The eclipse of Dec. 7, A.D. 671, seems to be associated with a comic tragedy. The Caliph Moawiyah had a fancy to remove Mahomet's pulpit from Medina to his own residence at Damascus. "He said that the walking-stick and pulpit of the Apostle of God should not remain in the hands of the murderers of Othman. Great search was made for the walking-stick, and at last they found it. Then they went in obedience to his commands to remove the pulpit, when immediately, to their great surprise and astonishment, the Sun was eclipsed to that degree that the stars appeared."[73] Once again the question of visible stars is in some sense a source of difficulty. Hind found that the eclipse was annular on the central line. At Medina the greatest phase occurred at 10h. 43m. a.m. when 85/100ths of the Sun's diameter was obscured. Hind suggests that in the clear skies of that part of the world such a degree of eclipse might be sufficient to bring out the brighter planets or stars. At any rate no larger eclipse visible at Medina occurred about this epoch. Prof. Ockley seems to refer to this eclipse in making, on the authority of several Arabian writers, the mention he does of an eclipse in the quotation just given.

Perhaps this will be a convenient place to bring in some remarks on certain Arabian observations of eclipses only made known to the scientific world in modern times. That the Arabians were very capable practical astronomers has long been recognised as a well-established fact, and if it had not been for them there would have been a tremendous blank in the history of astronomy during at least six centuries from about the year A.D. 700 onwards. In the year 1804 there was published at Paris a French translation of an Arabian manuscript preserved at the University of Leyden of which little was known until near the end of the last century. The manuscript was then sent to Paris on loan to the French Government which caused a translation to be made by "Citizen" Caussin, and this was published under the title of Le Livre de la grande Table Hakenate.[74] Caussin was Professor of Arabic at the College of France. Newcomb considers this to contain the earliest exact astronomical observations of eclipses which have reached us. He remarks that some of the data left us by Ptolemy, Theon, Albategnius and others may be the results of actual observations, but in no case, so far as is known, have the figures of the actual observations been handed down. For example, we cannot regard "midnight" nor "the middle of an eclipse" as moments capable of direct observation without instruments of precision; but in the Arabian work under consideration we find definite statements of the altitudes of the heavenly bodies at the moments of the beginning and ending of eclipses—data not likely to be tampered with in order to agree with the results of calculation. The eclipses recorded are 28 in number and usually the beginning and end of them were observed. The altitudes are given sometimes only in whole degrees, sometimes in coarse fractions of a degree. The most serious source of error to be confronted in turning these observations to account arises from the uncertainty as to how long after the first contact the eclipse was perceived and the altitude taken; and how long before the true end was the eclipse lost sight of. Making the best use he could of the records available Newcomb found that they could safely be employed in his investigations into the theory of the Moon.

The observations were taken, some at Bagdad and the remainder at Cairo. I do not propose to occupy space by transcribing the accounts in detail, but one extract may be offered as a sample of the rest—"Eclipse of the Sun observed at Bagdad, August 18, 928 A.D. The Sun rose about one-fourth eclipsed. We looked at the Sun on a surface of water and saw it distinctly. At the end when we found no part of the Sun was any longer eclipsed, and that its disc appeared in the water as a complete circle, its altitude was 12 deg. in the E., less the one-third of a division of the instrument, which itself was divided to thirds of a degree. One must therefore reduce the stated altitude by one-ninth of a degree, leaving, therefore, the true altitude as 11 deg. 53' 20"." The skill and care shown in this record shows that the Arab who observed this eclipse nearly a thousand years ago must have been a man of a different type from an ordinary resident at Bagdad in the year 1899. No description is given of the instrument used, but presumably it was some kind of a quadrant. It does not appear why some of the observations were made at Bagdad and some at Cairo. The Bagdad observations commence with an eclipse of the Sun on November 30, 829, and end with an eclipse of the Moon on November 5, 933. The Cairo observations begin with an eclipse of the Sun on December 12, 977, and end with an eclipse of the Sun on January 24, 1004. These statements apply to the 25 observations which Newcomb considered were trustworthy enough to be employed in his researches, but he rejected three as imperfect.

I have broken away from the strict thread of chronological sequence in order to keep together the notes respecting Arabian observations of eclipses. Let us now revert to the European eclipses.

Under the date of A.D. 733, the Anglo-Saxon Chronicle tells us that, "In this year AEthelbald captured Somerton; and the Sun was eclipsed, and all the Sun's disc was like a black shield; and Acca was driven from his bishopric." Johnston suggests that the reference is to an annular eclipse which he finds occurred on August 14, at about 81/4 h. in the morning. In Schnurrer's Chronik der Seuchen (pt. i., Sec. 113, p. 164), it is stated that, "One year after the Arabs had been driven back across the Pyrenees after the battle of Tours, the Sun was so much darkened on the 19th of August as to excite universal terror." It may be that the English eclipse is here referred to, and a date wrong by five days assigned to it by Schnurrer. Humboldt (Cosmos, vol. iv. p. 384, Bohn's ed.) reports this eclipse in an enumeration he gives of instances of the Sun having been darkened.

On May 5, A.D. 840, there happened an eclipse of the Sun which, amongst other effects, is said to have so greatly frightened Louis Le Debonnaire (Charlemagne's son) that it contributed to his death. The Emperor was taken ill at Worms, and having been removed to Ingelheim, an island in the Rhine, near Mayence, died there on June 20. Hind[75] found that this was a total eclipse, and that the northern limit of totality passed about 100 miles south of Worms. The middle of the eclipse occurred at 1h. 15m. p.m. with the Sun at an altitude of 57 deg.. The duration of the eclipse was unusually long, namely about 51/2 minutes. With the Sun so high and the obscuration lasting so long, this eclipse must have been an unusually imposing one, and well calculated to inspire special alarm.

On Oct. 29, 878, in the reign of King Alfred, there was a total eclipse visible at London. The mention of it in the Anglo-Saxon Chronicle is as follows:—"The Sun was eclipsed at 1 hour of the day." No month is given, and the year is said to have been 879, which is undoubtedly wrong. Hind found that the central line of the eclipse passed about 20 miles N. of London, and that the totality lasted 1m. 51s. Tycho Brahe in his Historia Coelestis quotes from the Annales Fuldenses a statement that the Sun was so much darkened after the 9th hour that the stars appeared in the heavens.

Thorpe in his edition of the Anglo-Saxon Chronicle quotes from Mr. Richard Price a note which assigns the date of March 14, 880, to this eclipse, and cites in confirmation a passage from the Chronicle of Florence of Worcester, anno 879. The 880 eclipse is mentioned by Asser in his De Vita et Rebus gestis Alfredi in the words following:—"In the same year [879] an eclipse of the Sun took place between three o'clock and the evening, but nearer three o'clock." The confusion of dates is remarkable.

In the Chronicon Scotorum, under the date of 885, we find:—"An eclipse of the Sun; and stars were seen in the heavens." The reference appears to be to the total eclipse of June 16, A.D. 885. The totality lasted more than four minutes, and as the stars are said to have been visible in the North of Ireland, doubtless that part of Ireland came within the eclipse limits.

On Dec. 22, 968, there was an eclipse of the Sun, which was almost total at London at about 8h. 33m. a.m., or soon after sunrise. The central line passed across the S.-W. of England, and thence through France to the Mediterranean. One Leon, a deacon at Corfu, observed this eclipse, and has left behind what probably is the first perfectly explicit mention of the Corona.[76]

On Aug. 30, 1030, there happened an eclipse visible in Norway, which has already been alluded to on a previous page under the name of the "eclipse of Stiklastad." This was one of those eclipses, the circumstances of which were examined many years ago in detail by Sir G. B. Airy,[77] because he thought that information of value might be obtained therefrom with respect to the motions of the Moon. Its availability for that purpose has, however, been seriously questioned by Professor Newcomb. Stiklastad is a place where a battle was fought, at which Olav, King of Norway, is said to have been killed. While the battle was in progress the Sun was totally eclipsed, and a red light appeared around it. This is regarded as an early record of the Corona, though not the first.[78] Johnston found that the eclipse was nearly total at about 2h. 21m. p.m.

In 1033 there happened on June 29 an eclipse of the Sun, which evidently had many observers, because it is mentioned by many contemporary writers. For instance, the French historian, Glaber,[79] says that "on the 3rd of the Calends of July there was an eclipse from the sixth to the eighth hour of the day exceedingly terrible. For the Sun became of a sapphire colour; in its upper part having the likeness of a fourth part of the Moon." This sufficiently harmonises with Johnston's calculations that about four-fifths of the Sun on the lower side was covered at 10h. 50m. in the morning.

FOOTNOTES:

[Footnote 61: Hist. Rome, Book lv., chap. 22.]

[Footnote 62: Letter in the Times, July 19, 1872.]

[Footnote 63: Hist. Rome, Book lx., chap. 26.]

[Footnote 64: Life of Apollonius of Tyana, Book viii., c. 23.]

[Footnote 65: Plut. Opera Mor. et Phil., vol. xix. p. 682 Ed. Lipsiae, 1778.]

[Footnote 66: Ast. Nach, No. 1838, vol. lxxvii. p. 223: March 31, 1871.]

[Footnote 67: Matheseos, Lib. i., cap. 2, p. 5, Basileae. 1533.]

[Footnote 68: Historiae, Lib. xx., cap. 3, sec. 1.]

