The application of the spectroscope to observations of eclipses of the Sun demands a few words of notice in this place, but it would not be consistent with the plan of this work to go into details. Though the spectroscope has been applied under many different circumstances to different parts of the Sun’s surroundings in connection with total eclipses yet it is in regard to the Corona that most has been done and most has been discovered. The substance of the discoveries made is that the Corona shines with an intrinsic light of its own, that is to say, that it is composed of constituents whose temperature is sufficiently elevated to be self-luminous. These constituents are chiefly hydrogen; the body which corresponds to the line D3 (of Fraunhofer’s scale), and which has been named “Helium”; and the body which corresponds to the bright green line 1474 of Kirchoff’s scale and which, since its existence was first suspected and then assured, has been named “Coronium.”

The reader will not be surprised to learn, from what has gone before, that an immense mass of records have accumulated respecting the appearance of the Corona. Correspondingly numerous and divergent are the theories which have been launched to explain the observations made. One thing is in the highest degree probable, namely, that electricity is largely concerned.

Going back to the question of Sun-spots regarded in their possible or probable association with the Corona, the present position of matters appears to be this: that there is a real connection between the general form of the Corona and disturbances on the Sun, taking Sun-spots as an indication of solar activity. When Sun-spots are at or near their maximum, the Corona has generally been somewhat symmetrical, with synclinal groups of rays making angles of 45° with its general axis. On the other hand, at the epochs of minimum Sun-spots, the Corona shows polar rifts much more widely open, with synclinal zones making larger angles with the axis, and being, therefore, more depressed towards the equatorial regions, in which, moreover, there is usually a very marked extension of Coronal matter in the form of elongated streamers reaching to several diameters of the Sun.

This generalisation is well borne out by the maximum-epoch Coronas of 1870 and 1871, and the minimum-epoch Coronas of 1867, 1874, 1875, 1878, and perhaps 1887, and certainly 1889. On the other hand, the eclipses of 1883, 1885 and 1886 do not strikingly confirm this theory. The eclipse of 1883 was at a time of rapidly decreasing solar activity, yet the Corona had the features of a Sun-spot maximum. The same, though in a somewhat less degree, may be said of the eclipses of 1885 and 1886. At the times of both of these eclipses the solar activity was decreasing.

The forthcoming eclipse of 1900 will nearly coincide with a Sun-spot minimum, and if the above conclusions are well founded the Corona in 1900 should resemble that of 1889, and be characterised by, amongst other things, some very elongated groups of rays extending in nearly opposite directions.

We are still a long way off from being able to state with perfect confidence what the Corona is. It is certainly a complex phenomenon, and the various streamers which we see are not, as was at one time imagined, a simple manifestation of one radiant light. Mrs. Todd thus conveniently summarises the present state of our knowledge:—“The true corona appears to be a triple phenomenon. First, there are the polar rays, nearly straight throughout their visible extent. Gradually, as these rays start out from points on the solar disc farther and farther removed from the poles, they acquire increasing curvature, and very probably extend into the equatorial regions, but are with great difficulty traceable there, because projected upon and confused with the filaments having their origin remote from the poles. Then there is the inner equatorial corona, apparently connected intimately with truly solar phenomena, quite like the polar rays; while the third element in the composite is the outer equatorial corona, made up of the long ecliptic streamers, for the most part visible only to the naked eye, also existing as a solar appendage, and possibly merging into the zodiacal light. The total eclipses of a half century have cleared up a few obscurities, and added many perplexities. There is little or no doubt about the substantial, if not entire, reality of the corona as a truly solar phenomenon. The Moon, if it has anything at all to do with the corona, aside from the fact of its coming in conveniently between Sun and Earth, so as to allow a brief glimpse of something startlingly beautiful which otherwise could never have been known, is probably responsible for only a very narrow ring of the inner radiance of pretty even breadth all round. This diffraction effect is accepted; but the problem still remains how wide this annulus may be, and whether it may vary in width from one eclipse to another. These questions once settled, the spurious structure may then be excerpted from the true. Indeed the coronal streamers, delicately curving and interlacing, may tell the whole story of the Sun’s radiant energy.”

CHAPTER VII.

WHAT IS OBSERVED AFTER THE TOTAL PHASE OF AN ECLIPSE OF THE SUN IS AT AN END.

