The Date of Stonehenge

Abstract

THE remarkable paper on Stonehenge, by Sir N. Lockyer and Mr. Penrose, in NATURE of November 21 has greatly interested me. Just two years ago, I was working at the subject, and wrote to Prof. Petrie to inquire what azimuth he had used for the axis of the temple in his estimate of the date, which he gives as 730 A.D. ± 200 years, with a possible date of 400 A. D. As I received no reply I employed the angle 50° 12′ E. of N., given in Mr. Edgar Barclay's “Stonehenge,” 1895. With this azimuth I obtained by means of a formula, kindly supplied by Dr. Downing, F.R.S., a date of 425 A.D. I find that, for the given azimuth, even this date is too early, as I did not allow, enough for refraction, &c. Applying the same formula to the figures given in Sir N. Lockyer's paper, the date comes out about 1700 B.C., as stated, so that the formula was correct, and the chief error was in the erroneous azimuth of the axis, which differs by about 38′ from the 49° 34′ 18″ so carefully determined in the published paper. Now as an increase of some 90′ in sunrise azimuth at the solstice means a decrease of some 46′ in declination and represents the lapse of about a century, the discrepancy is clearly explained. Allowing for refraction, &c., I make the present azimuth of the sun at sunrise at the solstice about 50° 26′ 21″ E. of N., the sun's declination being 23° 27′ 8″ N. Consequently since the date, 1700 B.C., the solstitial sunrise azimuth has shifted 52′ 3″ further E. and the declination has decreased 27′ 22″, representing a lapse of about 3600 years, when the appropriate formula is applied.