Now the most interesting and best defined line near this azimuth on the Ordnance map is the one stretching S.E. from the centre of the Stenness circle to the Barnstone, with an azimuth of 57° 15′. The line contains between the two points I have named another stone, the Watchstone, 181⁄2 feet high, in the precise alignment; and from the statements made and measures given it is to be inferred that a still more famous and perforated stone, the “Stone of Odin,” demolished seventy years since, was also in the same line within the extremities named.
If we may accept this we learn something about perforated stones, and can understand most of the folk lore associated with them, and few have more connected with them than the one at Stenness. I suggest that the perforation, which was in this case 5 feet from the ground, was used by the astronomer-priest to view the sunrise in November over the Barnhouse stone in one direction, and the sunset in May over the circle in the other. I hope to be able to return to this question subsequently.
There is another echo of this fundamental line; that joining the Ring of Bookan and the Stones of Via has the same azimuth and doubtless served the same purpose for the May year.
But this line, giving us the May sunset and November sunrise, not the December solstitial sunrise as Mr. Spence shows it, is not the only orientation connected with the May year at the stones of Stenness. The November sunset is provided for by a sight-line from the circle to a stone across the Loch of Stenness with an azimuth of S. 53° 30′ W.
To apply the table, given on [p. 120], to the solstitial risings and settings at Stenness, and the sight-lines which I have plotted on the map, it will be seen that the table shows us that the lines marked
N. 41° 16′ E
S. 41° 0′ E.
S. 36° 30′ W.
are solstitial lines; to get exact agreement with the table the heights of the hills must be found and allowed for.
I have roughly determined this height from the 1-inch map in the case of the Barnstone-Maeshowe alignment. On the N.E. horizon are the Burrien Hills, four miles away, 600 feet high at the sunrise place, gradually ascending to the E., vertical angle = 1° 36′ 30″. The near alignment is on and over the centre of Maeshowe. Colonel Johnston, the Director-General of the Ordnance Survey, has informed me that the true azimuth of this bearing is N. 41° 16′ E., and in all probability it represents the place of sunrise as seen from the Barnstone when Maeshowe was erected. What is most required in Orkney now is that some one with a good 6-inch theodolite should observe the sun’s place of rising and the angular height of the hills at the next summer solstice in order to determine the date of the erection of Maeshowe. Mr. Spence and others made an attempt to determine this value with a sextant in 1899, but not from the Barnstone.
In the absence of this observation we may use the [diagram] given on p. 121. With the height of hill previously given the sun should rise according to calculation at about the azimuth N. 41° 50′ E.