In a certain sense, a description of the incidents which precede the total disappearance of the Sun in connection with a total Eclipse will apply more or less to the second half of the phenomenon; only, of course, in the reverse order and on the opposite side of the compass. The Corona having appeared first of all on the W. side of the Sun, then having shown itself complete as surrounding the Sun, will begin to disappear on the W. side, and will be last seen on the E. side. Baily’s Beads may or may not come into view; the Sun will reappear first as a very thin crescent, gradually widening; the quasi-nocturnal darkness visible on the Earth will cease, and eventually the Moon will completely pass away from off the Sun, and the Sun once again will exhibit a perfect circle of light.

Whilst there is so much to look for and look at and think about, one thing must be sought for instantly after totality, or it will be gone for ever, and that is the Moon’s shadow on the Earth. We have already seen in the last chapter the startling rapidity and solemnity with which the shadow seems to rush forward to the observer from the horizon on the western side of the Meridian. Passing over him, or even, so to speak, through him, it travels onwards in an easterly direction and very soon vanishes. Its visibility at all depends a good deal upon whether the observer, who is looking for it, is sufficiently raised above the adjacent country to be able to command at least a mile or two of ground. If he is in a hollow, he will have but little chance of seeing the shadow at all: on the other hand, if he is on the top of a considerable hill (or high up on the side of a hill), commanding the horizon for a distance of 10 or 20 miles, he will have a fair chance of seeing the shadow. Sir G. B. Airy states, in 1851, “My eye was caught by a duskiness in the S.E., and I immediately perceived that it was the Eclipse-shadow in the air, travelling away in the direction of the shadow’s path. For at least six seconds, this shadow remained in sight, far more conspicuous to the eye than I had anticipated. I was once caught in a very violent hail and thunder-storm on the Table-land of the County of Sutherland called the “Moin,” and I at length saw the storm travel away over the North Sea; and this view of the receding Eclipse-shadow, though by no means so dark, reminded me strongly of the receding storm. In ten or twelve seconds all appearance of the shadow had passed away.”

Perhaps this may be a convenient place to make a note of what seems to be a fact, partly established at any rate, even if not wholly established, namely—that there seems some connection between eclipses of the Sun and Earthquakes. A German physicist named Ginzel[18] has found a score of coincidences between solar eclipses and earthquakes in California in the years between 1850 and 1888 inclusive. Of course there were eclipses without earthquakes and earthquakes without eclipses, but twenty coincidences in thirty-eight years seems suggestive of something.

CHAPTER VIII.

ECLIPSES OF THE SUN MENTIONED IN HISTORY—CHINESE.

This is the first of several chapters which will be devoted to historical eclipses. Of course the total eclipse of the Sun of August 9, 1896, observed in Norway and elsewhere, is, in a certain sense, an eclipse mentioned in history, but that is not what is intended by the title prefixed to these chapters. By the term “historical eclipses,” as used here, I mean eclipses which have been recorded by ancient historians and chroniclers who were not necessarily astronomers, and who wrote before the invention of the telescope. The date of this may be conveniently taken as a dividing line, so that I shall deal chiefly with eclipses which occurred before, say, the year 1600. There is another reason why some such date as this is a suitable one from which to take a new departure. Without at all avowing that superstition ceased on the Earth in the year 1600 (for there is far too large a residuum still available now, 300 years later), it may yet be said that the Revival of Letters did do a good deal to divest celestial phenomena of those alarming and panic-causing attributes which undoubtedly attached to them during the earlier ages of the world and during the “Dark Ages” in Western Europe quite as much as during any other period of the world’s history. No one can examine the writings of the ancient Greek and Roman historians, and the chronicles kept in the monasteries of Western Europe by their monkish occupiers, without being struck by the influence of terror which such events as eclipses of the Sun and Moon and such celestial visitors as Comets and Shooting Stars exercised far and wide. And this influence overspread, not only the unlettered lower orders, but many of those in far higher stations of life who, one might have hoped, would have been exempt from such feelings of mental distress as they often exhibited. Illustrations of this fact will be adduced in due course.

It has always been supposed that the earliest recorded eclipse of the Sun is one thus mentioned in an ancient Chinese classic—the Chou-King (sometimes spelt Shou-Ching). The actual words used may be translated:—“On the first day of the last month of Autumn the Sun and Moon did not meet harmoniously in Fang.” To say the least of it, this is a moderately ambiguous announcement, and Chinese scholars, both astronomers and non-astronomers, have spent a good deal of time in examining the various eclipses which might be thought to be represented by the inharmonious meeting of the Sun and the Moon as above recorded. To cut a long story short, it is generally agreed that we are here considering one or other of two eclipses of the Sun which occurred in the years 2136 or 2128 B.C. respectively, the Sun being then in the sidereal division “Fang,” a locality determined by the stars β, δ, π, and ρ Scorpii, and which includes a few small stars in Libra and Ophiuchus to the N. and in Lupus to the S. How this simple and neat conclusion, which I have stated with such apparent dogmatism, was arrived at is quite another question, and it would hardly be consistent with the purpose of this volume to attempt to work it out in detail, but a few points presented in a summary form may be interesting.