[Footnote 69: Epitome Historiae Ecclesiasticae, Lib. xii., cap. 8.]

[Footnote 70: Historia Francorum, Lib. ii., cap. 3 (ad fin.).]

[Footnote 71: Mrs. D. P. Todd, Total Eclipses of the Sun, p. 101.]

[Footnote 72: The Anglo-Saxon Chronicle, vol. ii. p. 14. Ed. B. Thorpe, 1861.]

[Footnote 73: Prof. S. Ockley, History of the Saracens, vol ii. p. 110. Camb. 1757.]

[Footnote 74: It should be stated that prior to the publication of the work in a book form the greater part of the eclipse observations had been published in the Memoires de l'Institut National des Sciences et Arts: Sciences Mathematiques et Physiques, tome ii.]

[Footnote 75: Letter in the Times, July 19, 1872.]

[Footnote 76: J. F. J. Schmidt, Ast. Nach., vol. lxxvii. p. 127, Feb. 1, 1871.]

[Footnote 77: Memoirs, R.A.S., vol. xxvi. p. 131, 1858.]

[Footnote 78: J. L. E. Dreyer, Nature, vol. xvi. p. 549, Oct. 25, 1877.]



CHAPTER XII.

ECLIPSES OF THE SUN MENTIONED IN HISTORY.— MEDIAEVAL AND MODERN.

One of the most celebrated eclipses of mediaeval times was that of August 2, 1133, visible as a total eclipse in Scotland. It was considered a presage of misfortune to Henry I. and was thus referred to by William of Malmesbury[80]:—

"The elements manifested their sorrow at this great man's last departure from England. For the Sun on that day at the 6th hour shrouded his glorious face, as the poets say, in hideous darkness agitating the hearts of men by an eclipse; and on the 6th day of the week early in the morning there was so great an earthquake that the ground appeared absolutely to sink down; an horrid noise being first heard beneath the surface."

This eclipse is also alluded to in the Anglo-Saxon Chronicle though the year is wrongly given as 1135 instead of 1133 as it certainly was. The Chronicle says:—"In this year King Henry went over sea at Lammas, and the second day as he lay and slept on the ship the day darkened over all lands; and the Sun became as it were a three-night-old Moon, and the stars about it at mid-day. Men were greatly wonder-stricken and affrighted, and said that a great thing should come hereafter. So it did, for the same year the king died on the following day after St. Andrew's Mass day, Dec. 2, in Normandy." The king did die in 1135, but there was no eclipse of the August new Moon, and without doubt the writer has muddled up the year of the eclipse and of the king's departure from England (to which he never returned) and the year of his death. Calvisius states that this eclipse was observed in Flanders and that the stars appeared.

Respecting the above-mentioned discrepancy Mrs. Todd aptly remarks:—"So Henry must have died in 1133, which he did not; or else there must have been an eclipse in 1135, which there was not. But this is not the only labyrinth into which chronology and old eclipses, imagination, and computation, lead the unwary searcher." Professor Freeman's explanation fairly clears up the difficulty:—"The fact that he never came back to England, together with the circumstances of his voyage, seems to have made a deep impression on men's minds. In popular belief the signs and wonders which marked his last voyage were transferred to the Lammas-tide before his death two years later."[81] The central line of this eclipse traversed Scotland from Ross to Forfar and the eclipse was of course large in every part of the country. The totality lasted 4m. 20s. in Forfarshire.

Hind has furnished some further information respecting this eclipse. It appears that during the existence of the Kingdom of Jerusalem created by the Crusaders an eclipse occurred which would appear to have been total at Jerusalem or in its immediate neighbourhood. No date is given and a date can only be guessed, and Hind guessed that the eclipse of 1133 was the one referred to. He found that after leaving Scotland and crossing Europe the central line of the 1133 eclipse entered Palestine near Jaffa and passed over Jerusalem where the Sun was hidden for 41/4 minutes at about 3h. p.m. From Nablous on the N. to Ascalon on the S. the country was in darkness for nearly the same period of time. The alternative eclipses to this one would be those of Sept. 4, 1187, magnitude at Jerusalem 9/10ths of the Sun's diameter; or June 23, 1191, magnitude at the same place about 7/10ths; but these do not seem to harmonise so well with the accounts handed down to us as does the eclipse of 1133.

In 1140, on March 20, there happened a total eclipse of the Sun visible in England which is thus referred to by William of Malmesbury[82]:— "During this year, in Lent, on the 13th of the Calends of April, at the 9th hour of the 4th day of the week, there was an eclipse, throughout England, as I have heard. With us, indeed, and with all our neighbours, the obscuration of the Sun also was so remarkable, that persons sitting at table, as it then happened almost everywhere, for it was Lent, at first feared that Chaos was come again: afterwards, learning the cause, they went out and beheld the stars around the Sun. It was thought and said by many, not untruly, that the King [Stephen] would not continue a year in the government."

The same eclipse is also thus mentioned in the Anglo-Saxon Chronicle:—"Afterwards in Lent the Sun and the day darkened about the noontide of the day, when men were eating, and they lighted candles to eat by; and that was the 13th of the Calends of April, March 20. Men were greatly wonder-stricken." The greatest obscuration at London took place at 2h. 36m. p.m., but it is not quite clear whether the line of totality did actually pass over London.

It was long supposed that this eclipse was total at London, an idea which seems to have arisen from Halley having told the Royal Society anent the total eclipse of May 3, 1715, that he could not find that any total eclipse had been visible at London since March 20, 1140. In consequence of this statement of Halley's, Hind carefully investigated the circumstances of this eclipse, and found that it had not been total at London. The central line entered our island at Aberystwith, and passing near Shrewsbury, Stafford, Derby, Nottingham, and Lincoln, reached the German Ocean, 10 miles S. of Saltfleet. The southern limit of the zone of totality passed through the South Midland counties, and the nearest point of approach to London was a point on the borders of Northamptonshire and Bedfordshire. For a position on the central line near Stafford, Hind found that the totality began at 2h. 36m. p.m. local mean time, the duration being 3m. 26s., and the Sun's altitude being more than 30 deg.. The stars seen were probably the planets Mercury and Venus, then within a degree of each other, and 10 deg. W. of the Sun, and perhaps the stars forming the well-known "Square of Pegasus." Mars and Saturn were also, at that time, within a degree of each other, but very near the western horizon. It is therefore necessary to look further back than 1140 to find a total solar eclipse visible in London.[83]

A solar eclipse seems to have been alluded to by certain historians as having happened in A.D. 1153. We have the obscure statement that "something singular happened to the Sun the day after the Conversion of St. Paul." A somewhat large eclipse having been visible at Augsburg in Germany, on January 26, this may have been the "something" referred to. It would seem that about 11/12ths of the Sun's diameter was covered.

On May 14, A.D. 1230, there happened a great eclipse of the Sun, thus described by Roger of Wendover[84]:—"On the 14th of May, which was the Tuesday in Rogation Week, an unusual eclipse of the Sun took place very early in the morning, immediately after sunrise; and it became so dark that the labourers, who had commenced their morning's work, were obliged to leave it, and returned again to their beds to sleep; but in about an hour's time, to the astonishment of many, the Sun regained its usual brightness." This eclipse, as regards its total phase, is said by Johnston to have begun in the horizon, a little to the N. of London, in the early morning.

On June 3, A.D. 1239, and October 6, 1241, there occurred total eclipses of the Sun, which have been very carefully discussed by Professor Celoria of Milan, with the view of using them in investigations into the Moon's mean motion.[85] The second of these eclipses is mentioned by Tycho Brahe.[86] He states that "a few stars appeared about noonday, and the Sun was hidden from sight in a clear sky." The eclipse was total in Eastern Europe.

Dr. Lingard,[87] the well-known Roman Catholic historian, speaking of the battle of Cressy, which was fought on August 26, 1346, says:—"Never, perhaps, were preparations for battle made under circumstances so truly awful. On that very day the Sun suffered a partial eclipse: birds in clouds, precursors of a storm, flew screaming over the two armies; and the rain fell in torrents, accompanied with incessant thunder and lightning. About 5 in the afternoon, the weather cleared up, the Sun in full splendour darted his rays in the eyes of the enemy; and the Genoese, setting up their shouts, discharged their quarrels." This was not an eclipse, for none was due to take place; and the phenomenon could only have been meteorological—dense clouds or something of that sort in the sky.

On June 16, 1406, there was a large eclipse of the Sun, 9/10ths of its diameter being covered at London; but on the Continent it seems to have been total. It is stated that the darkness was such that people could hardly recognise one another.

One of the most celebrated eclipses during the Middle Ages was undoubtedly that of June 17, 1433. This was long remembered in Scotland as the "Black Hour," and its circumstances were fully investigated some years ago by Hind. It was a remarkable eclipse in that the Moon was within 13 deg. of perigee and the Sun only 2 deg. from apogee. The central line traversed Scotland in a south-easterly direction from Ross to Forfar, passing near Inverness and Dundee. Maclaurin[88] who lived in the early part of the last century mentions that in his time a manuscript account of this eclipse was preserved in the library of the University of Edinburgh wherein the darkness is said to have come on at about 3 p.m., and to have been very profound. The duration of the totality at Inverness was 4m. 32s.; at Edinburgh 3m. 41s. The central line passed from Britain to the N. of Frankfort-on-the-Maine, through Bavaria, to the Dardanelles, to the S. of Aleppo and thence nearly parallel to the river Euphrates to the N.-E. border of Arabia. In Turkey, according to Calvisius, "near evening the light of the Sun was so overpowered that darkness covered the land."

