derived from such substances; they also, as Montègre observed, will feed upon animal matters; it seems more reasonable to believe, with De Blainville, that they swallow earth for the purpose of making progress in their galleries, than that they do this to extract humus or any other nutritious substance from it. They seek each other chiefly at night and in the latter part of spring, though some species have been noticed together at all times of the day, and during all the warm months; it is well known that they are most abundant on the surface of the ground during and after nocturnal rains. It has long been believed that this animal possesses a remarkable power of reproducing parts lost by accident or design, even to the extent of forming perfect individuals from separated portions; the experiments of Dugès prove that very important parts may be reproduced, and it may easily be believed that in a worm divided into two, the anterior portion might produce an anus by the simple contraction of the wound; but that the posterior portion should be able to reproduce cerebral ganglia, mouth, stomach, cardiac and sexual organs, cannot be admitted; the anterior may survive a long time, but the posterior division gradually dries up and dies. Dr. Williams, after attending to the experiments of Bonnet, Spallanzani, and others, to which Prof. Owen gives assent, says: "On the authority of hundreds of observations, laboriously repeated at every season of the year, the author of this report can declare with de liberate firmness, that there is not one word of truth in the above statement." In 1853 Mr. Newport exhibited before the Linnæan society of London 3 specimens of earth worms, one of which was living, in which more than of the anterior part of the body had been restored, smaller in diameter and with shorter segments than the anterior portion; and he says that it is not uncommon to find specimens with parts similarly restored. Though generally a despised creature, and occasionally marring the beauty of the garden walks by little hillocks of earth, they not only do not injure vegetation, but are really useful in permitting air and water to penetrate the ground through the channels which they pierce in every direction, manuring the fields, and throwing up fine dirt around the roots of grass; a field in which no worms exist can be safely put down as of little value to the agriculturist; they are most active in spring, when most needed, and retire during winter deep into the ground; according to Mr. Darwin, they perform under ground that which the plough and the spade do on the surface, and have covered a field manured with marl, in the course of 80 years, with a bed of earth 13 inches thick. Worms also furnish food for birds, moles, frogs, and other small animals, and are used as bait for many kinds of fish. The rapid ascent and descent of worms in the ground are easily understood from the action of their numerous setæ; they have often been seen high up on perpendicular surfaces, and in situations

which they could not have reached without climbing perpendicularly. In their movements they display great muscular force, each seta being moved by its appropriate system of muscles; Dr. Williams says that these setæ, with their fine hair-like appendages, will actually penetrate a deal board, and that the path of a worm on such a polished surface will show under the microscope 4 series of minute perforations. This would hardly explain their ascending perpendicular surfaces, especially when of glass or similar impenetrable material; in such cases, which are incontestable, they must retain their hold by means of the tenacious mucus with which their skin is covered. There is no question that many species have been confounded under L. terrestris (Linn.). The largest European species is called L. gigas, and is 18 inches long, and as large as the little finger; other common and smaller species are L. anatomicus and L. trapezoides. Whether all the American species are distinct or not has not been sufficiently demonstrated; there are certainly some species described peculiar to this country, but probably the L. terrestris is common to both hemispheres. The history and habits of this commonest of animals, trodden under foot by everybody, show how creatures apparently the best known may give rise to the most contradictory opinions among naturalists, and how a complete study of the most insignificant worm may illustrate some of the highest problems of animal physiology.-Those who wish to pursue this subject into its details are referred to the writings of Dufour, Dugès, Milne-Edwards, Blanchard, and especially Quatrefages in the Annales des sciences naturelles since 1828; to the article "Annelids," in the "Cyclopædia of Anatomy and Physiology;" to the report of Dr. Williams, above quoted; and to Siebold's "Comparative Anatomy," with its ample references to the best works.

EARTHENWARE. See POTTERY.

