Hapgood was to make one more important discovery: a Chinese map copied from an earlier original on to a stone pillar in AD 1137.23 This map incorporates precisely the same kind of high quality information about longitudes as the others. It has a similar grid and was drawn up with the benefit of spherical trigonometry. Indeed, on close examination, it shares so many features with the European and Middle Eastern maps that only one explanation seems adequate: it and they must have stemmed from a common source.24
