We were given a tip off about a bench mark at Carfax, the main meeting point in the middle of Oxford. It took a while to find it because it is below knee height. It's on the street side end of the buttress to the left of the door. Apparently they mapped the UK in the 1800s by going from bench mark to bench mark. I know about triangular points but I suppose I'd never stopped to think about how they filled in the contours on the map (and remember that contours were invented by physicists in about 1790 - see October 2009 piece about Schiehallion on this blog). Here is an example of one of their bench mark journeys that started at Carfax - though I think it was at a different marker. http://www.bench-marks.org.uk/line398
