[3290] See p. 576, n. 1, supra.
[3291] The Invasion of Britain, &c., 1862, p. xcii.
[3292] See pp. 728-30, infra.
[3293] Admiralty Tide Tables, p. 119; Tidal Streams, &c. Lewin tells us, in another passage (The Invasion of Britain, &c., 1862, pp. 82-3) that, according to the captain of one of the steamers running between Folkestone and Boulogne, ‘the maximum drift for a single tide, i.e. for the six hours that the stream runs in the same direction, is eighteen miles, and the minimum nine miles.’ ‘The fleet,’ he adds, ‘was heavily freighted, and therefore, sinking deep into the water, would receive the full shock of the tide ... the expedition was on the very day of the full moon [which he wrongly assigns to the 18th instead of the 21st of July], when, of course, it was a spring tide. The drift, therefore, would be the maximum or near it. Now, if we draw a straight line from Boulogne to Limne, and then a line of sixteen miles, or thereabouts, at right angles to it up the channel, it will take us to a point off the South Foreland.’
It will be observed that Lewin here assumes that Caesar was steering not for Hythe but for Lympne, and accordingly he is forced to make the length of the drift sixteen instead of twelve miles! Facts, from his point of view, were rather elastic than stubborn things. The expedition did not take place ‘on the very day of the full moon’, but about the time of new moon (see p. 729, infra). This mistake, indeed, is immaterial; but the estimate of eighteen miles is, as we have seen, greatly exaggerated; and, moreover, Lewin forgets that Caesar’s ships did not drift for the whole of one tide, but only from ‘about midnight’ till ‘daybreak’.
In a footnote to p. 82 he says that, according to ‘an experienced pilot’, a loaded vessel ‘would drift about 12 or 14 miles in the six hours, when the tide is at its greatest velocity’. Yes,—‘in the six hours’; but not in four hours. And even 12 miles is an excessive estimate. ‘As a rough general rule,’ says Admiral Sir Frederick Bedford (The Sailor’s Pocket-Book, 8th ed., 1898, pp. 232-3), ‘in the fair way of both the Irish and English Channels a vessel will be carried nine miles by the stream in a whole tide at Springs.’
[3294] Comm. de C. I. Caesaris bellis, vol. ii, p. 41; C. I. Caesaris b. G., libri VII, ed. A. Doberenz and B. Dinter, vol. ii, p. 40.
[3295] The direction of the ebb stream between the Goodwins and the shore varies between SW. and SW. ½ W. magnetic, or, approximately, between SW. by S. ½ S. and SSW. true; and its rate at springs varies from 1½ to 3 knots. Admiralty Tide Tables, p. 113.
[3296] The late George Dowker (Archaeol. Journal, xxxiii, 1876, pp. 67-8, 70) maintained that Caesar drifted ‘at the back of the Goodwin beyond the North Foreland’, and that he ‘returned on the other side of the Goodwin’, and anchored off Stonar. On this theory it is impossible to account for the efforts which the rowers were obliged to make; and, as I have shown (pp. 575-6, supra), it is impossible that Caesar should have drifted beyond the North Foreland.
[3297] See pp. 525-8, supra.