CHAPTER XI
ASTRONOMICAL HINTS FOR ARCHÆOLOGISTS
The foregoing chapters will have shown that in dealing with the ancient monuments from an astronomical point of view, we have to consider chiefly the direction of the sight-lines, whether they are marked as in Brittany by long rows of stones—alignments; as at Stonehenge by an avenue; as in some of our British circles, by two or more circles the direction being indicated from the central stone of one to the central stone of the other, or finally by a single standing stone or barrow.
It is important then that before we proceed further in our inquiries we should consider how a meaning is got out of these directions, and I propose to devote this chapter to this question, so that the full use of the “azimuths” already referred to and others which are to follow may be fully understood.
There is another matter, at which I hinted on [pp. 36] and [42]. We have to inquire whether there are any stones or barrows marking the direction of the rising or setting of stars, as well as those which deal with the rising and setting of the sun at different times of the year, which we have already found at Stonehenge and in Brittany. To face this question we have to consider the stellar as well as solar conditions of observations, and as the former are the simpler I will begin with them, especially as now there is no question whatever that the rising and setting of stars were provided for.
In continuation of my work in Egypt in 1891, and Mr. Penrose’s in Greece in 1892, I have recently endeavoured to see whether there are any traces in Britain of star observations, including those connected with the worship of the sun at certain times of the year. We both discovered that stars, far out of the sun’s course, especially in Egypt, were observed in the dawn as heralds of sunrise—“warning-stars”—so that the priests might have time to prepare the sunrise sacrifice. To do this properly the star should rise while the sun is still about 10° below the horizon. There is also reason to believe that stars rising not far from the north point were also used as clock-stars to enable the time to be estimated during the night in the same way as the time during the day could be estimated by the position of the sun.
I stated (Dawn of Astronomy, p. 319) that Spica was the star the heliacal rising of which heralded the sun on May-day 3200 B.C. in the temple of Menu at Thebes. Sirius was associated with the summer solstice at about the same time.
Mr. Penrose found this May-day worship continued at Athens on foundations built in 1495 B.C. and 2020 B.C., on which the Hecatompedon and older Erechtheum respectively were subsequently built, the warning star being now no longer Spica, but the cluster of the Pleiades rising, or Antares setting, in the dawn.
It is generally known that Stonehenge is associated with the solstitial year, and I have suggested that it was originally connected with the May year; but the probable date of its re-dedication, 1680 B.C., was determined by Mr. Penrose and myself by the change of obliquity.
Now if Stonehenge or any other British stone circle could be proved to have used observations of warning stars, the determination of the date when such observations were made would be enormously facilitated. Mr. Penrose and myself were content to think that our date might be within 200 years of the truth, whereas if we could use the rapid movement of stars in declination brought about by the precession of the equinoxes, instead of the slow change of the sun’s declination brought about by the change of the value of the obliquity, a possible error of 200 years would be reduced to one of 10 years.