This megalithic monument on the west coast of Argyll, Scotland, consists of a single standing stone four meters (thirteen feet) high situated between two round cairns. It probably dates to the late third or early second millennium b.c.e. It is well known because it was the place where, in the 1970s, an archaeological excavation was first used to test an astronomical theory deduced from alignment studies.

The horizon all around this site is relatively close except toward the southwest, where there is a distant view toward the Isle of Jura, some 45 kilometers (28 miles) away. Here two adjacent mountain peaks stand out prominently with a deep, sharp notch between them. As viewed from the standing stone, this notch aligns precisely with the midwinter sunset. Close to the winter solstice, the top part of the setting sun would reappear briefly in the bottom of the notch, but at the solstice itself it would be slightly too low, and only then would it disappear from view.

When Alexander Thom discovered this alignment, he also discovered a problem. The notch is just hidden from the standing stone itself by an intervening ridge; only a 2.5-meter (8-foot) giant would be able to see it from the standing stone. Undeterred, Thom followed the alignment back toward the northeast where it crosses a deep gorge and then climbs a steep hillside. Halfway up this precipitous slope is a narrow ledge, which would have provided the perfect spot from which to observe the setting sun. From here, the standing stone appears directly beneath the deep notch. But there was no obvious sign of human activity here, just two rounded boulders. Was the ledge simply a natural feature? Here was the perfect opportunity for an archaeological test of an astronomical theory: if the ledge could be shown by excavation to be artificial, then this would vindicate the idea that it was used as an observing platform.

Archaeologist Euan MacKie rose to the challenge in 1970 and 1971. Unfortunately, his excavations did not reveal any clear and direct signs of human activity. However, they did show that the flat part of the ledge was covered with rounded pebbles, which he suggested had been carefully placed there to form a viewing platform. The problem was that they might have arrived naturally, rolling down the hill and coming to rest behind the two larger boulders. Analyses were undertaken of the orientations of the pebbles, in the hope of distinguishing between the two possibilities, but no clear conclusion could be reached. Thus MacKie's excavations proved inconclusive.

One of the general questions that arises from Thom's theory of highly precise solstitial sightlines is how they could have been set up in the first place. One of the most plausible ideas is that a row of people, stretching perpendicularly to the sightline, watched the sunset on days leading up to the solstice. Each day, fewer or them would see the sun reappear in the notch, as the sun's setting path sank slightly in the sky (the opposite would be true at a notch where the sun rose or set at the summer solstice). Each evening a temporary marker would be set up to mark the limiting position where the sun could be seen to reappear in the notch. Day by day, this position would move sideways, by less and less as the solstice approached, until the limit was eventually reached and the position began to move back in the opposite direction. For the summer solstice, the limit would mark the spot where the tip of the sun would only appear in the notch on the solstice itself; for the winter solstice, as at Kintraw, it would mark the spot from which the sun would only disappear on the solstice itself. This, then, would be the spot where a permanent marker would be erected.

There are two serious problems with this procedure at Kintraw. First, there is no room to set out a line of people as just described, because the platform is situated on the side of a precipitous hillside above a deep gorge. Second, the intervening ridge blocks the view of the distant notch from those positions where one would have had to stand in order to watch the sunset on the days before and after the solstice. There are also more general problems that bring into question the whole idea that solstitial sightlines of pinpoint precision could have been established at British megalithic sites such as Kintraw, Ballochroy, or the Ring of Brodgar. An obvious imponderable would have been the British weather: the setting-up procedure would only work given a reasonable run of clear evenings, something that would have been far from guaranteed even given that the weather in western Scotland in later prehistoric times was somewhat different from now. Another is the possibility of significant day-to-day variations in atmospheric refraction due to changing atmospheric conditions, which would alter the apparent altitude of the setting sun.

The reappearance of the setting sun in the notch at Kintraw for a period around the December solstice would undoubtedly have formed a spectacular sight. Certainly, it may have been deeply significant to the people who constructed (not necessarily at the same time) the cairns and monolith: the larger cairn, for example, had a setting of stones resembling an entrance (known as a false portal) facing in this general direction. Perhaps no greater precision than this was needed. By trying too hard to fit prehistoric people into the mould of ancient "scientific" astronomers, and by focusing too closely on the possible existence of alignments of pinpoint precision, we risk failing to grasp more useful insights into the part that astronomy really played in prehistoric burial and ceremonial practices.

See also:

Science or Symbolism?; Solstitial Alignments; Thom, Alexander (1894-1985).

Ballochroy; Brodgar, Ring of; Megalithic Monuments of Britain and Ireland.


References and further reading

Ruggles, Clive. Astronomy in Prehistoric Britain and Ireland, 25-29. New Haven: Yale University Press, 1999.

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