferior in violence. Sir William Hamilton, who wrote a particular account of their effects, informs us, that "if, on a map of Italy, and with your compass on the scale of Italian miles you were to measure off 22, and then, fixing the central point in the city of Oppido (which seemed to be the spot where the earthquake had exerted its greatest force) form a circle (the radii of which will be 22 miles), you will then include all the towns, villages, &c. that have been utterly ruined, and the spots where the greatest mortality happened, and where there have been the most visible alterations on the face of the earth: then extend your compass on the same scale to 72 miles, preserving the same centre, and form another circle, you will include the whole country that has any mark of having been affected by the earthquake. A gradation was plainly observed in the damage done to the buildings, as also in the degree of mortality, in proportion as the countries were more or less distant from this supposed centre of the evil." Another circumstance was particularly remarked, and in which this earthquake differed very considerably from others, viz. that if two towns were situated at an equal distance from this centre, one on the hill, the other on the plain or in a bottom, the latter always suffered more by the shocks of the earthquakes than the former.

From the most authentic reports and accounts received by his Sicilian majesty's secretary of state, it was learned, that the part of Calabria which had been most affected by this heavy calamity, is that comprehended between the 38th and 39th degree of latitude: that the greatest force of the earthquake seemed to have exerted itself from the foot of those mountains of the Apennines called the Monte Dijo, Monte Sacro, and Monte Cau- lena, extending westward to the Tyrrhenic sea: that the towns, villages, and farm-houses nearest these mountains, situated either on the hills or the plain, were totally ruined by the shock of the 5th of February about noon: that as the towns and villages were at a greater distance from this centre, the damage they received was less considerable; but that even these more distant towns had been greatly damaged by the subsequent shocks of the earthquakes, and effectually by those of the 7th, 26th, and 28th of February, and that of the 1st of March; that from the first shock of the 5th of February, the earth had been in a continual tremor; and that the shocks were more sensibly felt at times in some parts of the afflicted provinces than at others; that the motion of the earth had been either whirling like a vortex, horizontal, or by pulsations, or by beatings from the bottom upwards. This variety of motions increased the apprehensions of the miserable inhabitants, who expected every moment that the earth would open under their feet, and swallow them up. It was said also that the rains had been continued and violent, frequently accompanied with irregular and furious gusts of wind; and that from all these causes, the face of that part of Calabria comprehended between the 38th and 39th degrees was entirely altered, particularly on the western side of the mountains above mentioned: that many openings and cracks had been made in those parts; some hills had been much lowered, and others entirely swallowed up; deep chasms had been made, by which many roads were rendered impassable; huge mountains were said to have been split asunder, and the parts of them driven to a considerable distance; deep valleys to have been filled up by the concourse of the mountains which formed them before; the course of rivers altered; many springs of water dried up, and new ones formed in their place, &c. A singular phenomenon was said to have been observed at Laureana in Calabria Ultra; viz. that two whole tenements, with large plantations of olive and mulberry trees, situated in a valley perfectly level, had been detached by the earthquake, and transplanted, with the trees still remaining in their places, to the distance of about a mile from their first situations; and that from the spot on which they formerly stood, hot water had sprung up to a considerable height, mixed with sand of a ferruginous nature: that near this place also some countrymen and shepherds had been swallowed up, with their teams of oxen, and their flocks of goats and sheep. The number of lives lost was estimated at 32,367; but Sir William Hamilton is of opinion, that, including strangers, it could not be less than 40,000.

The fate of the inhabitants of Scilla was extremely Fate of the affecting. On the first shock of the earthquake February 5th, they had fled along with their prince to the sea-shore, where they hoped for safety; but in the night-time a furious wave (said to have been boiling hot, and by which many people were alleged to have been scalded) overflowed the land for three miles, sweeping off in its return 2473 of the inhabitants, among whom was the prince himself, who were at that time either on the strand or in boats near the shore. But the most singular of all the phenomena enumerated A hill removed in these accounts was, that a hill, about 500 palms in moves from height, and 1300 in circumference at its basis, jumped its place, to the distance of about four miles from the place where it formerly stood. At the same time the hill on which the town of Oppido stood, which extended about three miles, parted in two; and as its situation was between two rivers, both of these were of course topped up; two great lakes were formed, and by their continual increase threatened to infect the air by their Authenti noxious exhalations.

Such were the accounts at first propagated and universally believed; but Sir William Hamilton, who made a tour through the ruined country that same year, found little. found that, though the effects in general were very dreadful, still there had been some exaggeration in several particulars. He set sail, for the purpose of making this tour, on the 2d of May, for Naples, and soon landed on the coast of Calabria Citra. The first appearances of the earthquake were observed at Cedraro; some of the principal inhabitants of that city having quitted their habitations, though Sir William could not perceive that any damage had been done. At St Lucido, the baron's palace and the church steeple had suffered, and most of the inhabitants were in barracks; but wishing to come as soon as possible to the centre of that scene of desolation, he set sail again, and landed on the 6th of May at the town of Pizzo in Calabria Ultra. This town is situated on a volcanic tufa, and had been greatly damaged by the earthquake of February 5th, but completely ruined by that of the 28th of March. Here he was assured, that the volcano of Stromboli, which is opposite, and in full view of the town, though distant about 50 miles, had smoked less and thrown up a smaller quantity of inflamed matter during the earthquakes than it had done for some years before; and that slight shocks still continued to be felt. Sir William had soon a convincing proof that this last information was true; for, sleeping that night in his boat, (called a Maltese Speronara), he was awakened with a smart shock, which seemed to lift up the bottom of the boat, but was not attended with any subterraneous noise.

From Pizzo he passed through a most beautiful country to Monteleone. This town, anciently called Vibo Valentia, is finely situated on a hill, overlooking the sea and the fine rich plains through which he had just passed; which are bounded by the Apennines, and crowned by Aspromonte the highest of them all. They were formerly interspersed with towns and villages; but at that time all of them lay in ruins. Monteleone suffered little on the 5th of February, but was greatly damaged on the 28th of March. Here every one agreed, that the shocks of the earthquake seemed to come with a rumbling noise from the westward; beginning usually with the horizontal motion, and ending with the vortices, by which last the greatest part of the buildings in this province were destroyed. It was a general observation also, that before a shock the clouds seemed to be still and motionless, and that immediately after a heavy shower of rain a shock quickly followed. Here Sir William had an opportunity of seeing many people who had been thrown down by the violence of the shocks. Several peasants told him, that the motion of the earth was so violent, that the heads of the largest trees almost touched the ground from side to side; that during a shock, the horses and oxen extended their legs wide apart, that they might not be thrown down; and that they gave evident signs of being sensible of the approach of each shock. "I myself (says he) have observed, that in those parts which have suffered most by earthquakes, the braying of an ass, the neighing of a horse, or the cackling of a goose, always drove people out of their barracks, and was the occasion of many prayers and Ave-marias being repeated, in expectation of a shock."

From Monteleone our author descended into the plain, having passed through many towns and villages which had been more or less ruined according to their vicinity to the plain. The town of Mileto, standing in a bottom, was totally ruined, not a house being left standing. At some distance he saw Soriano, and the noble Domitian convent, a heap of ruins. In this day's journey, he observes, that all habitations situated upon high grounds, the soil of which is a gritty sandstone, somewhat like a granite, but without the consistence, had suffered less than those situated on the plain; the latter being universally levelled with the ground. The soil of the plain is a sandy clay, white, red, and brown; but the white prevails most, and is full of marine shells, particularly scollops. It is intersected in many parts by rivers and torrents, which have produced wide and deep ravines all over the country. Passing through the ruined town of St Pietro, in his way to Rolarno, our author had a distant view of Sicily and the summit of Mount Etna, which then sent forth a considerable smoke. Just before his arrival at Rolarno, he passed over a swampy plain, in many parts of which he was shown small hollows in the earth, of the shape of an inverted cone. They were covered with sand, as was the soil near them. He was informed, that during the earthquake of the 5th of February, a fountain of water, mixed with sand, had been driven up from each of these spots to a considerable height. Here he spoke to a peasant who had been an eye-witness, and was even covered with the water and sand; but he assured him, that it was not hot, as had been represented. Before this appearance, he said, the river was dry; but soon after returned and overflowed its banks. He afterwards found, that the same phenomenon had been constant with respect to all other rivers in the plain, during the dreadful shock of the 5th of February. This phenomenon, our author thinks, may be easily explained by supposing the first impulse of the earthquake to have come from the bottom upwards, which all the inhabitants of the plain attested to be fact; the surface of the plain suddenly rising, the rivers, which are not deep, would naturally disappear, and the plain returning with violence to its former level, the rivers must naturally have returned and overflowed, as the sudden depression of the boggy grounds would naturally force out the water that lay hid under their surface. It was observed in the other parts where this phenomenon had been exhibited, that the ground was always low and muddy. Between this place and Rolarno they passed the river Messano or Metanaro (which is near the town above mentioned) on a bridge on strong timber-bridge, 700 palms long, lately built by the duke of Monteleone. From the cracks made in the banks and in the bed of the river by the earthquake, it was quite separated in one part; and the level on which the piers were placed having been variously altered, the bridge had taken an undulated form, so that the rail on each side was curiously scoloped; but the separated parts having been joined again, it was then passable. Our author was also informed, that at the time of the earthquake the river was perfectly dry for some seconds, and then returned with violence and overflowed; and that the bridge undulated in a most extraordinary manner. By the earthquake in the plain, our author understands the shock of the 5th of February, which did so much damage without giving any previous notice. The town of Rosarno, with the duke of Monteleone's palace there, was entirely ruined; but the walls remained about six feet high, and were at that time fitting up as barracks. The only building that remained unhurt at Rosarno was the town gaol, in which were three notorious villains, who would probably have lost their lives if they had remained at liberty.

