Ptolemy's Map of Scotland

Abstract

It has long been recognised as a puzzling fact that in Ptolemy's map of the British Isles Great Britain is turned abruptly to the east from about latitude 55° north (corresponding roughly to the area of Scotland) so as to make a right angle approximately with the southern part of the country. It may be of interest to review briefly various tentative explanations of this peculiar fact which have been advanced during the last three-quarters of a century, and to add yet another to the list.In 1885 H. Bradley suggested that either Ptolemy or one of his predecessors had before him three sectional maps representing respectively England, Scotland, and Ireland, and that in fitting the three maps together Ptolemy or his predecessor fell into the mistake of turning the oblong map of Scotland the wrong way. T. G. Rylands next put forward his view that the error was due to a faulty observation of a lunar eclipse at Duncansby Head causing an error of longitude, together with a faulty gnomonic observation at the same place causing an error of latitude. In 1894 H. Kiepert was clearly getting nearer the truth when he wrote: ‘The only coherent, though often deficient source for the knowledge of the [British] islands that has come down to us from the most flourishing period of the Empire, is the map of Ptolemy, the result of a combination of the lines of roads and of the coasting expeditions during the first century of Roman occupation. One great fault, however, has crept into the map by his having made use also of a totally different source, namely the astronomical fixations of latitude executed by Pytheas in the time of the earliest Greek mercantile expeditions to these regions of high latitudes.’ In a footnote to this observation he added: ‘These fixations stop at a borderline at the highest point reached in the north, which according to the itinerary sources would have been crossed in a northward direction, and thus the Alexandrian scholar was forced to give the northern half of the island a bend towards the east, the only possible direction, in consequence of which all the localities of Caledonia have been shifted from their proper positions by about a quarter of a circle.’