part iii

. 1899; _Proc. Zool. Soc. Lond._, 1898, 1899; and _Cambridge Natural History_, ii.). The following are found in the British area:--_E. pallasii_ (Guerin-Meneville), _Th. neptuni_ (Gaertner), and _Th. lankesteri_ (Herdman, _Q.J.M.S._, 1898).

_Affinities._--The occurrence of trochosphere larva and the temporary segmentation of the body have led to the belief that the Echiuroids are more nearly allied to the Annelids than to any other phylum. This view is strengthened by certain anatomical and histological resemblances to the genus _Sternaspis_, which in one species, _S. spinosa_, is said to carry a bifid proboscis resembling that of the Echiuroids. (A. E. S.)

ECHMIADZIN, or ITSMIADSIN, a monastery of Russian Transcaucasia, in the government of Erivan, the seat of the Catholicus or primate of the Armenian church. It is situated close to the village of Vagarshapat, in the plain of the Aras, 2840 ft. above the sea, 12 m. W. of Erivan and 40 N. of Mount Ararat. The monastery comprises a pretty extensive complex of buildings, and is surrounded by brick walls 30 ft. high, which with their loopholes and towers present the appearance of a fortress. Its architectural character has been considerably impaired by additions and alterations in modern Russian style. On the western side of the quadrangle is the residence of the primate, on the south the refectory (1730-1735), on the east the lodgings for the monks, and on the north the cells. The cathedral is a small but fine cruciform building with a Byzantine cupola at the intersection. Its foundation is ascribed to St Gregory the Illuminator in 302. Of special interest is the porch, built of red porphyry, and profusely adorned with sculptured designs somewhat of a Gothic character. The interior is decorated with Persian frescoes of flowers, birds and scroll-work. It is here that the Catholicus confers episcopal consecration by the sacred hand (relic) of St Gregory; and here every seven years he prepares with great solemnity the holy oil which is to be used throughout the churches of the Armenian communion. Outside of the main entrance are the alabaster tombs of the primates Alexander I. (1714), Alexander II. (1755), Daniel (1806) and Narses (1857), and a white marble monument, erected by the English East India Company to mark the resting-place of Sir John Macdonald Kinneir, who died at Tabriz in 1830, while on an embassy to the Persian court. The library of the monastery is a rich storehouse of Armenian literature (see Brosset's _Catalogue de la bibliotheque d'Etchmiadzin_, St Petersburg, 1840). Among the more remarkable manuscripts are a copy of the gospels dating from the 10th or 11th century, and three bibles of the 13th century. A type-foundry, a printing-press and a bookbinding establishment are maintained by the monks who supply religious and educational works for their co-religionists.

To the east of the monastery is a modern college and seminary. Half a mile to the east stand the churches of St Ripsime and St Gaiana, two of the early martyrs of Armenian Christianity; the latter is the burial-place of those primates who are not deemed worthy of interment beside the cathedral. From a distance the three churches form a fairly striking group, and accordingly the Turkish name for Echmiadzin is Uch-Kilissi, or the Three Churches. The town of Vagarshapat dates from the 6th century B.C.; it takes its name from King Vagarsh (Vologaeses), who in the 2nd century A.D. chose it as his residence and surrounded it with walls. Here the apostle of Armenia, St Gregory the Illuminator, erected a church in 309 and with it the primacy was associated. In 344 Vagarshapat ceased to be the Armenian capital, and in the 5th century the patriarchal seat was removed to Dvin, and then to Ani. The monastery was founded by Narses II., who ruled 524-533; and a restoration was effected in 618. The present name of the monastery was adopted instead of Vagarshapat in the 10th century. At length in 1441 the primate George brought back the see to the original site. (P. A. K.; J. T. Be.)

ECHO (Gr. [Greek: echo]), in Greek mythology, one of the Oreades or mountain nymphs, the personification of the acoustical phenomenon known by this name. She was beloved by Pan, but rejected his advances. Thereupon the angry god drove the shepherds of the district mad; they tore Echo in pieces, and scattered her limbs broadcast, which still retained the gift of song (Longus iii. 23). According to Ovid (_Metam._ iii. 356-401), Echo by her incessant talking having prevented Juno from surprising Jupiter with the Nymphs, Juno changed her into an "echo"--a being who could not speak till she was spoken to, and then could only repeat the last words of the speaker. While in this condition she fell in love with Narcissus, and in grief at her unrequited affection wasted away until nothing remained but her voice and bones, which were changed into rocks. The legends of Echo are of late, probably Alexandrian, origin, and she is first personified in Euripides.

In acoustics an "echo" is a return of sound from a reflecting surface (see SOUND: _Reflection_).

See F. Wieseler, _Die Nymphe Echo_ (1854), and _Narkissos_ (1856); P. Decharme in Daremberg and Saglio's _Dictionnaire des antiquites_.

ECHTERNACH, a town in the grand duchy of Luxemburg, on the Sure, close to the Prussian frontier. Pop. (1905) 3484. It is the oldest town in Luxemburg, and was the centre from which the English Saint Willibrord converted the people to Christianity in the 7th century. There are the Benedictine abbey, the hospital almshouse, which is said to be the oldest hospital in Europe except the Hotel-Dieu in Paris, and the church of St Peter and St Paul. The Benedictine abbey has been greatly shorn of its original dimensions, but the basilica remains a fair monument of Romano-Gothic art. The church of St Peter and St Paul stands on an isolated mound, and for the ascent sixty steps have been built in the side, and these are well worn by the tread of numerous pilgrims who come in each succeeding year. The interior of the church is curious more than imposing, and is specially noteworthy only for its gloom. Under the altar, and below a white marble effigy of himself, lies Saint Willibrord.

Echternach is famous, however, in particular for the dancing procession held on Whit-Tuesday every year. The origin of this festival is uncertain, but it dates at least from the 13th century and was probably instituted during an outbreak of cholera. Nowadays it is an occasion of pilgrimage, among Germans and Belgians as well as Luxemburgers, for all sick persons, but especially for the epileptic and those suffering from St Vitus' dance. The ceremony is interesting, and the Roman Catholic Church lends all its ritual to make it more imposing. The archbishop of Trier attends to represent Germany, and the bishop of Luxemburg figures for the grand duchy. There is a religious ceremony on the Prussian side of the bridge over the Sure, and when it is over the congregation cross into the duchy to join the procession, partly religious, partly popular, through the streets of the town. The religious procession, carrying cross and banners and attended by three hundred singers, comes first, chanting St Willibrord's hymn. Next comes a band of miscellaneous instruments playing as a rule the old German air "Adam had seven sons," and then follow the dancers. Many of these are young and full of life and health and dance for amusement, but many others are old or feeble and dance in the hope of recovery or of escaping from some trouble, but on all alike the conditions of the dance are incumbent. There are three steps forward and two back; five steps are thus taken to make one in advance. This becomes especially trying at the flight of steps mounting to the little church where the procession ends in front of the shrine of the great saint. There are sixty steps, but it takes three hundred to reach the top for the final time. It is said that those who fall from age or weariness have to be dragged out of the way by onlookers or they would be trampled to death by the succeeding waves of dancers. The procession, although it covers a distance of less than a mile, is said to take as much as five hours in its accomplishment. In olden days the abbey was the goal of the procession, and King William I. of the Netherlands--great-grandfather of Queen Wilhelmina--changed the day from Tuesday to Sunday so that a working day should not be lost. This reform did not answer, and the ancient order was restored. Some critics see in the dancing procession of Echternach merely the survival of the spring dance of the heathen races, but at any rate it invests the little town with an interest and importance that would otherwise be lacking.

ECHUCA, a borough of the county of Rodney, Victoria, Australia, 156 m. by rail N. of Melbourne. Pop. (1901) 4075. It is situated on the river Murray, across which it is connected by bridge with Moama, on the New South Wales side, whence a railway runs to Deniliquin. The town is the terminus of the Murray River railway and the entrepot of the overland intercolonial trade; it has large wool stores, saw-mills, coach factories, breweries and soap-works. The rich agricultural district is noted for its vineyards.

ECIJA, a town of southern Spain, in the province of Seville; on the Cadiz-Cordova railway and the left bank of the river Genil. Pop. (1900) 24,372. The river, thus far navigable, is here crossed by a fine old bridge; and the antiquity of the town betrays itself by the irregularity of its arrangement, by its walls and gateways, and by its numerous inscriptions and other relics. Its chief buildings include no fewer than twenty convents, mostly secularized. The principal square is surrounded with pillared porticoes, and has a fountain in the centre; and along the river bank there runs a fine promenade, planted with poplar trees and adorned with statues. From an early period the shoemakers of Ecija have been in high repute throughout Spain; woollen cloth, flannel, linen and silks are also manufactured. The vicinity is fertile in corn and wine, and cotton is cultivated. The heat is so great that the spot has acquired the sobriquet of _El Sarten_, or the "Frying-pan" of Andalusia. Ecija, called _Estija_ by the Arabs, is the ancient _Astigis_, which was raised to the rank of a Roman colony with the title of _Augusta Firma_. According to Pliny and Pomponius Mela, who both wrote in the 1st century A.D., it was the rival of Cordova and Seville. If local tradition may be believed, it was visited by the apostle Paul, who converted his hostess Santa Xantippa; and, according to one version of his life, it was the see of the famous St Crispin (q.v.) in the 3rd century.

ECK, JOHANN MAIER (1486-1543), German theologian, the most indefatigable and important opponent of Martin Luther, was born on the 13th of November 1486 at Eck in Swabia, from which place he derived his additional surname, which he himself, after 1505, always modified into Eckius or Eccius, i.e. "of Eck." His father, Michael Maier, was a peasant and bailiff (_Amtmann_) of the village. The boy's education was undertaken by his uncle Martin Maier, parish priest at Rothenburg on the Neckar, who sent him at the age of twelve to the university of Heidelberg, and subsequently to those of Tubingen, Cologne and Freiburg in the Breisgau. His academic career was so rapidly successful that at the age of twenty-four he was already doctor and professor of theology. During this period he was distinguished for his opposition to the scholastic philosophy; and, though he did not go to all lengths with the "modernists" (_Moderni_) of his day, his first work--_Logices exercitamenta_ (1507)--was distinctly on their side. This attitude brought him into conflict with the senate of the university, a conflict which Eck's masterful temper, increased by an extreme self-confidence perhaps natural in one so young and so successful, did not serve to allay. His position in Freiburg becoming intolerable, he accepted in 1510 an invitation from the duke of Bavaria to fill the theological chair at Ingolstadt, where he was destined for thirty years to exercise a profound influence as teacher and vice-chancellor (_Prokanzler_).

A ducal commission, appointed to find a means for ending the interminable strife between the rival academic parties, entrusted Eck with the preparation of fresh commentaries on Aristotle and Petrus Hispanus. He had a marvellous capacity for work, and between 1516 and 1520, in addition to all his other duties, he published commentaries on the _Summulae_ of Petrus Hispanus, and on the _Dialectics_, _Physics_ and lesser scientific works of Aristotle, which became the text-books of the university. During these early years Eck was still reckoned among the "modernists," and his commentaries are inspired with much of the scientific spirit of the New Learning. His aim, however, had been to find a _via media_ between the old and new; his temper was essentially conservative, his imagination held captive by the splendid traditions of the medieval church, and he had no sympathy with the revolutionary attitude of the Reformers. Personal ambition, too, a desire to be conspicuous in the great world of affairs, may have helped to throw him into public opposition to Luther. He had won laurels in a public disputation at Augsburg in 1514, when he had defended the lawfulness of putting out capital at interest; again at Bologna in 1515, on the same subject and on the question of predestination; and these triumphs had been repeated at Vienna in 1516. By these successes he gained the patronage of the Fuggers, and found himself fairly launched as the recognized apologist of the established order in church and state. Distinguished humanists might sneer at him as "a garrulous sophist"; but from this time his ambition was not only to be the greatest scientific authority in Germany but also the champion of the papacy and of the traditional church order. The first-fruits of this new resolve were a quite gratuitous attack on his old friend, the distinguished humanist and jurist Ulrich Zasius (1461-1536), for a doctrine proclaimed ten years before, and a simultaneous assault on Erasmus's _Annotationes in Novum Testamentum_.