In 1544, on Jan. 24, there occurred an eclipse of the Sun which was nearly but not quite total. The chief interest arises from the fact that it was one of the first observed by professed astronomers: Gemma Frisius saw it at Louvain.

Kepler says[89] that the day became dark like the twilight of evening and that the birds which from the break of day had been singing became mute. The middle of the eclipse was at about 9 a.m.

In 1560 an eclipse of the Sun took place which was total in Spain and Portugal. Clavius who observed it at Coimbra says[90] that "the Sun remained obscured for no little time: there was darkness greater than that of night, no one could see where he trod and the stars shone very brightly in the sky: the birds moreover, wonderful to say, fell down to the ground in fright at such startling darkness." Kepler is responsible for the statement that Tycho Brahe did not believe this, and wrote to Clavius to that effect 40 years afterwards.

In 1567 there was an annular eclipse visible at Rome on April 9. Clavius says[91] that "the whole Sun was not eclipsed but that there was left a bright circle all round." This in set terms is a description of an annular eclipse, but Johnston who calculated that at Rome the greatest obscuration took place at 20m. past noon points out that the augmentation of the Moon's semi-diameter would almost have produced totality. Tycho tells us that he saw this eclipse on the shores of the Baltic when a young man about 20 years of age.

The total eclipse of February 25, 1598, long left a special mark on the memories of the people of Scotland. The day was spoken of as "Black Saturday." Maclaurin states[92]:—"There is a tradition that some persons in the North lost their way in the time of this eclipse, and perished in the snow"—a statement which Hind discredits. The central line passed from near Stranraer, over Dalkeith, and therefore Edinburgh was within the zone of totality. Totality came on at Edinburgh at 10h. 15m. and lasted 1m. 30s. From the rapid motion of the Moon in declination, the course of the central line was a quickly ascending one in latitude on the Earth's surface, the totality passing off within the Arctic circle.

Kepler in his account of the new star in the constellation Ophiuchus[93] refers to the total eclipse of the Sun of October 12, 1605, as having been observed at Naples, and that the "Red Flames" were visible as a rim of red light round the Sun's disc: at least this seems to be the construction which may fairly be put upon the Latin of the original description.

The partial eclipse of the Sun of May 30, 1612, is recorded to have been seen "through a tube." No doubt this is an allusion to the newly-invented instrument which we now call the telescope. Seemingly this is the first eclipse of the Sun so observed, but it is on record that an eclipse of the Moon had been previously observed through a telescope. This was the lunar eclipse of July 6, 1610, though the observer's name has not been handed down to us.

The eclipse of April 8, 1652, is another of those Scotch eclipses, as we may call them, which left their mark on the people of that country. Maclaurin[94] speaks of it in his time (he died in 1746) as one of the two central eclipses which are "still famous among the populace in this country" [Scotland], and "known amongst them by the appellation of Mirk Monday." The central line passed over the S.E. of Ireland, near Wexford and Wicklow, and reaching Scotland near Burrow Head in Wigtownshire, and passing not far from Edinburgh, Montrose and Aberdeen, quitted Scotland at Peterhead. Greenock and Elgin were near the northern limit of the zone of totality, and the Cheviots and Berwick upon the southern limit. The eclipse was observed at Carrickfergus by Dr. Wyberd.[95] Hind found that its duration there was but 44s. This short duration, he suggested, may partly explain the curious remark of Dr. Wyberd that when the Sun was reduced to "a very slender crescent of light, the Moon all at once threw herself within the margin of the solar disc with such agility that she seemed to revolve like an upper millstone, affording a pleasant spectacle of rotatory motion." Wyberd's further description clearly applies to the Corona. A Scotch account says that "the country people tilling, loosed their ploughs. The birds dropped to the ground."

The eclipse of November 4, 1668, visible as a partial one in England, was of no particular interest in itself but deserves notice as having been observed by Flamsteed,[96] who gives a few diagrams of his observations at Derby. He states that the eclipse came on much earlier than had been predicted. It was well known at this time that the tables of the Sun and Moon then in use were very defective, and it was a recognition of this fact which eventually led to the foundation of the Greenwich Observatory in 1675.

On September 23, 1699, an eclipse of the Sun occurred which was total to the N. of Caithness for the very brief space of 10-15 secs. At Edinburgh, about 11/12ths of the Sun's diameter was obscured. In the Appendix to Pepys's Diary[97] there is a letter from Dr. Wallis mentioning that his daughter's attention was called to it by noticing "the light of the Sun look somewhat dim" at about 9 a.m., whilst she was writing a letter, she knowing nothing of the eclipse.

An eclipse of the Sun occurred on May 12, 1706, which was visible as a partial eclipse in England and was total on the Continent, especially in Switzerland. A certain Captain Stannyan who made observations at Berne, writes thus to Flamsteed[98]:—"That the Sun was totally darkened there for four and a half minutes of time; that a fixed star and a planet appeared very bright; and that his getting out of his eclipse was preceded by a blood-red streak of light from its left limb, which continued not longer than six or seven seconds of time; then part of the Sun's disc appeared all of a sudden as bright as Venus was ever seen in the night; nay, brighter; and in that very instant gave a light and shadow to things as strong as the Moon uses to do."

On this communication Flamsteed remarks:—"The Captain is the first man I ever heard of that took notice of a red streak preceding the emersion of the Sun's body from a total eclipse, and I take notice of it to you [the Royal Society], because it infers that the Moon has an atmosphere; and its short continuance, if only six or seven seconds' time, tells us that its height was not more than five or six hundredths part of her diameter."

On the whole, perhaps, the most celebrated eclipse of the Sun ever recorded in England was that of May 3, 1715. The line of totality passed right across England from Cornwall to Norfolk, and the phenomenon was carefully observed and described by the most experienced astronomer of the time, Dr. Edmund Halley. The line of totality passed over London amongst other places, and as the maximum phase took place soon after 9 a.m. on a fine spring morning, the inhabitants of the Metropolis saw a sight which their successors will not see again till many generations have come and gone. Halley has left behind him an exceedingly interesting account of this event, some allusions to which have already been made.

He seems to have seen what we call the Corona, described by him however as a "luminous ring," "of a pale whiteness, or rather pearl colour, a little tinged with the colours of the Iris, and concentric with the Moon." He speaks also of a dusky but strong red light which seemed to colour the dark edge of the Moon just before the Sun emerged from totality. Jupiter, Mercury, Venus, and the stars Capella and Aldebaran were seen in London, whilst N. of London, more directly under the central line, as many as twenty stars were seen.

The inhabitants of England who lived in the reign of George I. were singularly fortunate in their chances of seeing total eclipses of the Sun, for only nine years after[99] the one just described, namely, on May 22, 1724, another total eclipse occurred. The central line crossed some of the southern countries, and the phenomenon was well seen and reported on by Dr. Stukeley,[100] who stationed himself on Haraden Hill, near Salisbury. The Doctor says of the darkness that he seemed to "feel it, as it were, drop upon us ... like a great dark mantle," and that during the totality the spectacle presented to his view "was beyond all that he had ever seen or could picture to his imagination the most solemn." He could with difficulty discern the faces of his companions which had a ghastly startling appearance. When the totality was ending there appeared a small lucid spot, and from it ran a rim of faint brightness. In about 31/2 minutes from this appearance the hill-tops changed from black to blue, the horizon gave out the grey streaks previous to morning dawn, and the birds sprang joyously into the air.

This eclipse seems to have had royal observers. It was watched at Kensington apparently by the King or some of the royal family of England, and at Trianon (Paris) by the King of France,[101] under the competent guidance of Maraldi, Cassini and De Louville. It was the last which was visible as a total one in any part of England.

On May 2, 1733, there was an eclipse of the Sun, which was total in Sweden and partial in England. In Sweden the total obscuration lasted more than 3 minutes. Jupiter, the stars in Ursa Major, Capella, and several other stars were visible to the naked eye, as also was a luminous ring round the Sun. Three or four spots of reddish colour were also perceived near the limb of the Moon, but not in immediate contact with it. These so-called red "spots" were doubtless the Red Flames of the present century, and the luminous ring the Corona.

On March 1, 1737, a good annular eclipse was observed at Edinburgh by Maclaurin.[102] In his account he says:—"A little before the annulus was complete a remarkable point or speck of pale light appeared near the middle of the part of the Moon's circumference that was not yet come upon the disc of the Sun.... During the appearance of the annulus the direct light of the Sun was still very considerable, but the places that were shaded from his light appeared gloomy. There was a dusk in the atmosphere, especially towards the N. and E. In those chambers which had not their lights westwards the obscurity was considerable. Venus appeared plainly, and continued visible long after the annulus was dissolved, and I am told that other stars were seen by some." Lord Aberdour mentions a narrow streak of dusky red light on the dark edge of the Moon immediately before the ring was completed, and after it was dissolved. No doubt this is a record of the "Red Flames."