From Rosarno Sir William proceeded to Laureana, where he was conducted to the place where two tenements were said to have exchanged situations. This fact, which at the first relation appeared so incredible, Sir William assures us was true, and very easily accounted for. These tenements were situated in a valley surrounded by high grounds; and the surface of the earth, which was removed, had probably been undermined by little rivulets which come from the mountains, and were then plainly discernible on the bare spot which the tenements had quitted. Their course down the valley was sufficiently rapid to prove that it had not been a perfect level as was represented. The earthquake, he supposes, had opened some depots of rain-water in the clay-hills which surround the valley; which water, mixed with the loose soil, taking its course suddenly through the undermined surface, lifting it up with the large olive and mulberry trees, and a thatched cottage, floated the whole piece of ground, with all its vegetation, about a mile down the valley, where it then flooded with most of the trees erect. These two tenements were about a mile long and half a mile broad. In the neighbourhood were several cracks, none of them above a foot wide; but our author was assured, that during the earthquake they had opened wide, and swallowed up an ox with near 100 goats. In the above mentioned valley he saw the same sort of hollows in the form of inverted cones, out of which he had been assured that hot water mixed with sand issued during the earthquakes at Rosarno; but, on proper inquiry, no person was found who could positively declare that the water had really been hot. Some of the sand which was thrown up had a ferruginous appearance, and seemed to have been acted upon by fire. It was said also, that, when fresh, this sand had the smell of sulphur; but this our author could not perceive.

Passing through the same beautiful country to the town of Polifene, he did not perceive a single house standing. "I travelled (says he) four days in the plain, in the midst of such misery as cannot be described. The force of the earthquake there was so great, that all the inhabitants of the towns were buried, alive or dead, in the ruins of their houses in an instant. The town of Polifene was large, but ill situated between two rivers that were subject to overflow. Two thousand one hundred, out of 6000, lost their lives here on the fatal 5th of February." At Cafal Nuova, the princess Gerace Grimaldi, with 4000 of her subjects, perished on the same day by the explosion; for such it appears to have been. Some who had been dug alive out of the ruins, told our author, that they had felt their houses fairly lifted up, without having the least previous notice. An inhabitant of Cafal Nuova was at that moment on a hill overlooking the plain; when, feeling the shock, and turning round, instead of the town he saw only a thick cloud of white dust like smoke, the natural effect of the crushing of the buildings and the mortar flying off.

The town of Cafal Nuova was so effectually destroyed by this dreadful shock, that neither vestige of house or street remained, but all lay in one confused heap of ruins. Cafliaice and Milicuccio, which our author next visited, were both in the same situation. Terra Nuova, situated in the same plain, flood between two rivers, which, with the torrents from the mountains, had, in the course of ages, cut deep and wide chasms in the soft sandy clay soil of which it is composed. At Terra Nuova the ravine or chasm is not less than 500 feet deep, and three quarters of a mile broad. Here the accounts of the earthquake were confused, by not having the situation of the place and nature of the soil explained. It was said, that a town Terra Nuova had been thrown a mile from the place on which it stood, without mentioning a word of the ravine; that woods and corn-fields had been removed in the same manner, "when in truth (says our author) it was but upon a large scale, what we see every day upon a smaller; when pieces of the sides of hollow ways, having been undermined by rain waters, are detached by their own weight. Here, from the great depth of the ravine, and the violent motion of the earth, two huge portions of the latter, on which a great part of the town stood, which consisted of some hundred houses, had been detached into the ravine, and nearly across it, at about the distance of half a mile from the place where they formerly stood; and what is very extraordinary, many of the inhabitants who had taken this singular leap in their houses, were nevertheless dug out nary escape alive, and some unhurt." Our author's guide there, of some who was both a priest and physician, having been buried in the ruins of his house by the first shock, was blown out of it and delivered by the second, which immediately followed the first; and there were many well attested instances of the same thing having happened in different parts of Calabria. At Terra Nuova, however, only 400 out of 1600 inhabitants were left alive.

In other parts of the plain, situated near the ravine, and near the town of Terra Nuova, our author saw tracts of many acres of land, with trees and corn-fields, that had been detached into the ravine, frequently without having been overturned; so that the crops were growing as well as if they had been planted there. Other such pieces were lying in the bottom in an inclined situation; and others again that had been quite overturned. In one place, two of these immense pieces of land having been detached, opposite to one another, had filled the valley, and stopped the course of the river, the waters of which were forming a great lake; "and this (says our author) is the true state of what the accounts mention of mountains that had walked, and joined together, stopped the course of a river, and formed a lake."

At the moment of the earthquake the river disappeared as at Rosarno; and returning soon after, overflowed the bottom of the ravine about three feet in depth; so that the poor people who had been thrown with their houses into the ravine from the top of it, and had escaped with broken bones, were now in danger of being drowned. Our author was assured, that the water was salt like that of the sea; but this circumstance... cumstance seemed to want confirmation. The same cause, however, given for the sudden disappearing of the river Metauro at Rosarno will account for the like phenomenon here, and in every part of the country where the rivers were dried up at the moment of the earthquake.

The whole town of Molochi di Sotta was likewise detached into the ravine, and a vineyard of many acres lay near it in the bottom in perfect order, but in an inclined situation. There was a foot-path through this vineyard which had a singular effect in its then impracticable situation. Some water-mills which were on the river, being jammed between two such detached pieces as above described, were lifted up by them, and were then to be seen on an elevated situation many feet above the level of the river.

In several parts of the plain, the foil, with timber-trees and crops of corn, consisting of many acres, had sunk eight and ten feet below the level of the plain, and risen as many in other places. To explain this, it is necessary to remember, that the foil of the plain is a clay mixed with sand, which is easily moulded into any shape. In the plain, near the spots where the above mentioned pieces had been detached into the ravine, there were several parallel cracks; so that, had the violence of the earthquake continued, these pieces would also probably have followed. It was constantly remarked by our author, that near every ravine or hollow way, the parts of the plain adjoining were full of large parallel cracks. The earth rocking from side to side, and being supported only on one side, accounts very well for this circumstance.

From Terra Nuova our author continued his journey to Oppido. This city stands on a mountain of a ferruginous sort of gritty stone, unlike the clay foil of its neighbourhood; and is surrounded by two rivers in a ravine deeper and broader than that at Terra Nuova.

Instead of the mountain on which this city stands having split, as was reported, and by its fall stopped up the course of rivers, it was, as at Terra Nuova, huge pieces of the plain on the edge of the ravine, that had been detached into it, had nearly filled it up, and flopped the course of the rivers, the waters of which were then forming two great lakes. Part of the rock on which the city stood was indeed also detached, with several houses, into the ravine; "But that (says our author) is a trifling circumstance in comparison of the very great tracts of land with plantations of vines and olives which had been detached from one side of the ravine to the other, though the distance is more than half a mile. It is well attested, that a countryman, who was ploughing his field in this neighbourhood with a pair of oxen, was transported with his field and team clear, from one side of a ravine to the other, and that neither he nor his oxen were hurt.

"Having walked over the ruins of Oppido (says our author), I descended into the ravine, and examined carefully the whole of it. Here I saw indeed the wonderful force of the earthquake, which has produced exactly the same effects as those described in the ravine at Terra Nuova, but on a scale infinitely greater. The enormous masses of the plain, detached from each side of the ravine, lie sometimes in confused heaps, forming real mountains, and having stopped the course of two rivers (one of which is very considerable), great lakes are already formed; and if not afflitted by nature or art, so as to give the rivers their due course, must infallibly be the cause of a general infection in the neighbourhood. Sometimes I met with a detached piece of the surface of the plain (of many acres in extent) with the large oaks and olive-trees, with corn or lupins under them, growing as well and in as good order at the bottom of the ravine as their companions from whence they were separated do on their native soil, at least 500 feet higher, and at the distance of about three quarters of a mile. I met with whole vineyards in the same order in the bottom that had likewise taken the same journey. As the banks of the ravine from whence these pieces came are now bare and perpendicular, I perceived that the upper foil of the foil was a reddish earth, and the under one a sandy white clay, very compact, and like a soft stone. The impulse these huge masses received, either from the violent motion of the earth alone, or that assisted with of the additional one of the volcanic exhalations set in upon liberty, seems to have acted with greater force on the lower and more compact stratum than on the upper cultivated crust: for I constantly observed, where these cultivated lands lay, the under stratum of compact clay had been driven some hundred yards farther, and lay in confused blocks; and, as I observed, many of these blocks were in a cubical form. The under foil, having had a greater impulse, and leaving the upper in its flight, naturally accounts for the order in which the trees, vineyards, and vegetation fell, and remain at present in the bottom of the ravine.

"In another part of the bottom of the ravine there is a mountain composed of the same clay foil, and which was probably a piece of the plain detached by an earthquake at some former period: it is about 250 feet high, and 400 feet diameter at its basis. This Removal of mountain, as is well attested, has travelled down the hill across the ravine near four miles; having been put in motion by the earthquake of the 5th of February. The abundance of rain which fell at that time, the great weight of the fresh detached pieces of the plain which I saw heaped up at the back of it, the nature of the foil of which it is composed, and particularly its situation on a declivity, accounts well for this phenomenon; whereas the reports which came to Naples of a mountain having leaped four miles, had rather the appearance of a miracle. I found some single timber-trees also with a lump of their native foil at their roots, standing upright in the bottom of the ravine, and which had been detached from the bottom of the plain above mentioned. I observed also, that many confused heaps of the loose foil, detached by the earthquake from the plains on each side of the ravine, had actually run like a volcanic lava (having probably been afflitted by the heavy rain), and produced many effects much resembling those of lava during their course down a great part of the ravine. At Santa Cristina, near Oppido, the like phenomena have been exhibited, and the great force of the earthquake of the 5th of February seems to have been exerted on these parts, and at Cafal Nuova, and Terra Nuova."