It is, however, by his controversy with Luther and the other reformers that Eck is best remembered. Luther, who had some personal acquaintance with Eck, sent him in 1517 copies of his celebrated 95 theses. Eck made no public reply; but in 1518 he circulated, privately at first, his _Obelisci_, in which Luther was branded as a Hussite. Luther entrusted his defence to Carlstadt, who, besides answering the insinuations of Eck in 400 distinct theses, declared his readiness to meet him in a public disputation. The challenge was accepted, and the disputation took place at Leipzig in June and July 1519. On June 27 and 28 and on July 1 and 3 Eck disputed with Carlstadt on the subjects of grace, free will and good works, ably defending the Roman Semipelagian standpoint. From July 4 to 14 he engaged with Luther on the absolute supremacy of the papacy, purgatory, penance, &c., showing a brilliant display of patristic and conciliar learning against the reformer's appeals to Scripture. The arbitrators declined to give a verdict, but the general impression was that victory rested with Eck. He did, indeed, succeed in making Luther admit that there was some truth in the Hussite opinions and declare himself against the pope, but this success only embittered his animosity against his opponents, and from that time his whole efforts were devoted to Luther's overthrow. He induced the universities of Cologne and Louvain to condemn the reformer's writings, but failed to enlist the German princes, and in January 1520 went to Rome to obtain strict regulations against those whom he called "Lutherans." He was created a protonotary apostolic, and in July returned to Germany, as papal nuncio, with the celebrated bull _Exsurge Domine_ directed against Luther's writings. He now believed himself in a position to crush not only the Lutheran heretics, but also his humanist critics. The effect of the publication of the bull, however, soon undeceived him. Bishops, universities and humanists were at one in denunciation of the outrage; and as for the attitude of the people, Eck was glad to escape from Saxony with a whole skin. In his wrath he appealed to force, and his _Epistola ad Carolum V._ (February 18, 1521) called on the emperor to take measures against Luther, a demand soon to be responded to in the edict of Worms. In 1521 and 1522 Eck was again in Rome, reporting on the results of his nunciature. On his return from his second visit he was the prime mover in the promulgation of the Bavarian religious edict of 1522, which practically established the senate of the university of Ingolstadt as a tribunal of the Inquisition, and led to years of persecution. In return for this action of the duke, who had at first been opposed to the policy of repression, Eck obtained for him, during a third visit to Rome in 1523, valuable ecclesiastical concessions. Meanwhile he continued unabated in his zeal against the reformers, publishing eight considerable works between 1522 and 1526.

His controversial ardour was, indeed, somewhat damped by Luther's refusal to answer his arguments, and with a view to earning fresh laurels he turned his attention to Switzerland and the Zwinglians. At Baden-in-Aargau in May and June 1526 a public disputation on the doctrine of transubstantiation was held, in which Eck and Thomas Murner were pitted against Johann Oecolampadius. Though Eck claimed the victory in argument, the only result was to strengthen the Swiss in their memorial view of the Lord's Supper, and so to diverge them further from Luther. At the Augsburg diet in 1530 Eck was charged by Charles V. to draw up, in concert with twenty other theologians, the refutation of the Protestant Confession, but was obliged to rewrite it five times before it suited the emperor. He was at the colloquy of Worms in 1540 and at the diet of Regensburg (Ratisbon) in 1541. At Worms he showed some signs of a willingness to compromise, but at Regensburg his old violence reasserted itself in opposing all efforts at reconciliation and persuading the Catholic princes to reject the Interim.

Eck died at Ingolstadt on the 10th of February 1543, fighting to the last and worn out before his time. He was undoubtedly the most conspicuous champion produced by the old religion in the age of the Reformation, but his great gifts were marred by greater faults. His vast learning was the result of a powerful memory and unwearied industry, and he lacked the creative imagination necessary to mould this material into new forms. He was a powerful debater, but his victories were those of a dialectician rather than a convincing reasoner, and in him depth of insight and conviction were ill replaced by the controversial violence characteristic of the age. Moreover, even after discounting the bias of his enemies, there is evidence to prove that his championship of the Church was not the outcome of his zeal for Christianity; for he was notoriously drunken, unchaste, avaricious and almost insanely ambitious. His chief work was _De primatu Petri_ (1519); his _Enchiridion locorum communium adversus Lutherum_ ran through 46 editions between 1525 and 1576. In 1530-1535 he published a collection of his writings against Luther, _Opera contra Ludderum_, in 4 vols.

See T. Wiedemann, _Dr Johann Eck_ (Regensburg, 1865).

ECKERMANN, JOHANN PETER (1792-1854), German poet and author, best known owing to his association with Goethe, was born at Winsen in Hanover on the 21st of September 1792, of humble parentage, and was brought up in penury and privation. After serving as a volunteer in the War of Liberation (1813-1814), he obtained a secretarial appointment under the war department at Hanover. In 1817, although twenty-five years of age, he was enabled to attend the gymnasium of Hanover and afterwards the university of Gottingen, which, however, after one year's residence as a student of law, he left in 1822. His acquaintance with Goethe began in the following year, when he sent to him the manuscript of his _Beitrage zur Poesie_ (1823). Soon afterwards he went to Weimar, where he supported himself as a private tutor. For several years he also instructed the son of the grand duke. In 1830 he travelled in Italy with Goethe's son. In 1838 he was given the title of grand-ducal councillor and appointed librarian to the grand-duchess. Eckermann is chiefly remembered for his important contributions to the knowledge of the great poet contained in his _Conversations with Goethe_ (1836-1848). To Eckermann Goethe entrusted the publication of his _Nachgelassene Schriften_ (posthumous works) (1832-1833). He was also joint-editor with Friedrich Wilhelm Riemer (1774-1845) of the complete edition of Goethe's works in 40 vols. (1839-1840). He died at Weimar on the 3rd of December 1854.

Eckermann's _Gesprache mit Goethe_ (vols. i. and ii. 1836; vol. iii. 1848; 7th ed., Leipzig, 1899; best edition by L. Geiger, Leipzig, 1902) have been translated into almost all the European languages, not excepting Turkish. (English translations by Margaret Fuller, Boston, 1839, and John Oxenford, London, 1850.) Besides this work and the _Beitrage zur Poesie_, Eckermann published a volume of poems (_Gedichte_, 1838), which are of little value. See _J.P. Eckermanns Nachlass_, herausgegeben von F. Tewes, vol. i. (1905), and an article by R.M. Meyer in the _Goethe-Jahrbuch_, xvii. (1896).

ECKERNFORDE, a town of Germany, in the Prussian province of Schleswig-Holstein, on a fjord of the Baltic, 20 m. by rail N.W. from Kiel. Pop. (1905) 7088. It has a good harbour, fishing, trade in agricultural products, and manufactures of tobacco, salt and iron goods. There are a technical school of building and a Protestant teachers' seminary. Eckernforde is mentioned as far back as 1197. It was taken by Christian IV. of Denmark in 1628 from the Imperial troops. In 1813 the Danes were defeated here, while in 1849 the harbour was the scene of the blowing up of the Danish line-of-battle ship "Christian VIII." and of the surrender of the frigate "Gefion" after an engagement with the German shore batteries. The place lost most of its trade after the union with Germany in 1864, and suffered severely from a sea-flood in 1872. In the immediate neighbourhood is the village of Borby, much frequented for sea-bathing.

ECKERSBERG, KRISTOFFER (1783-1853), Danish painter, was born in south Jutland. He became successively the pupil of Nikolaj Abildgaard and of J.L. David. From 1810 to 1813 he lived at Paris under the direction of the latter, and then proceeded, as an independent artist, to Rome, where he worked until 1816 in close fellowship with Thorwaldsen. His paintings from this period--"The Spartan Boy," "Bacchus and Ariadne" and "Ulysses"--testify to the influence of the great sculptor over the art of Eckersberg. Returning to Copenhagen, he found himself easily able to take the first place among the Danish painters of his time, and his portraits especially were in extreme popularity. It is claimed for Eckersberg by the native critics that "he created a Danish colour," that is to say, he was the first painter who threw off conventional tones and the pseudo-classical landscape, in exchange for the clear atmosphere and natural outlines of Danish scenery. But Denmark has no heroic landscape, and Eckersberg in losing the golden commonplaces scarcely succeeds in being delightful. His landscapes, however, are pure and true, while in his figure-pieces he is almost invariably conventional and old-fashioned. He was president of the Danish Academy of Fine Arts in Charlottenburg.

ECKHART,[1] JOHANNES ["Meister Eckhart"] (?1260-?1327), German philosopher, the first of the great speculative mystics. Extremely little is known of his life; the date and place of his birth are equally uncertain. According to some accounts, he was a native of Strassburg, with which he was afterwards closely connected; according to others, he was born in Saxony, or at Hochheim near Gotha. Trithemius, one of the best authorities, speaks of him merely as "Teutonicus." 1260 has frequently been given as the date of his birth; it was in all probability some years earlier, for we know that he was advanced in age at the time of his death, about 1327. He appears to have entered the Dominican order, and to have acted for some time as professor at one of the colleges in Paris. His reputation for learning was very high, and in 1302 he was summoned to Rome by Boniface VIII., to assist in the controversy then being carried on with Philip of France. From Boniface he received the degree of doctor. In 1304 he became provincial of his order for Saxony, and in 1307 was vicar-general for Bohemia. In both provinces he was distinguished for his practical reforms and for his power in preaching. Towards 1325 we hear of him as preaching with great effect at Cologne, where he gathered round him a numerous band of followers. Before this time, and in all probability at Strassburg, where he appears to have been for some years, he had come in contact with the Beghards (see BEGUINES) and Brethren of the Free Spirit, whose fundamental notions he may, indeed, be said to have systematized and expounded in the highest form to which they could attain. In 1327 the opponents of the Beghards laid hold of certain propositions contained in Eckhart's works, and he was summoned before the Inquisition at Cologne. The history of this accusation is by no means clear. Eckhart appears, however, to have made a conditional recantation--that is, he professed to disavow whatever in his writings could be shown to be erroneous. Further appeal, perhaps at his own request, was made to Pope John XXII., and in 1329 a bill was published condemning certain propositions extracted from Eckhart's works. But before its publication Eckhart was dead. The exact date of his death is unknown. Of his writings, several of which are enumerated by Trithemius, there remain only the sermons and a few tractates. Till the middle of the 19th century the majority of these were attributed to Johann Tauler, and it is only from Pfeiffer's careful edition (_Deutsche Mystiker d. XIV. Jahrhunderts_, vol. ii., 1857) that one has been able to gather a true idea of Eckhart's

## activity. From his works it is evident that he was deeply learned in all

the philosophy of the time. He was a thorough Aristotelian, but by preference appears to have been drawn towards the mystical writings of the Neoplatonists and the pseudo-Dionysius. His style is unsystematic, brief and abounding in symbolical expression. His manner of thinking is clear, calm and logical, and he has certainly given the most complete exposition of what may be called Christian pantheism.

