Airy says that ‘on the day of Caesar’s landing the tide off Dover turned to the west about 1 h. in the afternoon, and at 3 h. it would be running with a strong stream to the west’.[2980] Airy, as we have seen,[2981] supposes that the day of Caesar’s landing was the 28th of August; but if the statement which I have just quoted is accurate, it follows that even on the 26th the tide at 3 p.m. was running westward. Again, in 1866, the Admiralty Hydrographer affirmed that on the 27th of August, 55 B.C., the current ran westward until 6.30 p.m.;[2982] and if he is right, it must on the previous day, unless the circumstances were abnormal, have continued flowing in the same direction until 5 p.m. or later. Lewin,[2983] relying upon a table compiled by a Mr. Barton of Dover, and based upon observations made by ‘some experienced pilot or fisherman’, and upon another table filled up from actual observation ‘on every day of July, 1862’, states that ‘with high water ... at 7.31 a.m., the tide could not turn eastward at the earliest until 4.26 p.m., and at the latest not until 5.21 p.m.’ Nevertheless, he admits[2984] that, with high tide at 7.31 a.m., the tide might possibly have turned eastward at 4 p.m. Finally, Mr. H. E. Malden tells us that ‘at any time that afternoon between two o’clock and seven, in any part of the Channel between Dunge Ness and Dover, the tidal current was running westward ... when Sir George Airy, the greatest authority of the century upon the tides, says that they were the same then as now, cadit quaestio. We are lifted out of the uncertainties of historical topography into the certainties of scientific knowledge.’[2985]
This pronouncement is certainly calculated to overawe the timid inquirer. Nevertheless, I venture to suggest that a man who knows little or nothing about the tides should refrain from patting on the back one who knew a great deal, but who did not think it necessary for his purpose to tell all that he knew.
Airy may have been the greatest authority of the century upon the tides: but, apart from his asseveration that they were the same then as now, in the contribution which he made to the solution of the problem which we are investigating he relied upon authorities which are accessible to everybody. Those authorities (I will mention a few besides those which Airy used) are the Nautical Almanac; Tide Tables for the British and Irish Ports (published by order of the Lords Commissioners of the Admiralty); the Channel Pilot; Tidal Streams, English and Irish Channels (an Atlas of 12 charts published at the Admiralty in 1899); Captain Usborne Moore’s Report on Observations ... in the Straits of Dover (also published at the Admiralty in 1899); an article by Admiral Sir F. W. Beechey published in Philosophical Transactions, volume cxli, 1851, pages 703-18; and an article published in Archaeologia, volume xxxix, 1863, pages 277-302. The last-named article includes a report of observations on the tidal streams in the Straits of Dover, made in 1862 under the superintendence of E. K. Calver, R.N. These observations were made for the purpose of settling the question whether the stream with which Caesar sailed from his anchorage ran up or down the Channel. They were made ‘in comparatively still weather’ on the 21st of August, the 4th and 5th of September, and the 4th of October, 1862, at eleven distinct stations within a space extending to one mile and a half from the shore, and from the South Foreland to Shakespeare’s Cliff. The days on which they were made were, reckoning inclusively, respectively the fifth before the new moon, and the fifth, the fourth, and the fourth before the full moon. ‘From the average of these observations,’ says Calver, ‘it appears that, when high water at Dover occurs about 7 h. 30 m. a.m., the inshore flood or easterly-going stream ... turns 4 h. 48 m. after it is high water upon the shore. Taking then, for example, a 7 h. 31 m. a.m. high water, and assuming that the ebb or westerly-going stream runs on the average for 6¼ hours, it follows that the flood or easterly-going stream on that day would turn off Dover at 12 h. 19 m., and the succeeding ebb ... would run to the westward until 6 h. 34 m. p.m.[2986]’ Vice-Admiral W. H. Smyth, summing up the results of the observations, remarked that the tide turned westward ‘soonest near the beach and latest in the offing’, and that ‘the turn is sooner to the east of Dover than to the west, still not differing more than one hour’.[2987]
So far as we have yet examined them, the results of these observations fully bear out what Airy and Lewin maintain,—if it is assumed that high tide at Dover on the day of Caesar’s landing must have occurred about 7.30 a.m. But if we scrutinize the tables more closely, and give due weight to certain other facts emphasized by our authorities, we shall see that the dogmatism of Airy and Lewin is unjustifiable. They and their followers make no allowance for the great influence which winds exert upon the tidal streams in the Channel.[2988] Moreover, it is useless to base conclusions upon the average of the results obtained in Surveyor Calver’s observations. If we scan the tables which give those results in detail, we shall find that although, on the average, the stream turned westward 4 h. 48 m. after high water at Dover, yet on the 21st of August it turned only 3 h. 40 m. after high water.[2989] We shall also find that the duration of the flood, as observed by Calver, varied from 4 to 7 hours; and although the duration of the ebb was only observed twice,[2990] it may actually have varied as much. On the first of the two occasions on which it was observed it was 6 hours, 10 minutes; on the second, only 5 hours, 53 minutes;[2991] and, according to the Channel Pilot,[2992] it is occasionally only 4 hours. Therefore it is possible that if on the day of Caesar’s landing high water occurred at Dover at 7.31 a.m., the tide may have turned westward as early as 11.11 a.m., and may have continued to run westward for a period not longer than 5 hours, 53 minutes, that is to say, until 5.4 p.m.