EARTHQUAKE. In every part of the world the surface is subject to be shaken at times by movements taking place in the interior and transmitted somewhat like a wave to distant regions. No country escapes these visitations, but in volcanic districts they occur more frequently than elsewhere; and commencing in these, they have been known to pass beneath sea and land, from one hemisphere to another, till full of the entire surface of the globe has been more or less disturbed by the movement. Such was the great earthquake of the year 1755, known as that of Lisbon, which will be described below. Some countries are so subject to these disturbances that the habitations of the people are built low, with broad bases and substantial walls, with particular reference to their stability against the shocks. This is the case throughout Central America, and in Chili, Peru, &c. Taking into account the whole surface of the earth, there is probably not a day that passes without the occurrence somewhere of a sensible disturbance of this kind, and hardly a month

without one or more worthy of note. The same countries have continued to be frequently visited by earthquakes from remote periods. Calabria, the southern extremity of Italy, has been repeatedly devastated since its early settlement by the Greek colonists, and, together with the neighboring island of Sicily, has been the scene of some of the most terrible earthquakes on record. From Feb. 1783, to the end of the year 1786, a period of nearly 4 years, this country was almost constantly disturbed. No fewer than 949 shocks were experienced in the first of these years, of which 501 were shocks of the first degree of force. Lyell observes that these convulsions were not remarkable above many others for their duration, violence, or extent, but great importance is given to them from the minuteness of the observations of men competent to collect and describe with accuracy the physical facts which throw light on geological questions. The details that have been recorded of the earthquakes in the countries bordering on the Mediterranean would make this region appear more subject to them than any other part of the globe; but had any other volcanic region been settled during the same periods by a population of the same degree of civilization, it is probable that the records of the two would not have materially differed in this respect. Among the earliest accounts of earthquakes of particular interest is that which resulted in the destruction of Herculaneum and Pompeii in the year 63, which was 16 years previous to the time when those cities were buried in the ashes from Vesuvius. The ancient city of Antioch in Syria was almost destroyed in the year 115, at the time of the visit of the emperor Trajan, who was himself hurt. In 458 it was again visited by an earthquake, and in 526 occurred the most disastrous one of which any record has been preserved. Gibbon states that 250,000 persons are said to have perished at this time, a conflux of strangers to the festival of the Ascension swelling the multitudes belonging to the city. "History," he remarks, will distinguish the periods in which these calamitous events have been rare or frequent, and will observe that this fever of the earth raged with uncommon violence during the reign of Justinian. Each year is marked by the repetition of earthquakes of such duration that Constantinople has been shaken above 40 days; of such extent that the shock has been communicated to the whole surface of the globe, or at least of the Roman empire." The approach of earthquakes is heralded by several premonitory symptoms of an unmistakable character. The air appears to be affected in some respect, perhaps in its electric condition, and the brute animals show a sensitiveness to this by uttering cries of distress and running wildly about. Men sometimes are affected with dizziness, and a sensation like seasickness. The atmosphere is often hazy for months, and the sun seen through it appears red and fiery. The weather suddenly changes from fierce gusts of wind to dead calms, and rains VOL. VI.-46