Eckhart has been called the first of the speculative mystics. In his theories the element of mystical speculation for the first time comes to the front as all-important. By its means the church doctrines are made intelligible to the many, and from it the church dogmas receive their true significance. It was but natural that he should diverge more and more widely from the traditional doctrine, so that at length the relation between his teaching and that of the church appeared to be one of opposition rather than of reconciliation. Eckhart is in truth the first who attempted with perfect freedom and logical consistency to give a speculative basis to religious doctrines. The two most important points in his, as in all mystical theories, are first, his doctrine of the divine nature, and second, his explanation of the relation between God and human thought. (See MYSTICISM.)

For the German writings of Eckhart see F. Pfeiffer, _Deutsche Mystiker_, vol. ii. (Leipzig, 1857), and F. Jostes, _Meister Eckhart und seine Junger_ (Freiburg, 1895); for the Latin works, H. Denifle in _Archiv f. Litt- und Kirchengeschichte d. Mittelalters_, ii. (1886), pp. 417-652, and v. (1889), pp. 349-364; German translations by G. Landauer, _Meister Eckarts mystische Schriften_ (Berlin, 1903), and Buttner (Leipzig, 1903 foll.). See also A. Lasson, _Meister Eckhart der Mystiker_ (1868); H.L. Martensen, _Meister Eckhart_ (1842); J. Bach, _Meister Eckhart der Vater der deutschen Speculation_ (1864); C. Ullmann, _Reformatoren vor der Reformation_ (1842); W. Preger, _Geschichte d. deutschen Mystik_, i. (1874); and "Ein neuer Traktat M. Eckharts und d. Grundzuge der Eckhartischen Theosophie" in _Zeitschr. f. hist. Phil._ (1864), pp. 163 foll.; A. Bullinger, _Das Christenthum im Lichte der deutschen Philos._ (Dillingen, 1895); H. Delacroix, _Le Mysticisme speculatif en Allemagne au XIV^e siecle_ (Paris, 1900); E. Kramm, _Meister Eckhart im Lichte der Denifleschen Funde_ (Bonn, 1889); R. Langenberg, _Uber die Verhaltnisse Meister Eckharts zur niederdeutschen Mystik_ (Gottingen, 1896); W. Schopff, _Meister Eckhart_ (Leipzig, 1889); A. Jundt, _Hist. du pantheisme populaire au moyen age_ (Paris, 1875); art. in Herzog-Hauck, _Realencyklopadie_ (S.M. Deutsch); R.M. Jones, _Mystical Religion_ (1909).

FOOTNOTE:

[1] The name is variously spelled: Eckehart, Eckart, Eckhard.

ECKHEL, JOSEPH HILARIUS (1737-1798), Austrian numismatist, was born at Enzersfeld in lower Austria, 1737. His father was farm-steward to Count Zinzendorf, and he received his early education at the Jesuits' College, Vienna, where at the age of fourteen he was admitted into the order. He devoted himself to antiquities and numismatics. After being engaged as professor of poetry and rhetoric, first at Steyer and afterwards at Vienna, he was appointed in 1772 keeper of the cabinet of coins at the Jesuits' College, and in the same year he went to Italy for the purpose of personal inspection and study of antiquities and coins. At Florence he was employed to arrange the collection of the grand duke of Tuscany; and the first-fruits of his study of this and other collections appeared in his _Numi veteres anecdoti_, published in 1775. On the dissolution of the order of Jesuits in 1773, Eckhel was appointed by the empress Maria Theresa professor of antiquities and numismatics at the university of Vienna, and this post he held for twenty-four years. He was in the following year made keeper of the imperial cabinet of coins, and in 1779 appeared his _Catalogus Vindobonensis numorum veterum_. Eckhel's great work is the _Doctrina numorum veterum_, in 8 vols., the first of which was published in 1792, and the last in 1798. The author's rich learning, comprehensive grasp of his subject, admirable order and precision of statement in this masterpiece drew from Heyne enthusiastic praise, and the acknowledgment that Eckhel, as the Coryphaeus of numismatists, had, out of the mass of previously loose and confused facts, constituted a true science. A volume of _Addenda_, prepared by Steinbuchel from Eckhel's papers after his death, was published in 1826. Among his other works are--_Choix de pierres gravees du Cabinet Imperial des Antiques_ (1788), a useful school-book on coins entitled _Kurzgefasste Anfangsgrunde zur alten Numismatik_ (1787), of which a French version enlarged by Jacob appeared in 1825, &c. Eckhel died at Vienna on the 16th of May 1798.

ECKMUHL, or EGGMUHL, a village of Germany, in the kingdom of Bavaria, on the Grosse Laaber, 13 m. S.E. of Regensburg by the railway to Munich. It is famous as the scene of a battle fought here on the 22nd of April 1809, between the French, Bavarians and Wurttembergers under Napoleon, and the Austrians under the Archduke Charles, which resulted in the defeat of the latter. Napoleon, in recognition of Marshal Davout's great share in the victory, conferred on him the title of prince of Eckmuhl. For an account of this action and those of Abensberg and Landshut see NAPOLEONIC CAMPAIGNS.

ECLECTICISM (from Gr. [Greek: eklego], I select), a term used specially in philosophy and theology for a composite system of thought made up of views borrowed from various other systems. Where the characteristic doctrines of a philosophy are not thus merely adopted, but are the modified products of a blending of the systems from which it takes its rise, the philosophy is not properly eclectic. Eclecticism always tends to spring up after a period of vigorous constructive speculation, especially in the later stages of a controversy between thinkers of pre-eminent ability. Their respective followers, and more especially cultured laymen, lacking the capacity for original work, seeking for a solution in some kind of compromise, and possibly failing to grasp the essentials of the controversy, take refuge in a combination of those elements in the opposing systems which seem to afford a sound practical theory. Since these combinations have often been as illogical as facile, "eclecticism" has generally acquired a somewhat contemptuous significance. At the same time, the essence of eclecticism is the refusal to follow blindly one set of formulae and conventions, coupled with a determination to recognize and select from all sources those elements which are good or true in the abstract, or in practical affairs most useful _ad hoc_. Theoretically, therefore, eclecticism is a perfectly sound method, and the contemptuous significance which the word has acquired is due partly to the fact that many eclectics have been intellectual trimmers, sceptics or dilettanti, and partly to mere

## partisanship. On the other hand, eclecticism in the sphere of abstract

thought is open to this main objection that, in so far as every philosophic system is, at least in theory, an integral whole, the combination of principles from hostile theories must result in an incoherent patchwork. Thus it might be argued that there can be no logical combination of elements from Christian ethics, with its divine sanction, and purely intuitional or evolutionary ethical theories, where the sanction is essentially different in quality. It is in practical affairs that the eclectic or undogmatic spirit is most valuable, and also least dangerous.

In the 2nd century B.C. a remarkable tendency toward eclecticism began to manifest itself. The longing to arrive at the one explanation of all things, which had inspired the older philosophers, became less earnest; the belief, indeed, that any such explanation was attainable began to fail. Thus men came to adopt from all systems the doctrines which best pleased them. In Panaetius we find one of the earliest examples of the modification of Stoicism by the eclectic spirit; about the same time the same spirit displayed itself among the Peripatetics. In Rome philosophy never became more than a secondary pursuit; naturally, therefore, the Roman thinkers were for the most part eclectic. Of this tendency Cicero is the most striking illustration--his philosophical works consisting of an aggregation, with little or no blending, of doctrines borrowed from Stoicism, Peripateticism, and the scepticism of the Middle Academy.

In the last stage of Greek philosophy the eclectic spirit produced remarkable results outside the philosophies of those properly called eclectics. Thinkers chose their doctrines from many sources--from the venerated teaching of Aristotle and Plato, from that of the Pythagoreans and of the Stoics, from the old Greek mythology, and from the Jewish and other Oriental systems. Yet it must be observed that Neoplatonism, Gnosticism, and the other systems which are grouped under the name Alexandrian, were not truly eclectic, consisting, as they did, not of a mere syncretism of Greek and Oriental thought, but of a mutual modification of the two. It is true that several of the Neoplatonists professed to accept all the teaching both of Plato and of Aristotle, whereas, in fact, they arbitrarily interpreted Aristotle so as to make him agree with Plato, and Plato so as to make his teachings consistent with the Oriental doctrines which they had adopted, in the same manner as the schoolmen attempted to reconcile Aristotle with the doctrines of the church. Among the early Christians, Clement of Alexandria, Origen and Synesius were eclectics in philosophy.

The eclectics of modern philosophy are too numerous to name. Of Italian philosophers the eclectics form a large proportion. Among the German we may mention Wolf and his followers, as well as Mendelssohn, J.A. Eberhard, Ernst Platner, and to some extent Schelling, whom, however, it would be incorrect to describe as merely an eclectic. In the first place, his speculations were largely original; and in the second place, it is not so much that his views of any time were borrowed from a number of philosophers, as that his thinking was influenced first by one philosopher, then by another.

In the 19th century the term "eclectic" came to be applied specially to a number of French philosophers who differed considerably from one another. Of these the earliest were Pierre Paul Royer-Collard, who was mainly a follower of Thomas Reid, and Maine de Biran; but the name is still more appropriately given to the school of which the most distinguished members are Victor Cousin, Theodore Jouffroy, J.P. Damiron, Barthelemy St Hilaire, C.F.M. de Remusat, Adolphe Garnier and Ravaisson-Mollien. Cousin, whose views varied considerably at different periods of his life, not only adopted freely what pleased him in the doctrines of Pierre Laromiguiere, Royer-Collard and Maine de Biran, of Kant, Schelling and Hegel, and of the ancient philosophies, but expressly maintained that the eclectic is the only method now open to the philosopher, whose function thus resolves itself into critical selection and nothing more. "Each system," he asserted, "is not false, but incomplete, and in reuniting all incomplete systems, we should have a complete philosophy, adequate to the totality of consciousness." This assumes that every philosophical truth is already contained somewhere in the existing systems. If, however, as it would surely be rash to deny, there still remains philosophical truth undiscovered, but discoverable by human intelligence, it is evident that eclecticism is not the only philosophy. Eclecticism gained great popularity, and, partly owing to Cousin's position as minister of public instruction, became the authorized system in the chief seats of learning in France, where it has given a most remarkable impulse to the study of the history of philosophy.

ECLIPSE (Gr. [Greek: ekleipsis], falling out of place, failing), the complete or partial obscuration of one heavenly body by the shadow of another, or of the disk of the sun by the interposition of the moon; then called an eclipse of the sun. Eclipses are of three classes: those of the sun, as just defined; those of the moon, produced by its passage through the shadow of the earth, and those of the satellites of other planets, produced by their passage through the shadow of their primary. Jupiter (q.v.) is the only planet of whose satellites the eclipses can be observed, unless under very rare circumstances.

[Illustration: FIG. 1.]

The geometrical conditions of an eclipse of the sun or moon are shown in fig. 1, which represents the earth E as casting its shadow towards C, and the moon M between the earth and sun as throwing its shadow towards some part of the earth and eclipsing the sun. The dark conical regions are those within which the sun is entirely hidden from sight. This portion of the shadow is called the _umbra_. Around the umbra is an enveloping shaded cone with its vertices directly towards the sun. To an observer within this region the sun is partly hidden from view. As the apparent path of the moon may pass to the north or south of the line joining the earth and sun, the axis of its shadow may pass to the north or south of the earth, and not meet it at all. An eclipse of the sun is called _central_ when the shadow axis strikes any part of the earth;

## partial when only the penumbra falls upon the earth. It is evident that

an eclipse can be seen as central only at those points of the earth's surface over which the axis of the shadow passes.

