THULE was the name given by Greek and Roman geographers to a land situated to the north of Britain, which they believed to be the most northerly portion of
Europe, or indeed of the known world. The first writer who mentioned the name was Pytheas of Massilia, whose statements concerning it have been already given under the heading PYTHEAS. But it is impossible for us to deter-mine with certainty what those statements, which have only been transmitted to us at second or third hand, really were, and still more so what was their real signification. It is almost certain that Pytheas did not himself profess to have visited Thule, but had only vaguely heard of its existence, as a land of unknown extent, situated, accord-ing to the information he had received, six days' voyage to the north of Britain. This account was adopted by Eratosthenes (though rejected by Polybius and Strabo), and accordingly this unknown land became a cardinal point in the systems of many ancient geographers, as the northern limit of the known world. Nothing more was learnt concerning it until the Bomans under Agricola (about 84 A.D.) accomplished the circumnavigation of the northern point of Britain, and not only visited, but according to Tacitus subdued, the Orcades or Orkney Islands. On this occasion, the historian tells us, they caught sight also of Thule, which in this instance could only mean the group of the Shetland Islands. No further account of this mysterious land is found in any ancient author, except vague statements, derived from Pytheas, but mostly in an inaccurate and distorted form, concern-ing its position and the astronomical phenomena resulting from this cause. It is probable that what Pytheas really reported was that at the summer solstice the days were twenty-four hours in length, and conversely at the winter solstice the nights were of equal duration, a statement which would indicate the notion of its position in about 66° N. lat., or under what we now call the Arctic Circle. The skill of Pytheas as an astronomer would have been quite sufficient to lead him to the conclusion that this would be the case at some point in proceeding northwards, and the rapid changes in this respect that would be reported to him by any navigators that had really followed the shores of Britain to any considerable extent in that direction would confirm him in the correctness of his views. He had, too, a very exaggerated notion of the extent of Britain (see PYTHEAS), and hence he would be led to place an island which was six days' voyage to the north of it much nearer to the Arctic Circle than its true position.
The statement of Pytheas on this point appears to have obtained almost universal belief until the time of Marinus of Tyre aud his successor Ptolemy, who were ledapparently from their knowledge that the group of islands to which the name of Thule had been applied by the Romans was really not very far distant from the Orcadesto bring down its position considerably more to the south, so that Ptolemy places the island of Thule, which he still regards as the most northerly point of Europe, in only 63° N. lat. Unfortunately this more reasonable view has been discarded by many modern writers, who have gone back to the statements of Pytheas concerning the length of the da}', and have in consequence insisted upon placing Thule within the Arctic Circle, and have thus been led to identify it with Iceland. The improbability of such an hypothesis, when we consider the state of ancient naviga-tion, is in itself a sufficient refutation, and there appears no reason-able doubt that the Thule of Pytheas, like that of the Romans and of Ptolemy, was merely an exaggerated and somewhat erroneous conception of the large group of the Shetland Islands, of which the principal, called Mainland, is in fact so predominant that the whole may well have been considered as one large island rather than a scattered group like the Orkneys. If we might trust to the accuracy of Strabo's quotation (ii. 5, p. 114), that Pytheas called Thule "the most northerly of the British Islands," this would be decisive on the point; but unfortunately the verbal accuracy of such references by ancient writers can seldom be relied on, and Strabo had evidently never seen Pytheas's original work.
It appears, however, to be certain that Iceland was really visited by some Irish monks long before its discovery by the Northmen, and is described under the name of Thule by a writer named Dicuil, himself an Irish monk, who wrote in the first half of the 9th century, in such a manner as to leave no doubt that his state-ments really refer to that extensive but remote island. See Letronne, Recherches sur Dicuil, Paris, 1814.
"Dispecta est et Thule," Tac., Agrie., c. 10.