From Oppido Sir William proceeded to the towns of Seminara and Palmi. The former, being situated higher up, had suffered less than Palmi which stood nearer the sea. Fourteen hundred lives were lost at this place, and some singular circumstances occurred. The town being a great market for oil, there were upwards of 4000 barrels of that liquid in it at the time of its destruction; so that by the breaking of these barrels and jars, a rivulet of oil ran from the ruins for many hours into the sea. Here our author was informed by the person who conducted him, that he had been buried in the ruins of his house by the first shock; and that after the second, which followed immediately, he found himself sitting astride a beam at least 15 feet high in the air. After Sir William’s departure from Palmi, in going through one of the narrow passes among the mountains of Bagnara and Solano, he felt a very smart shock of an earthquake attended with a loud explosion like that of springing a mine; but fortunately it did not detach any rocks or trees from the high mountains which hung over their heads. In this country he was assured by several fishermen, that during the earthquake on the 5th of February, at night, the sea was hot, and that they saw fire issue from the earth in many parts. This last circumstance was frequently repeated in different parts of the plain, so that there seems to remain no doubt of its authenticity.

The idea of Sir William Hamilton is, that “the exhalations which issued during the violent commotions of the earth were full of electrical fire; just as the smoke of volcanoes constantly is during violent eruptions; for I saw no mark (says he), in any part of my journey, of any volcanic matter having issued from the fissures of the earth; and I am convinced that the whole has been done by vapours and exhalations only. The first shock felt at this place, as I was assured, was lateral, and then vortical, and exceedingly violent; but what they call violent here must have been nothing in comparison of what was felt in the plain of Casa Nuova, Polistene, Palmi, Terra Nuova, Oppido, &c., &c., where all agreed that the violence of the fatal shock of February was instantaneous, without warning, and from the bottom upwards.”

At Reggio the shock had been much less violent than in the places hitherto visited by our author; and though there was not a house in it inhabited or habitable, yet (says he) after having been several days in the plain, where every building is levelled with the ground, a house with a roof, or a church with a steeple, was to me a new and refreshing object.” In this place he had an account from the archbishop of the earthquakes of 1770 and 1780, which obliged the inhabitants, in number 16,400, to encamp or remain in barracks for several months, without having done any considerable damage to the town. He was informed also, that all animals and birds are in a greater or lesser degree much more sensible of an approaching shock of an earthquake than any human being; but that geese, above all, seem to be the soonest and most alarmed at the approach of a shock: if in the water, they quit it immediately; and there are no means of driving them into it for some time after. The shock which damaged Reggio came on gently, so that the people had time to make their escape, and only 126 were killed; but in the plain this shock was as instantaneous as it was violent and destructive.

On the 14th of May, Sir William Hamilton having taken leave of Reggio, set sail for Messina, which he visited next morning; and found that the shock, though very violent there, had been far inferior to what he had seen the effects of in other places. Many houses, even in the lower part of the town, were standing, and some little damaged; but in the upper and more elevated situations, the earthquakes seemed to have scarce had any effect. “A strong instance (says our author) of this is, that the convent of Santa Barbara, and that called the Novitato de Gesuiti, both on an elevated situation, have not a crack in them; and that the clock of the latter has not been deranged in the least by the earthquakes, which have afflicted this country for four months past, and which still continue in some degree.”

Notwithstanding this comparative mildness, however, the shock at Messina had been very terrible. All there, the beautiful front of the palazzate, which extended in very lofty uniform buildings, in the shape of a crescent, had been in some parts totally ruined, in others less; and there were cracks in the earth of the quay, a part of which had sunk above a foot below the level of the sea. These cracks were probably occasioned by the horizontal motion of the earth in the same manner as the pieces of the plain were detached into the ravines at Oppido and Terra Nova; for the sea at the edge of the quay is so very deep, that the largest ships can lie along side. The earth, therefore, in its violent commotion, wanting support on that side next the sea, began to crack and separate; and as where there is one crack there are generally others less considerable in lines parallel to the first, our author supposes, that the great damage done to the houses near the quay was owing to such cracks below their foundations. It is said, that during the earthquake fire had been seen to issue from the cracks of the quay; but our author is persuaded that this, as in other cases, was only a vapour charged with electrical fire or a kind of inflammable air. Here also he was informed, that the shock of the 5th of February had been from the bottom upwards; but the subsequent ones generally horizontal or vortical. A remarkable circumstance was observed at Messina, and through the whole coast of Calabria, which had been most affected by the earthquake, viz. that a small fish called cicirelli, resembling the English white bait, but larger, and which usually lie at the bottom of the sea buried in the sand, had, ever after the commencement of the earthquakes to the time this account was written, continued to be taken near the surface, and that in such abundance as to be common food for the poorest sort of people; whereas before the earthquakes this fish was rare, and reckoned among the greatest delicacies. Fish of all kinds also were taken in greater abundance on these coasts after the commencement of the earthquakes than before; which our author supposes to have been occasioned either by the volcanic matter having heated the bottom of the sea, or that the continual tremor of the earth had forced them out of their retreats. At Messina our author was likewise informed, that on the 5th of February, and for three days following, the sea about a quarter of a mile from the citadel rose and boiled in an extraordinary manner, and near Messina with a most horrid and alarming noise; the water in other parts of the strait being perfectly calm. “This (says... Earthquake.

Account of the great wave which destroyed the inhabitants of Scilla.

The next inquiry made by this curious traveller was concerning the great wave which occasioned such destruction at Scilla, as has already been related. Having left Messina on the 17th of May, he proceeded in his boat to the entrance of the Faro, where he met with a priest who had been there on the night between the 5th and 6th of February, when the wave passed over that point of land. Here it carried off boats with 24 people, tore up trees by the roots, and left a considerable quantity of fish behind it. This priest had himself been covered by the wave, and with difficulty saved his life. He at first said the water was hot; but on being pressed with other questions, it amounted to no more than that the water was as warm as it usually is in summer. The wave, he said, rose to a great height, and came on with noise and such rapidity that it was impossible to escape.

On crossing over to Scilla, Sir William was perfectly satisfied concerning the nature of this formidable wave, and found that the following was the true state of the fact: "The prince of Scilla having remarked, that during the first horrid shock, which happened about noon the 5th of February, part of a rock near Scilla had been detached into the sea; and fearing that the rock of Scilla, on which his town and cattle are situated, might also be detached, he thought it safer to prepare boats, and retire to a little port or beach seated at the foot of it, and likewise surrounded by rocks. But the second shock of the earthquake about midnight, having detached a whole mountain much higher than that of Scilla, situated between the latter and Torre del Cavallo, it fell into the sea with such violence as to raise the fatal wave above mentioned. This having broken on the point of land called Punto del Faro, in the manner already related, instantly returned with great noise and celerity upon the beach, where the unfortunate prince and his subjects had taken refuge, and either dashed them with their boats and effects against the rocks, or whirled them into the sea. Those who had escaped the first and greatest wave, were carried off by a second and third less considerable, but which immediately followed the first. Our author spoke with many who had been involved in that wave, and violently hurt by it; but all of them agreed in asserting that the water was not hot.

The earthquakes were not perfectly settled even in 1784, when Sir William Hamilton wrote the account of the state of Vesuvius, &c., to the Royal Society. In a postscript to that letter he adds the following confirmation of his conjecture, that the volcanic matter, which he supposed to have occasioned the earthquakes, had vented itself at the bottom of the sea between Calabria and Sicily. "The pilot of one of his Sicilian majesty's sciabecques having some time after the earthquakes cast anchor off the point of Palizzi, where he had often anchored in 25 fathom water, found no bottom till he came to 65; and having sounded for two miles out at sea towards the point of Spartivento in Calabria, he still found the same considerable alteration in the depth. The inhabitants of Palizzi likewise declare, that during the great earthquake on the 5th of February 1783, the sea had boiled and frothed up tremendously off their point."

To explain the phenomena of earthquakes, various hypotheses have been invented. Till lately, the hypotheses of modern philosophers were much the same with those of the ancients. Anaxagoras supposed the cause of earthquakes to be subterranean clouds bursting out into lightning, which shook the vaults that contained them. Others imagined, that the arches, which had been weakened by continual subterranean fires, at length fell in. Others derived these accidents from the rarefied steam of waters, heated by some neighbouring fires; and some, among whom was Epicurus, and several of the Peripatetic school, ascribed these terrible accidents to the ignition of certain inflammable exhalations.

This last hypothesis has been adopted by many of the most celebrated moderns, as Gassendus, Kircher, Schottus, Varenius, Des Cartes, Du Hamel, Honorius, Fabri, &c. The philosopher last mentioned indeed supposed, that waters prodigiously rarefied by heat might sometimes occasion earthquakes. The others supposed, as their hypothesis necessarily requires, that there are many vast cavities underground which have a communication with one another; some of which abound with waters; others with vapours and exhalations, arising from inflammable substances, as nitre, bitumen, sulphur, &c. These combustible exhalations they supposed to be kindled by a subterraneous spark, or by some active flame gliding through a narrow fissure from without, or by the fermentation of some mixture; and when this happened, they must necessarily produce pulses, tremors, and ruptures at the surface, according to the number and diversity of the cavities, and the quantity and activity of the inflammable matter. This hypothesis is illustrated by a variety of experiments, such as mixtures of iron-flings and brimstone buried in the earth, gun-powder confined in pits, &c., by all which a shaking of the earth will be produced.

Dr Woodward suggests another hypothesis. He supposes that the subterraneous heat or fire, which is continually elevating water out of the abyss, which, according to him, occupies the centre of the earth, to furnish rain, dew, springs, and rivers, may be stopped in some particular part. When this obstruction happens, the heat causes a great swelling and commotion in the waters of the abyss; and at the same time, making the like effort against the superincumbent earth, that agitation and concussion of it is occasioned which we call an earthquake.

Mr Amontons of the Royal Academy of Sciences suggests an hypothesis entirely different from any of the above mentioned ones. According to the received philosophical principles, which suppose the atmosphere to be about 45 miles high, and that the density of the air increases in proportion to the absolute height of the superincumbent column of fluid; it is shown, that at the depth of 43,528 fathoms below the surface of the earth, air is but one-fourth lighter than mercury. Now, this depth of 43,528 fathoms is only... only a 74th part of the semidiameter of the earth; and the vast sphere beyond this depth, in diameter 6,451,538 fathoms, may probably be only filled with air; which will be here greatly condensed, and much heavier than the heaviest bodies we know of in nature. But it is found by experiment, that the more air is compressed, the more does the same degree of heat increase its spring, and the more capable does it render it of a violent effect; and that, for instance, the degree of heat of boiling water increases the spring of the air above what it has in its natural state, in our climate, by a quantity equal to a third of the weight wherewith it is pressed. Whence we may conclude, that a degree of heat, which on the surface of the earth will only have a moderate effect, may be capable of a very violent one below. And as we are assured, that there are in nature degrees of heat much more considerable than that of boiling water, it is very possible there may be some, whose violence, further assisted by the exceeding weight of the air, may be more than sufficient to break and overturn this solid orb of 43,528 fathoms; whose weight, compared to that of the included air, would be but a trifle.