pour down in torrents at times, or in places in which they are usually of rare occurrence. Immediately before the shocks occur, the air is generally very still, while the surface of the ocean or lakes is unusually disturbed. A sound then breaks upon the stillness like distant thunder, or like a carriage rumbling afar off upon a rough pavement; or it may break at once with an awful explosion, as when the peal and the flash come together from every part of the cloud in which one is enveloped; at the same time the ground is shaken and lifted upward, or thrown forward, as by the passage of an irresistible wave beneath it. The shocks may be repeated several times in quick succession, or recur after long intervals; the movements may be so great as to rend the surface into chasms, and these may open and shut again, or remain in fissures of the width of a few feet or yards, and extending to unknown depths; smoke and flames are occasionally sent forth from them during the continuance of the earthquake, even if the region be not volcanic. Torrents of water are ejected from these chasms, and springs of water are often forced by the convulsion into new outets and directions. Objects upon the surface, as dwellings, trees, and animals, are engulfed in the chasms; and by subsidence of the surface, large trees, mountains even, and whole cities are swallowed up. Occurring as they most frequently do along the seaboard, the water is observed commonly to retire to some distance, leaving the harbors dry, and then to return in a great wave of many feet in height, which sweeps every thing before it. This may occur by the progress of the great wave, the recession being occasioned in the same way as the similar movement upon a small scale noticed along the shore as a steamboat approaches it, the water first receding, and then returning in a great wave; or it may be owing to a tract being uplifted in the sea at some distance, toward which the waters would first be drawn from every direction, and immediately after be propelled back with redoubled force. Of all the calamities to which man is exposed, there are none of so fearful a character as earthquakes; none involve such terrible and devastating destruction to life and property. There are none of the approach of which he is less forewarned, and none against which he can take fewer precautions. The very mysteriousness of the danger oppresses him with terror. He is ignorant in what form it is most imminent, or in what direction to seek a way of escape. Of modern earthquakes, that of Lisbon, in 1755, and that of New Madrid, Mo., in 1811, present some of the most interesting details. That of Chili, in 1822, is interesting for the permanent elevation of the country between the Andes and the coast which attended it. The area thus raised has been estimated to equal fully 100,000 square miles, and the height of the elevation to vary from 2 to 7 feet. Lines of sea beaches at higher levels and further inland indicate the previous lifting up of the same region at different times along the same lines.

A depression of the land was occasioned in the island of Jamaica in 1692, when Port Royal, the capital, was carried down, with the greater part of the buildings in the city, beneath the surface of the water. A thousand acres or more thus sank in less than one minute, the sea rolling in and driving the vessels in the harbor over the tops of the houses. A similar catastrophe occurred on a much more gigantic scale in the island of Java in 1772, when Papandayang, then one of the loftiest of the volcanoes of this region, was in action; an area suddenly sank down, including the mountain of 15 m. long and 6 m. broad, carrying with it 40 villages, and destroying 2,957 of the inhabitants. The great earthquake of Lisbon commenced on Nov. 1, 1755. The rumbling sound below the surface was immediately followed by the shock, which threw down the principal portion of the city. In the short space of 6 minutes it is believed that 60,000 persons perished. The sea retired, leaving the bar dry, and returned in a great wave 50 feet or more in height. The mountains around were shaken with great violence, and were even rent and thrown in fragments into the valleys below. Multitudes of people sought safety from the falling buildings by crowding upon the marble quay, which had just been constructed at great expense. It suddenly sank with them like a ship foundering at sea; but when the waters closed over the place no fragments of the wreck, none of the boats and vessels near by that were drawn into the whirlpool, and not one of the thousands of bodies carried down, reappeared upon the surface. Over the spot the water stood 600 feet deep; and beneath this, locked in the fissured rocks, in chasms of unknown depth, lie the relics of what was the life and wealth of this portion of the earth's surface in the middle of the 18th century. These rocks are the clayey and other comparatively soft strata of the tertiary formation. When in some future epoch they are raised again to the surface by a convulsion of the same nature with that which engulfed them, the vestiges they contain may reappear, converted in part or wholly into stone, like fossils entombed when the strata were deposited. The portion of the surface of the earth that was shaken by this earthquake was estimated by Humboldt as equal to 4 times the extent of Europe. The shock was felt in the Alps and on the coast of Sweden. In Germany the thermal springs of Töplitz disappeared for a time, and again burst forth, deluging the region around with ochre-stained waters. The waters of the lakes in Scotland, as Loch Lomond especially, rose suddenly more than 2 feet, and then subsided below their usual level. On the shores of Barbados, Martinique, and Antigua, the tide suddenly rose 20 feet, and the sea was of inky blackness. Even the distant waters of Lake Ontario were strangely agitated, and the shock was sensibly felt along the coast of Massachusetts. In Deane's "History of Scituate" it is stated that the earth was seen to