In 1748 Scotland was again favoured with a central eclipse, but it was only annular. The Earl of Morton[103] and James Short, the optician, who observed the phenomenon at Aberdour Castle, 10 miles N.-W. of Edinburgh, just outside the line of annularity, saw a brown coloured light stretching along the circumference of the Moon from each of the cusps. A "star" (probably the planet Venus) was seen to the E. of the Sun.

The annular eclipse of April 1, 1764, visible as such in North Kent, was the subject of the following quaint letter by the Rev. Dr. Stukeley:—

"To the Printer of Whitehall Evening Post,—

"In regard to the approaching solar eclipse of Sunday, April 1, I think it advisable to remark that, it happening in the time of divine service, it is desired you would insert this caution in your public paper. The eclipse begins soon after 9, the middle a little before 11, the end a little after 12. There will be no total darkness in the very middle, observable in this metropolis, but as people's curiositys will not be over with the middle of the eclipse, if the church service be ordered to begin a little before 12, it will properly be morning prayer, and an uniformity preserved in our duty to the Supreme Being, the author of these amazing celestial movements,— Yours, RECTOR OF ST. GEO., Q.S."[104]

The year 1766 furnishes the somewhat rare case of a total eclipse of the Sun observed on board ship on the high seas. The observers were officers of the French man-of-war the Comte d'Artois. Though the total obscuration lasted only 53 secs., there was seen a luminous ring about the Moon which had four remarkable expansions, situate at a distance of 90 deg. from each other.[105] These expansions are doubtless those rays which we now speak of as "streamers" from the Corona.

Curiously enough the next important total eclipse deserving of notice was also observed at sea. This was the eclipse of June 24, 1778. The observer was the Spanish Admiral, Don Antonio Ulloa, who was passing from the Azores to Cape St. Vincent. The total obscuration lasted 4 minutes. The luminous ring presented a very beautiful appearance: out of it there issued forth rays of light which reached to the distance of a diameter of the Moon. Before it became very conspicuous stars of the 1st and 2nd magnitudes were distinctly visible, but when it attained its greatest brilliancy, only stars of the 1st magnitude could be perceived. "The darkness was such that persons who were asleep and happened to wake, thought that they had slept the whole evening and only waked when the night was pretty far advanced. The fowls, birds, and other animals on board took their usual position for sleeping, as if it had been night."[106]

On Sept. 5, 1793, there happened an eclipse which, annular to the N. of Scotland, was seen and observed in England by Sir W. Herschel[107] as a partial eclipse. He made some important observations on the Moon on this occasion measuring the height of several of the lunar mountains. Considerations respecting the shape of one of the Moon's horns led him to form an opinion adverse to the idea that there the Moon had an atmosphere.

FOOTNOTES:

[Footnote 79: Historiarum Sui Temporis, Lib. iv., cap. 9.]

[Footnote 80: Historia Novella, Lib. i., sec. 8.]

[Footnote 81: Norman Conquest, vol. v. p. 239.]

[Footnote 82: Historia Novella, Lib. ii., sec. 35.]

[Footnote 83: Letter in the Times, July 28, 1871.]

[Footnote 84: Rogerus de Wendover, Flores Historiarum, vol. ii. p. 535, Bohn's ed.]

[Footnote 85: Sugli Eclissi Solari Totali del 3 Giugno 1239, e del 6 Ottobre 1241 in the Memorie del R. Istituto Lombardo di Scienze e Littere, vol. xiii. p. 275.]

[Footnote 86: Historia Coelestis, vol. i. p. 38.]

[Footnote 87: Hist. Engl., vol. iii. chap. xviii. p. 50, 4to. ed.]

[Footnote 88: Phil. Trans., vol. xl. p. 194, 1737.]

[Footnote 89: Astronomiae Pars Optica, c. viii. sec. 3; Opera Omnia, vol. ii. p. 315. Ed. Frisch, 1859.]

[Footnote 90: Quoted by Kepler, as above, at p. 315.]

[Footnote 91: Commentarius in Sacroboscum, cap. iv.; quoted in Kepler's Astronomiae Pars Optica, c. viii. sec. 3; Opera Omnia, vol ii. p. 316. Ed. Frisch, 1859.]

[Footnote 92: Phil. Trans., vol. xl. p. 193; 1737.]

[Footnote 93: De Stella Nova in Pede Serpentarii, p. 115; Pragae, 1606.]

[Footnote 94: Phil. Trans., vol. xl. p. 193; 1737.]

[Footnote 95: V. Wing, Astronomia Britannica, p. 355.]

[Footnote 96: Historia Coelestis, vol. i. pp. 7 and 21.]

[Footnote 97: Diary of Samuel Pepys, vol. vi. p. 208; Ed. M. Bright, 1879.]

[Footnote 98: Phil. Trans., vol. xxv. p. 2240; 1706.]

[Footnote 99: Being half a Saros period (see p. 20, ante).]

[Footnote 100: Itinerarium Curiosum, 2nd ed., vol. i. p. 180.]

[Footnote 101: Mem. de Mathematique et de Physique de l'Acad. des Sciences, 1724, p. 259.]

[Footnote 102: Phil. Trans., vol. xl. pp. 181, 184. 1737.]

[Footnote 103: Phil. Trans., vol. xlv. p. 586. 1750. This is the man who under the designation of "Lord Aberdour" observed the eclipse of 1737 (ante).]

[Footnote 104: Rev. W. Stukeley, Rector of St. George's, Queen's Square, London, Diary, vol. xx. p. 44, ed. "Surtees Soc.," vol. lxxvi. p. 384.]

[Footnote 105: Le Gentil, Voyage dans les Mers de l'Inde, vol. ii. p. 16. Paris, 1769.]

[Footnote 106: Phil. Trans., vol. lxix. p. 105. 1779.]

[Footnote 107: Phil. Trans., vol. lxxxiv. p. 39. 1794.]



CHAPTER XIII.

ECLIPSES OF THE SUN DURING THE NINETEENTH CENTURY.

Observations of total solar eclipses during the 19th century have been, for the most part, carried on under circumstances so essentially different from everything that has gone before, that not only does a new chapter seem desirable but also new form of treatment. Up to the beginning of the 18th century the observations (even the best of them) may be said to have been made and recorded with but few exceptions by unskilled observers with no clear ideas as to what they should look for and what they might expect to see. Things improved a little during the 18th century and the observations by Halley, Maclaurin, Bradley, Don Antonio Ulloa, Sir W. Herschel, and others in particular rose to a much higher standard than any which had preceded them. However, it has only been during the 19th century, and especially during the latter half of it, that total eclipses of the Sun have been observed under circumstances calculated to extract from them large and solid extensions of scientific knowledge. Inasmuch as it has been deemed convenient to sort out and classify our knowledge under particular heads in previous chapters, I shall in this chapter speak only of the leading facts of each eclipse in such an outline form as will avoid as far as possible unnecessary repetition.

In 1806 a total eclipse of the Sun occurred, visible in N. America. Observations made in the United States have been handed down to us. Don Joachin Ferrer, a Spanish astronomer, observed the eclipse at Kinderhook in the State of New York. The totality lasted more than 41/2 m.—a somewhat unusual length of time. One or two planets and a few 1st magnitude stars were seen. During the totality there was a slight fall of dew.

On Nov. 19, 1816, there occurred the first total eclipse of the Sun in the 19th century, the central line of which passed over Europe. There is only one known observation of the total phase, and this was by Hagen at Culm in Bohemia, but he appears to have seen only the beginning of the totality and not the whole of it.

A partial eclipse of the Sun visible as such in England but which was annular in the Shetland Isles took place on Sept. 7, 1820. The only reason why this is worth mention is for its political associations. The trial of Queen Caroline was going on in the House of Lords, and the House suspended its sitting for a short time for the sake of the eclipse.

On May 15, 1836, there occurred an annular eclipse of the Sun, which though it was nowhere total, may be looked upon as the first of the modern eclipses the observations of which have taken such a great development during recent years. The annularity of this eclipse was observed in the N. of England and in the S. of Scotland; and it was at Jedburgh in Roxburghshire that Mr. Francis Baily[108] observed that feature of eclipses of the Sun now universally known as "Baily's Beads." Some indications of the Red Flames were also obtained at places where the eclipse was annular.

Probably it was the recognition of Baily's Beads as a regular concomitant of eclipses of the Sun, which helped to pave the way for the extensive preparations made in France, Italy, Austria, and Russia for observing the total eclipse of July 8, 1842. Many of the most eminent astronomers of Europe repaired to different stations on the central line in order to see the phenomenon. Amongst these may be named Arago, Valz, Airy, Carlini, Santini, and O. Struve. The eclipse was witnessed under favourable circumstances at all the various stations on the central line across Europe, from Perpignan in France in the West to Lipesk in Russia in the East.

Arago wrote[109] such an exceedingly graphic account of this eclipse from what may be termed the standpoint of the general public, that I will quote it at some length, because, with an alteration of date, it might be re-written and applied to every total eclipse visible in much populated tracts of country.

"At Perpignan persons who were seriously unwell alone remained within doors. As soon as day began to break the population covered the terraces and battlements of the town, as well as all the little eminences in the neighbourhood, in hopes of obtaining a view of the Sun as he ascended above the horizon. At the citadel we had under our eyes, besides numerous groups of citizens established on the slopes, a body of soldiers about to be reviewed.

