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In page Stonehenge:

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The inward-facing surfaces of the stones are smoother and more finely worked than the outer surfaces. The average thickness of the stones is 3.6 feet (1.1 m) and the average distance between them is 3.3 feet (1 m). A total of 75 stones would have been needed to complete the circle (60 stones) and the trilithon horseshoe (15 stones). It was thought the ring might have been left incomplete, but an exceptionally dry summer in 2013 revealed patches of parched grass which may correspond to the location of missing sarsens.[2] The lintel stones are each around 10 feet (3.2 m) long, 3.3 feet (1 m) wide and 2.6 feet (0.8 m) thick. The tops of the lintels are 16 feet (4.9 m) above the ground.[citation needed]