wave like the swellings of the sea, and occasionally break into fissures. This lasted for 15 minutes, during which chimneys were shaken down and houses disjointed. The sea roared with the unusual commotion, and with the rumbling of the earth the noise was more appalling than that of the loudest thunder. Water spouts burst forth, and springs opened, which continue to flow to this day. As the movement passed beneath the ocean, it was felt by several ships, the impression being like that produced by striking upon rocks. The motion is described as undulatory, and proceeding at the rate of about 20 m. a minute.—The earthquake of New Madrid, below St. Louis, on the Mississippi, in 1811, is the most important that has occurred in this country of which we have any record. Humboldt remarks that it presents one of the few examples of the incessant quaking of the ground for several successive months, far from any volcano. Over an extent of country 300 m. in length, from the mouth of the Ohio to that of the St. Francis, the ground rose and sank in great undulations, and lakes were formed, and were again drained. The surface burst open in fissures, from which mud and water were thrown as high as the tops of the trees. The direction of these fissures was generally from the N. E. toward the S. W., and the inhabitants, noticing this, felled the tallest trees at right angles to this line, and stationing themselves upon them, thus escaped being engulfed. Flint, the geographer, observed hundreds of these chasms 7 years after this catastrophe; and Lyell, who visited the same region in 1846, noticed many, which then appeared like artificial trenches, which might be traced for more than half a mile. They were generally parallel, and varied, according to his measurements, from 10° to 45° W. of N. The country is still called the "sunk country," and its extent, along the White Water and its tributaries, is 70 to 80 m. N. and S., and 30 m. E. and W. During the continuance of these convulsions the inhabitants distinguished 2 classes of earthquakes, those in which the movement was vertical, and those in which it was horizontal; the latter were regarded as far more desolating than the former. They continued until the destruction of the city of Caracas, which took place March 26, 1812. One evening, about this time, is described by the inhabitants of New Madrid as brilliant and cloudless, during which the western sky was a continued glare of vivid flashes of lightning, and peals of thunder were incessantly heard, proceeding apparently, as did the flashes, from below the horizon. In the destruction of Caracas, the whole city, with its splendid churches, was in an instant a heap of ruins, under which about 12,000 of its inhabitants were buried.-Fissures are occasionally met with in different parts of the country which extend through the solid rock to a great depth, and which were without doubt produced by earthquakes of some unknown period. A remarkable chasm of this nature may be followed

from the western base of the Shawangunk mountain at Ellenville, in Ulster co., N. Y., for about a mile to the summit. At the foot one may easily step across the fissure, but higher up it becomes wider till the hard vertical walls of sandstone are separated by a gorge several feet wide and of great depth. At the top the strata which sloped nearly with the mountain have curved over and assumed a horizontal position. An area of a hundred acres or more is here rent in every direction; the continuity of the surface is interrupted by sudden steps of rock, presenting abrupt walls, while the gorge traced up the mountain has spread out into a frightful abyss, more than a hundred feet wide. Among the loose rocks which lie upon the bottom, trees are seen growing, the tops of which hardly reach half way to the edge of the precipice.-Earthquakes of especial interest, from their late occurrence and destructive effects, are those of 1857 and 1858 of the kingdom of Naples, and of Mexico. The former commenced Dec. 16, 1857, and continued at intervals through the early part of January. In the city of Naples repeated shocks were felt, alarming the inhabitants, who often rushed from their houses into the streets, many fleeing from the city altogether. But as in former catastrophes of this nature, which laid waste the surrounding country, the city itself, though more or less injured, was singularly protected. This is supposed to be owing to the proximity of Vesuvius, which continued in eruption, discharging clouds of smoke, accompanied with terrific explosions. Resina at different times was in a continual state of vibration for hours together, the shocks appearing to procceed from the mountain. But the chief scene of destruction was in the provinces, particularly those of Principato Superiore and Basilicata. Potenza, the capital of the latter, was left without a single house inhabitable. Tito, Marsico Nuovo, Laurenzana, Porienza, Pollo, and other places, were reduced to heaps of ruins. The loss of lives was estimated by thousands; according to some statements made at the time, from 22,000 to 40,000. The late earthquake in Mexico occurred June 19, 1858. It extended throughout the valley of Mexico, demolishing many houses in the city, and also the aqueduct which supplies the city with water, and destroying property to the value of several millions of dollars. It was felt with more or less destructive effects in Guadalajara, Jalapa, San Luis Potosi, Toluca, &c. In the city of Morelis, the shock was the greatest ever experienced there, lasting 13 minutes; and in Patzacuaro, 15 leagues further west, it was still more severe, levelling 4 churches, and many private houses. The city of Quito in Ecuador was almost entirely destroyed by an earthquake, March 22, 1859, and many thousand lives are said to have been lost. Several small towns north of the capital were destroyed at the same time.-The cause which produces the earthquake shock, and the manner in which it is communicated over vast distances in short time, have been variously explained. Slight