Though none of these hypotheses were sufficient for explaining the phenomena of earthquakes in a satisfactory manner, one or other of them continued to be adopted by almost all philosophers till the year 1749. In the month of March that year, an earthquake was felt at London and several other places in Britain. Dr Stukely, who had been much engaged in electrical experiments, began to suspect that phenomena of this kind ought to be attributed not to vapours or fermentations generated in the bowels of the earth, but to electricity. In a paper published by him on this subject, he rejects all the above mentioned hypotheses for the following reasons.

1. That there is no evidence of any remarkable cavernous structure of the earth; but that, on the contrary, there is rather reason to presume that it is in a great measure solid, so as to leave little room for internal changes and fermentations within its substance; nor do coal-pits, he says, when on fire, ever produce anything resembling an earthquake.

2. In the earthquake at London, in March 1749, there was no such thing as fire, vapour, smoke, smell, or an eruption of any kind observed, though the shock affected a circuit of 30 miles in diameter. This consideration alone of the extent of surface shaken by an earthquake, he thought sufficient to overthrow the supposition of its being owing to the expansion of any subterranean vapours. For as small fire-balls bursting in the air propagate a sulphurous smell to the distance of several miles, it cannot be supposed, that so immense a force acting instantaneously on that compass of ground should never break the surface of it, nor become discoverable either to the sight or the smell: besides, that the operation of such a fermentation would be many days in continuance, and the evaporation of so much inflammable matter would require a long space of time. That such an effect, therefore, should be produced instantaneously, can be accounted for by electricity only; which acknowledges no sensible transition of time, no bounds.

3. If vapours and subterraneous fermentations, explosions and eruptions, were the cause of earthquakes, they would absolutely ruin the whole system of springs and fountains, wherever they had once been; which is contrary to fact, even when they have been frequently repeated. Even in the earthquake in Asia Minor, A.D. 17, which destroyed 13 great cities, and shook a mass of earth 300 miles in diameter, nothing suffered but the cities; neither the springs nor the face of the country being injured, which indeed remains the same to this day.

4. That any subterraneous power sufficient to move 30 miles in diameter, as in the earthquake which happened at London, must be lodged at least 15 or 20 miles below the surface; and therefore must move an inverted cone of solid earth, the base of which is 30 miles in diameter, and the axis 15 or 20; an effect impossible to any natural power whatever, except electricity. So in Asia Minor, such a cone must have been 300 miles in the diameter of the base, and 200 in the axis; which not all the gun-powder that has been made since the invention of it, much less any vapours generated so far below the surface, could possibly effect.

5. A subterraneous explosion will not account for the manner in which ships, far from land, are affected during an earthquake; which seem as if they struck upon a rock, or as if something thumped against their bottoms. Even the fishes are affected. A subterraneous explosion would only produce a gradual swell, and not give to quick an impulse to the water as would make it feel like a stone.

From comparing these circumstances, the Doctor His method says, he had always thought that an earthquake was a shock of the same kind as those which commonly occur in electrical experiments. And this hypothesis was confirmed by the phenomena attending earthquakes; particularly those of 1749 and 1750, which gave rise to his publication.

The weather, for five or six months before, had been uncommonly warm; the wind south and south-west, without rain; so that the earth must have been in a state peculiarly ready for an electrical shock. The flat country of Lincolnshire had been under an exceeding great drought. The uncommonness of the first of these circumstances, he remarks, is the reason why earthquakes are less frequently experienced in the northern than in the southern regions of the world, where the warmth and dryness of the air, so necessary to electricity, are more usual: And the latter shows how fit the dry surface was for an electrical vibration; and (which is of great importance) that earthquakes reach but little below the surface of the earth.

Before the earthquake at London, all vegetables had been uncommonly forward. And electricity is well known to quicken vegetation. The aurora borealis had been frequent about that time; and just before the earthquake, had been twice repeated in such colours as had never been seen before. It had also removed southerly, contrary to what is common in England; so that the Italians, and those among whom earthquakes were frequent, actually foretold the earthquake. The year had been remarkable for fire-balls, lightning, and coruscations; and these are rightly judged to be meteors of an electrical nature. In these circumstances of the earth and air, nothing, he says, is wanting to produce an earthquake, but the touch of some non-electric body; which must necessarily be had ab extra from the region of the air or atmosphere. Hence he infers, that if a non-electric cloud discharge its contents upon any part of the earth, in that highly electrical state, an earthquake must necessarily ensue. As the discharge from an excited tube produces a commotion in the human body, so the discharge of electric matter from the compass of many miles of solid earth must needs be an earthquake; and the snap from the contact, the horrid uncouth noise attending it.

The Doctor had been informed by those who were up and abroad the night preceding the earthquake, and early in the morning, that coruscations in the air were extremely frequent; and that a little before the earthquake, a large and black cloud suddenly covered the atmosphere, which probably occasioned the shock by the discharge of a shower.

A sound was observed to roll from the Thames towards Temple Bar before the houses ceased to nod; just as the electrical snap precedes the shock. This noise (which generally precedes earthquakes) the Doctor thought could be accounted for only on electrical principles: for, in a subterraneous eruption, the direct contrary would happen.

The flames and sulphurous smells, which are sometimes observed in earthquakes, might, he thought, be more easily accounted for, on the supposition of their being electrical phenomena, than from their being occasioned by eruptions from the bowels of the earth. So also the suddenness and expedition of the concussion, it being felt at the same instant over such a large surface, and the little damage also which earthquakes generally occasion; sufficiently point out what sort of a motion it is: not a convulsion of the bowels of the earth; but an uniform vibration along its surface, like that of a musical string, or a glass when rubbed on the edge with one's finger.

The circumstance of earthquakes chiefly affecting the sea-coast, places along rivers (and, adds Doctor Priestley, eminences), is a farther argument of their being electrical phenomena. This is illustrated by a particular account of the direction in which the earthquake was conveyed.

The last argument he uses is taken from the effects which it had on persons of weak constitutions, who were, for a day or two after it happened, troubled with pains in the back, rheumatisms, hysterics, and nervous disorders; just in the same manner as they would have been after an actual electrification: to some these disorders proved fatal.

As to the manner in which the earth and atmosphere are put into this state, which prepares them to receive such a shock, and whence the electric matter comes, the Doctor does not pretend to determine; but thinks it as difficult to be accounted for as magnetism, gravitation, and many other secrets of nature.

The same hypothesis was advanced by Signor Beccaria, without knowing anything of Dr Stukeley's discoveries. But this learned Italian imagined the electric matter which occasions earthquakes to be lodged deep in the bowels of the earth, agreeably to his hypothesis concerning lightning.

Now, as it appears that the quantity of electric matter in the simplest thunder-storms is so inconceivably great, that it is impossible to be contained by any cloud or number of clouds; and as, during the progress of a thunder-storm which he observed, though the lightning frequently struck to the earth, the same clouds were the next moment ready to make a still greater discharge; it was evident, that they must have received at one place, the moment a discharge was made from them in another. Let us suppose these clouds ever so great, if the lightning proceeded only from them, the quantity must be lessened by every discharge; and no recruits that any new clouds might bring can bear any proportion to the discharge which must ensue from the collision of so great a number as combine to form a thunder-storm. It seems therefore most likely, that the electric matter is continually darting from the clouds in one place, at the same time that it is discharged from the earth in another; and, consequently, that the clouds serve as conductors to convey the electric fluid from those places of the earth which are overloaded with it, to those which are exhausted.

This theory being admitted, there will, he thinks, be little difficulty in attributing earthquakes to the same cause. For if the equilibrium of the electric matter be by any means lost in the bowels of the earth; so that the best method of restoring it shall be by the fluid bursting into the air, and traversing several miles of the atmosphere, to come at the place where it is wanted; it may be easily imagined, that violent concussions will be given to the earth by the sudden passage of so powerful an agent. This, in his opinion, was confirmed by the flashes of light, exactly resembling lightning, which have been frequently seen to rush from the top of Mount Vesuvius, at the time that ashes and other light matters have been carried out of it into the air, and dispersed uniformly over a large tract of country. And it is well known, that volcanoes have a near connection with earthquakes.

A rumbling noise like thunder, and flashes of light rising from the ground, have been generally observed to attend earthquakes. And lightning itself has been known to be attended with small shakings of the earth. So also ignis fatui, in mines, he looked upon as an argument that the electric fluid was sometimes collected in the bowels of the earth.

Dr Priestley, in his History of Electricity, observes upon these theories, that a more probable hypothesis may perhaps be formed out of both of them. "Suppose (says he) the electric matter to be, some way or other, accumulated on one part of the surface of the earth, and on account of the dryness of the season not easily to diffuse itself; it may, as Signor Beccaria supposes, force its way into the higher regions of the air, forming clouds in its passage out of the vapours which float in the atmosphere, and occasion a sudden shower, which may further promote the passage of the fluid. The whole surface, thus unloaded, will receive a concussion, like any other conducting substance, on parting with, or receiving a quantity of the electric fluid. The rushing noise will likewise sweep over the..." whole extent of the country. And upon this supposition also, the fluid, in its discharge from the country, will naturally follow the course of the rivers, and also take the advantage of any eminences to facilitate its ascent into the higher regions of the air."

The Doctor, making experiments with a battery on the passage of the electrical fluid over different conducting substances, and among these, over water;—and remarking a resemblance between its passage over the surface of the water, and that which Dr Stukeley supposed to sweep the surface of the earth, when a considerable quantity of it is discharged to the clouds during an earthquake; immediately suspected that the water over which it passed, and which was visibly thrown into a tremulous motion, must receive a concussion resembling that which is given to the waves of the sea on such an occasion.

