The current at this point in the Hellespont does not follow the middle line of the strait. There is a strong bend off Abydos, the channel, which up to this point comes from the Propontis in a south-west direction, turning due south. The current accordingly struck the European shore near Sestos, and then rebounded on to the Asian shore at Abydos (_cf_. Strabo, xiii. p. 591). The eastern bridge, therefore, which went from Abydos in a line not greatly divergent from the direct line from Abydos to Sestos, would have an axis inclined at an acute angle to the line of the current at this point; therefore, when Herodotus says its supporting vessels were oblique, does he mean oblique to this line of current, as they would be, if their axes were in their ordinary position at right angles to the axis of the bridge; or has he in his mind a different kind of obliquity, _i.e._ were they slewed round in such a way that their prows pointed up the stream, which was itself oblique at this point? As a practical question of engineering, it is infinitely more probable that the latter was the case. The capable engineers who constructed the bridge were extremely unlikely, in view of the fate of their predecessors, to expose their work to the enormous strain which the position of its supporting boats all but broadside on to the line of current would have involved. It cannot, however, be said that it is certain that Herodotus would have thus interpreted his own description. At the same time, descriptions by the ancients involving a reference to relative positions have to be treated with the greatest caution. It is often the case that the strictest meaning of their words is proved by the context not to be the sense they wish to convey. In these days of maps and instruments of precision, we are infinitely more strict, or, perhaps, less liable to error in orientation, than those who did not possess such things, save in the rudest possible form. One of the commonest forms of mistake among ancient writers, in the course of a description, is to alter the point of view, or the object to whose position the positions of other objects are being referred. Polybius conspicuously does so in describing the valley running up from Lake Trasimene. A few chapters further on, Herodotus does the same thing (vii. 42), for he describes the Persians in their march as leaving Mount Ida on the _left_, whereas he should have said _right_, thus confusing his own point of view from the sea with theirs.