C. 6.--All these preparations, though they seem to have been carried out with extreme celerity, lasted long enough to alarm the Britons. Several clans sent over envoys, to promise submission if only Caesar would refrain from invading the country. This, however, did not suit Caesar's purpose. Such diplomatic advantages would be far less impressive in the eyes of the Roman "gallery" to which he was playing than his actual presence in Britain. So he merely told the envoys that it would be all the better for them if he found them in so excellent and submissive a frame of mind on his arrival at their shores, and sent them back, along with Commius, who was to bring in his own clan, the Atrebates, and as many more as he could influence. And the Britons on their part, though ready to make a nominal submission to "the mighty name of Rome," were resolved not to tolerate an actual invasion without a fight for it. In every clan the war party came to the front, all negotiations were abruptly broken off, Commius was thrown into chains, and a hastily-summoned levy lined the coast about Dover, where the enemy were expected to make their first attempt to land. C. 7.--Dover, in fact, was the port that Caesar made for. It was, at this date, the obvious harbour for such a fleet as his. All along the coast of Kent the sea has, for many centuries, been constantly retreating. Partly by the silting-up of river-mouths, partly by the great drift of shingle from west to east which is so striking a feature of our whole southern shore, fresh land has everywhere been forming. Places like Rye and Winchelsea, which were well-known havens of the Cinque Ports even to late mediaeval times, are now far inland. And though Dover is still our great south-eastern harbour, this is due entirely to the artificial extensions which have replaced the naturally enclosed tidal area for which Caesar made. There is abundant evidence that in his day the site of the present town was the bed of an estuary winding for a mile or more inland between steep chalk cliffs,[77] not yet denuded into slopes, whence the beach on either side was absolutely commanded.