# Avebury

28 29 Professor Alexander Thom, the foremost surveyor of stone circles to date, published this solution for the strange shape of Avebury in his book Megalithic Sites in Britain in 1967. Thom had discovered an ancient unit of measure, the megalithic yard of 2.72 feet, in many ancient stone circles, and Avebury further confirmed his theory. He noticed that the complex shape of the outer circle basically consists of seven separate curves and that four of these, labelled opposite as a, b, c and d, have the same radius, of 260 MY. The two flat sections both have radii of 750 MY. Especially interesting was his finding that three of these four centres of curvature lie in a precise 345 Druids triangle shown opposite, here with sides 75, 100 and 125 MY. Professor Thom also measured the two inner circles both as 125 MY across, with 145 MY between their centres. The triangularshaped feature of small stones near the Obelisk in the south circle is still unexplained but it looks uncannily like the 345 triangle. You can clearly see the Cove at the centre of the northern circle. A cove at nearby Stanton Drew stone circles points, like Aveburys, to the northernmost moonrise another at Arbor Low stone circle in Derbyshire points to the southern most moonset. The geomeTry of Avebury Professor Thoms breakthrough 29 The Pythagorean 345 Triangle at the heart of Aveburys strange shape