[Illustration: FIG. 2.]

[Illustration: FIG. 3.]

A central eclipse is _total_ when the umbra actually reaches the earth; _annular_ when it does not. These two cases are shown in figs. 2 and 3. In the first of these the sun is entirely hidden within the region uu'. In fig. 3 within the region aa' the apparent diameter of the sun is slightly greater than that of the moon, and at the moment of greatest eclipse a narrow ring of sunlight is seen surrounding the dark body of the moon.

We shall treat the subject in the following sections:--

I. Phenomena of Eclipses of the Sun and conclusions derived from their observation.

II. Eclipses of the Moon.

III. The Laws and Cycles of recurrences of Eclipses of the Sun and Moon.

IV. Chronological list of remarkable eclipses of the Sun, past and future, to the end of the 20th century.

V. Description of the methods of computing eclipses.

I. _Phenomena of Eclipses of the Sun._

While an eclipse of the sun, whether partial, annular or total, is in progress, no striking phenomena are to be noted until, in the case of total eclipses, the moment of the total phase approaches. It will, however, be noticed that as the moon advances on the solar disk the sharply defined and ragged edge of the moon's disk contrasts strongly with the soft and uniform outline of the sun's limb. As the total phase approaches, the phenomenon known as _shadow bands_ may sometimes be seen. These consist of seeming vague and rapidly moving wave-like alternations of light and shade flitting over any white surface illuminated by the sun's rays immediately before and after the total phase. They are probably due to a flickering of the light from the thin crescent, produced by the undulations of the air, in the same way that the twinkling of the stars is produced. The rapid progressive motion sometimes assigned to them may be regarded as the natural result of an optical illusion. A few seconds before the commencement of the total phase the red light of the chromosphere becomes visible, and will be seen most distinctly as continuations of the solar crescent at its two ends. Owing to the inequalities of the lunar surface, the diminution of the solar crescent does not go on with perfect uniformity, but, just before the last moment, what remains of it is generally broken up into separate portions of light, which, magnified and diffused by the irradiation of the telescope, present the phenomenon long celebrated under the name of "Baily's beads." These were so called because minutely and vividly described by Francis Baily as he observed them during the annular eclipse of May 15, 1836, when he compared them to a string of bright beads, irregular in size and distance from each other. The disappearance of the last bead is commonly taken as the beginning of totality. An arc of the chromosphere will then be visible for a few seconds at and on each side of the point of disappearance, the length and duration of which will depend on the apparent diameter of the moon as compared with that of the sun, being greater in length and longer seen as the excess of diameter of the moon is less. The red prominences may now generally be seen here and there around the whole disk of the moon, while the effulgence of soft light called the corona surrounds it on all sides. Before the invention of the spectroscope, observers of total eclipses could do little more than describe in detail the varying phenomena presented by the prominences and the corona. Drawings of the latter showed it to have the appearance of rays surrounding the dark disk of the moon, quite similar to the glory depicted by the old painters around the head of a saint. The discrepancies between the outlines as thus pictured, not only at different times, but by different observers at the same time and place, are such as to show that little reliance can be placed on the details represented by hand drawings.

During the eclipse of July 8, 1842, the shadow of the moon passed from Perpignan, France, through Milan and Vienna, over Russia and Central Asia, to the Pacific Ocean. Very detailed physical observations were made, but none which need be specially mentioned in the present connexion.

The eclipse of July 28, 1851, was total in Scandinavia and Russia. It was observed in the former region by many astronomers, among them Sir George B. Airy and W.R. Dawes. It was specially noteworthy for the first attempt to photograph such a phenomenon. A daguerreotype clearly showing the protuberances was taken by Berkowski at the Observatory of Konigsberg. An attempt by G.A. Majocchi to daguerreotype the corona was a failure. Photographs of the eclipse of July 18, 1860, were taken by Padre Angelo Secchi and Warren De La Rue, which showed the prominences well, and proved that they were progressively obscured by the edge of the advancing moon. It was thus shown that they were solar appendages, and did not belong to the moon, as had sometimes been supposed. The corona was barely visible on De La Rue's plates, but those of Secchi showed it, with its rifts and the bases of the tall coronal wings, to about 15' from the sun's limb. The sketches taken at this eclipse proved that the corona extended in some regions 1 deg. from the sun's limb. As the sensitiveness of photographic plates has increased, they have gradually been wholly relied upon for information respecting the corona, so that at the present time naked-eye descriptions are regarded as of little or no scientific value. Owing to the great contrast between the brilliancy of the coronal light at its base and its increasing faintness as it extends farther from the sun, no one photograph will bring out all the corona. An exposure of one or two seconds is ample to show the details of inner corona to the best advantage, while longer exposures give greater extent of the brighter portions. The most extended streamers are very little brighter than the sky, and must be photographed with long exposures.

The first application of the spectroscope to the phenomenon was made during the total solar eclipse of August 18, 1868, by P.J.C. Janssen and other observers in India. By them was made the capital discovery that the red solar prominences give a spectrum of bright lines, and are therefore immense masses of incandescent gases, chiefly hydrogen and the vapours of calcium and helium. Janssen also found that this bright-line spectrum could be followed after the eclipse was over, and, in fact, could be observed at any time when the air was sufficiently transparent. By one of those remarkable coincidences which frequently occur in the history of science, this last discovery was made independently by Sir Norman Lockyer in England before the news of Janssen's success had reached him. It was afterwards found that, by giving great dispersing power to the spectroscope, the prominences could be observed in a wide slit, in their true form. At this eclipse the spectrum of the corona was also observed, and was supposed to be continuous, while polariscopic observation by Lieutenant Campbell showed it polarized in planes passing through the sun's centre. The conclusion from these two observations was that the light was composed, at least in great part, of reflected sunlight.

At the total eclipse of August 7, 1869, it was independently found by Professors C.A. Young of Princeton and W. Harkness of Washington that the continuous spectrum of the corona was crossed by a bright line in the green, which was long supposed to be coincident with 1474 of Kirchhoff's scale. This coincidence is, however, now found not to be real, and the line cannot be identified with that of any terrestrial substance. The name "coronium" has therefore been given to the supposed gas which forms it. It is now known that 1474 is a double line, one component of which is produced by iron, while the other is of unknown origin. The wave-length of the principal component is 5317, while that of the coronal line was found at the eclipses of 1896 and 1898 to be 5303.

The eclipse of December 28, 1870, passed over the south-western corner of Spain, Gibraltar, Oran and Sicily. It is memorable for the discovery by Young of the "reversing layer" of the solar atmosphere. This term is now applied to a shallow stratum resting immediately upon the photosphere, the absorption of which produces the principal dark lines of the solar spectrum, but which, being incandescent, gives a spectrum of bright lines by its own light when the light of the sun is cut off. This layer is much thinner than the chromosphere, and may be considered to form the base of the latter. Owing to its thinness, the phenomenon of the reversed bright lines is almost instantaneous in its nature, and can be observed for a period exceeding one or two seconds only near the edge of the shadow-path, where the moon advances but little beyond the solar limb. Near the central line it is little more than a flash, thus giving rise to the term "flash-spectrum." Young also at this eclipse saw bright hydrogen lines when his spectroscope was directed to the centre of the dark disk of the moon. This can only be attributed to the reflection of the light of the prominences and chromosphere from the atmosphere between us and the moon. The coronal light as observed in the spectroscope may thus be regarded as a mixture of true coronal light with chromospheric light reflected from the air, and it is therefore probable that the H and K (calcium) lines of the coronal spectrum are not true coronal lines, but chromospheric.

At the eclipse of December 12, 1871, visible in India and Australia, Janssen observed, as he supposed, some of the dark lines of the solar spectrum in the continuous spectrum of the corona, especially D, b and G. This would show that an important part of the coronal light is due to reflected sunshine. This feature of the spectrum, however, is doubtful in the most recent photographs under the best conditions. At this eclipse the remarkable observation was also made by Colonel John Herschel and Colonel J.F. Tennant that the characteristic line of the coronal spectrum is as bright in the dark rifts of the corona as elsewhere. This would show that the gas coronium does not form the streamers of the corona, but is spherical in form and distributed uniformly about the sun. Photographs were also taken on wet plates by a party in Java and by the parties of Lord Lindsay (at Baikul, India) and of Colonel Tennant (at Dodabetta). The Baikul and Dodabetta photographs were of small size (moon's diameter = 3/10 in.), but of excellent definition. A searching study was made of them by A. C Ranyard and W.H. Wesley (_Memoirs R.A.S._ vol. xli., 1879), and for the first time a satisfactory representation of the corona was obtained. The drawings in the volume quoted show its polar rays, wings, interlacing filaments and rifts as they are now known to be, as well as the forms and details of the prominences.

The eclipse of April 16, 1874, was observed in South Africa by E.J. Stone, H.M. astronomer at the Cape, who traced the coronal line about 30' (430,000 m.) from the sun's limb. The visual corona was seen to extend in places some 90' from the limb.

The eclipse of April 6, 1875, was observed in Siam by Sir J. Norman Lockyer and Professor Arthur Schuster. Their photographs showed the calcium and hydrogen lines in the prominence spectrum.

The eclipse of July 29, 1878, was observed by many astronomers in the United States along a line extending from Wyoming to Texas. A number of the stations were at high altitudes (up to 14,000 ft.), and the sky was generally very clear. The visible corona extended on both sides of the sun along the ecliptic for immense distances--at least twelve lunar diameters, about eleven million miles. Photographs taken by the parties of Professors A. Hall and W. Harkness gave the details of the inner corona and of the polar rays, showing the filamentous character of the corona, especially at its base in the polar regions. A photograph taken by the party of Professor E.S. Holden showed the outer corona to a distance of 50' from the moon's limb. The bright-line spectrum of the corona was excessively faint and, as the solar activity (measured by sun-spot frequency) was near a minimum, it was concluded that the brilliancy of the coronium line varied in the sun-spot period, a conclusion which subsequent eclipse observations seem to have verified. It is not yet certain that the other coronal spectrum lines vary in the same way.

The eclipse of May 17, 1882, was observed in Egypt. On the photographs of the corona the image of a bright comet was found, the first instance of the sort. (A faint comet was found on the plates of the Lick Observatory eclipse expedition to Chile in 1893.) The slitless spectroscope showed the green line (coronium) and D3 (helium) in the coronal spectrum.

The eclipse of May 6, 1883, was observed from a small coral atoll in the South Pacific Ocean by parties from America, England, France, Austria and Italy. A thorough search was made by Holden (with a 6 in. telescope) for an intra-Mercurial planet, without success, during an unusually long totality (5 m. 23 s.). J. Palisa also searched for such a planet. Janssen again reported the presence of dark lines in the coronal spectrum. "White" prominences were seen by P. Tacchini.

