Take a good look at Stonehenge. Impressive isn’t it? With its carefully crafted lintels and the neatly worked mortice and tenon joints that ensure the lintels slot securely onto their uprights.
Now take another look at the sarsens – those great grey stones that give us the iconic image of Stonehenge that is so instantly recognisable . Do you notice anything about the uprights? Spot anything slightly odd about them?
The answer, in case you’ve missed it is that their sides aren’t straight. Not really that odd you say. Maybe the builders of Stonehenge couldn’t be bothered. Perhaps they just weren’t concerned with things being straight. Or maybe they weren’t skilled enough sarsen workers to produce straight edges. Well take a look at the lintels with their nice neat, level tops. The Neolithic builders who constructed this great edifice were perfectly capable of producing a good straight edge in sarsen. Which rather begs the question of why they chose to give the uprights bulging sides.
Well the answer is they were employing an architectural technique not commonly seen until much, much later. Not only do the sides appear to bulge when you stand close up but the bottoms of the uprights are thicker than their tops. What you are looking at is a technique called entasis, something we’re much more familiar with in buildings of the classical world of the 5th century BC rather than the 25th century BC.
Why did they do it? The general consensus is that entasis was employed to counteract an optical illusion. When the viewer is standing at a distance columns or uprights with straight sides appear concave. The use of entasis ensures that instead the uprights appear straight. Which only goes to show that the Neolithic builders of Stonehenge really were concerned with keeping up appearances.