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 Hun's first ray, suddenly admitted into the darkness, formed a fundamental part of the cultus.
While the actual observation of sunrise was doubtless made within the building 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 can probably be determined with greater accuracy than that of the temple axis itself, the estimate of date in this paper is based upon the orientation of the avenue. Further evidence will be given, however, to show that the direction of the axis of the temple, so far as it can now be determined, is sufficiently accordant with the direction of the avenue.
The orientation of this avenue may be examined upon the same principles, that have been found successful in the case of Greek and Egyptian temples that is, on the assumption that Stonehenge was a solar temple, and that the greatest function took place at sunrise on the longest day of the year. This not only had a religious motive ; it had also the economic value of marking officially and distinctly that time of the year and the beginning of an annual period.
It is, indeed, probable that the structure may have had other capa- bilities, such as being connected with the equinoxes or the winter solstice ; but it is with its uses at the summer solstice alone that this paper deals.
There is this difference in treatment between the observations required for Stonehenge and those which are available for Greek or Egyptian solar temples -viz., that in the case of the latter the effect of the precession of the equinoxes upon the stars, which as warning clock stars Avere almost invariably connected with those temples, offers the best measure of the dates of foundation ; but here, owing to the brightness of twilight at the summer solstice, such a star could not have been employed, so that we can rely only on the secular changes of the obliquity as affecting the azimuth of the point of sunrise. This requires the measurements to be taken with very great precision, towards which care has not been wanting in regard to those which we submit to the Society.
The main architecture of Stonehenge consisted of an external circle of about 100 feet in diameter, composed of thirty large upright stones, named sarsens, connected by continuous lintels, and an inner structure of ten still larger scones, arranged in the shape of a horseshoe, formed by five isolated trilithons. About one-half of these uprights have fallen and a still greater number of the lintels which they originally carried. There are also other lines of smaller upright stones, respecting which the only point requiring notice in this paper is that none of them would have interrupted the line of the axis of the avenue. This
