The Story of Eclipses

by George F. Chambers

Here lie the bodies of Ho and Hi,
Whose fate though sad was visible—
Being hanged because they could not spy
Th’ eclipse which was invisible.

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.