“With regard to the elevations of the horizon, the existence of trees on or just below the sky-line renders readings to the nearest minute uncertain. In all cases I have tried to give the most probable value, supposing the trees to be absent. In some places the heights will have altered slightly during recent years owing to the construction of railways. “The values given are the means of observations. They are not corrected for height of instrument above ground, which might increase the angles by about 5 mins. Trees on the sky-line appear to make a difference of some 35 mins.” The azimuths as found by Mr. Morrow and myself are as under: Height of horizon (excluding trees). Morrow. Lockyer. Morrow. [23]From centre of great circle to Hauteville’s quoit N. 17° 59′ E. 17° 2° 23′ From centre of great circle to N.E. circle 53° 0′ 51° 1° 5′ From centre of great circle along great circle avenue 68° 43′ 65° 0° 38′ From centre of N.E. circle along N.E. circle avenue S. 83° 52′ E. 79° 1° 40′ From centre of S.W. circle to centre of great circle N. 19° 51′ E. 20° 1° 44′ The azimuths to which I first direct attention are these: Az. Great circle to quoit N. 17° E. S.W. circle to great circle N. 20° E. These azimuths indicate that at Stanton Drew as at the Hurlers and elsewhere we are dealing with Arcturus as a clock-star. The facts are: Az. N. Decln. Height Star. Date. of hills. N. 17° E. 38° 59′ 0″ 2° 23′ Arcturus 1690 20° 37° 26′ 50″ 1° 44′ „ 1410 One of the greatest differences between Mr. Morrow’s local observation and my reading of the 25-inch Ordnance map occurs in the case of the direction of the avenue from the great circle. It may be suggested that the use of this avenue was to observe the May and August sunrises of the May year. If we take the sun’s declination at 16° 20′ N., see p. 22, the azimuth should be about N. 64° E.; this is 1° from my value and 5° from that given by Mr. Morrow, but it must not be forgotten that the choice of a day in May and August slightly differing from the normal date might easily produce such a variation. It seems probable that the great circle was one of the first erected, and the fact that, like Stonehenge, it had an avenue, but that, unlike Stonehenge, the avenue was directed towards the May and not the June (solstitial) sunrise further, I think, suggests that the May worship was considered the most important and was the first provided for.