In the first place, be it understood, that though it is fashionable to cast ridicule on John Chinaman, especially by way of retaliation for his calling us “Barbarians,” yet it is a sure and certain fact that not only have the Chinese during many centuries been very attentive students of Astronomy, but that we Westerns owe a good deal of our present knowledge in certain departments to the information stored up by Chinese observers during many centuries both before and after the Christian Era.

This, however, is a digression. The circumstances of this eclipse as regards its identification having been carefully examined by Mr. R. W. Rothman,[19] in 1839 were further reviewed by Professor S. M. Russell in a paper published in the proceedings of the Pekin Oriental Society.[20] The substance of the case is that in the reign of Chung-K’ang, the fourth Emperor of the Hsia Dynasty, there occurred an eclipse of the Sun, which is interesting not only for its antiquity, but also for the dread fate of the two Astronomers Royal of the period, who were taken by surprise at its occurrence, and were unprepared to perform the customary rites. These rites were the shooting of arrows and the beating of drums, gongs, etc., with the object of delivering the Sun from the monster which threatened to devour it. The two astronomers by virtue of their office should have superintended these rites. They were, however, drunk and incapable of performing their duties, so that great turmoil ensued, and it was considered that the land was exposed to the anger of the gods. By way of appeasing the gods, and of suitably punishing the two State officials for their neglect and personal misconduct, they were forthwith put to death, a punishment which may be said to have been somewhat excessive, in view of the fact that the eclipse was not a total but only a partial one. An anonymous verse runs:—

It appears beyond all reasonable doubt that the eclipse in question occurred on October 22, 2136 B.C. The preliminary difficulties to be got over in arriving at the date arose from the fact that there was an uncertainty of 108 years in the date when the Emperor Chung-K’ang ascended the throne; and within these limits of time there were 14 possible years in which an eclipse of the Sun in Fang could have occurred. Then the number was further limited by the necessity of finding an eclipse which could have been seen at the place which was the Emperor’s capital. The site of this, again, was a matter of some uncertainty. However, step by step, by a judicious process of exhaustion, the year 2136 B.C. was arrived at as the alternative to the previously received date of 2128 B.C. Considering that we are dealing with a matter which happened full 4000 years ago, it may fairly be said that this discrepancy is not perhaps much to be wondered at, seeing what disputes often happen nowadays as to the precise date of events which may have occurred but a few years or even a few months before the controversy springs up.

Professor Russell says that:—“Some admirers of the Chinese cite this eclipse as a proof of the early proficiency attained by the Chinese in astronomical calculations. I find no ground for that belief in the text. Indeed, for many centuries later, the Chinese were unable to predict the position of the Sun accurately among the stars. They relied wholly on observation to settle their calendar, year by year, and seem to have drawn no conclusions or deductions from their observations. Their calendar was continually falling into confusion. Even at the beginning of this dynasty, when the Jesuits came to China, the Chinese astronomers were unable to calculate accurately the length of the shadow of the Sun at the equinoxes and solstices. It seems to me therefore very improbable that they could have been able to calculate and predict eclipses.”

I am not at all sure that this is quite a fair presentation of the case. I do not remember ever to have seen the power to predict eclipses ascribed to the Chinese, but it is a simple matter of fact that we owe to them during many centuries unique records of a vast number of celestial phenomena. Their observations of comets may be singled out as having been of inestimable value to various 19th-century computers, especially E. Biot and J. R. Hind.

The second recorded eclipse of the Sun would seem to be also due to the Chinese. Confucius relates that during the reign of the Emperor Yew-Wang an eclipse took place. This Emperor reigned between 781 B.C. and 771 B.C., and it has been generally thought that the eclipse of 775 B.C. is the one referred to, but Johnson doubts this on the ground that this eclipse was chiefly visible in the circumpolar regions, and if seen at all in China must have been of very small dimensions. He leans to the eclipse of June 4, 780 B.C. as the only large one which happened within the limits of time stated above.