But this is not all. It is desirable that the reader should become acquainted with Lewin’s methods of reasoning. Lewin himself, after studying the Admiralty Tide Tables for the year 1859, admits that ‘on January 14th, being the fourth day before the full moon, high water at Dover is at 5.31 a.m.’, and that it may possibly have occurred as early on the day of Caesar’s landing. This admission throws a breaking strain upon his theory; but by dint of dexterous manipulation of the facts he is just able to make a show of saving it from ignominious collapse. ‘As’ he says, ‘the stream turns at four hours after high water, and continues for seven hours, it turns at the earliest at 9.31 a.m. and runs till 4.31 p.m.... In no case, therefore, would the tide be running east at 3 p.m.’ But Lewin is here compelled to ignore observations of which, in another part of his book, he makes free use. As we have already seen, he admits[2993] that on a day when high tide occurred at 7.31 a.m. the stream might turn eastward at 4.26 or even at 4 p.m. If he is right, it follows that on a day when high tide occurred at 5.31 a.m. the stream might turn eastward at 2.26 or even at 2 p.m. To make this admission, from which, if he had been confronted with his own words, he could by no subtlety have escaped, would have been to throw up his case; and such candour would have been too much to expect from a professional advocate. Let him, however, shift his ground, if he pleases, and rely upon Calver’s observations. They will not avail him. We have just seen that, according to Calver, the stream turned westward on the 21st of August, 1862, 3 h. 40 m. after high water; and the duration of the westward stream, on one of the two occasions on which he observed it, was only 5 h. 53 m.[2994] According to these data, if, on the day of Caesar’s landing, high tide had occurred at 5.31 a.m., the westward stream might have ceased at 3.4 p.m. It would have been impossible for Lewin, if he had been required to take account of this statement, to deny it. But to admit it would have been to sign the death-warrant of his own theory.
So far I have only been concerned to show that Lewin’s whole train of reasoning, examined in the light of the evidence which he himself adduces, is radically unsound. I have argued on his hypothesis—that high tide at Dover, on the day of Caesar’s landing, may have occurred at the earliest time at which it can possibly occur on the fourth day before the full moon. Neither Lewin nor Airy nor any other commentator has attempted to determine, by the aid of lunar tables, the hour at which, on the day in question, high tide did actually occur.[2995] Nevertheless, if the problem which we intend to solve is to be attacked in a scientific spirit, the hour ought to be determined. Messrs. John A. Sprigge, William Fraser Doak, M.A., F.R.A.S., and T. Charlton Hudson, B.A., F.R.A.S., all of the Nautical Almanac Office, have been so kind as to determine it for me. Their calculations are preserved; and at the end of this article, on page 665, will be found a memorandum, in which they have described the method on which they worked. It will be sufficient here to state the results, the error in which, as they point out, is probably insignificant. On the 26th of August, 55 B.C., the Greenwich mean time of high water at Dover was 6.21 a.m.; on the 27th, 7.42 a.m.; and on the 28th, 8.44 a.m.[2996] Thus it turns out that on the day of Caesar’s landing high water did not occur at all early. This fact, however, will not sustain the theory of Airy and Lewin. Since high water at Dover on the 26th of August occurred at 6.21 a.m., and since the tidal stream, according to one of Calver’s observations, turned 3 hours, 40 minutes after high water, the stream may have turned westward at 10.1 a.m. Assuming that the duration of the westward stream was 5 hours, 53 minutes—the same as that recorded on one occasion by Calver—the stream would have ceased at 3.54 p.m. But Calver’s observations were made ‘in comparatively still weather’;[2997] and, to quote Admiral Beechey, ‘winds greatly affect the time of turn of the stream.’[2998] Now Caesar sailed from his anchorage with wind as well as tide in his favour; and the wind which carried him to his landing-place may have accelerated the turn of the stream. It is clear, therefore, that on the day of Caesar’s landing the stream may have turned eastward earlier than 3.54 p.m.; and if it turned twenty-five minutes earlier, it turned in ‘the ninth hour’.
But, it will be objected, Caesar may have landed on the 27th of August; and in that case the stream could not have turned eastward before the close of the ninth hour. Certainly it could not have done so unless it had turned westward unusually early, or unless its westward duration had but little exceeded four hours; and although this has been shown to be within the bounds of possibility,[2999] it is to the last degree improbable. But if he landed on the 26th of August, an assumption which has been proved to be not inconsistent with his narrative,[3000] it is not improbable that the stream may have turned eastward in the ninth hour; and this is all that I am concerned at present to show.
It may be said that, in order to refute the dogma of Airy and Lewin, I have supposed an extreme case. I can only say that I did not start with the intention either of refuting or defending that dogma: I merely examined it, and found that it would not bear examination. And I am justified in supposing an extreme, or rather an exceptional, case because Airy and Lewin have both affirmed that it is absolutely impossible that in the ninth hour on the day of Caesar’s first landing in Britain the tidal stream can have been running towards the east. But, supposing that it did not turn eastward until after the ninth hour, still the theory that Caesar must have sailed in the opposite direction will not stand. For the reader, if he has patience to bear with me to the end, will convince himself, from Caesar’s own words, that Caesar did not stir from his anchorage until after the ninth hour had passed.
VII. THE THEORY THAT CAESAR LANDED AT PEVENSEY
The two distinguished advocates of the theory that Caesar landed at Pevensey are not in complete accord. Airy holds that he sailed both in 55 and in 54 B.C. from the mouth of the Somme;[3001] Professor Ridgeway from Wissant.[3002] It has been proved in my article on the Portus Itius that he started from Boulogne; and whoever accepts that proof will, perhaps, skip this section. I am willing, however, for the sake of argument, to accept in turn both Airy’s identification of the Portus Itius and that of Professor Ridgeway: but I may remark that when Airy wrote he had forgotten that in Caesar’s time there was a natural harbour at Pevensey;[3003] and if Caesar had landed in a harbour he would not have left the fact unnoticed.