The eclipse of August 29, 1886, was observed in the West Indies. The English photographs of the corona, taken with a slitless spectroscope, show the hydrogen lines as well as K and f. Tacchini devoted his attention to the spectra of the prominences, and showed that their upper portions contained no hydrogen lines, but only the H and K lines of calcium. He also observed a very extensive "white" prominence. It was shown on the photographs of the corona, but could not be seen in the H[alpha] line with the spectroscope. It has been suggested by Professor G.E. Hale that the colour of a "white" prominence may be due to the fact that the H and K lines (calcium) are of their normal intensity, while the less refrangible prominence lines are, from some unknown cause, comparatively faint. It is known that the intensity of such lines does, in fact, vary, though it is not yet certain that the "white" prominences are produced in this way. The subject is one demanding further observation. High prominences are generally "white" at their summits, "red" at their bases. The Harvard College Observatory photographs show the corona out to 90' from the moon's limb, though no detail is visible beyond 60'. W.H. Pickering made a series of photographic photometric measures of the corona, some of which are given below, together with results deduced by Holden from the eclipses of January and December 1889:--

+--------------------------------------+---------+---------+---------+ | | August | January | December| | | 1886. | 1889. | 1889. | +--------------------------------------+---------+---------+---------+ | Intrinsic actinic brilliancy of the | | | | | brightest parts of the corona | 0.031 | 0.079 | 0.029 | | Do. of the polar rays | . . | 0.053 | 0.016 | | Do. of the sky near the sun | 0.0007 | 0.0050 | 0.0009 | | Ratio of intrinsic brilliancy of the | | | | | brightest parts of the corona to | | | | | that of the sky (actinic) | 44 to 1 | 16 to 1 | 32 to 1 | | Magnitude of the faintest star | | | | | shown on the eclipse negatives | . . | 2.3 | . . | +--------------------------------------+---------+---------+---------+

The results in the first and third columns are derived from plates taken in a very humid climate, and are not very different.

The eclipse of August 19, 1887, was total in Japan and Russia, but cloudy weather prevented successful observations except in Siberia and eastern Russia.

The eclipse of January 1, 1889, was observed in California and Nevada by many American astronomers. The photographs of the corona, especially those by Charoppin and E.E. Barnard, show a wealth of detail. Those of Barnard, of the Lick Observatory party, were studied by Holden, and exhibited the fact that rays, like the "polar-rays," extended all round the sun, instead of being confined to the polar regions only. The outer corona was registered out to 100' from the moon's limb on Charoppin's negatives, to 130' on those of Lowden and Ireland. On other plates the outline of the moon is visible projected on the corona before totality began. The spectrum of the corona showed few bright lines besides those of coronium and hydrogen.

The eclipse of December 22, 1889, was observed in Cayenne, S. America, by a party from the Lick Observatory under rather unfavourable conditions. Expeditions sent to Africa were baffled by cloudy weather. Father Stephen Joseph Perry observed at Salute Islands, French Guiana, and obtained some photographs of value. The effort cost him his life, for he died of malarial fever five days after the eclipse.

The eclipse of April 16, 1893, was observed by British and French

## parties in Africa and Brazil, and by Professor J.M. Schaeberle of the

Lick Observatory in Chile. The Chile photographs of the corona were taken with a lens of 40 ft. focus, and are extremely fine. They show a faint comet near the sun. No great extensions to the corona were shown on any of the negatives, or seen visually, though they were specially looked for by British parties. The neighbourhood of the sun was carefully examined by G. Bigourdan without finding any planet. The spectrum of the corona was the usual one. The following lines were photographed in slitless spectroscopes, and undoubtedly belong to the corona: W. L. 3987; 4086; 4217; 4231; 4240; 4280; 4486; 5303 (the last number is the wave-length of the green coronium line). All of these have been seen in slit spectroscopes also. It is possible that two lines observed by Young in 1869, namely, W. L. (Angstrom) 5450 and 5570, should be added to the list of undoubted coronal lines. It is not likely that helium or hydrogen or calcium vapour forms part of the corona. The wave-lengths of some 700 lines belonging to the chromosphere and prominences were determined by the British parties.

The eclipse of August 9, 1896, was total in Norway, Novaya Zemlya and Japan. The day was very unfavourable as to weather, but good photographs of the corona were obtained by Russian parties in Siberia and Lapland. Shackelton, in Novaya Zemlya, with a prismatic camera obtained a photograph of the reversing-layer at the beginning of totality. This photograph completely confirms Young's discovery, and shows the prominent Fraunhofer lines bright, the bright lines of the chromosphere spectrum being especially conspicuous.

At the solar eclipse of January 22, 1898, the shadow of the moon traversed India from the western coast to the Himalaya. The duration of totality was about 2 m. The eclipse was very fully observed, more than 100 negatives of the corona being secured. The equatorial extension of the visible corona was short and faint, and the invisible (spectroscopic) corona was also very faint. The spectrum of the reversing-layer was successfully photographed; one set of negatives shows the polarization of one of the longest streamers of the corona, and proves the presence of dust particles reflecting solar light. The bright-line spectrum of hydrogen in the chromosphere was followed to the thirtieth point of the series, and the wave-lengths were shown to agree closely with Balmer's formula (see SPECTROSCOPY). The wave-length of coronium was found to be 5303 (not 5317 as previously supposed), and the brightness of the corona was measured. E.W. Maunder made the curious observation of coronal matter enveloping a prominence in the form of a hood.

Observations of the eclipse of May 28, 1900, were favoured in a remarkable degree by the absence of clouds. The photographs of the corona obtained by W.W. Campbell extended four diameters of the sun on the west side. The sun's edge was photographed with an objective-prism spectrograph composed of two 60 deg. prisms in front of a telescope of 2 in. aperture and 60 in. focus. A fine photograph, 6 in. long, of the bright-and dark-line spectra of the sun's edge at the end of totality was thus obtained. It shows 600 bright lines sharply in focus besides the dark-line spectrum, to which the bright lines gave way as the sun reappeared. The coronal material radiating the green light was found to be markedly heaped up in the sun-spot regions. No dark lines were found in the spectrum of the inner corona. G.E. Hale and E.B. Frost also photographed the combined bright-and dark-line spectra of the solar cusps at the instants before and after totality. On one photograph showing no dark lines 70 bright lines could be measured between 4070 and 4340. On another were 70 bright lines between Hb and Hs. On a third were 266 bright lines between 4026 and 4381, and some dark lines. These lines show a marked dissimilarity from the solar spectrum. (S. N.)

The eclipse of May 18, 1901, was observable in Mauritius with 3-1/2 minutes of totality, and in Sumatra with 6-1/2 minutes. Unfortunately there was cloudy weather in Sumatra, which at some stations prevented observations entirely and at others neutralized the advantages promised by the long duration of totality. Thus spectroscopic observations for the detection of motion of the corona, for which the long totality gave a special opportunity, failed owing to cloud; and the search for intra-Mercurial planets had only a negative result, though stars down to magnitude 8.8 were photographed on the plates. But though no particular step in advance was taken, successful records of the eclipse were obtained, which will enable comparison to be made with other eclipses and will contribute their share to the discussion of the whole series. These include photographs of the corona, showing that it was of the sun-spot minimum type, and available for measures of its brightness; photographs of the spectra of the chromosphere and corona which are of the same general character as those obtained at previous eclipses; photographs showing the polarization of the corona, available for quantitative measures of polarization at different points. Photographs of the spectrum of the outer corona taken by the Lick Observatory party show a strong Fraunhofer dark-line spectrum, consistent with the view that the light is reflected sunlight. At Mauritius there was no cloud, but the definition was poor. Successful photographs of the corona were obtained for comparison with those taken in Sumatra one and a half hours later, but nothing of great interest was revealed by the comparison.

The eclipse of August 30, 1905, offered a duration of 3-1/2 minutes in Spain, the track running from Labrador through Spain to North Africa, and affording excellent opportunities for observers, who flocked to the central line in great numbers. Unfortunately it was cloudy in Labrador, so that the special advantages of the long line of possible stations were lost. Exceptionally good weather conditions were enjoyed in Algeria and Tunisia, and full advantage was taken of them by H.F. Newall, C. Trepied and others at Guelma, by the party from Greenwich and G. Bigourdan at Sfax. That G. Newall's spectroscopic photographs for rotation of the corona again gave no result is a clear indication of the faintness of the corona at 3' from the limb; but F.W. Dyson at Sfax obtained two new lines at 5536 and 5117 in the spectrum of the corona; and a very large number of photographs of the corona (including many in polarized light on several different plans), of its spectrum, and of the spectrum of the chromosphere, were obtained by the various parties, which will afford copious material for discussion. Newall also obtained a polarized spectrum of the corona. Altogether no less than eighty stations were occupied. There were English, American, Russian and German observers in Egypt; English and French in Algeria and Tunisia; English in Majorca; observers of almost all nationalities in Spain; and English and American in Labrador. In Egypt the weather was bright, though the sun was low; in Majorca and Spain there were local clouds. Consequently many observations, in addition to those in Labrador, were lost, notably the special spectroscopic observations undertaken by Evershed on the northern limit of totality, and the observations of radiation undertaken by H.L. Callendar. A search for intra-Mercurial planets was conducted on an elaborate plan, with similar batteries of telescopes, in Egypt, Spain and Labrador, by three parties from the Lick Observatory, but the examination of the plates showed nothing noteworthy. Pending discussion of the greater part of the material, some interesting preliminary results were published in 1906 by the French observers. C.E.H. Bourget and Montangerand conclude that there is a marked division of the chromosphere into two regions or shells, a lower or "reversing-layer," extending only 1" from the limb, and a chromospheric layer extending to 3" or 4"; and that the coronal light contains less blue and violet, but more green and yellow, than sunlight; while Fabry, by visual methods, obtained measures of the total and intrinsic intensity of the light from the corona closely confirming recent photographic observations, finding the total brightness about equal to that of the full moon, and the intrinsic brightness at 5' from the limb about one quarter of that of the full moon. (H. H. T.)

II. _Eclipses of the Moon._

The physical phenomena attending eclipses of the moon are no longer of a high order of interest either to the layman or scientific observer. A brief statement of them and their causes will therefore be sufficient. An observer watching such an eclipse from the moon would see the earth, which has nearly four times the apparent diameter of the sun, impinging on the sun's disk and slowly hiding it. The phenomenon would be quite similar to that of an eclipse of the sun seen from the earth, until the sun was completely covered. During the progress of this partial eclipse the moon would be passing into the earth's penumbra. As the moment of total obscuration approached, a red band of light would rapidly form in the neighbourhood of the disappearing limb of the sun, and gradually extend around the earth. This would arise from the refraction of the sun's light by the earth's atmosphere, and the absorption of its blue rays. When the light of the sun was completely hidden, a reddish ring of great brilliancy would, owing to this cause, surround the entire dark body of the earth during the period of the total eclipse.

The aspect of the moon, as seen from the earth, corresponds to this view from the moon. The fading of the moon's light, due to its entrance into the penumbra, is scarcely noticeable without direct photometric determination until near the beginning of the total phase. Then, as the limb of the moon approaches the earth's shadow, it begins to darken. When only a small portion has entered into the shadow, that portion is completely hidden. But, as the total phase approaches, the part of the moon's disk immersed in the penumbra becomes visible by a reddish coppery light--that of the sun refracted through the lower parts of the earth's atmosphere. The brightness of this illumination is different in different eclipses, a circumstance which may be attributed to the greater or less degree of cloudiness in those regions of the earth's atmosphere through which the light of the sun passes in order to reach the moon. Its colour is due to absorption in passing through the earth's atmosphere.

III. _Laws and Cycles of Recurrences of Eclipses of the Sun and Moon._

It has been known since remote antiquity that eclipses occur in cycles. These cycles are known now to be determined principally by the motion of the moon's node and the relations between the revolutions of the earth round the sun and the moon round the earth.

