VIII.] THE NORTHERN SEA. 159 second hand ; indeed many of the difficulties which arise in con- nexion with this part of his narrative disappear, if we suppose that he is interpreting the reports of others. He was acquainted with the remarkable inrush of the sea, and the consequent rise of the water at springtides, which takes place in the Pentland Firth1; but the existence of this he would learn from the mainland, because that strait passes between the north of Scotland and the Orkneys. He received information also concerning an island called Thule, and it was through him that this name, which was destined to become famous in the works of Roman authors, was reported to the dwellers land in the ' r Shetlands). about the Mediterranean. He states that it was the northernmost of the British islands2, and six days' voyage north of Britain, and in the neighbourhood of the frozen ocean8. From these notices it would seem most probable that the island here intended was Mainland, the chief of the Shetland islands. The interval between it and Britain, no doubt, is greatly overestimated, but the same is" the case with all Pytheas' computations by sea- Some authorities have supposed that Iceland is meant, and others Lapland ; but these conjectures seem to carry us too far afield. Another point of great interest connected with the subject of Thule is his statement that it lay under the Arctic circle, or, as he or his reporter Strabo expressed it, circle. ArCti° " where the Arctic circle coincides with the summer tropic4." That this conclusion was based, not on measurements or personal observation, but on the reports of the Celts of North Britain, seems to be proved by a passage in Geminus the astro- nomer (drc. 80 B.C.), who quotes Pytheas as saying, that the barbarians pointed out to him the sleeping-place of . the sun; and also that in those regions the nights place of the were excessively short, extending in some parts un' 1 Pliny, i. 217; Octogenis cubitis supra Britanniam intumescere aestus Pytheas Massiliensis auctor est. Cp. Mullenhoff, p. 366. 2 Strabo, 2. 5. 8; 6 p& otiv MaovoXufrn?* TLv&tas rh, vepl Qotihqv -rip Pop€LQTOLT1)V T&V 'BpCTTOl'lSw iJtfTara X£y«. 8 ibid.) I. 4. 2 ; fy #)