From the Thorley Archives

The Case of the Phantom Chancel

Some years ago I was asked by Adrian Gibson to assist in investigating his theory that geometric calculations could possibly point to the origins of the chancel at St James.

" The church at Thorley is a typical smaller Hertfordshire example with nave, chancel and west tower. The earliest work comprises a Norman south doorway and thirteenth century lancet windows in both nave and chancel.

The nave is of average size, but the chancel is wide and large in proportion, for a Norman building, suggesting replacement of something older. I was recently asked to look at the building to see if more could be learnt about the construction phases as I had been looking at the geometry used in the design of churches and barns.

The plan of the nave is approximately rectangular but is in fact a trapezium with the east end considerably out of square and the west end slightly skew. Its exterior measurements, 49ft 6ins long by 29ft 9ins, do not make sense without some understanding of medieval units and geometry. 49ft 6ins long is precisely equal to 3 rods (pole or perch). One rod, the old unit length of 16ft 6ins, is a quarter of a chain. (1 chain = 66 feet = 22 yards = length of a cricket pitch). For those who are rusty 10 chains = one furlong, 8 furlongs = 1 mile.

It would seem that the north side was precisely measured and right angles set out, probably using a 3:4:5 triangle of rope (Pythagoras). The width, of 29ft 9ins relates to nothing that we see now, but appears to have derived from the size of an earlier chancel, replaced by one longer and wider in the thirteenth century. The present chancel internally, is 30ft 19ins long, comparable in size to the nave. If, on a drawing board, a smaller square chancel is reconstructed, of one rod square, 16ft 6ins by 16ft 6ins, it is much more in proportion to the nave and typical of early churches, both Saxon and Norman. Commonly, at that time, the wall thickness was laid out by swinging a diagonal of the square round at 45 degrees giving an overall outside dimension of the square-root-of-two times the internal size. Here this comes to 23ft 4ins. In the early churches the nave width was made virtually the same as the exterior size of the chancel. With this proposed theoretical model, it can be seen that a good fit to what we see now.

It would appear that there was a simple square chancel once, which, in the thirteenth century was removed. A new one was constructed whose side walls were moved out to approximately half the exterior north and south, inset between the nave and chancel. This gave a new wider interior width of 20ft 7ins which was then multiplied by 1 to give a 2:3 ratio within the chancel and an interior length of 30ft 10ins.

Two other conclusions can be drawn from the plan. The western edge of the Norman doorway is 29ft 9ins (the same as the overall nave width), from the exterior nave east end, and was clearly set off as a square proportion. The two lancet windows of the nave are approximately set off in the same way from the western end and no doubt replace Norman originals. " AVG

Bill Hardy
September 2006

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