An ancient Chinese historical work, known as the Chun-Tsew, written by Confucius, makes mention of a large number of solar eclipses which occurred before the Christian Era. This work came under the notice of M. Gaubil, one of the French Jesuit missionaries who laboured in China some century and a half ago, and he first gave an account of it in his Traité de la Chronologie Chinoise, published at Paris in 1770.[21]

The Chun-Tsew is said to be the only work really written by Kung-Foo-Tze, commonly known as Confucius, the other treatises attributed to him having been compiled by disciples of his either during his life-time or after his decease. The German chronologist, Ideler, was acquainted with this work, and in a paper of his own, presented to the Berlin Academy, remarked:—“What gives great interest to this work is the account of 36 solar eclipses observed in China, the first of which was on Feb. 22, 720 B.C., and the last on July 22, 495 B.C.”

In 1863 Mr. John Williams, then Assistant Secretary of the Royal Astronomical Society, communicated to the Society in a condensed form the particulars of these eclipses as related in Confucius’s book, together with some remarks on the book itself. The Chun-Tsew treats of a part of the history of the confederated nations into which China was divided during the Chow Dynasty, that is between 1122 B.C. and 255 B.C. The particular period dealt with is that which extended from 722 B.C. to 479 B.C. It was during the latter part of this interval of about 242 years that Confucius flourished. But the book is not quite a general history for it is more particularly devoted to the small State of Loo of which Confucius was a native, where he passed a great portion of his life, and where he was advanced to the highest honours. It contains the history of twelve princes of this State with incidental notices of the other confederated nations. The number of the years of each reign is accurately determined, and the events are classed under the years in which they occurred. Each year is divided into sections according to the four seasons, Spring, Summer, Autumn, Winter, and the sections are subdivided into months, and often the days are distinguished. The name Chun-Tsew is said to have been given to this work from its having been commenced in Spring and finished in Autumn, but Williams thinks that the name rather refers to the fact that its contents are divided into seasons as stated. The style in which it is written is very concise, being a bare mention of facts without comment, and although on this account it might appear to us dry and uninteresting, it is much valued by the Chinese as a model of the ancient style of writing. It forms one of the Woo-King or Five Classical Books, without a thorough knowledge of which, and of the Sze-Shoo or Four Books, no man can attain to any post of importance in the Chinese Empire.

The account of each eclipse is but little more than a brief mention of its occurrence at a certain time. The following is an example of the entries:—“In the 58th year of the 32nd cycle in the 51st year of the Emperor King-Wang, of the Chow Dynasty, the 3rd year of Yin-Kung, Prince of Loo, in the spring, the second moon, on the day called Kea-Tsze, there was an eclipse of the Sun.” This 58th year of the 32nd cycle answers to 720 B.C. Mr. Williams in the year 1863 presented to the Royal Astronomical Society a paper setting out the whole of the eclipses of which I have cited but one example, converting, of course, the very complicated Chinese dates into European dates.

These Chinese records of eclipses were in 1864 subjected to examination by the late Sir G. B. Airy,[22] with results which were highly noteworthy, and justify us in reposing much confidence in Chinese astronomical work. Airy remarks:—“The period through which these eclipses extend is included in the time through which calculations of eclipses have been made in the French work entitled L’Art de vérifier les Dates. I have several times had occasion to recalculate with great accuracy eclipses which are noted in that work (edition of 1820), and I have found that, to the limits of accuracy to which it pretends, and which are abundantly sufficient for the present purpose, it is perfectly trustworthy. I have therefore made a comparison of the Chun-Tsew eclipses with those of L’Art de vérifier les Dates. The result is interesting. Of the 36 eclipses, 32 agree with those of the Art de vérifier les Dates, not only in the day, but also in the general track of the eclipse as given in the Art de vérifier, which appears to show sufficiently that the eclipse would be visible in that province of China to which the Chun-Tsew is referred.” Airy then proceeds to point out that, with regard to the four eclipses which he could not confirm, there cannot have been eclipses in April 645 B.C. or in June 592 B.C. It appears, however, from a note by Williams, that the date attached to the eclipse of 645 B.C. is, in reality, an erroneous repetition (in the Chinese mode of expressing it) of that attached to the next following one, and in the absence of correct date it must be rejected. In the record of 592 B.C., June 16, no clerical error is found, and there must be an error of a different class. The eclipses of 552 B.C., September 19, and 549 B.C., July 18, to which there is nothing corresponding in the Art de vérifier, are in a different category. These occur in the lunations immediately succeeding 552 B.C., August 20, and 549 B.C., June 19, respectively, and there is no doubt that those which agree with the Art de vérifier were real eclipses. Now there cannot be eclipses visible at the same place in successive lunations, because the difference of the Moon’s longitudes is about 29°, and the difference of latitudes is therefore nearly 3°, which is greater than the sum of the diameters of the Sun and Moon increased by any possible change of parallax for the same place. These, therefore, were not real eclipses. It seems probable that the nominal days were set down by the observer in his memorandum book as days on which eclipses were to be looked for. Airy conjectured that the eclipses of 552 B.C., August 20, and 549 B.C., June 19, were observed by one and the same person, and that he possessed science enough to make him connect the solar eclipses with the change of the Moon, but not enough to give him any idea of the limitations to the visibility of an eclipse.

