Fifty three massive slabs of Lewis gneiss were brought here and erected with immense labor, each stone in its special place. Who could have performed such feats of heavy engineering and mathematical precision, ages ago, and what motive could have been powerful enough to drive them to such an achievement?
From four points of the compass, lines of standing stones converged on the north marching down towards the village straggled away below. Archaeologists found charred fragments of human bones in this place during the last century. Many theories and legends surround the stones including those with overtones of aboriginal barbarism. Druid priests figure in many of these misty tales, conducting blood sacrifices—perhaps, dare one hope, human sacrifices?
Latter-day natives of Lewis may even have taken a perverse pleasure in explaining away the Stones in dark tales of how the pagan giants were turned to stone by Saint Kiaran even as they sat discussing how to overthrow the new Christian religion.
Rear Admiral Boyle T. Sommerville’s survey in 1912 suggested the possibility that the circle and its associated alignments of stones could have been used for astronomical observations. The west and east alignments and the middle line of the northern avenue all met at a point inside the central ring, which seemed to indicate the spot where an observer should stand.
In 1965, Gerald Hawkins wrote in a publication suggesting that these stones can be used to calculate an accurate calendar and predict solar and lunar eclipses and the knowledge used in building Callanish may even have been used later in the construction of the Stonehenge.
A thoroughly documented research of Professor Alexander Thom was published shortly after Hawkin’s findings. His meticulous work on many megalithic sites in Britain, but particularly on the west coast, had arrived at conclusions which suggested a common unity of purpose and accuracy of method that brought the Callanish sit sharply into focus as a vital center of prehistoric culture.
Thom’s relentless compilation of probabilities went on to suggest an accurate date for the construction of the Callanish circle as 1800 B.C or B.C.E. Thom had deduced, from careful measurements of many megalithic alignments and stone circles, the existence of common techniques of sophisticated mathematics throughout Britain. There was the so-called Megalithic Yard, equivalent to 2.72 feet, which recurred time after time in his accurate surveys of sites all over the country as the fundamental unit of length. He found that the megalithic mathematicians, in their quest for a perfect circle whose perimeter was a multiple of the same whole units that made up the diameter, had discovered that such a shape was an impossibility, because of the nature of the facto pi. Accordingly, they constructed their “circles” as flattened ellipses, in order to achieve this harmonious relationship between diameter and perimeter. The unit they chose was, of course, the megalithic yard.
Callanish incorporated all the factors that Thom has found elsewhere, including an ellipse based on a triangle whose sides measured three, four, and five megalithic yards. It is a Pythagorean triangle, in fact, except that Pythagoras was born over a thousand years later than the megalithic mathematicians.
Dr. Hawkins had suggested that while the alignments did indicate crucial astronomical sightings, they could not be exceptionally accurate because of the comparatively short distance between stones in the Callanish grouping, so that any small movement of the observer’s head would produce a large apparent shift in the position of the observed point. However, Thom surveyed no fewer than six other megalithic circles and alignments built within three miles of the main Callanish group, and showed that very precise observations and calendar calculations could be obtained using sightings between one site and the next, and also employing the shapes of the distant mountain profile as an accurate foresight.
Thom showed that this method could be so accurate that an observer standing at the main Callanish site could measure the tiny irregularity—only nine seconds of an arc—in the lowest maximum position of the moon. At one extreme of this tiny lunar “wobble” the lowest part of the moon’s disc would touch the bottom of the dip of the mountain profile of Clisham, Harris, while at the upper extreme the highest point of the disc would graze the summit of the mountain.
Thom’s case, based as it is on a multitude of observed facts and a wealth of statistical evidence appears very convincing, and the possibility of his results being explained by coincidence is remote in the extreme. The conclusions defy refutation and invite – beg for—all manner of further research, be it archaeological, astronomical, or mathematical.
However that may turn out, one will always be left with the original sense of mystery, which is only deepened by the investigators’ revelations of the skill which the lost builders of Callanish possessed.