Eclipse seasons.

Owing to the inclination of the moon's orbit to the plane of the ecliptic, an eclipse of the sun can occur only when the conjunction of the sun and moon takes place within about 16 deg. of one of the nodes of the moon's orbit. The eclipse can be total only within about 11 deg. of the node. An eclipse of the moon can occur only when the line sun-moon-earth makes an angle less than about 11 deg. with the line of nodes; and the eclipse can be total only within about 8 deg. of the node, the average limiting distances varying 1 deg. or 2 deg. according to the circumstances. These conditions being understood, the cycles of recurrence of eclipses of either kind can be worked out geometrically from the mean motions of the sun, moon, node and perigee by the aid of geometric conceptions shown in their simplest form in fig. 4. Here E is the earth, at the centre of a circle representing the mean orbit of the moon around it. MN is the line of nodes which is moving in the retrograde direction from N towards S1, at a rate of about 19.3 deg. in a year, making a complete revolution in 18.6 years. Let the sun at the moment of some new moon be in the line ES1, continued. If the angle NES1 is less than 16 deg. there will probably be an eclipse of the sun, which may be central if the angle is less than 11 deg. Let the next new moon take place in the line ES2 a month later. The mean value of the angle S1ES2 is about 29 deg.; but as the node N has moved towards S1 about 1.4 deg. during the interval, the sum of the angles NES1 and NES2 will be somewhat greater than S1ES2 by about 1.6 deg. The result is that if these two angles are nearly equal there may be two small partial eclipses of the sun, after which no more can occur until, by the annual revolution of the earth, the direction of the sun approaches the opposite line of nodes EM, nearly six months later. The result is that there are in the course of any one year two "eclipse seasons" each of about one month in duration, in which at least one eclipse of the sun, or possibly two small partial eclipses, may occur. One eclipse of the moon will generally, but not always, occur during a season.

[Illustration: FIG. 4.]

Owing to the retrograde motion of the node the direction ES of the sun returns to the node at the end of about 347 days, so that a third eclipse season may commence before the end of a year. In this way there is a possible but very rare maximum of five eclipses of the sun in a year. Owing to the motion of the line of nodes each eclipse season occurs about 19 days earlier in the year than it did the year before. Another conclusion from the greater eclipse limit for the sun than for the moon is that in the long run eclipses of the sun, as regards the earth generally, occur oftener than those of the moon. But as any eclipse of the sun is visible only from a limited region of the earth's surface, while one of the moon may be seen from an entire hemisphere, more eclipses of the moon are visible at any one place than of the sun.

If, starting with a conjunction along some line ES1, we mark by radial lines from E the successive conjunctions year after year, we shall find that at the end of 18 years and about 11 days the 223rd conjunction will fall once more very near the line ES1, the angle NES1 being about 24' greater than before. Successive eclipses will then occur very nearly in the same order as they did 18 years and 11 days before. This period of recurrence has been known from remote antiquity and is called the _Saros_. What is most remarkable in this period is that in addition to the distance from the node being nearly the same as before, the longitude of the sun increases by only 11 deg. and the distance of the moon from its perigee has changed less than 3 deg. The result of this approach to coincidence is that the recurring eclipse will generally be of the same kind--total, annular or partial--through a number of successive periods.

To see the law of recurrence of corresponding eclipses in the successive periods let us suppose the line of conjunction ES1 to be that at which there is a very small eclipse, visible only in high northern or southern latitudes. At the end of 18 years 11 days a second eclipse will occur along a line nearly half a degree nearer EN, the line of nodes. The successive eclipses will occur at the same interval through about ten periods, or 180 years, when the line of conjunction will pass within 11 deg. of EN. Then the eclipse will be central, whether annular or total depending on circumstances: in the first one the central lines will pass only over the polar regions; but in successive eclipses of the series it will pass nearer and nearer to the equator until the conjunction line coincides with the node. The path of centrality will then cross in the equatorial region. During 22 or 23 more recurrences the path will continually approach to the opposite pole and finally leave the earth entirely. The entire number of central eclipses in any one series will generally be about forty-five. Then a series of continually diminishing

## partial eclipses will go on for about ten periods more. The whole series

of eclipses will therefore extend through about sixty-five periods; and interval of time of about twelve hundred years.

Another remarkable eclipse period recurs at the end of 358 lunations. At the end of this period the line of mean conjunction ES1 falls so near its former position relative to the node that we find each central eclipse visible in our time to be one of an unbroken series extending from the earliest historic times to the present, at intervals equal to the length of the period. The recurring eclipses in this period do not, however, have the remarkable similarity of those belonging to the Saros, but may differ to any extent, owing to the different positions of the line of conjunction with respect to the moon's perigee. Moreover, they recur alternately at the ascending and descending node. The length of the period is 10,571.95 days, or 29 Julian years less 20.3 days. Hence 18 periods make 521 years, so that at the end of this time each eclipse recurs on or about the same day of the year. As an example of this series, starting from the eclipse of Nineveh, June 15, 763 B.C., recorded on the Assyrian tablets, we find eclipses on May 27, 734 B.C., May 7, 705 B.C., and so on in an unbroken series to 1843, 1872 and 1901, the last being the 93rd of the series. Those at the ends of the 521-year intervals occurred on June 15, O.S., of each of the years 763, 242 B.C., A.D. 280, 801, 1322 and 1843. As the lunar perigee moves through 242.4 deg. in a period, the eclipses will vary from total to annular, but at the end of 3 periods the perigee is only 7.1 deg. in advance of its original position relative to the node. Hence in a series including every third eclipse the eclipses will be of the same character through a thousand years or more. Thus the eclipses of 1467, 1554, 1640, 1727, 1814, 1901, 1988, &c., are total.

IV. _Chronological Lists of Eclipses of the Sun._

Notable eclipses.

The following is a brief chronological enumeration of those total eclipses of the sun which are of interest, either from their historic celebrity or the nature of the conclusions derived from them. In numbering the years before the Christian era the astronomical nomenclature is used, in which the number of the year is one less than that used by the chronologists. The Chinese eclipses are passed over, owing to the generally doubtful character of the records pertaining to them.

--1069 June 20 and --1062 July 31; total eclipses recorded at Babylon.

--762, June 14; a total eclipse recorded at Nineveh. Computation from the modern tables shows that the path of totality passed about 100 m. or more north of Nineveh.

--647, April 6; total eclipse at or near Thasos, mentioned by Archilochus.

--584, May 28; the celebrated eclipse of Thales. For an account of this eclipse see THALES.

--556, May 19, the eclipse of Larissa. The modern tables show that the eclipse was not total at Larissa, and the connexion of the classical record with the eclipse is doubtful.

--430, August 3; eclipse mentioned by Thucydides, but not total by the tables.

--399, June 21; eclipse of Ennius. Totality occurred immediately after sunset at Rome. The identity of this eclipse is doubtful.

--309, August 14; eclipse of Agathocles. This eclipse would be one of the most valuable for testing the tables of the moon, but for an uncertainty as to the location of Agathocles, who, at the time of the occurrence, was at sea on a voyage from Syracuse to Carthage.

F.K. Ginzel (_Spezieller Kanon der Finsternisse_) has collected a great number of passages from classical authors supposed to refer to eclipses of the sun or moon, but the difficulty of identifying the phenomenon is frequently such as to justify great doubt as to the conclusions. In a few cases no eclipse corresponding to the description can be found by our modern table to have occurred, and in others the latitude of interpretation and the uncertainty of the date are so wide that the eclipse cannot be identified.

Of medieval eclipses we mention only the dates of those visible in England, referring for details to the works mentioned in the bibliography. The letter C following a date shows that the eclipse is mentioned in the Anglo-Saxon Chronicles. The dates in question are:--

A.D. 538, February 15, C. (partial). | A.D. 878, October 29, C. 540, June 12, C. (partial). | 885, June 15. 594, July 23. | 1023, January 24. 603, August 12. | 1133, August 1, C. 639, September 3. | 1140, March 20, C. 664, May 1, C. | 1185, May 1, C. 733, August 14 (annular). | 1191, June 23, C. (annular). 764, June 4 (annular). | 1330, July 16.

Besides these, the tables show that the shadow of the moon passed over some part of the British Islands on 1424, June 26; 1433, June 17; 1598, March 6; 1652, April 8; 1715, May 2; 1724, May 22. Of these the eclipse of 1715 is notable for the careful observations made in England, and published by Halley in the _Philosophical Transactions_. The next dates are 1927, June 29, when a barely total eclipse will be seen soon after sunrise in the northern counties near the Scottish border, and 1999, August 11, when the moon's shadow will graze England at Land's End.

We give below, in tabular form, a list of the principal total eclipses during the 19th and 20th centuries, omitting a few visible only in the extreme polar regions, and some others of which the duration is very short. The first column gives the civil date of the point on the earth's surface at which the eclipse is central at noon. The next two columns give the position of this point to the nearest degree. The fourth column shows the Greenwich astronomical time of conjunction in longitude. The next column gives the duration of the total phase at the noon-point; this is sometimes 0.1' less than the absolutely greatest duration at any point. Next is given the node near which the eclipse occurs; and then the number in the Saros. Corresponding eclipses at intervals of 18 y. 11 d. have the same number, and occur near the same node of the noon, which is indicated in the next column.