To try this, he himself and others present put their hands into the water at the time that the electrical flash passed over its surface; and they felt a sudden concussion given to them, exactly like that which is supposed to affect ships at sea during an earthquake. This concussion was felt in various parts of the water, but was strongest near the place where the explosion was made. The same experiment, with a little variation, being afterwards made with a single jar, at some distance below the surface of the water, produced the like effect, though in a weaker degree. "This similarity in the effect (the Doctor observes) is a considerable evidence of a similarity in the cause.

"Pleased with this resemblance of the earthquake (says he), I endeavoured to imitate that great natural phenomenon in other respects: and it being frosty weather, I took a plate of ice, and placed two sticks about three inches high on their ends, so that they would just stand with ease; and upon another part of the ice I placed a bottle, from the cork of which was suspended a brass ball with a fine thread. Then, making the electrical flash pass over the surface of the ice, which it did with a very loud report, the nearer pillar fell down, while the more remote stood; and the ball which had hung nearly still, immediately began to make vibrations about an inch in length, and nearly in a right line from the place of the flash.

"I afterwards diversified this apparatus, erecting more pillars, and suspending more pendulums, &c., sometimes upon bladders stretched on the mouth of open vessels, and at other times on wet boards swimming in a vessel of water. This last method seemed to answer the best of any: for the board representing the earth, and the water the sea, the phenomena of them both during an earthquake may be imitated at the same time; pillars, &c., being erected on the board, and the electric fluid being made to pass either over the board, over the water, or over them both."

These three hypotheses concerning the cause of earthquakes, though somewhat differing from one another, yet agree in the main; but if a particular solution of the phenomena is required, every one of them will be found deficient.

If, according to Dr Stukeley's hypothesis, the electric matter is lodged only on the surface of the earth, or but at a small depth below, how are we to account for those violent effects which often take place in the bowels of the earth? In the earthquake at Lisbon, a large quay sunk to an unfathomable depth. We are certain that the cause of the earthquake must have been below this depth, however great it was, and have opened the earth for an immense way downwards. At the same time an hill in Barbary clave asunder, and the two halves of it fell different ways. This shows, that the cause of the earthquake operated not on the surface of the hill, but on the solid foundation and contents of it; nor can it be explained by any superficial action whatever. From what the miners at Eyam bridge in Derbyshire observed, it is also evident, that the shock was felt at the depth of 396 feet below the surface of the ground more than at the surface itself; and consequently there is all the reason in the world to think that the cause lay at a depth vastly greater.

Again, though the earthquake at London was supposed to begin with a black cloud and shower; yet in that of 1755, the effects of which were incomparably greater, the air was calm and serene almost in every place where it was felt. It doth not appear that there is at any time a considerable difference between the electricity of the atmosphere and that of the earth, or indeed that there can be so. For if the earth is electrified plus and the atmosphere minus, there are innumerable points on the surface of the earth which must be imperceptibly drawing off the superfluous electric matter into the air. The vapours also, with which the atmosphere abounds, would always be ready in the same service; and thus thunder and lightning might indeed sometimes be produced, but not earthquakes. But lastly, neither the air nor the earth does always show any remarkable signs of electricity before earthquakes happen. For, the summer before the earthquake at Manchester in 1777, there had scarce been any thunder, lightning, or other signs of electricity in the atmosphere, and vegetation had been extremely backward; and, according to the best accounts, the weather continued remarkably fine.

For these reasons, Dr Stukeley's hypothesis seems not to be satisfactory. That of Signor Beccaria is not indeed liable to the above mentioned objections; but seems highly improbable on another account. The atmosphere is known to be a substance through which the electric matter makes its way with the utmost difficulty. It is a vastly worse conductor than water or than moist earth. If therefore the equilibrium of this fluid is lost in the bowels of the earth, it is impossible to give a reason why it should not rather go to the places where it is wanted through the earth itself, than through the atmosphere. Besides, if this was the case, the shock of an earthquake could only be felt at those places where the electric fluid issued from the earth, and where it entered. All the intermediate places ought to be free from any shock, and to be sensible only of a violent concussion in the atmosphere; but of this we have no example in any history of earthquakes whatever.

Dr Priestley's hypothesis is liable to the same objections with that of Dr Stukeley; for any superficial operation will never account for these effects above mentioned, which take place at great depths below the surface. His experiment cannot be admitted as any way conclusive with regard to the cause of earthquakes, because no quantity of electric fire is seen to pass over the earth and sea, like the flash attending the explosion of an electric battery; and the force of his earthquake (being but just able to throw down a stick that could hardly stand by itself) seems by far too little. The utmost force of electricity which man can raise, is indeed very trifling, when compared with the great operations of nature: but it is certain, that the force of an electric battery is by no means contemptible; and was its whole power to be employed in producing an imitation of an earthquake, it certainly would do much more than throw down a small stick. The bad success of this experiment therefore shows, that the Doctor's theory is erroneous: for almost the whole of his electric power was spent another way; and we cannot suppose that any considerable part of the force which produces earthquakes is spent any other way than in the very production of the earthquake itself.

If it is attempted to give an explanation of the phenomena of earthquakes, which shall be free from the objections above mentioned, and from all others, it will be necessary, in the first place, to consider those parts of the system of nature which seem to be most affected during the terrible phenomena we treat of. These parts are, the air, the solid earth, and the water. Of these the two former are electrics per se; the latter is a conductor, though a bad one*. Hence it follows,

1. That in proportion to the quantity of earth which is mixed with any quantity of water, that mixture will approach nearer to the nature of an electric per se, and vice versa.

2. It also follows, that whatever quantity of electricity is communicated to the solid earth, will be quickly taken off from it by the water which is mixed with it, in the same manner that the electric matter is carried off from an excited globe by a metallic conductor.

3. The whole earth is moist, and therefore in some degree a conductor. Nevertheless, as earth of all kinds, when perfectly dry, is found to be an electric capable of receiving a charge like glass, it is therefore possible, that the electric power of the earth may be excited to such a degree, that the moisture of the solid parts cannot easily contain the quantity of electricity communicated.

4. In this case, the earth must either give undoubted signs of its being excited in the same manner that other excited electrics do, or the electricity must be discharged somewhere else.

5. To receive any superfluous quantity of electric matter that may be communicated to the solid earth, the waters of the ocean are always ready. These, being a much better conductor than earth, must be a principal mean of preserving the equilibrium of electricity in the different parts of the earth; and hence we see a natural reason why the waters of the ocean should cover so large a proportion of the globe as they are known to do. See Ocean.

6. It is known, that fire is also a conductor of electricity. Therefore, wherever a quantity of electric matter is collected in any part of the solid earth, if it can neither be conveniently received by the moisture which the earth naturally contains, nor by the ocean in its neighbourhood, it will discharge itself by any volcano that happens to be in an active state, near the place where that collection of electric matter is.

Vol. VI. Part I.

7. It is also found, that the electric fluid, being violently resifted by the superincumbent atmosphere, hath always a tendency to discharge itself in those places where that resistance is least. The tops of high mountains, therefore, where the weight of the atmosphere is greatly diminished, will also afford a ready passage for the electric fluid when it is collected in very great quantity in the bowels of the earth.

8. If, from some natural causes, the electric matter shall happen to be collected in the bowels of the earth in any particular place, and at the same time such obstacles are thrown in its way, that it can neither discharge itself into the ocean, nor into the atmosphere by the tops of high mountains, nor by the more open passages of volcanoes; the most terrible consequences must ensue: the matter being pent up, and the cause by which it is collected continuing still to act, its impulse becomes at last irresistible. It then flies against every obstacle with inconceivable violence. It breaks out in all those places where there is the least resistance, and therefore the shock is directed a great number of different ways at once. Houses, steeples, trees, &c. by their height take off somewhat of the pressure of the atmosphere; and therefore the electric matter flies against them very violently. The houses and other buildings being bad conductors, are thrown down; the trees affording a readier passage to the fluid are not hurt, though even they also are sometimes split. The height of the mountains renders them the objects of the destructive force of this fluid much more than any buildings whatever. Hence they are often rent, and rocks thrown down from them. The water contained in the solid parts of the earth, being a conductor of electricity, becomes overloaded with it; and when it can receive no more, is forced to yield to the impulse of the rest, and therefore is thrown out of the earth in great quantities. For the same reason, the waters on the surface of the earth are most violently agitated. The small quantities contained in wells are thrown out at the tops of them: The rivers and lakes, which contain too great a quantity of water to be thrown off from the earth, rise in billows: The ocean itself, receiving more electric matter than can be immediately dispersed through the whole body of water, or evaporate into the atmosphere, retreats from the land, and is raised in vast mountains. The solid earth, being unable either to conduct the fluid quietly to those parts where it is wanted, or to retain it, is violently shaken or rent in multitudes of places; and this not only on the surface, but to great depths. The electricity being now in some measure discharged from the earth, the ocean rushes forward with fury to discharge in its turn the excess of electric matter it just before received from the earth. If there are volcanoes in the neighbourhood, the violent discharge of electricity is sure to manifest itself by setting them in a flame; and thus, till the equilibrium is restored, all nature seems to be threatened with dissolution.—Even in those places where the force of the electric fluid is not able to shake the solid parts of the earth, it manifests its power by agitating the waters in the manner above described. Water being a much better conductor of electricity than earth, this subtle fluid, as soon as it can get out from the solid earth, flies to the water. The consequence is, that the water immediately swells up, and is attracted by whatever part of the earth has less electricity than itself. Hence those strange irregular motions of the waters in different places, so particularly observed at the time of the earthquake at Lisbon; and which it seems impossible to account for from any other cause than an immediate discharge of electric matter from the earth into them.

9. As it is impossible that any part of the earth can be electrified without communicating a proportionable share of electricity to the animals that live upon it, and have a constant communication with it, it thence follows, that there can be no considerable commotion in the electric matter lodged in the bowels of the earth, without affecting that which is contained in the bodies of the animals. Hence the brutes, who seem to be more sensible of such commotions than we, run about, and show signs of fear, before the earthquake comes on; and hence the giddiness, sickness, &c. which the human race are subject to during the time of the shock, even though they do not feel it, as was the case at Gibraltar.

