Volume 3 — A DISCOURSE tending to prove at what Time and Place, Julius Cesar made his first Descent upon Britain: Read before the Royal Society by E. Halley.

Though Chronological and Historical Matters, may not seem so properly the Subject of these Tracts, yet there having, in one of the late Meetings of the Royal Society, been some Discourse about the Place where Julius Cesar Landed in Britain, and it having been required of me to shew the Reason why I concluded it to have been in the Downs; in doing thereof, I have had the good Fortune so far to please those worthy Patrons of Learning I have the Honour to serve, that they thought fit to command it to be inserted in the Philosophical Transactions, as an instance of the great Use of Astronomical Computation for fixing and ascertaining the Times of memorable Actions, when omitted or not duly delivered by the Historian.

1. The Authors that mention this Expedition with any Circumstances, are Cæsar in his Commentaries lib. 4, and Dion Cassius in lib. 39; Livy's account being lost, in whose 105th. Book might possibly have been found the Story more at large. It is certain that this Expedition of Cæsars, was in the Year of the Consulate of Pompey and Crassus, which was in the Year of Rome 699. or the 55th before the usual Æra of Christ: And as to the time of the Year, Cæsar says that Exigua parte æstatis reliqua, he came over only with two Legions, viz. the 7th and 10th and all Foot, in about 80 Sail of Merchant Ships, 18 Sail that were ordered to carry the Horse not being able to get out at the same time from another Port, where they lay Wind-bound. He says that he arrived about the 4th hour of the Day, viz. between Nine and Ten in the Morning, on the Coast of Britain, where he found the Enemy drawn up on the Cliffs ready to repel him, which place he thus describes. Loci hæc erat natura, adeo montibus augustis mare continebatur ut ex locis superioribus in littus telum adjicit possit, by which the Cliffs of Dover and the South Foreland are justly described, and could be no other Land, being he says in the 5th Book of his Commentaries, in Britanniam trajectum esse cognoverit circitur millium passum triginta à continenti, the Cliffs of the North-Foreland being at a much greater distance. Here he says he came to an Anchor, and staid till the 9th hour, or till about between Three and Four in the Afternoon, expecting till his whole Fleet was come up; and in the mean time called a Council of War, and advertised his Officers, after what manner they were to make their Descent, particularly in relation to the Stuff of the Sea, whose motion he calls celerem atq. instabilem, quick and uneven. Then, viz. about Three in the Afternoon he weighed Anchor, and having gotten the Wind and Tide with him, he Sail'd about Eight Miles from the first place, and Anchor'd against an open and plain Shore.

2. Here he made his Descent, and having told us the opposition that was made, and the means he used to get on Shore, he comes to say, that after he had been Four Days in Britain, the 18 Ships with his Horse put to Sea, and were come in sight of his Camp, when a suddain Tempest arose, with contrary Wind, so that some of the Ships put back again, others were driven to the Westwards, not without great danger, and coming to Anchor, they found they could not ride it out: so when Night came on, they put off to Sea and returned from whence they came. That same Night it was Full-Moon, which makes the greatest Tides in the Ocean, and they being ignorant thereof, their Gallies, which were drawn on Shore, were filled by the Tide, &c.

3. Then he says that the Day of the Autumnal Equinox being at hand, after some Days stay, wherein there passed no Action because he kept close in his Camp by the shore; and not thinking it proper to stay till the Winter came on, he returned into Gallia: The next Year he made a further Expedition with 5 Legions and a good Body of Horse, but there is but little in the History thereof serving to our purpose, excepting that he says he set Sail from the Portus Icius about Sun Set, with a gentle S. W. Wind, leni Africo profectus; that about Midnight it fell Calm, and being carried away with the Tide, by the time it was Day, he found he had left Britain on the left hand; but then the Tide turning they fell to their Oars, and by Noon reached that part of the Island where he Landed before, and came on Shore without opposition: and then March'd up into the Country, leaving his Ships at Anchor in littora molli & aperto.

4. This is all in Cæsar that is any thing pertinent, and I find no where else any thing to guide us farther, except one passage in Dion Cassius, who speaking of the first Landing of Cæsar, says οὐ μέντοι καὶ ᾗ ἔδει προσέσχεν, that is, as I Translate it. But he Landed not where he intended, for that the Britains hearing of his coming, had possest all usual Places of Landing Ἄκραν οὖν τινὰ προέχουσαν περιπλεύσας ἑτέρωσε παρεκομίσθη. Κἀνταῦθα τοὺς προσμίξαντάς οἱ ἐς τὰ τενάγη ἀποβαίνοντι νικήσας, ἔφθη τῆς γῆς κρατήσας, in my English. Wherefore doubling a certain head Land, he made to the Shore on the other side, where he overcame those that Skirmished with him at the Waters edg, and so got well on Land. Here I make bold to translate the Words ἐς τὰ τενάγη, at the water edge, which in H. Stephens Edition is interpreted in paludibus, but I have the Authority of Suidas, who says τέναγος, πελαγία ἰλὺς, or the Sea Mud, and is therefore properly the Ouse on the Sea Shore, and by an easie Figure may be put for the Shore it self, where such Ouse commonly is found.