impulses sometimes produce perceptible movements in what appears to be solid and fixed. Thus at Greenwich observatory the shutting of the outer gate has so jarred the transit telescope as to throw the star to which it pointed out of the field of view. The effect of the jarring of dams by the fall of water is also felt miles off. Various agents are well known to be at work in the interior of the earth, producing chemical changes, which are often attended with violent movements. By such forces immense columns of lava are lifted up in the craters of volcanoes, and stones of vast size are ejected. One mass of rock thrown from Cotopaxi, a distance of 8 or 9 m., was estimated to contain about 100 cubic yards of matter, consequently weighing over 200 tons. It has been suggested that many of the gases which are evolved from volcanoes may, under the immense pressure to which they are subjected in the interior, exist in a liquid or solid form, and that by a considerable increase of heat these are made to assume the gaseous form, and in doing this display an elastic power which no superincumbent mass can resist. It has been found that when powder is exploded in rocks a shock is communicated to distances varying with the quantity fired and the quality of the rock as to elasticity; and the rate of progress of this impulse has been observed to be from about 1,000 to 1,700 feet per second. Many instances have been recorded of the velocity of the earthquake shock, ascertained by noting the time at which chronometers at different localities have been stopped by it, and this has been found to vary from 1,000 to 5,000 feet per second. The movement in both these cases is no doubt of analogous character, though accompanied in the earthquake by a vastly increased display of force. Mr. R. Mallet, who has recounted these and other observations in his valuable essay on the dynamics of earthquakes, defines their efficient cause to be "a wave of elastic compression, produced either by the sudden flexure and constraint of the elastic materials forming a portion of the earth's crust, or by the sudden relief of this constraint by withdrawal of the force, or by their giving way and becoming fractured." When, as frequently is the case, the shock originates beneath the ocean, its effect is transmitted first in the wave of sound, which, rushing forward through the rocky crust of the earth at the rate of 8,000 to 10,000 feet per seccond, gives notice by its rumbling of the vibrating motion that is following behind. The great sea wave generated by the same movement, advances still more slowly than the vibration transmitted through the rocky strata, but at last pours in upon the land, its effects modified by the contour of the coasts and the depth of the waters through which it has passed. Lastly may come the atmospheric agitation and the sound of the outbreak, transmitted through the air. The vibrating movement imparted to the solid strata is the chief agency in the diasastrous effects of earthquakes. Its rate of progress must vary with the varying elasticity

of the rocks, and a greatly increased shock must consequently be experienced in the passage of the wave from soft alluvial strata into the hard crystalline rocks, or vice versa. It was on this line of junction of the 2 formations that the most disastrous effects were experienced in the great earthquake in Calabria in 1783. It is by such an elastic wave, moving forward and suddenly back again, that Mr. Mallet explains the curious effects which have been observed in the twisting movement given to the blocks which form portions of columns, as if the upper stones had been partially turned around on the lower. Such effects were noticed by Darwin in the cathedral at Concepcion, and others of the same nature are described as having occurred to 2 obelisks in a convent in Calabria. The effect has also been referred to a vorticose or whirling motion, and by others to a rotary movement caused by the crossing of 2 waves of horizontal vibration. The Profs. Rogers "attribute the movement to an actual pulsation engendered in the molten matter itself by a linear disruption under enormous tension, giving vent explosively to elastic vapors, escaping either to the surface or into cavernous spaces beneath." By others the movement had previously been ascribed to elastic vapors, passing between the strata or between the crust and the fluid lava beneath it. For further details the reader is referred to the work of Robert Mallet, C.E., and John W. Mallet, professor of chemistry in the university of Alabama, published in an octavo volume in 1858. It contains the able papers published from 1852 to 1858 in the "Transactions" of the British association for the advancement of science; that of 1858 reviewing the facts and theories of earthquakes, and illustrated by several fine maps. Mr. Mallet has also collected some interesting data respecting the distribution of earthquakes, having compiled a catalogue embracing nearly 6,000. In Guinea and southern Africa no earthquakes are recorded. The same may probably be said of Greenland. One spot in the Atlantic ocean, near the equator and about midway between Guinea and Brazil, appears to be peculiarly subject to them. Vessels passing over this tract almost always experience shocks, and the soundings are found to be subject to sudden and extreme variations, a depth of 400 fathoms being often directly succeeded by one beyond the reach of the sounding line. It is naturally inferred that this may be a submarine volcanic region.