10. As the atmosphere hath a communication with the earth, it is scarce to be supposed that the earth can, for any length of time, contain a considerable quantity of electric matter, without communicating to the atmosphere a proportionable quantity. Before an earthquake, therefore, we must suppose the electricity of the earth and air to be in perfect equilibrio. Hence the weather is serene, there is no wind, nor any other sign in the atmosphere, of the terrible catastrophe that is about to ensue. But the moment the discharge is made from the earth, the equilibrium between the terrestrial and atmospherical electricity is broken; the air either begins to receive the fluid from the earth, or the earth from the air. As there is not then time for the collection of thunder-clouds by which the electricity may be brought down in sudden flashes of lightning, the fluid breaks through the substance of the air itself with dismal and horrid noises, which always accompany an earthquake. That this is the case, seems highly probable from an experiment of M. de Romas, when, having brought down a vast quantity of electric matter from the clouds by means of a kite, he heard the noise it made in the air, like the continual blowing of a small forge bellows. In general, a considerable change of weather takes place at the time of an earthquake, though not always. In the earthquake which happened in England in 1777, there was no remarkable change of weather there; but, soon after, there was a great deal of thunder and lightning in the southern parts of Scotland: which seems to indicate, that the electric fluid discharged from the earth in England had taken its course northward, and produced the phenomena before mentioned in Scotland. The same observation may likewise be made with regard to 1789, when there were slight shocks of an earthquake both in England and Scotland. That in England being the first, was followed by an uncommon frequency of thunder and lightning in the southern parts of Scotland; by reason of the progress of the electric matter northward after it was discharged into the atmosphere: but the shocks which happened in the northern part of Scotland (viz. about Crief in Stirlingshire) were not followed by any thunder to the southward; because the electric matter, though discharged into the atmosphere, cannot return to the south without first going north, and rising up into the higher regions.

In the earthquakes in Calabria, in the year 1783, there were some circumstances which seem to militate against the theory just now laid down. The most remarkable of these is their attacking the places situated on the plain much more than those which stood on the higher grounds. This is particularly insisted upon by Sir William Hamilton. "If two towns (says he) were situated at an equal distance from the centre (of the force of the earthquake), the one on a hill, the other on the plain or in a bottom, the latter always suffered greatly more from the shocks of the earthquake than the former; a sufficient proof to me of the cause coming from beneath, as this must naturally have been productive of such an effect. And I have reason to believe, that the bottom of the sea, being still nearer the volcanic cause, would be found, if it could be seen, to have suffered still more than the plain itself; but the philosophers, who do not easily abandon their ancient systems, make the present earthquakes to proceed from the high mountains of the Apennines that divide Calabria Ultra, such as the Monte Dejo, Monte Caulone, and Aspromonte. I would ask them this simple question: Did the Eolian or Lipari islands (all which rose from volcanic explosions, at different and perhaps very distant periods) owe their birth to the Apennines in Calabria, where, or to veins of minerals in the bowels of the earth and under the bottom of the sea? Stromboli, an active volcano, and probably the youngest of those islands, is not above 50 miles from those parts of Calabria that have suffered most by the late earthquakes. The vertical shocks, or, in other words, those whose impulse was from the bottom upwards, have been the most destructive to the unhappy towns in the plain. Did they proceed from Monte Dejo, Monte Caulone, or Aspromonte? In short, the idea I have of the present local earthquakes is, that they have been caused by the same kind of matter that gave birth to the Eolian islands; the cause of that perhaps an opening may have been made at the bottom of the sea, and most probably between Stromboli and Calabria Ultra; for from that quarter all agree that the subterraneous noises seem to have proceeded; and that the foundation of a new island or volcano may have been laid, though it may be ages, which to nature are but moments, before it is completed and appears above the surface of the sea. Perhaps, too, the whole destruction I have been describing may have proceeded simply from the exhalations of confined vapours generated by the fermentation of such minerals as produce volcanoes, which have escaped where they meet with the least resistance, and must naturally, in a greater degree, have affected the plain than the high and solid grounds around it."

In a memoir on this earthquake by M. Dolomieu, Electricity that author endeavours to exclude electricity from having any share in the matter. "The sea (says he), during the earthquakes of 1783, had little share in the shocks of the main land. The mass of water experienced no general movement of fluctuation or oscillation; the waves did not rise above their ordinary limits. Those which, on the night of the 5th of February, beat against the coast of Scilla, and which afterwards... terwards covered the point of the Faro of Messina, were only the effects of a particular cause. The fall of a mountain into the sea raised the waters, which received an undulating motion, as happens always in similar cases. The undulation reached from the point of Sicily beyond the Cape of Rofalcolmo, extending in length along the coast which runs to the south; but always with a decrease in elevation as it was more remote from Sicily. Whatever inquiries the author has made, he has not been able to discover, in all the details which have been given him, any proofs of the existence of electrical phenomena: no spark, no disengagement of the electrical fluid, which the Neapolitan naturalists wish to assign as the cause of earthquakes.

"The state of the atmosphere was not the same in the whole range of earthquakes. While the tempests and the rain seemed to have conspired with them for the destruction of Messina, the interior part of Calabria enjoyed very fine weather. A little rain fell in the plain in the morning of the 5th of February; but the sky was clear during the rest of the day. This month and that of March were not only pretty serene, but likewise warm. There were some storms and rain; but they were the natural attendants of the season.

"The moving force seems to have resided under Calabria itself, since the sea which surrounds it had no share in the oscillations or vibrations of the continent. This force seems also to have advanced along the ridge of the Apennines in ascending from the south to the north. But what power in nature is capable of producing such effects? I exclude electricity, which cannot accumulate continually during the course of a year, in a country surrounded with water, where everything conspires to place this fluid in equilibrium. Fire remains to be considered. This element, by acting directly upon the solids, can only dilate them; then their expansion is progressive, and cannot produce violent and instantaneous movements. When fire acts upon fluids, such as air and water, it gives them an astonishing expansion; and we know that then their elastic force is capable of overcoming the greatest resistances. These appear the only means which nature could employ to operate the effects we speak of; but in all Calabria there is no vestige of a volcano; nothing to point out any interior combustion; no fire concealed in the centre of mountains, or under their base; a fire which could not exist without some external signs. The vapours dilated, the air rarefied by a heat constantly active, must have escaped through some of the crevices or clefts formed in the soil; they must there have formed currents. Both flame and smoke must have issued by some one or other of these passages. These once opened, the prejudice would have ceased; the force not meeting with any more resistance, would have lost its effect; and the earthquakes could have no longer continued. None of these phenomena took place: we must then renounce the supposition of a combustion acting directly under Calabria. Let us see if having recourse to a fire at some distance from this province, and acting upon it only as an occasional cause, we shall be able to explain all the phenomena which have accompanied the shocks. Let us take for example Etna in Sicily, and suppose large cavities under the mountains of Calabria; a supposition which cannot be refused. It is certain that immense subterraneous cavities do exist, since Etna, in elevating itself by the accumulation of its explosions, must leave in the heart of the earth cavities proportioned to the greatness of the mass.

"The autumn of 1782 and the winter of 1783 were very rainy. The interior waters, augmented by water from those of the surface, may have run into those caverns sufficient to which form the focus of Etna: there they must have produced been converted into vapour capable of the highest degree of expansion, and must have pressed forcibly against every thing which opposed their dilatation. If they found canals to conduct them into the cavities of Calabria, they could not fail to occasion there all the calamities of which I have given the description.

"If the first cavity is separated from the second by a wall (to speak) or some slight division, and this separation is broken down by the force of the elastic vapour, the whole force will act against the bottom and sides of the second. The focus of the shocks will appear to have changed place, and become weaker in the space which was agitated most violently by the first earthquake.

"The plain, which was undoubtedly the most slender part of the vault, yielded most easily. The city of Messina, placed upon low ground, experienced a shock which the buildings on higher grounds did not. The moving force ceased at once as suddenly as it acted violently. When, at the periods of the 7th of February and the 28th of March, the focus appeared changed, the plain scarce suffered anything. The subterraneous noise, which preceded and accompanied the shocks, appeared always to come from the southwest, in the direction of Messina. It seemed like thunder underground, which resounded beneath vaults.

"If Etna, then, has been the occasional cause of the earthquakes, it has also prepared, for some time, the misfortunes of Calabria, by gradually opening a passage along the coast of Sicily to the foot of the Neptunian mountains: for during the earthquakes of 1789, which disturbed Messina the whole summer, they felt the whole length of that coast, from Taormina even to the Faro, considerable shocks; but near the village of Alli and Fiume de Nisi, which are situated about the middle of that line, shocks so violent were experienced, that they dreaded lest the mouth of a volcano should open. Each shock resembled the effort of a mine that had not strength to make an explosion. It appears, that then the volcano opened a free passage for the expansion of its vapours, and that they have since circulated without restraint; since in the year 1783 the earthquake was almost nothing upon that part of Sicily, at the time that Messina buried under its ruins the half of its inhabitants."

On this theory it is first to be observed, that there is a considerable disagreement in points of fact betwixt me and M. Dolomieu and Sir William Hamilton. The former could find no account of any spark or other electrical phenomenon: the latter, on the contrary, was assured that flames had often been seen to issue from and Sir the earth; and these he expressly attributes to a vast William pour charged with electrical fire. M. Dolomieu takes little notice of the rains that fell; while Sir William Hamilton attributes to them several of those disruptions of the earth, which, without them, would have seemed very extraordinary. The latter likewise informs us, that before a shock the clouds remained motionless; and that, after a heavy shower of rain, a smart shock followed. These were phenomena that showed some connection between what passed in the earth and in the atmosphere; but betwixt these two there is no agent that we know of excepting electricity, at least there is none of sufficient strength to produce any violent effects by communication between the one and the other. The most enthusiastic imagination cannot suppose that huge cauldrons of boiling water under Mount Etna should make the clouds stand still over Calabria; and the quick succession of the shock to an heavy shower of rain showed that the cause, whatever it was, lay in the ground on which the rain fell, and that it could be put in action by what affected the surface of the ground. But the cause of earthquakes appears, from the facts related n° 25, to lie at a greater depth in the earth than 396 feet; but no shower of rain could affect the earth to this depth unless by making some alteration in its electricity. These phenomena, which M. Dolomieu has overlooked, evidently show that electricity was concerned in this earthquake as well as others.

