AN investigation was undertaken by Mr. Penrose and myself in the spring of 1901, as a sequel to analogous work in Egypt and Greece, with a view to determine whether the orientation theory could throw any light upon the date of the foundation of Stonehenge, concerning which authorities vary in their estimates by some thousands of years. Ours was not the first attempt to obtain the date of Stonehenge by means of astronomical considerations. In Mr. Godfrey Higgins’ work 2 he refers to a method of attack connected with precession. This furnished him with the date 4000 B.C. More recently, Prof. W. M. Flinders Petrie, 3 whose plan of the stones is a valuable contribution to the study of Stonehenge, was led by his measures of the orientation to a date very greatly in the opposite direction, but, owing to an error in his application of the change of obliquity, clearly a mistaken one. The chief astronomical evidence in favour of the
These earthen banks defining the avenue do not exist alone. As will be seen from the sketch plan (Fig. 15), there is a general common line of direction for the avenue and the principal axis of the structure; and the general design of the building, together with the position and shape of the naos, indicates a close connection of the whole temple structure with the direction of the avenue. There may have been other pylon and screen equivalents as in other ancient temples; which have disappeared, the object being to confine the illumination to a small part of the naos. There can be little doubt, also, that the temple was originally roofed in, and that the sun's first ray, suddenly shining into the darkness, formed a fundamental part of the cultus. With regard to the question of the roof, however, the above suggestion, I now find, is not new, the view having been held by no less an authority than Dr. Thurnham, who apparently was led to it by the representations of the Scandinavian temples as covered and enclosed structures. Since the actual observation of sunrise was doubtless made within the sanctuary itself, we seem justified in taking the orientation of the axis to be the same as that of the avenue, and, since in the present state of the S. W. trilithon the direction of the avenue canASTRONOMICAL OBSERVATIONS AT STONEHENGE IN 1901 1
The real point was to determine the direction of the so-called avenue. Measurements taken from the line of the bottom of the ditch assisted materially those taken from the crown of the bank itself. With this help and by using the southern bank and ditch whenever it admitted of recognition a fair estimate of the central line could be arrived at. To verify this, two pegs were placed at points 140 feet apart along the line near the commencement of the avenue, and four others at distances averaging 100 feet apart nearer the further recognisable extremity, and their directions were measured with the theodolite, independently by two observers, the reference point being Salisbury Spire, of which the exact bearing had been communicated by Colonel Johnston.
This bearing was also measured locally by observations of the Sun and of Polaris, the mean of which differed by less than 20″ from the Ordnance value. The resulting observations gave for the axis of the avenue nearest the commencement an azimuth of 49° 38´ 48″, and for that of the more distant part
It is to be understood that on account of the slight uncertainty as to the original line of observation and the
62:1 This chapter and the end of the previous one are mainly based the paper communicated by Mr. Penrose and myself to the Royal Society (see Proceedings, Royal Society, vol. 69, p. 137 et seq. 62:2 The Celtic Druids. 4to. London. 1827. 62:3 Stonehenge, &c. 1880. 67:1 Smithsonian Contributions to Knowledge, vol. xviii. No. 232, table 9. Washington. 1873. For curve, see page 130.
