History of Julius Caesar Vol. 2 of 2. Napoleon III
is the period of the highest tides of the ocean, Post diem quartam, quam est in Britanniam ventum(381)… tanta tempestas subita coorta est… Eadem nocte accidit, ut esset luna plena, qui dies maritimos æstus maximos in Oceano efficere consuevit.
According to this, we consider that the tempest took place after four days, counted from the day of landing; that the full moon fell on the following night; and lastly, that this period coincided not with the highest tide, but with the highest tides of the ocean. Thus we believe that it would be sufficient for ascertaining the exact day of landing, to take the sixth day which preceded the full moon of the month of August, 699; now this phenomenon, according to astronomical tables, happened on the 31st, towards three o’clock in the morning. On the eve, that is, on the 30th, the tempest had occurred; four full days had passed since the landing; this takes us back to the 25th. Cæsar then landed on the 25th of August. Mr. Airy, it is true, has interpreted the text altogether differently from our explanation: he believes that the expression post diem quartum may be taken in Latin for the third day; on another hand, he doubts if Cæsar had in his army almanacks by which he could know the exact day of the full moon; lastly, as the highest tide takes place a day and a half after the full moon, he affirms that Cæsar, placing these two phenomena at the same moment, must have been mistaken, either in the day of the full moon, or in that of the highest tide; and he concludes from this that the landing may have taken place on the second, third, or fourth day before the full moon.
Our reasoning has another basis. Let us first state that at that time the science of astronomy permitted people to know certain epochs of the moon, since, more than a hundred years before, during the war against Perseus, a tribune of the army of Paulus Æmilius announced on the previous day to his soldiers an eclipse of the moon, in order to counteract the effect of their superstitious fears.382 Let us remark also, that Cæsar, who subsequently reformed the calendar, was well informed in the astronomical knowledge of his time, already carried to a very high point of advance by Hipparchus, and that he took especial interest in it, since he discovered, by means of water-clocks, that the nights were shorter in Britain than in Italy.
Everything, then, authorises us in the belief that Cæsar, when he embarked for an unknown country, where he might have to make night marches, must have taken precautions for knowing the course of the moon, and furnished himself with calendars. But we have put the question independently of these considerations, by seeking among the days which preceded the full moon of the end of August, 699, which was the one in which the shifting of the currents of which Cæsar speaks could have been produced at the hour indicated in the “Commentaries.”
Supposing, then, the fleet of Cæsar at anchor at a distance of half a mile opposite Dover, as it experienced the effect of the shifting of the currents towards half-past three o’clock in the afternoon, the question becomes reduced to that of determining the day of the end of the month of August when this phenomenon took place at the above hour. We know that in the Channel the sea produces, in rising and falling, two alternate currents, one directed from the west to the east, called flux (flot), or current of the rising tide; the other directed from the east to the west, named reflux (jusant), or current of the falling tide. In the sea opposite Dover, at a distance of half a mile from the coast, the flux begins usually to be sensible two hours before high tide at Dover, and the reflux four hours after.
So that, if we find a day before the full moon of the 31st of August, 699, on which it was high tide at Dover, either at half-past five in the afternoon or at midday, that will be the day of landing; and further, we shall know whether the current carried Cæsar towards the east or towards the west. Now, we may admit, according to astronomical data, that the tides of the days which preceded the full moon of the 31st of August, 699, were sensibly the same as those of the days which preceded the full moon of the 4th of September, 1857; and, as it was the sixth day before the full moon of the 4th of September, 1857, that it was high tide at Dover towards half-past five in the afternoon (see the Annuaire des Marées des Côtes de France for the year 1857),383 we are led to conclude that the same phenomenon was produced also at Dover on the sixth day before the 31st of August, 699; and that it was on the 25th of August that Cæsar arrived in Britain, his fleet being carried forward by the current of the rising tide.
This last conclusion, by obliging us to seek the point of landing to the north of Dover, constitutes the strongest theoretic presumption in favour of Deal. Let us now examine if Deal satisfies the requirements of the Latin text.