On a subsequent occasion Mr. Williams laid before the Society a further list of solar eclipses observed in China, and extending from 481 B.C. to the Christian Era. He collected these from a Chinese historical work, entitled Tung-Keen-Kang-Muh. This work, which runs to 101 volumes, contains a summary of Chinese history from the earliest times to the end of the Yuen Dynasty, A.D. 1368, and was first published about 1473. The copy in Mr. Williams’s possession was published in 1808. The text is very briefly worded, and consists merely of an account of the accessions and deaths of the emperors and of the rulers of the minor states, with some of the more remarkable occurrences in each reign. The appointments and deaths of various eminent personages are also noticed, together with special calamities such as earthquakes, inundations, storms, etc. The astronomical allusions include eclipses and comets. Amongst the eclipses are also all, or most of those which are recorded in the Chun-Tsew as having occurred prior to 479 B.C. Though no particular expressions are used to define the exact character of the eclipses, it is to be presumed that some of them must have been total, because it is stated that the stars were visible, albeit that seemingly in only one instance is a word attached which specifically expresses the idea of totality. Here again all the dates were expressed in Chinese style, but, as published by Williams, were rendered, as before, in European style by aid of chronological tables, published about 1860 in Japan. Mr. Williams, in his second paper, from which I have been quoting, states that he brought his published account down to the Christian Era only as a matter of convenience, but that he had in hand a further selection of eclipses from the Tung-Keen-Kang-Muh, the interval from the Christian Era to the 4th century A.D. yielding nearly 100 additional eclipses. This further transcript has not yet been published, but remains in MS. in the Library of the Royal Astronomical Society. Mr. Williams died in 1874 at the age of 77, one of the most experienced Chinese scholars of the century.

It is remarkable that none of the Chinese annals to which reference has been made include any mention of eclipses of the Moon; but the records of Comets are exceedingly numerous and, as I have already stated, have proved of the highest value to astronomers who have been called upon to investigate the ancient history of Comets.

CHAPTER IX.

ARE ECLIPSES ALLUDED TO IN THE BIBLE?

An interesting question has been suggested: Are there any allusions to eclipses to be found in Holy Scripture? It seems safe to assert that there is at least one, and that there may be three or four.

In Amos viii. 9 we read:—“I will cause the Sun to go down at noon, and I will darken the Earth in the clear day.” This language is so very explicit and applies so precisely to the circumstances of a solar eclipse that commentators are generally agreed that it can have but one meaning;[23] and accordingly it is considered to refer without doubt to one or other of the following eclipses:—791 B.C., 771 B.C., 770 B.C., or 763 B.C. Archbishop Usher,[24] the well-known chronologist, suggested the first three more than two centuries ago, whilst the eclipse of 763 B.C. was suggested in recent times and is now generally accepted as the one referred to. The circumstances connected with the discovery and identification of the eclipse of 763 B.C. are very interesting.

The date when Amos wrote is set down in the margin of our Bibles as 787 B.C. and if this date is correct it follows that for his statement to have been a prediction he must be alluding to some eclipse of later date than 787 B.C. This obvious assumption not only shuts out the eclipse of 791 B.C., but opens the door to the acceptance of the eclipse of 763 B.C.

Apparently the first modern writer who looked into the matter after Archbishop Usher was the German commentator Hitzig who suggested the eclipse of Feb. 9, 784 B.C. Dr. Pusey was so far taken with this idea that he thought it worth while to secure the co-operation of the Rev. R. Main, F.R.A.S., the Radcliffe Observer at Oxford, for the purpose of a full investigation. Mr. Main had the circumstances of that eclipse calculated, with the result that though the eclipse was indeed total in Africa and Hindostan, yet at Samaria it was only partial and of no considerable magnitude. Dr. Pusey’s words, summing up the situation are:—“The eclipse then would hardly have been noticeable at Samaria, certainly very far indeed from being an eclipse of such magnitude, as could in any degree correspond with the expression, ‘I will cause the Sun to go down at noon.’” ... “Beforehand, one should not have expected that an eclipse of the Sun, being itself a regular natural phenomenon, and having no connection with the moral government of God, should have been the subject of the prophet’s prediction. Still it had a religious impressiveness then, above what it has now, on account of that wide-prevailing idolatry of the Sun. It exhibited the object of their false worship, shorn of its light, and passive.”

