The first of these localities, we think, must be rejected, for it answers none of the conditions of the relation given in the “Commentaries,” which inform us that, in the second expedition, the fleet sailed with a gentle wind from the south-west. Now, this is the least favourable of all winds for taking the direction of Hastings, when starting from the coasts of the department of the Pas-de-Calais. In this same passage, Cæsar, after having been drawn away from his course during four hours of the night, perceived, at daybreak, that he had left Britain to his left. This fact cannot possibly be explained if he had intended to land at St. Leonards. As to Richborough, this locality is much too far to the north. Why should Cæsar have gone so far as Sandwich, since he could have landed at Walmer and Deal? Lymne, or rather Romney Marsh, will suit no better. This shore is altogether unfit for a landing-place, and none of the details furnished by the “Commentaries” can be made to suit it.[381] There remains Deal; but before describing this place, we must examine if, on his first passage, when Cæsar sailed, after remaining five days opposite the cliffs of Dover, the current of which he took advantage carried him towards the north or towards the south. (_See Page_ 177.) Two celebrated English astronomers, Halley and Mr. Airy, have studied this question; but they agree neither on the place where Cæsar embarked, nor on that where he landed. We may, nevertheless, arrive at a solution of this problem by seeking the day on which Cæsar landed. The year of the expedition is known by the consulate of Pompey and Crassus--it was the year 699. The month in which the departure took place is known by the following data, derived from the “Commentaries;” the fine season was near its end, _exuigua parte œstatis reliqua_ (IV. 20); the wheat had been reaped everywhere, except in one single spot, _omni ex reliquis partibus demesso frumento, una pars erat reliqua_ (IV. 32); the equinox was near at hand, _propinqua die œquinoctii_ (IV. 36). These data point sufficiently clearly to the month of August. Lastly, we have, relative to the day of landing, the following indications:--After four days past since his arrival in Britain.... there arose suddenly so violent a tempest.... That same night it was full moon, which is the period of the highest tides of the ocean, _Post diem quartam, quam est in Britanniam ventum_([382]).... _tanta tempestas subita coorta est.... Eadem nocte accidit, ut esset luna plena, qui dies maritimos æstus maximos in Oceano efficere consuevit_.