EARTHS, in chemistry, a class of certain compounds of metallic bases and oxygen, which before the decomposition of some of them by Sir Humphry Davy were regarded as elementary bodies. The earths proper are alumina, glucina, zirconia, thoria, didymia, lantana, ceria, yttria, terbia, erbia. Silica, formerly regarded as an earth, is a combination of silicon with oxygen, and possesses the properties of an acid. The following possess alkaline properties, and are classed as alkaline earths: baryta, strontia, lime, magnesia, lithia. Excepting alumina, the

pure earths are rarely seen; they are insoluble in water, and when taken up by acid solvents are precipitated white by ammonia or soda. EARWIG, an orthopterous insect, of the family cursoria or runners, which also includes the cockroach; it belongs to the genus forficula (Linn.). All the 6 feet are formed for running; the wings are 4, the upper pair very short, coriaceous like the elytra of coleoptera, without veins, enclosing the under wings, which are folded both longitudinally and transversely; the mouth is formed for mastication; the body is long and somewhat flattened, and armed at the hinder end with a pair of curved blades shutting like scissors or nippers; there are 3 joints to the tarsus; the antennæ are filiform. These insects undergo a partial metamorphosis. They seem to form the connecting link between coleoptera and orthoptera, resembling the former in their elytra, and the latter in the shape of the wings and mouth, and the metamorphosis; for these reasons most English entomologists adopt for them the order dermaptera of Mr Kirby and Dr. Leach, considering them coleoptera with the metamorphosis and caudal appendages of orthoptera. They are common in moist earth, under stones, in decayed wood, and in similar damp and dark places; they are considered in Europe injurious to peaches, pears, apples, to greenhouse plants, and to pinks, dahlias, and other favorites of the flower garden. The full-grown insect, including its caudal forceps, is not quite an inch long, and its width is of an inch; the color is light brown. Being nocturnal insects, they creep in the daytime into any crevice or hole which can conceal them, and this has given rise to the popular belief that they enter the human ear; they might attempt this, but the waxy bitter secretion of the ear would probably prevent their entrance; there are no well authenticated instances of their doing this, and no harm could result if they did, as the drum of the ear would arrest them, and a drop or two of oil would soon destroy them by stopping up their respiratory trachea. The common way of catching them in England is by hanging up any convenient vessel or tube for them to crawl into in the morning, from which they are shaken and killed. In the larvæ there are no wings nor elytra, but the skin is changed several times; the nymph differs little from the perfect insect; in both these conditions they are voracious, even devouring each other. In this country there are several species, rather uncommon, and never injurious to vegetation.The many-footed creeping animal erroneously called earwig in America (genus iulus), is not an insect, but a myriapodous crustacean, equally innocent of entering the human ear.

EASDALE, or EISDALE, an island of the Hebrides group, about 14 m. long, and of nearly the same width, and noted for its slate quarries, which have been worked 150 years. The island consists entirely of slate stone, and has been so much cut away that a large part of it is now even with or below the level of the sea.

EAST (Anglo-Saxon, East; the corresponding