Dr. Pusey’s Commentary from which the above quotation is made[25] bears the date 1873, but he appears not to have been acquainted with the important discovery announced no less than six years previously by the distinguished Oriental scholar, Sir H. C. Rawlinson. The discovery to which I allude is a contemporary record on an Assyrian tablet of a solar eclipse which was seen at Nineveh about 24 years after the reputed date of Amos’s prophecy. This tablet had been described by Dr. Hinckes in the British Museum Report for 1854 but its chronological importance had not then been realised. Sir H. Rawlinson[26] speaks of the tablet as a record of or register of the annual archons at Nineveh. He says:—“In the eighteenth year before the accession of Tiglath-Pileser there is a notice to the following effect—‘In the month Sivan an eclipse of the Sun took place’ and to mark the great importance of the event a line is drawn across the tablet although no interruption takes place in the official order of the Eponymes. Here then we have notice of a solar eclipse which was visible at Nineveh which occurred within 90 days of the (vernal) equinox (taking that as the normal commencement of the year) and which we may presume to have been total from the prominence given to the record, and these are conditions which during a century before and after the era of Nabonassar are alone fulfilled by the eclipse which took place on June 15, 763.”

This record was submitted to Sir G. B. Airy and Mr. J. R. Hind, and the circumstances of the eclipse were computed by the latter, by the aid of Hansen’s Lunar Tables and Le Verrier’s Solar Tables. The result, when plotted on a map, showed that the shadow line just missed the site of Nineveh, but that a very slight and unimportant deviation from the result of the Tables would bring the shadow over the city of Nineveh where the eclipse was observed, and over Samaria where it was predicted. The identification of this eclipse, both as regards its time and place, has also proved a matter of importance in the revision of Scripture chronology, by lowering, to the extent of 25 years, the reigns of the kings of the Jewish monarchy. The need for this revision is further confirmed, if we assume that the celebrated incident in the life of King Hezekiah, described as the retrogradation of the Sun’s shadow on the dial of Ahaz, is to be interpreted as connected with a partial eclipse of the Sun.

We will now consider this event, and see what can be made out of it. One Scripture record (2 Kings xx. 11) is as follows:—“And Isaiah the prophet cried unto the Lord: and he brought the shadow ten degrees backward, by which it had gone down in the dial of Ahaz.” This passage has greatly exercised commentators of all creeds in different ages of the Church; and the most divergent opinions have been expressed as to what happened. This has been due to two causes jointly. Not only is the occurrence incomprehensible, looked at on the surface of the words, but we are entirely ignorant of the construction of the so-called “dial” of Ahaz, and have little or no material directly available from outside sources to enable us to come to a clear and safe conclusion. No doubt, however, it was a sun-dial, or gnomon of some kind. Bishop Wordsworth lays stress on the apparent assertion that the miracle was not wrought on any other dial at Jerusalem except that of Ahaz, the father of Hezekiah, and he treats as a confirmation of this the statement in 2 Chron. xxxii. 31, that ambassadors came from Babylon to Jerusalem, being curious to learn all about “the wonder that had been done in the land” (i.e. in the land of Judah). But there is more taken for granted here than is necessary, or, as we shall presently see, is justifiable. To begin with, how do we know that there was any other dial at Jerusalem like that of Ahaz? But, in point of fact, we must make a new departure altogether, for it has been suggested (I know not exactly by whom, or when for the first time) that an eclipse of the Sun, under certain circumstances, would explain all that happened, and reconcile all that has to be reconciled. What happened to Hezekiah is thought by many to imply clearly a miracle, and it may be said that an eclipse of the Sun cannot be held to be a miracle[27] by the ordinary definition of the word. But, on the other hand, it certainly might count as such in the eyes of ignorant spectators, who know nothing of the theory or practice of eclipses, and who would regard such a thing as quite unforeseen, unexpected, and alarming. Illustrations of this might be multiplied from all parts of the world, in all ages of the world’s history.

Let us see now what the argument is, as it was worked out by the late Mr. J. W. Bosanquet, F.R.A.S. Shortly before the invasion of Judæa by Sennacherib—say in the beginning of the year 689 B.C.—Hezekiah was sick unto death. In answer to his fervent prayer for recovery the prophet Isaiah was sent to him with this message:—“Thus saith the Lord, the God of David thy Father, I have heard thy prayer, I have seen thy tears; behold, I will add unto thy days fifteen years ... and I will defend this city, and this shall be a sign unto thee from the Lord, that the Lord will do this thing that He hath spoken. Behold, I will bring again the shadow of the degrees, which is gone down in the sun-dial of Ahaz ten degrees backward. So the Sun returned ten degrees, by which degrees it had gone down.” (Isaiah xxxviii. 5-8).

