eing the instant when the edge of the sun's disk first
appears, while in his attempts to date the Egyptian temple of Karnak he
defined it as the moment when the sun's centre reached the horizon. We
cannot say which alternative the builders would have chosen, and
therefore we cannot determine the date of building.

Sir Norman Lockyer has since modified his views. He now argues that the
trilithons and outer circle are later additions to an earlier temple to
which the blue-stones belong. This earlier temple was made to observe
"primarily but not exclusively the May year," while the later temple
"represented a change of cult, and was dedicated primarily to the
solstitial year." This view seems to be disproved by the excavations of
1901, which made it clear that the trilithons were erected before and
not after the blue-stones.

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 respecti