iron age.

At the same time it must not be forgotten that Sir Arthur Evans has
spoken in favour of a date in the first half of the third century B.C.
He believes that the great circles are religious monuments which in form
developed out of the round barrows, and that Stonehenge is therefore
much later than some at least of the round barrows around it. That it is
earlier than others is clear from the occurrence in some of them of
chips from the sarsen stones. He therefore places its building late in
the round barrow period, and sees confirmation of this in the fact that
the round barrows which surround the monument are not grouped in regular
fashion around it, as they should have been had they been later in
date.

Many attempts have been made to date the monuments by means of
astronomy. All these start from the assumption that it was erected in
connection with the worship of the sun, or at least in order to take
certain observations with regard to the sun. Sir Norman Lockyer noticed
that the avenue at Stonehenge pointed approximately to the spot where
the sun rises at the midsummer solstice, and therefore thought that
Stonehenge was erected to observe this midsummer rising. If he could
find the exact direction of the avenue he would know where the sun rose
at midsummer in the year when the circle was built. From this he could
easily fix the date, for, owing to the precession of the equinoxes, the
point of the midsummer rising is continually altering, and the position
for any year being known the date of that year can be found
astronomically. But how was the precise direction of this very irregular
avenue to be fixed? The line from the altar stone to the Friar's Heel,
which is popularly supposed to point to the midsummer rising, has
certainly never done so in the last ten thousand years, and therefore
could not be used as the direction of the avenue. Eventually Sir Norman
decided to use a line from the centre of the circle to a modern
benchmark on Sidbury Hill, eight miles north-east of Stonehenge. On this
line the sun rose in 1680 B.C. with a possible error of two hundred
years each way: this Sir Norman takes to be the date of Stonehenge.

Sir Norman's reasoning has been severely handled by his
fellow-astronomer Mr. Hinks, who points out that the direction chosen
for the avenue is purely arbitrary, since Sidbury Hill has no connection
with Stonehenge at all. Moreover, Sir Norman determines sunrise for
Stonehenge as b