The difference between the new and old azimuth then, on the assumption that az. N. 41° 16′ E. really represents an observation over Maeshowe, gives us the difference of date.

Treating these figures then as we have done in the case of Stonehenge in [Chapter VII], the result is as follows. The Barnhouse-Maeshowe line was established about 700 B.C., when the obliquity had a value of 23° 48′ according to Stockwell’s tables. ([Fig. 40].)

I confess the late date does not surprise me. The masonry of Maeshowe differs widely from that of other similar structures in that the sides of the gallery and chamber, instead of being composed of upright stones, are built in regular courses.

I do not believe that the Maeshowe structure was built to observe a winter sunrise twenty days from the solstice, nor can I think it was set up at midsummer by someone who had only dealt with a high sun and a sea horizon, and imagined that the sunrise and sunset points were exactly opposite to each other. It was a priest’s house, and the alignment of the passage to the Barnstone was for the exchange of signals, probably by lights in Maeshowe itself.

[Larger diagram]

Fig. 40.—Variation of the Obliquity of the Ecliptic, 100 A.D.-4000 B.C. (Stockwell’s Values.)

Horizontal axis: Years. From left: AD 0-BC 4000.

Vertical axis: Obliquity. From bottom: 23.40-24.10.

The Ordnance maps give no indication of stones, &c., by which the direction of the midsummer setting or the midwinter rising and setting might have been indicated from either the Maeshowe or the Barnstone.