If the West Kennet Avenue had followed a largely straight line (as John Aubrey portrayed it in a drawing carried out shortly after his survey in September 1663), Keiller’s 80’ wide corridor would have done the job. Unfortunately its course was rather sinuous (hats off to William Stukeley) as indicated by a single surviving stone (Keiller’s #34, Smith’s 21A) on the other side of the road running along the eastern edge of the field.
As a result Keiller knew that sooner or later his corridor of regular blocks and cuttings would have to pivot. This eventually came at a distance of just over 243m (800’) from the fence marking the southern end of the field, though it was clear from about 180m that the line of paired standing stones was drifting to the east of the corridor axis. This in turn prompted some nimble footwork (tapework?) on the part of Keiller to modify and extend his cuttings – more about these in a later post.
You can get a sense of the drift from the photograph below I took from the midpoint of the avenue on the southern boundary fence looking northwards towards Avebury.
So, using point R as the pivot (marking the 800’ point and north-eastern corner of block VIII – check out the sketch in post #3), he tilted the axis of the entire grid 6 degrees to the east. And then carried on.
Never missing a chance to repurpose a unique identifier, the original north-west corner of block VIII (point Q) was replaced by point Q* precisely 2.499m (8.2’) away. The corridor then trundled on until it met the boundary of the field long its northern edge, slowly intersecting the fenceline on the east as it did so. And that was essentially that.
As a visual thinker, the plotting out by hand of the cuttings has proven invaluable in helping me to make sense of the complex textual descriptions and step-by-step annotated drawings in Keiller’s Plotting book. I now understand better not only what he had done, but how he went about doing it.
The next step will be to replicate this digitally in the GIS. The first stage in that process is going to be identifying points on the digital ground today (i.e. the Ordnance Survey map coverage) that correspond to points established in 1934 by Keiller. More of that in the next post.