These two short comments on Mann’s eclipse theory appeared in Nature, 126, 743 (8 November 1930) and Nature, 126, 893 (6 December 1930).


Curious Markings on Stones in Scotland.

THE Glasgow Herald of Sept. 17 contains an article by Mr. L. MacLellan Mann describing the markings on some stones at Langside and Cleuch, near Glasgow. The markings on the two stones are nearly alike, consisting of series of rings, arcs, and cup-like depressions. Mr. Mann claims that these have astronomical significance; some of the groups of cups are shown to resemble the Sickle in Leo and (more doubtfully) a star-group in Scorpio. He further claims that he can identify records of ancient eclipses; it would, however, need a fuller explanation of his method to induce astronomers to accept his claims in full. He states that he identified the date of a recorded eclipse as b.c. 2983 Mar. 28* Gregorian reckoning from the stone itself, and afterwards found by consulting astronomers in Berlin that there was a total eclipse on that date, the track of totality passing over or near Glasgow. The writer of the present note has verified this latter fact independently, making use of the new-moon tables by the late C. Schoch that are contained in “The Venus Tablets of Ammizaduga” (Langdon and Fotheringham, 1928). These tables make use of the latest values of the solar and lunar accelerations; but there is of necessity a considerable margin of uncertainty in computing the tracks of very early eclipses.

* Mr. Mann gives Mar. 27, but 28 appears to be correct.

This eclipse affords a good illustration of the use of M. Oppert’s long eclipse cycle of 1805 years; the name ‘megalosaros’ has been suggested for it; it is about a hundred times as long as the ‘saros’, and shares with it the useful property that the parallaxes of sun and moon nearly repeat themselves. The following table gives the tracks of the three successors of this eclipse; they are from Oppolzer’s “Canon” and Schrader’s sequel to it:

Date. Sunrise Point. Noon Point. Sunset Point.
    ° °  ° °  ° ° 
−2982April21.6      47W.       
−1177April16.43 41W.1N. 20E.40N. 99E.58N.
628April10.03 99W.9N. 161E.51N. 104W.63N.
2433April20.46 50W.6N. 13E.48N. 106E.56N.

The first three dates are by the Julian calendar, the fourth by the Gregorian one.

It will be seen that the cycle enables us to make a close approximation to the latitude of the eclipse track; the longitude offers greater difficulty owing to the large effect of the secular acceleration in such a long period. Oppolzer’s older eclipses themselves require a considerable shift in longitude to reduce to Schoch’s values of the accelerations.

Mr. Mann claims to have found similar records of still older eclipses; thus he refers to one in New Mexico of the date b.c. 3457 Sept. 5. It would, however, be well for him to make the full case for the 2983 eclipse accessible to astronomers before asking them to consider these more remote ones.


Our Astronomical Column.

Ancient Eclipses in Scotland.—Mr. L. MacLellan Mann writes with reference to his claim of having identifed a record on stone of the eclipse of b.c. 2983 Mar. 28 (see Nature, Nov. 8, p. 743). As regards the time of day at which the eclipse occurred, he notes that the 0·6 day (about 2.30 p.m. Greenwich) found by the writer of the note in Nature, is in good agreement with the value 0·63 found by C. Schoch, and with the value 0·66 which Mr. Mann obtains from the record on the stone; he notes that this may be the end of the eclipse. He states that he obtained the year by his interpretation of the system of wheel-like markings on the stone, which he takes to be cycles of years.

Referring to the cycle of 1805 years, Mr. Mann claims that this was probably known in ancient times; M. Oppert, the discoverer of the cycle, made a similar claim, but most astronomers hesitated to accept it. Mr. Mann makes an evident mistake when he speaks of the related cycle of 100 saroses: there is no such cycle—the greatest possible number of returns of an eclipse in the saros cycle is about 84; further, the eclipses at the beginning of a series would be visible in regions near one of the terrestrial poles, while those at the end would be visible near the opposite pole. Some thirty returns, or not many more, would suffice to carry the region of visibility away from a given latitude. Mr. Mann states that his investigations of these old stone records have occupied him for some twenty-five years, and he promises to make his results accessible to students at an early date.