Arabia according to Ptolemy — his sixth Asian sheet — is reduced from the original compilation by A. Sprenger (Die Alte Geographie Arabiens, Bern 1875). This version reproduces precisely the original of Ptolemy, unlike the many manuscript and printed versions which are usually roughly copied at several removes from an original which may itself have been inaccurately plotted. Ptolemy himself appreciated the danger and intended that his work be handed down in the form of lists of co-ordinates which could be re-plotted with precision at any time.

It will be evident from a comparison …