The cliffs which border the coasts of England towards the southern part of the county of Kent form, from Folkestone to the castle of Walmer, a vast quarter of a circle, convex towards the sea, abrupt on nearly all points; they present several bays or creeks, as at Folkestone, at Dover, at St. Margaret’s, and at Oldstairs, and, diminishing by degrees in elevation, terminate at the castle of Walmer. From this point, proceeding towards the north, the coast is flat, and favourable for landing on an extent of several leagues.
The country situated to the west of Walmer and Deal is itself flat as far as the view can reach, or presents only gentle undulations of ground. We may add that it produces, in great quantities, wheat of excellent quality, and that the nature of the soil leads us to believe that it was the same at a remote period. These different conditions rendered the shore of Walmer and Deal the best place of landing for the Roman army.
Its situation, moreover, agrees fully with the narrative of the “Commentaries.” In the first expedition, the Roman fleet, starting from the cliffs of Dover and doubling the point of the South Foreland, may have made the passage of seven miles in an hour; it would thus have come to anchor opposite the present village of Walmer. The Britons, starting from Dover, might have made a march of eight kilomètres quickly enough to oppose the landing of the Romans. (See Plate 16.)
The combat which followed was certainly fought on the part of the shore which extends from Walmer Castle to Deal. At present the whole extent of this coast is covered with buildings, so that it is impossible to say what was its exact form nineteen centuries ago; but, from a view of the locality, we can understand without difficulty the different circumstances of the combat described in Book IV. of the “Commentaries.”
Four days completed after the arrival of Cæsar in Britain, a tempest dispersed the eighteen ships which, after quitting Ambleteuse, had arrived just within sight of the Roman camp. All the sailors of the Channel who have been consulted believe it possible that the same hurricane, according to the text, might have driven one part of the ships towards the South Foreland and the other part towards the coast of Boulogne and Ambleteuse. The conformation of the ground itself indicates the site of the Roman camp on the height where the village of Walmer rises. It was situated there at a distance of 1,000 or 1,200 mètres from the beach, in a position which commanded the surrounding country. And it is thus easy to understand, from the aspect of the locality, the details relative to the episode of the 7th legion, surprised while it was mowing.384 It might be objected that at Deal the Roman camp was not near to a water-course, but they could dig wells, which is the only method by which the numerous population of Deal at the present day obtain water.
From all that has just been said, the following facts appear to us to be established in regard to the first expedition. Cæsar, after causing all his flotilla to go out of the port the day before, started in the night between the 24th and 25th of August, towards midnight, from the coast of Boulogne, and arrived opposite Dover towards six o’clock in the morning. He remained at anchor until half-past three in the afternoon, and then, having wind and tide in his favour, he moved a distance of seven miles and arrived near Deal, probably between Deal and Walmer Castle, at half-past four. As in the month of August twilight lasts till after half-past seven, and its effect may be prolonged by the moon, which at that hour was in the middle of the heaven, Cæsar had still four hours left for landing, driving back the Britons, and establishing himself on the British soil. As the sea began to ebb towards half-past five, this explains the anecdote of Cæsius Scæva told by Valerius Maximus; for, towards seven o’clock, the rocks called the Malms might be left uncovered by the ebb of the tide.
After four entire days, reckoned from
Word for word, this expression signifies that the ships set sail four days after the arrival of the Romans in England. The Latin language often employed the ordinal number instead of the cardinal number. Thus, the historian Eutropius says, “Carthage was destroyed 700 years after it was founded,
Titus Livius, XLIV. 37.
We must now go back to the fourteenth day before the full moon, that is, to the 17th of August, 699, to find a day on which high tide took place at Dover towards midday.
Mr. Lewin has stated that the country between Deal and Sandwich produces no wheat. This assertion is tolerably true for the tongue of marshy land which separates those two localities; but what does it signify, since wheat grows in great quantities in all the part of the county of Kent situated to the west of the coast which extends from the South Foreland to Deal and Sandwich?