Most churches in our part of Oxfordshire were built using flint from the nearby Chalk hills, or sandy limestone from the Corallian outcrops around Oxford. But the church of St James in Sotwell is different, its exterior walls built mainly of shaped rectangular blocks of a hard grey sandstone. The interior walls are of softer local chalk. The masonry dates from 1884 when the ancient chapel on the site, its original walls made of wattle and daub, was largely rebuilt under the direction of architect S.R. Stephenson. Where did the unusual sandstone come from?
Thanks to some detective work by the retired Reading University Geology professor, John Allen, this stone has been identified as Sarsen stone - similar to that used to build Stonehenge, the Avebury Stone Circle and Wayland’s Smithy near Uffington. His conclusions are contained in a monograph “Late Churches and Chapels in Berkshire” published in the 2007 British Archaeological Report, Series 432.
Sarsen stone has a curious geological origin. It is a relatively young rock, formed from the sand deposited by rivers of the Paleocene Period, some 60 million years ago. Exposed to tropical weathering, the quartz sand grains became locally cemented by deposition of crystalline quartz, to form large slabs of unusually hardened rock. Here and there within the stone, tube-like holes remained where tree and plant roots had once penetrated the sand. The tabular slabs were later broken apart during the Ice Ages and became scattered over the surface of the Chalk downs. They were widespread across the Wiltshire area.
The Sarsen stones were obvious material for construction of megalithic monuments, which have survived intact for thousands of years. But being so hard to break or cut they were not much use as a regular building stone, although smaller, unshaped stones can be seen in rubbly walls of cottages around Ashbury and Uffington. Only in the mid-19th Century did viable dressing techniques develop, leading to a short-lived industry, based in the Kennet valley of Wiltshire, supplying cut blocks, setts and kerbstones. But by the early 20th Century this industry had died away with the lack of available remaining Sarsen stones. These can now only be found in a number of protected sites, such as Fyfield Down and by Ashdown Park.
Professor Allen records very few chapels or churches in historic Berkshire which use this stone. So why did the architect Mr Stephenson choose the unusual Sarsen stone for rebuilding St James in Sotwell? One clue might be the opening of the railway branch line to Wallingford in 1866, greatly reducing the cost of bringing a building stone from as far afield as Wiltshire. Perhaps he intended that the stonewalls of St James should, like the megalithic monuments, also survive for thousands of years.
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