"The hour of the commencement of the eclipse drew nigh. More than twenty thousand persons, with smoked glasses in their hands, were examining the radiant globe projected upon an azure sky. Although armed with our powerful telescopes, we had hardly begun to discern the small notch on the western limb of the Sun, when an immense exclamation, formed by the blending together of twenty thousand different voices, announced to us that we had anticipated by only a few seconds the observation made with the unaided eye by twenty thousand astronomers equipped for the occasion, whose first essay this was. A lively curiosity, a spirit of emulation, the desire of not being outdone, had the privilege of giving to the natural vision an unusual power of penetration. During the interval that elapsed between this moment and the almost total disappearance of the Sun we remarked nothing worthy of relation in the countenances of so many spectators. But when the Sun, reduced to a very narrow filament, began to throw upon the horizon only a very feeble light, a sort of uneasiness seized upon all; every person felt a desire to communicate his impressions to those around him. Hence arose a deep murmur, resembling that sent forth by the distant ocean after a tempest. The hum of voices increased in intensity as the solar crescent grew more slender; at length the crescent disappeared, darkness suddenly succeeded light, and an absolute silence marked this phase of the eclipse with as great precision as did the pendulum of our astronomical clock. The phenomenon in its magnificence had triumphed over the petulance of youth, over the levity which certain persons assume as a sign of superiority, over the noisy indifference of which soldiers usually make profession. A profound stillness also reigned in the air; the birds had ceased to sing. After an interval of solemn expectation, which lasted about two minutes, transports of joy, shouts of enthusiastic applause, saluted with the same accord, the same spontaneous feeling, the first reappearance of the rays of the Sun. To a condition of melancholy produced by sentiments of an indefinable nature there succeeded a lively and intelligible feeling of satisfaction which no one sought to escape from or moderate the impulses of. To the majority of the public the phenomenon had arrived at its term. The other phases of the eclipse had few attentive spectators beyond the persons devoted especially to astronomical pursuits."

The total eclipse of July 28, 1851, may be said to have been the first which was the subject of an "Eclipse Expedition," a phrase which of late years has become exceedingly familiar. The total phase was visible in Norway and Sweden, and great numbers of astronomers from all parts of Europe flocked to those countries. Amongst those who went from England were Sir G. B. Airy, the Astronomer Royal (then Mr. Airy), Mr. J. R. Hind and Mr. Lassell. The Red Flames were very much in evidence, and the fact that they belonged to the Sun and not to the Moon was clearly established. Hind mentions that "the aspect of Nature during the total eclipse was grand beyond description." This feature is dwelt upon with more than usual emphasis in many of the published accounts. I have never seen it suggested that the mountainous character of the country may have had something to do with it, but that idea would seem not improbable.

In the year 1858, two central eclipses of the Sun occurred, both presenting some features of interest. That of March 15 was annular, the central line passing across England from Lyme Regis in Dorsetshire to the Wash, traversing portions of Somersetshire, Wiltshire, Berkshire, Oxfordshire, Northamptonshire, Lincolnshire, and Norfolk. The weather generally was unfavourable and the annular phase was only observed at a few places, but important meteorological observations were made and yielded results, as regards the diminution of temperature, which were very definite. All over the country rooks and pigeons were seen returning home during the greatest obscuration; starlings in many places took flight; at Oxford a thrush commenced its evening song; at Ventnor a fish in an aquarium, ordinarily visible in the evening only, was in full activity about the time of greatest gloom; and generally, it was noted that the birds stopped singing and flew low from bush to bush. The darkness, though nowhere intense, was everywhere very appreciable and decided. The second central eclipse of 1858 took place on September 7 and was observed in Peru by Lieutenant Gilliss of the U.S. Navy. The totality only lasted one minute, and the general features of a total eclipse do not appear to have been very conspicuously visible. Gilliss remarks[110]:—"Two citizens of Olmos stood within a few feet of me, watching in silence, and with anxious countenances, the rapid and fearful decrease of light. They were wholly ignorant that any sudden effect would follow the total obscuration of the Sun. At that instant one exclaimed in terror "La Gloria," and both, I believe, fell to their knees, filled with awe. They appreciated the resemblance of the Corona to the halos with which the old masters have encircled their ideals of the heads of our Saviour and the Madonna, and devoutly regarded this as a manifestation of the Divine Presence."

The year 1860 saw the departure from England of the first great Ship Expedition to see an eclipse. One was due to happen on July 18, and a large party went out from England to Spain in H.M.S. Himalaya. Mr. De La Rue took a very well-equipped photographic detachment, and his photographs were eminently successful. This eclipse settled for ever the doubt as to whether the Red Flames belonged to the Sun or the Moon, and in favour of the former view.

The years 1868, 1869, and 1870 were each marked by total eclipses, which were observed to a greater or less extent. In the first-named year the eclipse occurred on August 18, the central line passing across India. The weather was not everywhere favourable, but several expeditions were dispatched to the East Indies. The spectroscope was largely brought into play with the immediate result of showing that the Corona was to be deemed a sort of atmosphere of the Sun, not self-luminous, but shining by reflected light. The eclipse of 1869 was observed by several well-equipped parties in the United States, and a very complete series of excellent photographs was obtained.

To view the eclipse of December 22, 1870, several expeditions were dispatched, the central line passing over some very accessible places in Spain, Sicily, and North Africa. The English observers went chiefly in H.M.S. Urgent, though some of them travelled overland to Sicily. The expenses, both of the sea and land parties, were to a large extent defrayed by Her Majesty's Government. It deserves to be noted that so great was the anxiety of the French astronomer Janssen to see this eclipse, that he determined to try and escape in a balloon from Paris (then besieged by the Germans) and succeeded, carrying his instruments with him. The weather seriously interfered with the work of all the observers who went out to see this eclipse, which was the more to be regretted because the preparations had been on a very extensive and costly scale. The chief result was that it was ascertained that the Red Flames (hence forward generally called "Prominences") are composed of hydrogen gas in an incandescent state.

The year 1871 saw, on December 12, another Indian eclipse, noteworthy for the numerous and excellent photographs which were obtained of the Corona, of the rifts in it, and of the general details, which were well recorded on the plates.

There was an eclipse visible in South Africa on April 16, 1874. Some useful naked eye views were obtained and recorded, but as no photographic work was done, this eclipse cannot be said to come into line with those which preceded or followed it.

In the following year, that is to say on April 6, 1875, there was a total eclipse of the Sun, visible in the far East, especially Siam; but the distance from England, coupled with the very generally unfavourable weather, prevented this from being anything more than a second-class total eclipse, so to speak, although extensive preparations had been made, and the sum of L1000 had been granted by the British Government towards the expenses. A certain number of photographs were obtained, but none of any very great value.

Perhaps of the next eclipse which we have to consider, it may be said that the circumstances were more varied than those of any other during the second half of the 19th century. The eclipse in question occurred on July 29, 1878.

Several favourable circumstances concurred to make it a notable event. In the first place, the central line passed entirely across the United States; in other words, across a long stretch of inhabited and civilised territory, accessible from both sides to a nation well provided with the requisite scientific skill and material resources of every kind. But there was another special and rare facility available: the central line crossed the chain of the Rocky Mountains, an elevated locality, which an American writer speaks of as overhung by "skies of such limpid clearness, that on several evenings Jupiter's satellites were seen with the naked eye." On the summit of a certain peak, known as Pike's Peak, a party of skilled observers, headed by Professor Langley, observed the wonderful developments of the Corona, mentioned on a previous page. The fact that such a display came under the eyes of man was no doubt mainly due to the superbly clear atmosphere through which the observations were made. That this is not a mere supposition may be inferred from the fact that at the lower elevation of only 8000 feet, instead of 14,000 feet, the Coronal streamers were seen by Professor Newcomb's party, far less extended than Langley saw them. Perhaps the best proof of the importance of a diaphanous sky is to be found in the fact that on the summit of Pike's Peak, the Corona remained visible for fully 4 minutes after the total phase had come to an end. A comparison of the descriptions shows that even at the elevation of 10,200 ft. the observers placed there, whilst they were better off than those at 8000 ft., assuredly did not see so much or so well as those at 14,000 ft.

There occurred a total eclipse on July 11, 1880, visible in California, but as the totality lasted only 32 secs. and the Sun's elevation was only 11 deg., not much was got out of this eclipse notwithstanding that it was observed in a cloudless sky at a station 6000 ft. above the sea.

The eclipse of May 17, 1882, yielded several interesting and important features although the totality was short—only about 11/4 minutes. Here again favourable local circumstances helped astronomers in more ways than one. It was in Egypt that the eclipse was visible, and Egypt is a country which it is exceedingly easy for travellers to reach, and it is also noted for its clear skies. These were doubtless two of the reasons which combined to inspire the elaborate preparations which were made for photographic and spectroscopic observations. The former resulted in a very unprecedented success. One of Dr. Schuster's photographs of the totality showed not only the expected Corona, but an unexpected comet.

Though on more than one previous occasion in history the darkness which is a special accompaniment of a total eclipse had caused a comet to be seen, yet the 1882 eclipse was the first at which a comet had thrust itself upon the notice of astronomers by means of a photographic plate. It will be remembered that the political circumstances of Egypt in 1882 were of a somewhat strained character and probably this contributed to the development of an unusual amount of astronomical competition in connection with this eclipse. Not only did the Egyptian Government grant special facilities, but strong parties went out representing England, France, and Italy, although not perhaps in set terms at the direct instigation of their respective Governments.

