Now what is the meaning of this multiplicity, and of all this interest in preserving such a multiplicity even by artificial means? The tide is the clue to the problem. Consider a man starting from the continental shore to reach England; consider him sailing with a fresh breeze, for if the breeze was not fresh his chances of crossing in a reasonable time and of making any particular place of landing were small. Consider the fact that if he crossed in a fresh breeze that breeze would be, three times out of four, from the south or west. He runs under the lee of Gris Nez, and when he is beyond that point of rock, he gets into the short, sharp tumble of the sea which is raised by such a wind against the tide, for he has started at the ebb. He runs down with the wind abeam perhaps as far as the end of the Varne (where we now have the Varne Buoy), for the tide so takes him. He sees the water breaking and boiling at this shallow place. It settles near the turn of the tide. He holds on easily, making less westing and pointing well up to the shore. There opens before him a broad but very shallow lagoon with probably some central channel which he knows. He enters and has made the most favourable of the many crossings he knows. It is the Portus Lemanis--our Lympne. But there are other chances. The wind might fail him, or the wind might so increase that he had to run before it. Did it fail him he would be caught by the flood tide some miles from land. He would drift up along the English shore, getting a few hundred yards nearer with every catspaw, and looking impatiently for some place to which he could steer. The dip in the cliffs at Dover would give him a chance perhaps. If he missed that he would round the South Foreland; he would have the advantage of smooth water, and he would make for the island Rutupiae, which stood at the southern entrance of the strait between the Isle of Thanet and the mainland. If his bad luck preserved, he might be swept up in what we now call the Gull Stream round the North Foreland; but the tide would have been making so long by this time as to be curling round Longnose, and even without the wind he could trust to it almost alone to make Reculvers. Similarly if the wind made him run before it and caused him to miss the Portus Lemanis, he would have the advantage of a weather shore once he was round the South Foreland, and could run with smooth water under him into Rutupiae. With the prevalent winds, then, and the tidal conditions of the Straits, a multiplicity of harbours was a necessity for this crossing. In a tideless sea--such as the Mediterranean--one harbour, and one alone, would have absorbed the trade of Kent. Under our tidal conditions, a coast most ill-provided was compelled to furnish no less than six.