Another circumstance, which M. Dolomieu himself mentions, is a sufficient proof of electricity being concerned; and that is the premonition which animals had of its approach. "The premonition of animals (says he) at the approach of earthquakes, is a singular phenomenon, and which cannot fail to surprise us to much the more, as we know not by what organs it is communicated to them. Every species of animals experiences it, especially dogs, geese, and poultry. The howlings of the dogs in the streets of Messina were so loud, that orders were issued to kill them." Now, we know that many animals have a premonition of a change of weather; which may happen either from a change of the density of the atmosphere, or from some alteration in its electricity: but steam pent up in the bowels of the earth could affect no animal until it began to exert its effects. Sir William Hamilton likewise informs us, that geese seemed more affected by this cause when in the water than out of it; which may easily be explained upon electrical principles, but not at all, at least not without the most extravagant suppositions, by steam pent up in caverns nobody knows where.

Again, it is evident that Mr Dolomieu's hypothesis is supported in the worst manner imaginable, viz. by arguing from things unknown to what we see; but the true method of argument always is from what we see to things unknown. By this unhappy error he has made choice of causes which cannot possibly answer the purpose. Let any quantity of water we please be poured into the focus of mount Etna; nay, let the sea itself break into it: the consequence could only have been what happened in 1755, viz. not an earthquake in Calabria, but a vast effusion of boiling water from the top of the mountain itself. Nature here made the experiment; and we have no reason to imagine that any other consequence would have followed, though it had been repeated ever so often. Our author seems also to have forgot, that aqueous steam is capable of condensation, and that when it is admitted into a cold place it instantly loses its expansive power. Let us suppose caverns upon caverns extended in any way he pleases: the greater their bulk, the more will he be embarrassed; for thus the steam would have room to circulate; and far from producing those dreadful convulsions, must have returned quietly into water, without being able to stir the earth in the least. Comparison would appear indeed, that the power of aqueous steam between volcanoes and steam-engines; and expresses his surprize that nobody has taken notice of it sooner. "A steam-engine (says he), consists of a caldron or boiler, covered with a lid, having an opening in the middle, to which is fitted an hollow cylinder, &c. The boiler is set over a fire, and from the water in it rises a vapour, the expansive force of which raises the piston of the machine. The action of the vapour is afterwards instantaneously annihilated by a jet of cold water into the cylinder through a hole, when the weight of the atmosphere takes place, forces down the piston, and consequently raises the water in the pump.

"It is known that vapour occupies a space 15,000 or 16,000 times greater than the bulk of the water which produced it; hence it follows, that the smaller the space is in which it is contained, the force of its expansion will be the greater. It has sometimes happened, that vapour, in a steam-engine, not having sufficient play, has burnt the vessels in which it was contained, destroyed the building, and thrown the stones and boiling water to a great distance. It is now furnished with holes, by which the quantity of water can be ascertained, and with a valve which gives way when the vapour is superabundant. When the vapour issues by this valve, it strikes the air with such force as to occasion a very loud hissing noise. The force of vapour sufficient for raising a piston of a given diameter is equal to the weight of a column of water 22 feet in height, and of a base equal to the piston; so that, suppose a cubic foot of water to weigh 70 pounds, and the piston to be a foot square, the force of the vapour sufficient for raising it will be 1540 pounds; an agent so powerful, that hardly anything else in nature can be compared with it.

"Now if we recollect the descriptions of volcanoes, Volcanoes, their eruptions, the earthquakes and hissing noises which sometimes precede or accompany them; the quakes, &c., flames of different sorts, boiling water, sulphur, and all suppos'd bitumens which they discharge; if we hear of rocks thrown to the distance of seven or eight miles from the mouth of the volcano; clouds of ashes, and torrents of lava, seas overflowing, rivers left dry, &c. &c. we will find all these the effects of great natural steam-engines: that is to say, they are produced by masses of combustible matter set on fire by fermentation, placed in the neighbourhood of caverns filled with the waters of the sea, of rivers or lakes. We cannot doubt that the interior parts of the earth are hollowed out into numberless caverns that extend in different directions, and to various depths; and that mountains and other inequalities, and the buildings raised by men, are merely the lid or covering, more or less thick, of these caverns, which vary in shape, and in the materials of which they are composed. Places therefore covered with buildings and mountains, are more liable... ble to earthquakes, because they are less able to give way to the shock; and the farther places are distant from volcanoes, the less they have to fear from earthquakes; because the vapour having room to expand itself by the ramifications of the subterraneous passages, the shocks will be less violent and less frequent. It is this which, in all probability, has hitherto saved Naples.

"Now, let it not be said, that we have mistaken the cause of earthquakes; for if, on the one hand, we attentively consider the steam-engine and its effects, and on the other, observe volcanoes always in the neighbourhood of water, we will be convinced, that they differ in nothing from that machine, but because this is under the command and direction of art. The disappearance and formation of islands and mountains may be explained from the sinking in of caverns, or from their being lifted up by the force of vapour.—Lastly, those vapours which, in the year 1783, covered at the same time, and almost during four months, a part of Europe, Asia, and Africa, were probably vapour escaped from those great internal caverns, heated by a sufficient quantity of combustible matters, set on fire by fermentation in the great chemical laboratories in the bowels of the earth. In certain districts of Burgundy, these vapours were found to be hot, for they dried up and destroyed the grapes."

That the power of steam-engines is very great, there is no doubt; but all that we see them usually perform, is little more than merely overcoming the pressure of the atmosphere on the piston of the cylinder. Now this pressure is equally strong over the whole surface of the earth; so that before the ground could be shaken in the smallest degree, the whole pressure of the atmosphere incumbent upon it must be removed. But if we begin to make any calculations with regard even to this force, which must be removed as a preliminary, we shall find it to be inconceivably great. A square mile contains 27,878,400 square feet; and upon each of these the pressure is 2160 pounds. The atmospheric pressure on a square mile is the product of these two numbers, or 60,217,344,000 pounds; but the great earthquake of 1755 shook no less than 4,000,000 of square miles of the earth; and therefore must in the first place have overcome a pressure of more than 240,000 millions of millions of pounds; and after all this, it had still a much greater obstacle, viz. the immense weight and cohesion of the earth itself. Dr. Stukely* has calculated, that no conceivable quantity of gunpowder could have moved the earth shaken by the earthquake in Asia Minor, which affected a circle of 300 miles diameter; but the earthquake of 1755 must have required not only a much greater power to move the earth, as affecting a surface much greater than that of a circle 300 miles in diameter, but also the atmospheric pressure above mentioned, which does not enter into the Doctor's calculation. There cannot therefore be any conceivable quantity of water, of fire, or of steam in the bowels of the earth, sufficient to produce such effects; nor is there any power in nature to which we can with the smallest probability attribute them, electricity alone excepted. Calculations have indeed been made, that the force of steam is 28 times greater than that of gunpowder; but this seems only to be in one particular case, viz. when water is thrown upon melted copper; which cannot possibly take place in the bowels of the earth. In other cases water explodes with much less violence; and, when thrown upon melted glass, does not explode at all. The very violent effects of explosion water when thrown upon copper in fusion, therefore, of water most probably are to be attributed to a decomposition of the water, one part of it being united to the calx of the metal, and the other suddenly converted into an aerial vapour; the instantaneous production and rarefaction of which seems in most cases to be the cause of explosion*. The simple pressure of steam, and the bursting of a vessel by it when long continued, cannot at all be introduced as a parallel case, nor are the effects in any degree similar; because we cannot imagine solid metallic vessels in the bowels of the earth to confine the steam till it acquired such strength. At all events the steam must have penetrated the loose earth, which it could not fail to meet with in many places, loosened it, and condensed itself; and if any person will cover a steam engine with stones and rubbish instead of a clothe lid, he will certainly find this to be the case.

The only power with which we are acquainted, and of which is capable of producing earthquakes, then, being that of the electrical fluid, it only remains to consider what uses they may be thought to answer in the system of nature. As they are the effects of the very highest natural power, it cannot be supposed that they are produced merely for the purposes of destruction; and, on the other hand, as they certainly do a great deal of mischief, it seems as difficult to assign any benevolent purpose they can answer. It is very generally supposed, indeed, that earthquakes are the means by which Nature raises mountains and land from the bottom of the sea; but this can never be admitted. We have many instances of mountains being swallowed up and lost by earthquakes, but not a single well attested one of a mountain being raised by them; and even when volcanoes are taken into the account, by which some mountains and islands have certainly been raised, the balance appears against them, and more land seems to have been sunk by them than ever was raised*. It seems most probable therefore that earthquakes are accidental, and that the mischief they do is only to prevent a greater evil. This we see takes place throughout the whole system of nature. Thunder and lightning, violent rains, storms of wind, &c., are all productive of much damage on certain occasions; but we by no means suppose these phenomena to take place merely for destruction; and therefore we name such effects accidents. To the same account, though on a larger scale, must we place earthquakes; and it only now remains to consider what are the disasters still more terrible than earthquakes which we should have occasion to dread, did they not interpose to prevent them.

