Nothing is more likely than that the builders of the megaliths had some knowledge of the movements of the sun in connection with the seasons, and that their priests or wise men determined for them, by observing the sun, the times of sowing, reaping, etc., as they do among many savage tribes at the present day. They may have been worshippers of the sun, and their temples may have contained 'observation lines' for determining certain of his movements. But the attempt to date the monuments from such lines involves so many assumptions and is affected by so many disturbing elements that it can never have a serious value for the archaeologist. The uncertainty is even greater in the case of temples supposed to be oriented by some star, for in this case there is almost always a choice of two or more bright stars, giving the most divergent results. [Illustration: FIG. 2. Avebury and the Kennet Avenue. (After Sir R. Colt Hoare.)] Next in importance to Stonehenge comes the huge but now almost destroyed circle of Avebury (Fig. 2). Its area is five times as great as that of St. Peter's in Rome, and a quarter of a million people could stand within it. It consists in the first place of a rampart of earth roughly circular in form and with a diameter of about 1200 feet. Within this is a ditch, and close on the inner edge of this was a circle of about a hundred upright stones. Within this circle were two pairs of concentric circles with their centres slightly east of the north-and-south diameter of the great circle. The diameters of the outer circles of these two pairs are 350 and 325 feet respectively. In the centre of the northern pair was a cover-slab supported by three uprights, and in the centre of the southern a single menhir. All the stones used are sarsens, such as are strewn everywhere over the district. An avenue flanked by two rows of stones ran in a south-easterly direction from the rampart towards the village of Kennet for a distance of about 1430 yards in a straight line. At a distance of 1200 yards due south from Avebury Circle stands the famous artificial mound called Silbury Hill. It is 552 feet in diameter, 130 in height, and has a flat top 102 feet across. A pit was driven down into its centre in 1777, and in 1849 a trench was cut into it from the south side to the centre, but neither gave any result. It is quite possible that there are burials in the mound, whether in megalithic chambers or not. South-west of Avebury is Hakpen Hill, where there once stood two concentric ellipses of stones. A straight avenue is said to have run from these in a north-westerly direction. Whether these three monuments near Avebury have any connection with one another and, if so, what this connection is, is unknown.