+----------------+--------------+---------------+---------+------+-------+------------------------------------------------------------+ | | Point where |Greenwich M.T. |Duration | | | | | Date at | Central at |of conjunction | of | | | | | Noon-Point. | Noon. | in Longitude. |Totality.| Node |Series.| Regions Swept by Shadow. | | +------+-------+---------------+---------+ | | | | | Lat. | Long. | d. h. m. | m. | | | | +----------------+------+-------+---------------+---------+------+-------+------------------------------------------------------------+ | 1803, Feb. 21 | 11 S.| 136 W.| 21 9 20 | 4.2 | Asc. | 1 | Pacific Ocean, Mexico. | | 1804, Aug. 5 | 38 S.| 66 W.| 5 4 6 | 1.2 | Desc.| 2 | Pacific Ocean, Chile, Argentina. | | 1806, June 16 | 42 N.| 66 W.| 16 4 22 | 4.6 | Desc.| 3 | New England, Atlantic, Africa. | | 1807, Nov. 29 | 11 N.| 2 E.| 28 23 48 | 1.4 | Asc. | 4 | Central Africa, Areolia. | | 1810, April 4 | 12 N.| 154 E.| 3 13 41 | Ann. | Desc.| 5 | Pacific Ocean, Borneo. | | 1811, Mar, 24 | 39 S.| 26 W.| 24 2 19 | 3.4 | Desc.| 6 | South Atlantic to and across South Africa. | | 1814, July 17 | 31 N.| 84 E.| 16 18 33 | 6.6 | Asc. | 7 | Africa, Central Asia, China. | | 1815, July 6 | 88 N.| 175 W.| 6 11 52 | 3.2 | Asc. | 8 | Polar Regions, Western Siberia. | | 1816, Nov. 19 | 43 N.| 30 E.| 18 22 9 | 1.8 | Desc.| 9 | Eastern Europe, Central Asia. | | 1817, Nov. 9 | 7 S.| 149 E.| 8 13 53 | 4.7 | Desc.| 10 | Burma, Pacific Ocean. | | 1821, Mar. 4 | 8 S.| 96 E.| 3 17 50 | 4.3 | Asc. | 1 | Indian and Pacific Oceans. | | 1822, Aug. 16 | 36 S.| 176 W.| 16 11 22 | 1.4 | Desc.| 2 | Australia, Pacific Ocean. | | 1824, June 26 | 47 N.| 175 W.| 26 11 43 | 4.4 | Desc.| 3 | Pacific Ocean, Japan, China. | | 1825, Dec. 9 | 9 N.| 127 W.| 9 8 27 | 1.5 | Asc. | 4 | Pacific Ocean, Mexico. | | 1828, April 14 | 18 N.| 39 E.| 13 21 18 | 0.3 | Desc.| 5 | Northern Africa, India. | | 1829, April 3 | 32 S.| 149 W.| 3 10 24 | 4.1 | Desc.| 6 | South Pacific Ocean. | | 1832, July 27 | 24 N.| 28 W.| 27 2 2 | 6.8 | Asc. | 7 | West Indies and across Central Africa. | | 1833, July 17 | 78 N.| 76 E.| 16 19 16 | 3.5 | Asc. | 8 | North-eastern Asia and Polar Regions. | | 1834, Nov. 30 | 40 N.| 101 W.| 30 6 48 | 1.9 | Desc.| 9 | Southern and Western United States. | | 1835, Nov. 20 | 10 S.| 20 E.| 19 22 31 | 4.6 | Desc.| 10 | Central Africa, Madagascar. | | 1839, Mar. 15 | 6 S.| 31 W.| 15 2 14 | 4.4 | Asc. | 1 | South America, Africa, Egypt. | | 1840, Aug. 27 | 34 S.| 72 E.| 26 18 45 | 1.6 | Desc.| 2 | Africa, Madagascar, Indian Ocean. | | 1842, July 8 | 51 N.| 77 E.| 7 19 2 | 4.1 | Desc.| 3 | Spain, France, Russia to China, and Pacific Ocean. | | 1843, Dec. 21 | 8 N.| 102 E.| 20 17 10 | 1.6 | Asc. | 4 | Indian and North Pacific Oceans and India. | | 1846, April 25 | 25 N.| 75 W.| 25 4 49 | 0.9 | Desc.| 5 | Mexico, West Indies, Africa. | | 1847, April 15 | 24 S.| 90 E.| 14 18 22 | 4.7 | Desc.| 6 | Indian Ocean, Australia. | | 1850, Aug. 7 | 18 N.| 142 W.| 7 9 34 | 6.8 | Asc. | 7 | Pacific Ocean. | | 1851, July 28 | 70 N.| 34 W.| 28 2 41 | 3.7 | Asc. | 8 | Scandinavia, Russia and North America. | | 1852, Dec. 11 | 37 N.| 127 E.| 10 15 32 | 2.0 | Desc.| 9 | China, Pacific Ocean. | | 1857, Mar. 25 | 4 S.| 155 W.| 25 10 30 | 4.5 | Asc. | 1 | Pacific Ocean, Mexico. | | 1858, Sept. 7 | 33 S.| 41 W.| 7 2 16 | 1.7 | Desc.| 2 | Peru, South Brazil, Uruguay. | | 1860, July 18 | 56 N.| 31 W.| 18 2 21 | 3.7 | Desc.| 3 | British America, France, Egypt. | | 1861, Dec. 31 | 9 N.| 29 W.| 31 1 55 | 1.8 | Asc. | 4 | Caribbean Sea to North Africa. | | 1864, May 6 | 32 N.| 173 E.| 5 12 14 | 1.4 | Desc.| 5 | Pacific Ocean. | | 1865, April 25 | 16 S.| 30 W.| 25 2 13 | 5.3 | Desc.| 6 | Brazil to Central Africa. | | 1868, Aug. 18 | 10 N.| 103 E.| 17 17 12 | 6.8 | Asc. | 7 | India to Pacific Ocean. | | 1869, Aug. 7 | 61 N.| 145 W.| 7 10 8 | 3.8 | Asc. | 8 | United States and Alaska. | | 1870, Dec. 22 | 36 N.| 5 W.| 22 0 19 | 2.1 | Desc.| 9 | Gibraltar, Northern Africa, Sicily. | | 1871, Dec. 12 | 12 S.| 118 E.| 11 16 2 | 4.4 | Desc.| 10 | Southern India, Northern Australia. | | 1875, April 6 | 2 S.| 83 E.| 5 18 36 | 4.7 | Asc. | 1 | Indian Ocean, Siam, Pacific. | | 1876, Sept. 17 | 33 S.| 156 W.| 17 9 54 | 1.8 | Desc.| 2 | Pacific Ocean. | | 1878, July 29 | 60 N.| 139 W.| 29 9 40 | 3.2 | Desc.| 3 | United States and Canada. | | 1880, Jan. 11 | 10 N.| 160 W.| 11 10 40 | 2.1 | Asc. | 4 | Pacific Ocean, California. | | 1882, May 17 | 39 N.| 63 E.| 16 19 34 | 1.8 | Desc.| 5 | Egypt, Central Asia, China. | | 1883, May 6 | 9 S.| 147 W.| 6 9 58 | 6.0 | Desc.| 6 | Pacific Ocean, Caroline Islands. | | 1886, Aug. 29 | 3 N.| 14 W.| 29 0 54 | 6.6 | Asc. | 7 | South America, Central Africa. | | 1887, Aug. 19 | 53 N.| 102 E.| 18 17 39 | 3.8 | Asc. | 8 | Northern Europe, Siberia, Japan. | | 1889, Jan. 1 | 37 N.| 138 W.| 1 9 8 | 2.2 | Desc.| 9 | California, Oregon, British America. | | 1889, Dec. 22 | 12 S.| 13 W.| 22 0 52 | 4.2 | Desc.| 10 | Central Africa and South America. | | 1893, April 16 | 1 S.| 37 W.| 16 2 35 | 4.8 | Asc. | 1 | Venezuela to West Africa. | | 1894, Sept. 29 | 34 S.| 86 E.| 28 17 43 | 1.8 | Desc.| 2 | East Africa, Indian Ocean. | | 1896, Aug. 9 | 65 N.| 112 E.| 8 17 2 | 2.7 | Desc.| 3 | North Europe, Siberia, Japan. | | 1898, Jan. 22 | 13 N.| 69 E.| 21 19 24 | 2.3 | Asc. | 4 | East Africa, India, China. | | 1900, May 28 | 45 N.| 45 W.| 28 2 50 | 2.1 | Desc.| 5 | United States, Spain, North Africa. | | 1901, May 18 | 2 S.| 97 E.| 17 17 38 | 6.5 | Desc.| 6 | Sumatra, Borneo. | | 1904, Sept. 9 | 5 S.| 133 W.| 9 8 43 | 6.4 | Asc. | 7 | Pacific Ocean. | | 1905, Aug. 30 | 45 N.| 12 W.| 30 1 13 | 3.8 | Asc. | 8 | Canada, Spain, North Africa. | | 1907, Jan. 14 | 39 N.| 89 E.| 13 17 57 | 2.3 | Desc.| 9 | Russia, Central Asia. | | 1908, Jan. 3 | 12 S.| 145 W.| 3 9 44 | 4.2 | Desc.| 10 | Pacific Ocean. | | 1911, April 28 | 1 S.| 155 W.| 28 10 26 | 5.0 | Asc. | 1 | Australia, Polynesia. | | 1912, Oct. 10 | 35 S.| 33 W.| 10 1 41 | 1.8 | Desc.| 2 | Colombia, Ecuador, Brazil. | | 1914, Aug. 21 | 71 N.| 2 E.| 21 0 27 | 2.1 | Desc.| 3 | Scandinavia, Russia, Asia Minor. | | 1916, Feb. 3 | 16 N.| 62 W.| 3 4 6 | 2.5 | Asc. | 4 | Pacific Ocean, Venezuela, West Indies. | | 1918, June 8 | 51 N.| 152 W.| 8 10 3 | 2.4 | Desc.| 5 | British Columbia, United States. | | 1919, May 29 | 4 N.| 18 W.| 29 1 12 | 6.9 | Desc.| 6 | Peru, Brazil, Central Africa. | | 1922, Sept. 21 | 12 S.| 106 E.| 20 16 38 | 6.1 | Asc. | 7 | East Africa, Australia. | | 1923, Sept. 10 | 38 N.| 128 W.| 10 8 53 | 3.6 | Asc. | 8 | California, Mexico, Central America. | | 1925, Jan. 24 | 42 N.| 44 W.| 24 2 46 | 2.4 | Desc.| 9 | United States. | | 1926, Jan. 14 | 10 S.| 82 E.| 13 18 35 | 4.2 | Desc.| 10 | East Africa, Sumatra, Philippines. | | 1927, June 29 | 78 N.| 84 E.| 28 18 32 | 0.7 | Asc. | 11 | England, Scotland, Scandinavia. | | 1929, May 9 | 1 S.| 89 E.| 8 18 8 | 5.1 | Asc. | 1 | Sumatra, Malacca, Philippines. | | 1930, Oct. 21 | 36 S.| 155 W.| 21 9 47 | 1.9 | Desc.| 2 | Pacific Ocean, Patagonia. | | 1932, Aug. 31 | 78 N.| 109 W.| 31 7 55 | 1.5 | Desc.| 3 | Canada. | | 1934, Feb. 14 | 19 N.| 168 E.| 13 12 44 | 2.7 | Asc. | 4 | Borneo, Celebes. | | 1936, June 19 | 56 N.| 101 E.| 18 17 15 | 2.5 | Desc.| 5 | Greece to Central Asia and Japan. | | 1937, June 8 | 10 N.| 131 W.| 8 8 43 | 7.1 | Desc.| 6 | Pacific Ocean, Peru. | | 1940, Oct. 1 | 19 S.| 16 W.| 1 0 42 | 5.7 | Asc. | 7 | Colombia, Brazil, South Africa. | | 1941, Sept. 21 | 30 N.| 114 E.| 20 16 39 | 3.3 | Asc. | 8 | Central Asia, China, Pacific Ocean. | | 1943, Feb. 4 | 47 N.| 176 W.| 4 11 31 | 2.5 | Desc.| 9 | China, Alaska. | | 1947, May 20 | 2 S.| 25 W.| 20 1 44 | 5.2 | Asc. | 1 | Argentina, Paraguay, Central Africa. | | 1948, Nov. 1 | 37 S.| 82 E.| 31 18 3 | 1.9 | Desc.| 2 | Central Africa, Congo. | | 1952, Feb. 25 | 22 N.| 39 E.| 24 21 17 | 3.0 | Asc. | 4 | Nubia, Persia, Siberia. | | 1954, June 30 | 62 N.| 5 W.| 30 0 27 | 2.5 | Desc.| 5 | Canada, Scandinavia, Russia, Persia. | | 1955, June 20 | 15 N.| 117 E.| 19 16 12 | 7.2 | Desc.| 6 | Ceylon, Siam, Philippines. | | 1958, Oct. 12 | 26 S.| 139 W.| 12 8 52 | 5.2 | Asc. | 7 | Chile, Argentina. | | 1959, Oct. 2 | 23 N.| 6 W.| 2 0 32 | 3.0 | Asc. | 8 | Canaries, Central Africa. | | 1961, Feb. 15 | 53 N.| 53 E.| 14 20 11 | 2.6 | Desc.| 9 | France, Italy, Austria, Siberia. | | 1962, Feb. 5 | 4 S.| 179 E.| 4 12 11 | 4.1 | Desc.| 10 | New Guinea. | | 1963, July 20 | 62 N.| 126 W.| 20 8 43 | 1.5 | Asc. | 11 | Alaska, Hudson's Bay Territory. | | 1965, May 30 | 4 S.| 137 W.| 30 9 14 | 5.3 | Asc. | 1 | Pacific Ocean. | | 1966, Nov. 12 | 38 S.| 43 W.| 12 2 27 | 1.9 | Desc.| 2 | Bolivia, Argentina, Brazil. | | 1970, Mar. 7 | 25 N.| 88 W.| 7 5 43 | 3.3 | Asc. | 4 | Mexico, Georgia, ? Florida. | | 1972, July 10 | 67 N.| 111 W.| 10 7 40 | 2.7 | Desc.| 5 | North-East Asia, North-East America and Atlantic Ocean. | | 1973, June 30 | 19 N.| 6 E.| 29 23 39 | 7.2 | Desc.| 6 | South America, Africa and Atlantic Ocean. | | 1974, June 20 | 32 S.| 107 E.| 19 16 56 | 5.3 | Desc.| 12 | South-West Australia and Indian Ocean. | | 1976, Oct. 23 | 31 S.| 95 E.| 22 17 10 | 4.9 | Asc. | 7 | Africa, Australia, Indian and Pacific Oceans. | | 1977, Oct. 12 | 16 N.| 127 W.| 12 8 31 | 2.8 | Asc. | 8 | Venezuela, Pacific Ocean. | | 1979, Feb. 26 | 61 N.| 77 W.| 26 4 47 | 2.7 | Desc.| 9 | United States, British America, Pacific Ocean, N. Polar Sea| | 1980, Feb. 16 | 1 N.| 48 E.| 15 20 52 | 4.3 | Desc.| 10 | Africa, Atlantic and Indian Oceans, and India. | | 1981, July 31 | 54 N.| 127 E.| 30 15 53 | 2.2 | Asc. | 11 | Pacific Ocean, Asia. | | 1983, June 11 | 7 S.| 111 E.| 10 16 38 | 5.4 | Asc. | 1 | Java, Atlantic Ocean. | | 1984, Nov. 22 | 39 S.| 170 W.| 22 10 58 | 2.1 | Desc.| 2 | Pacific Ocean, Patagonia. | | 1987, Mar. 29 | 17 S.| 6 W.| 29 0 45 | 0.3 | Asc. | 13 | Atlantic, Equatorial Africa. | | 1988, Mar. 18 | 28 N.| 146 E.| 17 14 3 | 4.0 | Asc. | 4 | Indian and Pacific Oceans, Sumatra. | | 1990, July 22 | 72 N.| 142 E.| 21 14 54 | 2.6 | Desc.| 5 | Finland, North Atlantic. | | 1991, July 11 | 22 N.| 105 W.| 11 7 6 | 7.1 | Desc.| 6 | Pacific Ocean, Hawaii, Central America. | | 1992, June 30 | 26 S.| 5 W.| 30 0 19 | 5.4 | Desc.| 12 | South Atlantic. | | 1994, Nov. 3 | 36 S.| 31 W.| 3 1 36 | 4.6 | Asc. | 7 | Pacific Ocean, South America. | | 1995, Oct. 24 | 10 N.| 110 E.| 23 16 37 | 2.4 | Asc. | 8 | Pacific and Indian Oceans. | | 1997, Mar. 9 | 71 N.| 154 E.| 8 13 16 | 2.8 | Desc.| 9 | North-East Asia, Arctic Sea. | | 1998, Feb. 26 | 6 N.| 81 W.| 26 5 27 | 4.4 | Desc.| 10 | Pacific and Atlantic Oceans, Central America. | | 1999, Aug. 11 | 46 N.| 18 E.| 10 23 8 | 2.6 | Asc. | 11 | Central and Southern Europe touching England. | +----------------+------+-------+---------------+---------+------+-------+------------------------------------------------------------+