In these words we evidently have mention of some instrument erected in Hezekiah’s palace, in the days of his father Ahaz, for showing the change in the position of the shadow cast by the Sun from day to day. This statement is confirmed by a profane writer, Glycas, who states: “They say that Ahaz, by some contrivance, had erected in his palace certain steps, which showed the hours of the day, and also measured the course of the Sun.”

The idea involved in “bringing again,” through “ten degrees backward,” “the shadow of the degrees” which had gone down, is very noteworthy. We seem intended to learn from these words several things. For one thing (to begin with) that the steps (as we must consider them to have been) on this sun-dial of Ahaz, were turned away from the Sun. For only in that position could they cast their shadow, or could the number of the illuminated steps be varied, upwards or downwards, according to the varying altitude of the sun. The only conceivable use of a fixed instrument so placed would be to show the rise and fall of the shadow from day to day, as the Sun on the meridian gradually rose higher between mid-winter and mid-summer, or descended lower between mid-summer and mid-winter, in passing of course through the winter and summer solstices in turn. No simple motion of the Sun in its ordinary diurnal progress would produce the effect described. On the other hand, it is equally clear that the shadow cast by a gnomon properly adjusted at the head of such a series of steps would travel upwards and downwards upon the steps “with the Sun,” from winter to summer and from summer to winter, indicating at each noon the meridian altitude of the Sun from day to day, the latitude of Jerusalem being 31° 47′, and the Sun’s altitude there on the shortest day being 34° 41′. If the gnomon were raised above the topmost step so as to bring the tip of the gnomon or any aperture in it so much above the step as would be the equivalent of 2° 54′ or slightly more, then the top of the shadow of the gnomon (or a spot of light passing through a hole in it) would, on the shortest day of the year, fall just beyond the lowermost step. An instrument constructed on the principle just set forth was known to and used by the Greek astronomers of antiquity under the name of a Sciotheron or shadow-taker. Sometimes, and perhaps more properly, it was called a Heliotropion, that is, an instrument designed to indicate the turning of the Sun at the Tropics.[28] This, be it remembered, was information needed by the ancients for the correct regulation of the seasons of the year, and of special service to the Jews whose greater festivals were fixed in connection with the seasons. There is reason to believe that instruments of this character were of early invention, going back perhaps to the times of Homer, for we find a passage in the Odyssey, (xv. 403) as follows:—

Pope’s rendering of this passage fails, however, to bring out the salient idea involved. Butcher and Lang translate the passage thus:—“There is a certain isle called Syria, if haply thou hast heard tell of it, over above Ortygia, and there are the turning-places of the Sun.” Merry[29] calls these island names mere “inventions of the poet.” It seems to me a great question whether Homer’s words really support the statement I have made just before quoting it.

Diogenes Laërtius refers to this same instrument when he speaks of the Heliotropion preserved in the Island of Syra.[30]

According to Laërtius, Anaximander[31] was the first Greek to use gnomons, which he placed on the Sciothera of Lacedæmon, for the express purpose of indicating the Tropics and Equinoxes. These Sciothera were pyramidal in form.

An obelisk was the simplest, though an imperfect form of Heliotropion, marking indistinctly the length of a shadow at different times of the year, especially the extremes of length and shortness at mid-winter and mid-summer. It is perhaps interesting to mention that travellers have recorded, in various places, various devices for furnishing information respecting these matters. For instance, in Milan Cathedral the meridian line is marked on the pavement, and along this line, an image of the Sun coming through an aperture in the southern wall travels backwards and forwards during the year according to the seasons. Some Jesuit missionaries who visited China about the middle of the last century, noticed a device of this character in operation at the Observatory at Pekin. A gnomon had been set up in a low room and one of the missionaries, M. Le Comte, describes in the following words what they saw in connection with this gnomon:—“The aperture through which the rays of the Sun came was about 8 ft. above the floor; it is horizontal and formed of two pieces of copper, which may be turned so as to be farther from, or closer to, each other to enlarge or contract the aperture. Lower was a table with a brass plate in the middle on which was traced a meridian line 15 ft. long, divided by transverse lines which are neither finished nor exact. All round the table there are small channels to receive the water, whereby it is to be levelled.”[32]

All this may seem rather a digression, and so it is, but I am following Mr. Bosanquet herein in order the better to justify the argument that it was an eclipse of the Sun which marked the important incident in Hezekiah’s life which has been handed down to us by the sacred writer. It is evident that if a flight of steps were erected on the principles which were set forth above, the steps sloping upwards and southwards (for the Northern Hemisphere) from the lowest step to within a few inches below an aperture in the gnomon suitably arranged, the ray or image of the Sun, whichever it was, would travel day by day up and down such steps between solstice and solstice. We may conclude, therefore, that the instrument which Hezekiah gazed at, and which is called in Scripture, the “Dial” of Ahaz, was what the Greeks would have termed a Heliotropion.