The next eclipse, that of May 6, 1883, had some dramatic features about it. To begin with its duration was unusually long—nearly 51/2 minutes, and Mrs. Todd in her genial American style remarks:—"After the frequent manner of its kind, the path lay where it would be least useful—across the wind-swept wastes of the Pacific. But fortunately one of a small group of coral islands lay quite in its line, and, nothing daunted, the brave scientific men set their faces toward this friendly cluster, in cheerful faith that they could locate there. Directed to take up their abode somewhere on a diminutive island about which nothing could be ascertained beforehand, save the bare fact of its existence at a known spot in mid-ocean, the American observers were absent from the United States more than three months, most of which time was spent in travelling, 15,000 miles in all, with ten full weeks at sea. Their tiny foothold in the Pacific was Caroline Island, a coral atoll on the outskirts of the Marquesas group."

In spite of the unattractive, not to say forbidding, character of the place to which they would have to go, parties of astronomers went out from England, France, Austria, and Italy, and although rain fell on the morning of the day the sky became quite clear by the time of totality and the observations were completely successful. One of the pictures of the Corona obtained by Trouvelot, an observer of French descent, but belonging to the American party, has been often reproduced in books and exhibited the Corona in a striking form. How few were the attractions of Caroline Island as an eclipse station may be judged from the fact that the inhabitants consisted of only four native men, one woman, and two children who lived in three houses and two sheds.

On September 8, 1885, there occurred a total eclipse, which was seen as such in New Zealand, but the observations were few, and with one exception, unimportant and uninteresting. A certain Mr. Graydon, however, made a sketch which showed at one point a complete break in the Corona so that from the very edge of the Moon outwards into space, there was a long and narrow black space showing nothing but a vacuity. If this was really the condition of things, such a break in the Corona is apparently quite unprecedented.

In 1886, on August 29, there occurred a total eclipse, visible in the West Indies, which yielded various important results. It was unfortunate that for the greater part of its length, the zone of totality covered ocean and not land, the only land being the Island of Grenada and some adjacent parts of South America. The resulting restriction as regards choice of observing stations was the more to be regretted because the duration of the totality was so unusually long, and therefore favourable, being more than 61/2 minutes in the middle of the Atlantic Ocean. Parties of English, American, and Italian astronomers assembled, however, at Grenada, and though the weather was not the best possible, some interesting photographs were obtained which exhibited an unusual development of hydrogen protuberances. The central line in this eclipse not only stretched right across the Atlantic, but entered Africa on the West Coast where a missionary saw the eclipse as a mere spectator, and afterwards expressed his regret that no astronomers were within reach with instruments to record the remarkable Corona which was displayed to his gaze.

Though the unusual opportunities which, so far as the Sun and the Moon were concerned, were afforded by the eclipse of 1886 were lost, astronomers looked out hopefully for August 19, 1887, when another eclipse was due to happen which, weather permitting, would be observable over a very long stretch of land, from Berlin through Russia and Siberia to Japan. Unusually extensive preparations were made in Russia at one end and in Japan at the other, but clouds prevailed very generally, and the pictures of the Corona which were obtained fell far short in number and quality from what had been hoped for, having regard to the number and importance of the stations chosen, and of the astronomers who made their preparations thereat. An enthusiastic Russian, in the hopes of emancipating himself from the risks of terrestrial weather at the Earth's surface, went up in a balloon to an elevation of more than two miles. His enthusiasm was so far rewarded that he had a very clear view of a magnificent Corona; but as, owing to some mischance, the balloon rose, conveying only the astronomer and leaving behind his assistant who was to have managed the balloon, all his time was engrossed by the management of the balloon, and he could do very little in the way of purely astronomical work.

The year 1889 afforded two total eclipses of the Sun for which the usual preparations were made. The first occurred on New Year's Day, and the path of the shadow crossed the North American Continent from California to Manitoba. The weather was nearly everywhere very favourable, and an enormous number of observers and instruments were assembled along the central line. The consequence was that a very large number of photographs were obtained. It may be said generally of this eclipse, that as it coincided with a Sun-spot minimum, it left us in a position to learn very distinctly what are the characteristic features of a solar Corona at a period which is one of rest and repose on the Sun, at least, so far as regards visible Sun-spots.

The second eclipse of 1889 occurred on December 22, and should have been visible off the northern coast of South America and on the West Coast of Africa. Attempts were made to utilise the South American chances by English and American parties, whilst a small expedition comprising astronomers of both nations went to Cape Ledo in West Africa. The African efforts failed entirely owing to clouds, but the South American parties at Cayenne were successful. One very deplorable result, however, arising out of the expedition to Cayenne was the illness and subsequent death of the Rev. S. J. Perry, S.J., who was struck down by malaria and died at sea on the return journey. None who knew Mr. Perry personally could fail to realise what a loss he was both to astronomy generally and to his own circle of friends particularly.

On April 16, 1893, there happened a total eclipse of the Sun, which was successfully watched by a large number of skilled observers throughout its entire length. Indeed it is believed that only one party was unsuccessful. The line of totality started on the coast of Chili, passed over the highlands of that country, across the borders of Argentina and Paraguay, and over the vast plains and forests of Central Brazil, emerging at about noon of local time at a short distance to the N.-W. of Ceara on the North Atlantic seaboard. Crossing the Atlantic nearly at its narrowest part, it struck the coast of Africa N. of the river Gambia, and finally disappeared somewhere in the Sahara. The South American observations were the most extensive and successful, the latter fact being due to the circumstance that the sky at many of the principal stations was pre-eminently favourable, owing to the clearness and dryness of the atmosphere.

On Sept. 29, 1894, there was a total eclipse of the Sun, but as its duration was brief and the zone of totality lay chiefly over the Indian Ocean, practically nothing came of it.

Things seemed, however, much more promising for the total eclipse of Aug. 9, 1896, and a very large number of observers went out to the North of Norway hoping to catch the shadow at its European end, whilst a yacht party went to Nova Zembla in the Arctic Ocean, and a few observers travelled as far as Japan. So far as the very large number of would-be observers who went from England to Norway were concerned, the eclipse was a profound disappointment, for owing to bad weather practically nothing was seen in Norway except on the West coast near Bodoe, where the weather was beautifully fine, but where no adequate preparations had been made, because nobody believed that the coast would be free from fog. Exceptionally fine weather prevailed at Nova Zembla, and the small but select party who were kindly taken there by the late Sir G. B. Powell, M.P., in his yacht, were very fortunate, and an excellent series of photographs was secured. One important result obtained at Nova Zembla was a full confirmation by Mr. Shackleton of Prof. Young's discovery in 1870 of the "Reversing Layer," a discovery which was long and vehemently disputed by Sir Norman Lockyer. Fairly successful observations were made of this eclipse in Siberia and Japan.

The last total eclipse of the Sun which has to be noticed as an accomplished fact was the "Indian Eclipse" of Jan. 22, 1898, which was very successfully seen by large numbers of people who went to India from all parts of the world. As usual in all total eclipses of the Sun nowadays, the photographers were very much to the front, and the photographs of the inner Corona, taken by the Astronomer Royal, are thought to have been probably the best that have yet been done. Amongst the miscellaneous observations made, it may be mentioned that more stars were seen during the second partial phases than during totality (a circumstance which had been noticed by Don A. Ulloa as far back as 1778). It is stated also that a mysterious object was seen between Mars and Venus by two officers of H.M.S. Melpomene, which was not put down on the published chart as a star to be looked for. The identity of this object has not been ascertained.

FOOTNOTES:

[Footnote 108: Memoirs, R.A.S., vol. x. p. 5.]

[Footnote 109: L'Annuaire, 1846, p. 303.]

[Footnote 110: Month. Not., R.A.S., vol. xx. p. 301; May 1860.]



CHAPTER XIV.

THE ELECTRIC TELEGRAPH AS APPLIED TO ECLIPSES OF THE SUN.

Amongst the auxiliary agencies which have been brought into use in recent years, to enable astronomers the better to carry out systematic observations of eclipses of the Sun, the electric telegraph occupies a place which may hereafter become prominent. As it is not likely that this little book will fall into the hands of any persons who would be able to make much use of telegraphy in connection with eclipse observations, it will not be necessary to give much space to the matter, but a few outlines will certainly be interesting. When the idea of utilising the telegraph wire first came into men's minds, it was with the object of enabling observers who saw the commencement of an eclipse at one end of the line of totality, to give cautionary notices to observers farther on, or towards the far end, of special points which had been seen at the beginning of the totality, and as to which confirmatory observations, at a later hour, were evidently very desirable. It is obvious that a scheme of this kind depends for its success upon each end (or something like it) of the line of totality being in telegraphic communication with the other end, and this involves a combination of favourable circumstances not likely to exist at every occurrence of a total eclipse, and in general only likely to prevail in the case of eclipses visible over inhabited territory, such as the two Americas, Europe, and parts of Asia. This use of the telegraph was, I think, first proposed as far back as 1878, by an American astronomer, in connection with the total eclipse of that year. His proposal fell upon sympathetic ears, with the result that arrangements were concluded with the Western Union Telegraph Company of North America for the expeditious forwarding of messages from northern stations on the eclipse line to southern stations. Some attention was being given at that time to the question of Intra-Mercurial planets, and it was thought that if by good fortune any such objects were unexpectedly found at the northern station, and observers at a southern station could be advised of the fact, there might be a better chance of procuring an accurate and precise record of the discovery. As it happened, nothing came of it on that occasion, but the idea of utilising the telegraph having once taken possession of men's minds, it was soon seen what important possibilities were opened up.