5. From these data, That it was in the Year of the Consulate of Pompey, and Crassus; That it was Exigua parte æstatis reliqua, and Four Days before a Full-Moon, which fell out in the Night time. The time of this Invasion will be determined to a Day: For by the Eclipse of the Moon, whereof Drusus made so good use to quiet a Mutiny in the Pannonian Army, upon the News of the Death of Augustus, it follows that Augustus Died Anno Christi 14. which was reckoned Anno Vrbis conditæ 767. and that this Action was 68 Years before, viz. in the 55th Year before Christ Current. In which Year the Full Moon fell out August 30. after Midnight, or 31 in the Morning before Day; and the preceeding Full-Moon, was August 1. soon after Noon; so that this could not be the Full-Moon mentioned, as falling in the Day time: nor that in the beginning of July, it being not 10 Days after the Summer solstice, when it would not have been said exigua parte æstatis reliqua. It follows therefore that the Full-Moon spoken of, was on August 30. at Night, and that the Landing on Britain was August 26. in the Afternoon, about a Month before the Autumnal equinox; which agrees to all the Circumstances of the Story in point of Time.

6. As to the Place, the high Land and Cliffs described, could be no other than those of Dover, and are allowed to have been so by all, it remains only to examine whether the Descent was made to the Northward or Southward of the place where he first Anchored. The data to determine this are first that it was Four Days before the Full-Moon. 2. That that Day by Three of the Clock in the Afternoon the Tide ran the same way he Sail'd. 3dly. That a S. by E. Moon makes High-Water on all that Coast, the Flood coming from the Southward: hence it will follow, that that Day it was High-Water there about Eight in the Morning, and consequently Low-Water about Two, wherefore by Three the Tide of Flood was well made up, and it is plain that Cæsar went with it, and the Flood setting to the Northward shews that the open plain Shore where he Landed was to the Northward of the Cliffs, and must be in the Downs; and this I take to be little less than Demonstration. A second Argument is drawn from the Wind wherewith he set out on his second Expedition, viz. S. W. as appears by the Words leni Africo profectus, with which the Navigation of those times would hardly permit a Ship to Sail nearer the Wind than Eight Points, or a N. W. Course; which would serve indeed to go into the Downs, but would by no means fetch the Low-land towards Dengyness, which is much about West from Calais, and not more than W. N. W. from Boulogne, if it shall be said that that was the Portus Icius from which Cæsar set out. Whence I take it to be evident that if Cæsar was not bound more Northerly than the South-Foreland, he could not have thought the Africus or S. W. Wind proper for his passage, which was then intended for the place where he first Landed the year before.

7. Justly to determine which the Portus Icius was I find no where sufficient grounds; only Ptolemy calls the Promontory of Calais-Cliffs by the name of Ἴκιον ἄκρον, whence there is reason to conjecture, that the Portus Icius was very near thereto, and that it was either Ambletuse on one side, or Calais on the other. The same Ptolemy places Γισοῤῥίακον ἐπίνειον in the same Latitude with the ἴκιον ἄκρον, but something more to the East, which seems to refute those that have supposed the Ancient Port of Gessoriacum to have been Boulogne, whereas by Ptolemy's position, it must be either Dunkirk or Graveling, but the former most likely, both by the distance from the Ἴκιον ἄκρον, being about 20 Miles or half a degree of Longitude to the East, or ⅔ of the whole Coast of Flanders, which he makes but a degree and quarter from the Acron Icion to the mouth of the Scheld which he calls Ostia Tabudæ: As also for that Pliny l. 4. c. 16. speaking of Gessoriacum, says the Proximus Trajectus into Britain from thence is 50 Miles, which is too much unless Gessoriacum were something more Easterly than Calais. Dion Cassius makes the distance between France and Britain 450 stadia or 56 Miles, and says likewise 'tis the nearest, τὸ Συντομώτατον. But this is in part amended by the explication given in the Itinerary of Antoninus, where the space between Gessacorum and Rutupium is said to be 450 stadia (for this was the ordinary passage of the Romans into Britain,) Rutupium being more Northerly and Gessoriacum more Easterly than the termini of Cæsars Voyage, and consequently the distance greater than 30 Miles which Cæsar had observ'd; and now lately an accurate Survey has proved the distance between Land and Land to be 26 English Miles or 28½ Roman Miles, which shews how near Cæsars estimate was to the Truth.

A farther Argument (but not of equal force with the former because of the modernness of the Author, who writ above 250 Years after) may be drawn from the words of Dion Cassius, where he says ἄκραν τινὰ προέχουσαν περιπλεύσας ἑτέρωσε παρεκομίσθη, that after his first Anchoring he Sail'd about a Promontory to the place where he Landed: Now there are no other Promontories on all that Coast but the South-Foreland and Dengyness; the latter of which it could not be, because Cæsar says he Sail'd but 8 Miles, and the Ness it self is about 10 Miles from the South and nearest end of the Chalk-Cliffs by the Town of Hith; and to have gone round that Point to the other side, the distance must have been much greater. So that the Promontory spoken of by Dion, must needs be the South-Foreland, and Cæsar must Anchor near over against Dover, from whence Sailing 8 Miles, he would double a Head-land and come to the Downs; which is such a Coast as he describes in one place by apertum ac planum littus, and in his 5th Book by molle ac apertum littus. As to Dions word εἰς τὰ τενάγη, what I have already said about it seems sufficient to prove that he means no more than the Waters edg; and the Etymologists derive it from τέγγω madefacio, because the wash and breach of the Sea does always keep it wet. And this word τὰ τενάγη is used by Polybius for the Sea Ouse; and in another place he speaks of the difficulty of Landing at the mouth of a River, Διὰ τὴν τεναγώδη πάροδον, ob limosum accessum, so that it is not to be doubted that it ought to be rendred in this place, ad vadum maris rather than in paludibus. And so this objection against the assertion that Cæsar Landed in the Downs, which is known to be a firm Champain Country without Fenns and Morasses, will be removed; and the whole Argument will 'tis hoped be admitted by the Curious.

FINIS.