These evils are naturally to be dreaded from any prevalent general commotion of the electric fluid dispersed throughout the whole globe of earth. That it does pervade it to the centre, is what we can have no reason to doubt; but in the internal parts it seems to lie dormant, or to be employed in operations which never manifest themselves to us. Towards the surface it is manifestly set in motion by the light of the sun, which, as proved under the article Electricity, and in various other parts of this work, is the very same fluid. This produces... duces a constant current through the bowels of the earth from the equator towards the poles; for as the equatorial parts absorb more of the light than those farther south or north, it must naturally be driven out in the northern and southern regions in proportion to the quantity absorbed at the equator. In what manner earthquakes are then produced by it, has already been explained at length. They are the shocks occasioned by its passing in great quantity from one place where it is prefled and confined, to another from which it has a free passage; or from a part of the earth positively electrified, to one that is negatively so. Let us suppose, however, that such obstructions are thrown in its way, that it cannot get out of the earth by any passage. The consequence of this must very soon be, that the motion of the light acting upon the equatorial parts would be propagated through the whole globe; and this would be productive of consequences much more terrible than any we can conceive. We see that by setting it in motion in a small part of the atmosphere or of the earth, the most violent effects ensue; but should this tremendous fluid be obliged to put forth all its strength, the earth must be shaken from the centre. Instead of plantations and little hills removed from their places, as in Calabria, it is more than probable that the largest islands and continents would be detached from their bases, or perhaps an universal dissolution ensue. Happily, however, such an effect never can take place, because the electric matter always vents itself by the superficial parts; for the depths to which even the causes of earthquakes and volcanoes descend, are undoubtedly superficial in comparison of the vast thicknesses of the body of the earth itself. The great bulk of electric fluid therefore lies quietly in the central parts; and is never moved by the commotions of that which lies on the surface, any more than the water at the bottom of the ocean is moved by the storms which ruffle the upper part.

In the earthquakes in Calabria, the progress of the electric matter northward might be traced both thro' the bowels of the earth and through the atmosphere. The great shocks happened in the month of February, but continued more or less through the whole summer. It was observed that Stromboli smoked less than usual, and no particular eruption happened either of Ætna or Vesuvius. This showed that the electric matter was going somewhere else; nor was it long of discovering the course it had taken. In the beginning of summer a violent volcanic eruption took place in Greenland; its extent and power, however, were not known; but in the beginning of June a volcanic earthquake commenced in Iceland, and continued for eleven days without intermission. This was followed by the most extraordinary effusion of lava recorded in history, which continued till the 12th of August. All this time there were violent and numerous thunder storms, first in the southern and then in the more northerly parts of Europe; the air was covered with a never-ceasing haze, not of a moist nature, as our author in the Journal de Physique supposes, and which he absurdly says dried the grapes in Burgundy, but plainly of some other kind, and which prevented the light of the sun from having its usual effect. Six days after the immense volcanic eruption in Iceland had ceased, the great meteor made its appearance, which no doubt was the very same quantity of electric matter that had raised such horrid commotions in the earth and atmosphere, returning thro' the higher spaces to the south from whence it had originally proceeded.

Before we dismiss this article, it may still be necessary to obviate an objection which may be raised from what is said under the article Lightning. It is not happen there shown, that in the time of a thunder storm, the parts of the earth which lie directly under the cloud flows, are divided for some space downward into alternate zones positively and negatively electrified; that the lightning from the cloud strikes not the uppermost stratum directly, but only as it is impossible to avoid it, because it lies betwixt the cloud and the zone by which the electric matter is attracted. It may then be asked, Why an earthquake is not produced by the discharge of these two opposite electricities into one another directly, without the production of any thunder? Here, however, we must observe, that the electricity is originally accumulated in the atmosphere, where the vapours serve as conductors, and the surrounding air and upper surface of the earth being electrified the same way, prevent the electric matter from silently discharging itself, by inflating the clouds in the same manner that the conductor of a machine is insulated by the electric substance on which it stands. The flash of lightning must therefore burst out from these conductors in the very same manner that a spark proceeds from the prime conductor of an electrical machine, rather than from the globe or atmosphere next to it, though both of them are undoubtedly very highly electrified at the time the machine is set in motion. At the same time it must be considered, that this continual flashing of the atmospherical electricity towards the earth, prevents any very high degree of it from accumulating in either of the terrestrial zones already mentioned, so as to produce any discharge between them, which would indeed produce a shock of an earthquake.

From an unhappy accident which happened in 1785, Of electricity related by Mr Brydone in the Phil. Trans. for that year, cal explosions proceeding from spherical electricity and that of the earth are the same, yet at some distance there is a difference betwixt them, earth, and discharges are made from the one to the other. The accident alluded to was the destruction of a man and two horses by an electrical explosion from the vicinity of the earth in the time of a thunder storm. At the place where the explosion happened, there was an interval of 25 or 30 seconds betwixt the flash and the clap of thunder, so that it must have been at the distance of between five and six miles; the great explosion suddenly burst out from the spot over which the cart-wheels passed to which the horses were yoked, partially melted the iron of the wheels, killed the man who sat on the fore-part of the cart, and tore his clothes almost to pieces. Two circular holes of about 20 inches diameter were made in the ground, and the earth and stones scattered about; but no fire was perceived. About an hour before the explosion, some fishermen were caught in a violent whirlwind, which felt hot and fultry. A lamb was killed by another explosion about a quarter of an hour before the great one, and a woman received a violent stroke on the foot without being able to tell whence it proceeded. At the time the lamb was killed, the shepherd shepherd said he felt a sensation as if fire had passed over his face.

By these explosions, particularly the great one, the equilibrium of electricity in the atmosphere was instantly restored, and the clouds forthwith began to separate. The reason of this is explained under the article Lightning; here it is sufficient to observe, that where there is a difference between the electricity of the atmosphere and that of the earth, an earthquake cannot happen. Those electrical explosions experimentally demonstrate the truth of what is argued from the principles of electricity, n° 82, viz. that just before an earthquake there is a perfect equilibrium between the electricity of the atmosphere and that of the surface of the earth. When this equilibrium is broken, the earth discharges its superfluous quantity either silently, by means of trees, grass, &c., or sometimes by explosions in different places; but as there is no general conductor, there cannot be any general discharge of the whole at once. The singular case of the great discharge in 1785 was owing only to the accidental presence of a good conductor, viz. the iron of the cart-wheels passing over the spot where the electric matter happened to be collected in great quantity. Had not this taken place, it is possible that a fireball might have risen from the earth; for the explosion produced effects extremely similar to those of the bursting of fire-balls*: but still this could have no effect in producing any shock of an earthquake; because the latter would have required a general discharge between two great strata of earth, where there cannot be any conductor to make partial ones.

In the time of earthquakes, however, there are undoubtedly many such electrical discharges from the earth as those just mentioned; and they are most probably the cause of those conical hollows observed by Sir William Hamilton. When water is abundant in any part of the earth, it serves as a conductor for some quantity of the electricity, and that fluid is violently thrown out into the air; but where there is a deficiency of water, the fire breaks forth in its proper form with loud explosions, as was observed; as well as the water spouts in Calabria in the year 1783. That year also the quantity of electric matter discharged by the earth into the air was manifest by the vast number of thunder storms which immediately followed them. No fire was observed at the time of the explosion which put an end to the thunder-storm above mentioned; but this must have arisen partly from its happening in the day-time, and partly from the electric matter having so many conductors to spend its force upon.

Having thus explained all the phenomena attending earthquakes, it remains only to show by what means the equilibrium of electricity can be broken in the bowels of the earth in such a manner as to produce these phenomena. The ultimate cause of this is mentioned under the article Aurora Borealis, n° 5. It is there shown, that the warmth of the sun must necessarily bring down to the earth much greater quantities of electric matter in the regions within the tropics than in the northern and southern climates. It is impossible, as is there also observed, that there can be a perpetual accumulation of electricity in one part of the earth, unless there is a passage for it into the atmosphere through some other. Hence, if the electric matter descends from the air into one place of the earth, it must necessarily ascend from the earth into the air in some other place. There must be therefore a continual current of electricity through the bowels of the earth, beginning at the equator, and extending northward and southward to both poles. While this current has a free passage from the earth in the northern and southern regions, everything goes on quietly; and whatever storms may happen in the atmosphere, the solid earth cannot be affected. Innumerable circumstances, however, may tend to hinder this discharge, and consequently to accumulate the electric matter in particular places. One very obvious cause of this kind, is an excessive frost taking place in any part of the earth whence the electric matter was wont to be discharged. This renders the air itself so electric, that it cannot receive the fluid; at the same time that the water on the surface of the earth, being hard frozen, becomes electric also, and incapable of conducting. Very dry seasons likewise contribute to produce the same effect; and thus the accumulation of electricity in the warmer climates becomes prodigiously great. Hence perhaps we have some reason to conclude, that the excessive cold which prevailed over all Europe in 1782 was a principal cause of the earthquakes in 1783.

It must, however, be observed, that with regard to the operations of nature we cannot always reason analogically from our electric experiments. If a quantity of electricity is collected in any substance by artificial means, that quantity is taken off in a moment by the touch of any metallic substance or other good conductor. As the whole earth, therefore, is filled with a conducting substance, namely water, it may very naturally be asked, Why does not the superfluous quantity of electric matter collected in one place, immediately disperse itself through all other parts of the earth by means of the water with which it abounds?—To obviate this difficulty, however, it needs only be remembered, that as the earth is quite full of electric matter all round, no quantity can enter any particular part without being resisted by the rest which is diffused through the whole globe. This resistance will be proportioned to the facility with which it can escape at other places; and this it never can do, unless the earth is in a proper condition for emitting, and the atmosphere for receiving, it. The pressure, therefore, upon the accumulated quantity of electric matter soon becomes exceedingly great, and its disposition to burst out with violence is every day increased. At last, as the sun still continues to occasion the deficient of more and more of the electric fluid, that particular part of the earth becomes fully charged. The consequence of this is, that the waters of fountains become foul; the electric matter being lodged in great quantity in the water, forces it into unusual agitations, by which the earth is mixed with it. The ocean, for the same reason, is raised in huge billows, &c.; and these appearances prognosticate the shock, in the same manner that slight flashes from the knob of an electrified bottle prognosticate a discharge of all the electricity contained in it.

Besides the earthquakes above described, of which the cause seems to depend entirely on a collection of electric matter in the bowels of the earth, there are others frequently felt in the neighbourhood of volcanoes, which Which are plainly owing to the efforts of the burning matter to discharge itself. There, however, are but slight, and seldom extend to any considerable distance from the burning mountain. For a particular account of them, see the article Volcano.