The want of telegraph organisation curiously made itself felt in the Egyptian eclipse of 1882. It is stated in another chapter of this work that during the total phase a comet was unexpectedly discovered. Now comets sometimes move very rapidly (especially when they are near the Sun), and had it been possible to have warned some observer to the E. of Egypt to look out for this comet, and had he seen it even only a couple of hours after it had been found in Egypt, some data respecting its position might have been obtained which would have permitted a rough estimate being formed of its movement through the heavens. Such an estimate might have enabled astronomers to have hunted up the comet at sunset or sunrise on the days immediately following the eclipse. As it happened, however, the comet was not seen again in 1882, and, so far as we know, may never be seen again.

It was not till 1889 that a complete organisation of a telegraph service in connection with an eclipse was accomplished. The eclipse of January 1 of that year began in the Pacific and the line of totality touched land in California, passing across North America to Manitoba. The first Californian station was at Willows, and was occupied by a party from Harvard College Observatory, who were supplied with an unusually complete equipment of photographic apparatus, together with a large camera for charting all the stars in the neighbourhood of the Sun, so as to detect an Intra-Mercurial planet if one existed. The telegraph scheme which had to be worked out was somewhat complicated, and one of the chief actors in the scene has furnished a fairly full account of what was done. First of all, a complete list of the instruments and of the work proposed to be done by them had to be prepared. The weather probabilities being everywhere very unsatisfactory, there was a possibility of all degrees of success or failure, and one thing which had to be prearranged for each station was a cypher code which should be available for all the likely combinations of instruments, weather and results. It was found that about one hundred words would suffice for the necessary code, including words which would indicate in a sufficiently precise manner the position of any new planet which a photograph might disclose.

The following, being a part of the code prescribed for use at Willows, will serve to indicate the nature of the whole scheme:—

Africa, Perfectly clear throughout the whole eclipse. Alaska, Perfectly clear during totality. Belgium, Clear sky for the partial phases, but cloudy for totality. Bolivia, Entirely cloudy throughout the whole eclipse. Brazil, Observed all the contacts. Bremen, Observed three of the contacts. Ceylon, Made observations on the shadow-bands. Chili, Observed lines of the reversing layer visually. China, The Corona showed great detail. Cork, Obtained 40-50 negatives during totality. Corsica, Obtained 50-60 negatives during totality. Crimea, Obtained 60-70 negatives during totality. Cuba, Observed a comet.

Upwards of twenty codes were prepared for the like number of stations, and the observers were to report their results at the earliest possible moment. On a rehearsal of the programme the thought occurred that the sending and reception of so many cypher messages in the ordinary course of business might lead to delays which would be productive of serious inconvenience, and that the success of the whole scheme could be only well assured if a special wire, in direct circuit from New York to the eclipse stations in turn, could be dedicated to the work. Thanks to the liberality of the Western Union Telegraph Company this privilege was secured, and a branch wire was led across from the Company's New York office to the office of the New York Herald, which journal had undertaken to be responsible for the non-astronomical part of the business.

Mrs. Todd gives the following account of the final arrangements, and of how they began to work when the moment for action arrived:—"From San Francisco every California observer was within easy telegraphic reach, and the wire thus extended by direct circuit to each eclipse station in turn. From the editorial rooms of the Herald Professor Todd was in immediate communication with any observers whom he chose to call. As previously intimated, arrangements had been made with the Harvard astronomers at Willows to receive their message first and with the utmost despatch, in order to test the feasibility of outstripping the Moon. Shortly before 5 o'clock in the afternoon despatches began to come in. Of course a slight delay was unavoidable, as the observers at the various stations were some rods distant from the local telegraph offices, and it would take a few minutes after the eclipse was over to prepare the suitable message from the cypher code. On the astronomer's table in the Herald office were a large map and a chronometer. The latter indicated exact Greenwich time, and the former showed the correct position of the Moon's shadow at the beginning of every minute by the chronometer. In this way it was possible to follow readily the precise phase of the eclipse at every station. About the rooms and accessible for immediate use were arranged the cypher codes pertaining to the several stations and other papers necessary in preparing the reports for the press. Everything being, as was supposed, in working order, New York about a quarter of an hour before totality commenced inquired of Willows the state of the weather. The answer was that the sky was getting dark, and that there were no clouds anywhere near the Sun. At that time the Moon's shadow was travelling across the open waters of the Pacific. It rapidly rushed along; totality came and went at Willows; a two minutes' glimpse of the Corona was had, and the Corona swept rapidly eastwards. After a brief interval Professor Pickering sent off from Willows a telegram which began—"Alaska, China, Corsica," and then the connection failed. The break was located somewhere between California and Utah, and more than half an hour elapsed ere the circuit was re-established, and the rest of the message received. The remainder of the thrilling incidents of that eventful day cannot possibly be better told than in Mrs. Todd's crisp and striking language[111]:—

"During this interval the lunar shadow, advancing over Montana and Dakota, had left the Earth entirely, sweeping off again into space. Still, however, the prospect that the telegraph might win the race was hopeful. Had New York been located in the eclipse path as well as Willows, with both stations symmetrically placed, the total eclipse would have become visible at New York about an hour and a quarter after the shadow had left California. Thus there was time to spare. Having recovered the wire, Professor Pickering's message was completed at 10h. 36m. [G.M.T.], the cypher translated, and the stenographer's notes were written out and despatched to the composing-room six minutes later. The "copy" was quickly put in type, and the hurried proof handed to Professor Todd at 10h. 50m., exactly an hour of absolute time after the observations were concluded. Had the Moon's shadow been advancing from California toward New York, there was still a margin of several minutes before the eclipse could become total at the latter place. In point of fact, while the proof sheet of the first message was being read, the lunar shadow would have been loitering among the Alleghanies. Man's messenger had thus outrun the Moon. The telegraphic reports of the other astronomers were gradually gathered and put in type, and the forms of the Herald were ready for the stereotyper at the proper time, some two hours after midnight. At 3 o'clock a.m. the European mails closed, and the pouches put on board the steamship Aller carried the usual copies for the foreign circulation. Within twenty-four hours after the observations of the eclipse were made near the Pacific coast, the results had been telegraphed to the Atlantic seaboard, collected and printed, and the papers were well out on their journey to European readers."

The foregoing narrative will make amply clear the future possibilities of telegraphy as a coadjutor of Astronomy in the observation of total eclipses of the Sun. And if the will and the funds are forthcoming, the eclipse of May 28, 1900, will afford an excellent opportunity of again putting to the test the excellent ideas of which our American friends worked out so successfully ten years ago. The zone of totality in that eclipse passing as it will through so many of the densely populated Southern States of North America, and then through Portugal, Spain, and Algiers, great facilities will present themselves for telegraphic combinations, if political and financial difficulties do not interfere.

FOOTNOTES:

[Footnote 111: There is a want of uniformity in Mrs. Todd's references to times which I have not thought it necessary to put straight. "Greenwich Mean Time," "Eastern U.S. Standard Time," and "Pacific Time," are all severally quoted in happy-go-lucky confusion.]



CHAPTER XV.

ECLIPSES OF THE MOON—GENERAL PRINCIPLES.

In dealing with eclipses generally, but with more especial reference to eclipses of the Sun, in a previous chapter, it was unavoidable to mix up in some degree eclipses of the Moon with those of the Sun. There are, however, distinctions between the two phenomena which make it convenient to separate them as much as possible. Eclipses of the Moon are, like those of the Sun, divisible into "partial" and "total" eclipses, but those words have a different application in regard to eclipses of the Moon from what they have when eclipses of the Sun are in question. A little thought will soon make it clear why this should be the case. A partial eclipse of the Sun results from the visible body of the Sun being in part concealed from us by the solid body of the Moon, and so in a total eclipse there is total concealment of the one object by the other.

But when we come to deal with partial and total eclipses of the Moon, the situation, is materially different. The Moon becomes invisible by passing into the dark shadow cast by the Earth into space.