_Recurrence of Remarkable Eclipses._

From the property of the Saros it follows that eclipses remarkable for their duration, or other circumstances depending on the relative positions of the sun and moon, occur at intervals of one saros (18 y. 11 d.). Of interest in this connexion is the recurrence of total eclipses remarkable for their duration. The absolute maximum duration of a total eclipse is about 7' 30"; but no actual eclipse can be expected to reach this duration. Those which will come nearest to the maximum during the next 500 years belong to the series numbered 4 and 6 and in the list which precedes. These occurring in the years 1937, 1955, &c., will ultimately fall little more than 20" below the maximum. But the series 4, though not now remarkable in this respect, will become so in the future, reaching in the eclipse of June 25, 2150, a duration of about 7' 15" and on July 5, 2168, a duration of 7' 28", the longest in human history. The first of these will pass over the Pacific Ocean; the second over the southern part of the Indian Ocean near Madras.

All the national annual Ephemerides contain elements of the eclipses of the sun occurring during the year. Those of England, America and France also give maps showing the path of the central line, if any, over the earth's surface; the lines of eclipse beginning and ending at sunrise, &c., and the outlines of the shadow from hour to hour. By the aid of the latter the time at which an eclipse begins or ends at any point can be determined by inspection or measurement within a few minutes.

V. _Methods of computing Eclipses of the Sun._

Elements of eclipses.

The complete computation of the circumstances of an eclipse ab initio requires three distinct processes. The geocentric positions of the sun and moon have first to be computed from the tables of the motions of those bodies. The second step is to compute certain elements of the eclipse from these geocentric positions. The third step is from these elements to compute the circumstances of the eclipse for the earth generally or for any given place on its surface. The national Astronomical Ephemerides, or "Nautical Almanacs," give in full the geocentric positions of the sun and moon from at least the early part of the 19th century to an epoch three years in advance of the date of publication. It is therefore unnecessary to undertake the first part of the computation except for dates outside the limits of the published ephemerides, and for many years to come even this computation will be unnecessary, because tables giving the elements of eclipses from the earliest historic periods up to the 22nd century have been published by T. Ritter von Oppolzer and by Simon Newcomb. We shall therefore confine ourselves to a statement of the eclipse problem and of the principles on which such tables rest.

Two systems of eclipse elements are now adopted in the ephemerides and tables; the one, that of F.W. Bessel, is used in the English, American and French ephemerides, the other--P. A. Hansen's--in the German and in the eclipse tables of T. Ritter von Oppolzer. The two have in common certain geometric constructions. The fundamental axis of reference in both systems is the line passing through the centres of the sun and moon; this is the common axis of the shadow cones, which envelop simultaneously the sun and moon as shown in figs. 1, 2, 3. The surface of one of these cones, that of the umbra, is tangent to both bodies externally. This cone comes to a point at a distance from the moon nearly equal to that of the earth. Within it the sun is wholly hidden by the moon. Outside the umbral cone is that of the penumbra, within which the sun is partially hidden by the moon. The geometric condition that the two bodies shall appear in contact, or that the eclipse shall begin or end at a certain moment, is that the surface of one of these cones shall pass through the place of the observer at that moment. Let a plane, which we call the fundamental plane, pass through the centre of the earth perpendicular to the shadow axis. On this plane the centre of the earth is taken as an origin of rectangular co-ordinates. The axis of Z is perpendicular to the plane, and therefore parallel to the shadow axis; that of Y and X lie in the plane. In these fundamental constructions the two methods coincide. They differ in the direction of the axis of Y and X in the fundamental plane. In Bessel's method, which we shall first describe, the intersection of the plane of the earth's equator with the fundamental plane is taken as the axis of X. The axis of Y is perpendicular to it, the positive direction being towards the north. The Besselian elements of an eclipse are then:--x, y, the co-ordinates of the shadow axis on the fundamental plane; d, the declination of that point in which the shadow axis intersects the celestial sphere; [mu], the Greenwich hour angle of this point; l, the radius of the circle, in which the penumbral or outer cone intersects the fundamental plane; and l', the radius of the circle, in which the inner or umbral cone intersects this plane, taken positively when the vertex of the cone does not reach the plane, so that the axis must be produced, and negatively when the vertex is beyond the plane.

Hansen's method differs from that of Bessel in that the ecliptic is taken as the fundamental plane instead of the equator. The axis of X on the fundamental plane is parallel to the plane of the ecliptic; that of Y perpendicular to it. The other elements are nearly the same in the two theories. As to their relative advantages, it may be remarked that Hansen's co-ordinates follow most simply from the data of the tables, and are necessarily used in eclipse tables, but that the subsequent computation is simpler by Bessel's method.

Several problems are involved in the complete computation of an eclipse from the elements. First, from the values of the latter at a given moment to determine the point, if any, at which the shadow-axis intersects the surface of the earth, and the respective outlines of the umbra and penumbra on that surface. Within the umbral curve the eclipse is annular or total; outside of it and within the penumbral curve the eclipse is partial at the given moment. The penumbral line is marked from hour to hour on the maps given annually in the American Ephemeris. Second, a series of positions of the central point through the course of an eclipse gives us the path of the central point along the surface of the earth, and the envelopes of the penumbral and umbral curves just described are boundaries within which a total, annular or partial eclipse will be visible. In particular, we have a certain definite point on the earth's surface on which the edge of the shadow first impinges; this impingement necessarily takes place at sunrise. Then passing from this point, we have a series of points on the surface at which the elements of the shadow-cone are in succession tangent to the earth's surface. At all these points the eclipse begins at sunrise until a certain limit is reached, after which, following the successive elements, it ends at sunrise. At the limiting point the rim of the moon merely grazes that of the sun at sunrise, so that we may say that the eclipse both begins and ends at that time. Of course the points we have described are also found at the ending of the eclipse. There is a certain moment at which the shadow-axis leaves the earth at a certain point, and a series of moments when, the elements of the penumbral cone being tangent to the earth's surface, the eclipse is ending at sunset. Three cases may arise in studying the passage of the outlines of the shadow over the earth. It may be that all the elements of the penumbral cone intersect the earth. In this case we shall have both a northern and a southern limit of partial eclipse. In the second case there will be no limit on the one side except that of the eclipse beginning or ending at sunrise or sunset. Or it may happen, as the third case, that the shadow-axis does not intersect the earth at all; the eclipse will then not be central at any point, but at most only partial.

The third problem is, from the same data, to find the circumstances of an eclipse at a given place--especially the times of beginning and ending, or the relative positions of the sun and moon at a given moment. Reference to the formulae for all these problems will be given in the bibliography of the subject.

AUTHORITIES.--The richest mine of information respecting eclipses of the sun and moon is T.R. von Oppolzer's "Kanon der Finsternisse," published by the Vienna Academy of Sciences in the 52nd volume of its _Denkschriften_ (Vienna, 1887). It contains elements of all eclipses both of the sun and moon, from 1207 B.C. to A.D. 2161, a period of more than thirty centuries. Appended to the tables is a series of charts showing the paths of all central eclipses visible in the northern hemisphere during the period covered by the table. The points of the path at which the eclipse occurs, at sunrise, noon and sunset, are laid down with precision, but the intermediate points are frequently in error by several hundred miles, as they were not calculated, but projected simply by drawing a circle through the three points just mentioned. For this reason we cannot infer from them that an eclipse was total at any given place. The correct path can, however, be readily computed from the tables given in the work. Eduard Mahler's memoir, "Die centralen Sonnenfinsternisse des 20. Jahrhunderts" (_Denkschriften_, Vienna Academy, vol. xlix.), gives more exact paths of the central eclipses of the 20th century, but no maps. General tables for computing eclipses are Oppolzer's "Syzygientafeln fur den Mond" (Publications of the _Astronomische Gesellschaft_, xvi.), and Newcomb's, in _Publications of the American Ephemeris_, vol. i.