The historian’s record is to the effect that on the day of Hezekiah’s recovery an extraordinary motion of the shadow was observed on the “Steps of Ahaz” by the rising of the shadow “ten steps” from the point to which it had “gone down with the Sun.” This effect is spoken of not as a miracle but as “a sign.” It should also be remembered that the cure of Hezekiah was effected not by a miracle but by a simple application of a lump of figs. The promise of his recovery was confirmed by the motion of the shadow as already stated. We are justified, therefore, in looking for some ordinary natural phenomenon by which to account for this peculiar motion on the dial, and something miraculous is not essential. Dean Milman once suggested that the effect might have been produced “by a cloud refracting the light.” No doubt a dark cloud might produce an apparent interference with the shadow, but it is well pointed out by Bosanquet that such a cause as a cloud would have been so manifest to everyone, and the effect so transient, that the phenomenon could hardly have been referred to afterwards as it was in another place as “a wonder that was done in the land.” (2 Chron. xxxii. 31).

It becomes, therefore, alike an obvious and a simple explanation that a shadow caused by the Sun might be deflected downwards on such an instrument with a regular and steady motion by the Moon passing slowly over the upper part of the Sun’s disc, as Sun and Moon both approached the meridian.

The critical question has now to be raised: “Can astronomers inform us whether a considerable eclipse of the Sun occurred at the beginning of the year 689 B.C. anywhere near noon and which was visible at Jerusalem?” And the answer to this it is interesting to be able to say is a plain and distinct affirmative. There was a large partial eclipse of the Sun on January 11, 689 B.C., about 11.30 A.M., and it was the upper limb which underwent eclipse.

This eclipse fulfils all the requirements of the case, both from the historian’s and the astronomer’s point of view. It occurred about the year fixed by Demetrius as that of Hezekiah’s illness: it occurred while the Sun was approaching and actually passing the meridian; the obscuration was on that part of the Sun’s disc (namely the upper part) which would have had the effect of causing the point of light, which would seem to emanate from the Sun, to appear to be depressed downwards; and it was visible at Jerusalem. But there still remains for consideration the final and most important question, “Would a deflection of light proceeding from the Sun, regarded as a moving body, be capable of affecting, to the extent of ‘ten steps,’ the shadow on such an instrument as has been described?” And arising out of this, there is the subordinate question, “Would January, being the month when this eclipse certainly occurred, also be a month suitable for the exhibition of such a phenomenon?”

It is ascertainable by calculation that the time occupied by the Moon in passing over the Sun, in the way it did during this eclipse, was about 2½ hours. But from the time of central conjunction, when the obscuration was the greatest and the point of light depressed the most, to the time when the uppermost portion of the Sun’s disc was released by the eastward motion of the Moon, and the light from that uppermost portion was again manifest, was about 20 minutes, and this, therefore, was the time during which the phenomenon of retrogression on the “steps” would have been exhibited to the King’s eyes. Assuming then that the time when the ascending shadow had travelled upwards to the tenth step coincided, or nearly so, with the time when the Sun had reached its highest altitude for the day, at noon, we infer that the time of central conjunction during this eclipse was not later than from 20 to 15 minutes before noon. It could not have been much earlier, because the phenomenon of the resting of the shadow for a time at its apparently highest point for the day (which preceded the promise that it should rise ten steps) has also to be accounted for, and this cessation of its motion upwards could not have taken place till about 25 minutes before noon, when the decreasing motion of the Sun in altitude (or its slackening motion upwards as it approached mid-day) would have become counteracted by the coming on of the eclipse. Now at 11.35 A.M. the sun’s disc would have risen to the altitude of 35° 8′; and the highest visible point of light would, owing to the eclipse, then have been about 35° 4′; and at 11.40 A.M., being the time of greatest obscuration, the extreme cusps of light produced by the intervention of the Moon would still have stood at about 35° 4′, just 23′ below the highest point of light at noon (Fig. 12). The whole disc of the sun had now risen above the gnomon, yet no motion of the shadow on the steps had been observed for fully five minutes. The time shown by the dial was seemingly mid-day.