Fig. 13 will make this clear without the necessity of much verbal explanation. S represents the Sun, E the Earth, and mn the orbit of the Moon. It is obvious that whilst the Moon is moving from m to n it becomes immersed in the Earth's shadow. But before actually reaching the shadow the Moon passes through a point in its orbit at which it begins to lose the full light of the Sun. This is the entrance into the "penumbra" (or "Partial shade"). Similarly, after the eclipse, when the Moon has emerged from the full shadow it does not all at once come into full sunshine, but again passes through the stage of penumbral illumination,[112] and under such circumstances (to speak in the style of Old "Oireland") the invisible Moon is very often not invisible, and the part partially eclipsed is often not eclipsed, and when the Moon is totally eclipsed it is frequently still visible. Of course the general idea involved in all cases of a body passing into the shadow of another body is that the body which so passes disappears, because all direct light is cut off from it. In the case, however, of a lunar eclipse this state of things is not always literally accomplished, and very often some residual light reaches the Moon (of course from the Sun) with the result that traces of the Moon may often be discerned. The laws which govern this matter are very ill-understood. The fact remains that if we examine a series of reports of observed eclipses of the Moon extending over many centuries (and records exist which enable us to do this) we shall find that in some instances when the Moon was "totally" eclipsed in the technical sense of that word, it was still perfectly visible, whilst during other eclipses it absolutely and entirely disappeared from view. Such eclipses are sometimes spoken of as "black" eclipses of the Moon, but the phrase is not a happy one. Many instances of both kinds will be found mentioned in the chapter on historical lunar eclipses.[113]



The different conditions of eclipses of the Moon are illustrated by Fig. 14 which must be studied with the aid of the remarks made in a former chapter concerning the apparent movements of the Sun and Moon and their nodal passages. Suffice it to state here that in Fig. 14 AB represents the ecliptic, and CD the Moon's path. The three black circles are imaginary sections of the Earth's shadow as cast when the Earth is in three successive positions in the ecliptic. If when the Earth's shadow is near A the Moon should be at E, and in Conjunction with the Earth the Moon will escape eclipse; if the Conjunction takes place with both the Earth's shadow and the Moon a little further forward, say at F, the Moon will be partially obscured; but if the Moon is at or very near its node, as at G, it will be wholly involved in the Earth's shadow and a total eclipse will be the result. In the case contemplated at G in the diagram, the Moon is concentrically placed with respect to the shadow, but the eclipse will equally be total even though the two bodies are not concentrically disposed, so long as the Moon is wholly within the cone of the Earth's shadow.[114]

Just as in the case of the Sun so with the Moon there are certain limits on the ecliptic within which eclipses of the Moon may take place, other (narrower) limits within which they must take place, and again other limits beyond which they cannot take place. Reverting to what has been said on a previous page[115] with respect to these matters when an eclipse of the Sun is in question it is only necessary to substitute for the word "Conjunction," the word "Opposition"; and for 181/2 deg. and 151/4 deg. of longitude the figures 121/2 deg. and 91/4 deg.. The limits in latitude will be 1 deg. 3' and 0 deg. 52' instead of 1 deg. 34' and 1 deg. 23'. These substitutions made, the general ideas and facts stated with regard to the conditions of an eclipse of the Sun will apply also to the one of the Moon.

It is to be noted that whereas eclipses of the Sun always begin on the W. side of the Sun, eclipses of the Moon begin on the E. side of the Moon. This difference arises from the fact that the Sun's movement in the ecliptic is only apparent (it being the Earth which really moves), whilst the Moon's movement is real.

Eclipses of the Moon, though more often and more widely visible than eclipses of the Sun, do not offer by any means the same variety of interesting or striking phenomena to the mere star-gazer, and it was long thought that they were in a certain sense of no use to science. Now, however, astronomers are inclined to utilise them for determining the diameter of the Moon by noting occultations[116] of stars by the Moon, the duration of a star's invisibility behind an eclipsed Moon being a measure of the lunar diameter when such an observation is properly transformed and "reduced." Observations of the heat radiated (or rather reflected) by an eclipsed Moon have also been made with the interesting result of showing that during an eclipse the Moon's power to reflect solar heat to the Earth sensibly declines.

The duration of an eclipse of the Moon is dependent on its magnitude. Where the eclipse is total the darkness, or what counts for such, may last for nearly 4 hours, though this is an extreme limit rarely attained. An eclipse of from 6 to 12 digits (to use the old-fashioned nomenclature which has been already explained) will continue from 21/2 to 31/2 hours. An eclipse of 3 to 6 digits will last 2 or 3 hours, and a smaller eclipse only 1 or 2 hours. The visual observations to be made in connection with partial or total eclipses of the Moon chiefly relate to the appearances presented by our satellite when immersed in the Earth's shadow. On such occasions, as has been already stated, it frequently happens that the Moon does not wholly disappear, but may be detected either with a telescope or even without one. It may exhibit either a dull grey appearance, or more commonly a pinkish-red hue to which the designation "coppery" is generally applied. Perhaps the most remarkable instance of this was the eclipse of March 19, 1848.

Mr. Forster who observed the phenomenon at Bruges thus describes[117] what he saw:—"I wish to call your attention to the fact which I have clearly ascertained, that during the whole of the late eclipse of March 19 the shaded surface presented a luminosity quite unusual, probably about three times the intensity of the mean illumination of the eclipsed lunar disc. The light was of a deep red colour. During the totality of the eclipse the light and dark places on the face of the Moon could be almost as well made out as on an ordinary dull moonlight night, and the deep red colour where the sky was clearer was very remarkable from the contrasted whiteness of the stars. My observations were made with different telescopes, but all presented the same appearance, and the remarkable luminosity struck everyone. The British Consul at Ghent, who did not know there was an eclipse, wrote to me for an explanation of the blood-red colour[118] of the Moon at 9 o'clock."

In striking contrast to this stands the total eclipse of Oct. 4, 1884, which is described by Mr. E. J. Stone[119] as "much the darkest that I have ever seen, and just before the instant of totality it appeared as if the Moon's surface would be invisible to the naked eye during totality; but such was not the case, for with the last appearance of the bright reflected sunlight there appeared a dim circle of light around the Moon's disc, and the whole surface became faintly visible, and continued so until the end of totality."

A total eclipse of the Moon which happened on January 28, 1888, was observed in many places under exceptionally favourable circumstances as regards weather. The familiar copper colour is spoken of by many observers. The Rev. S. J. Perry makes mention[120] of patches of colour even as bright as "brick red, almost orange in the brighter parts," and this, 20 minutes before the total phase began. Mr. Perry conducted on this occasion spectroscopic observations for the first time on an eclipsed Moon, but no special results were obtained.

Various explanations have been offered for these diversities of appearance. Undoubtedly they depend upon differences in the condition of the Earth's atmosphere, such as the unusual presence or unusual absence of aqueous vapour; but it cannot be said that the laws which control these diversities are by any means capable of being plainly enunciated, notwithstanding that the explanation generally in vogue dates from as far back as the time of Kepler. He suggested that the coppery hue was a result of the refraction of the Earth's atmosphere which had the effect of bending the solar rays passing through it, so that they impinged upon the Moon even when the Earth was actually interposed between the Sun and the Moon. That the outstanding rays which became visible are red may be considered due to the fact that the blue rays are absorbed in passing through the terrestrial atmosphere, just as both the eastern and western skies are frequently seen to assume a ruddy hue when illuminated in the morning or evening by the solar rays at or near sunrise or sunset.

Owing to the variable meteorological condition of our atmosphere, the actual quantity of light transmitted through it is liable to considerable fluctuations, and no wonder therefore that variations occur in the appearances presented by the Moon during her immersion in the Earth's shadow.

It has been suggested that if the portion of the Earth's atmosphere through which the Sun's rays have to pass is tolerably free from aqueous vapour, the red rays will be almost wholly absorbed, but not the blue rays; and the resulting illumination will either only render the Moon's surface visible with a greyish blue tinge, or not visible at all. This will yield the "black eclipse"—to recall the phrase quoted elsewhere. If, on the other hand, the region of the Earth's atmosphere through which the Sun's rays pass be highly saturated, it will be the blue rays which suffer absorption, whilst the red rays will be transmitted and will impart a ruddy hue to the Moon. Finally, if the Earth's atmosphere is in a different condition in different places, saturated in some parts and not in others, a piebald sort of effect will be the result, and some portions of the Moon's disc will be invisible, whilst others will be more or less illuminated. Further illustrations of all these three alternatives will be found amongst the eclipses of the Moon recorded in the chapter[121] devoted to historical matters.

A few instances are on record of a curious spectacle connected with eclipses of the Moon which must have a word of mention. I refer to the simultaneous visibility of the Sun and the Moon above the horizon, the Moon at the time being eclipsed. At the first blush of the thing this would seem to be an impossibility, remembering that it is a cardinal principle of eclipses, both of the Sun and of the Moon, that the three bodies must be in the same straight line in order to constitute an eclipse. The anomalous spectacle just referred to is simply the result of the refraction exercised by the Earth's atmosphere. The setting Sun which has actually set has apparently not done so, but is displaced upwards by refraction. On the other hand, the rising Moon which has not actually risen is displaced upwards by refraction and so becomes, as it were, prematurely visible. In other words, refraction retards the apparent setting of one body, the Sun, and accelerates the apparent rising of the other body, the Moon. The effect of these two displacements will be to bring the two bodies closer by more than 1 deg. of a great circle than they really are, this being the conjoint amount of the double displacements due to refraction.

Amateur observers of eclipses of the Moon will find some pleasure, and profit as well, in having before them on the occasion of an eclipse a picture of the Moon's surface in diagrammatic form with a few of the principal mountains marked thereon; and then watching from time to time (say by quarters of an hour) the successive encroachments of the Earth's shadow on the Moon's surface and the gradual covering up of the larger mountains as the shadow moves forward. The curved lines represent the gradual progress of the shadow during the eclipse named. This diagram, ignoring the curved lines actually marked on it, may be used over and over again for any number of eclipses, simply noting from the Nautical Almanac or other suitable ephemerides the points on the Moon's disc at which the shadow first touches the disc as it comes on, and last touches the disc as it goes off. The Almanac indicates these points by stating that the eclipse begins, or ends, as the case may be, at a point which is so many degrees from the N. point of the Moon measured round the Moon's circumference by the E. or by the W. as the case may be.