The Natural Corridor for the Bluestones Route

A fascinating and opportune paper has been published which sheds light on the likely route that the Bluestones were brought along from Wales to Stonehenge.

Estimating the Scale-Dependent Influence of Natural Terrestrial Corridors on the Positioning of Settlements: A Multi-Scale Study of Roman Forts in Wales 

Joseph Lewis  @josephlewis1992

University of Cambridge 0000-0002-0477-1756 

He shows the "natural corridors", identified by analysing "the path of least-resistance from a chosen origin and destination location based on costs associated with traversing" it. He is interested in the Romans, but what have they ever done for us? Far more interesting is the implications for earlier populations and their routes.

The paper is admirably brief and understandable and is well worth reading.

One simple map from it, slightly enhanced for this format, shows how the A40 route, or the version of it just undertaken by Keith Ray, is the natural route for the Bluestones to have been brought along, with or without help from river transport.

Click to embiggen - adapted from Fig 3 "walking with rivers acting as potential conduits for movement"

https://josephlewis.github.io/RW_Natural_Corridors.pdf

I look forward to further work using this technique.

I have compared the  southern natural routes to the Drovers Roads in Davies, Margaret. Wales in Maps. United Kingdom, University of Wales Press, 1958. 

Map from https://twitter.com/jackthurston/status/1373233813611016196/photo/1

And to the modern road network - base map from https://ontheworldmap.com/uk/wales/detailed-map-of-wales.html

Click any picture to embiggen

They show the question of whether to follow the A40 route to Monmouth or loop north to Hereford. Keith Ray preferred the latter as it leads to an easier crossing of the River Severn.

They also show that the natural route, and incidentally a Roman road, cut off the Llandovery corner of the A40. There is a valley route they follow.