Thus it is physically impossible that any very considerable number of men can have come over seas at any one moment in the small and shallow boats of the time, but for all the rest we have nothing but legend and our varying estimate of how the society attacked would probably have behaved and what the internal reactions within it under the strain of such an anxiety would probably have been. We can be fairly certain that an attack of this sort could not deal with a defended Roman town, though here and there a garrison on the coast may have been overwhelmed. We can be morally certain from all that we know of that society that men coming for loot would not kill slaves. On the other hand, we do not know how far the anarchy may have been increased by the presence of numerous escaped slaves in the welter. We have a right to exclude the fantastic--such as the astonishing idea that a great Roman town like London could be wiped out _and then resettled by a totally new population_, and we have a right to exclude as very nearly worthless odd stories cropping up hundreds of years later in the _Anglo-Saxon Chronicle_. On the other hand, we are bound to pay more respect to such a remark as that of the Venerable Bede when he testifies to the migration of a whole body of pirate population from the capital of Schleswig to that of Britain. If we could discover what happened between the first generation of the fifth century and the first generation of the seventh, the discovery would be the most important and interesting that could be made in connection with our history. For in Britain as in every other province of Europe the process by which civilisation entered into the Dark Ages is the explanation of all that followed. But the discovery has not yet been granted to us, and in all human probability never will be. We know that the avenue of approach from the Continent to Britain, that is, the coasts of the south and east, were so far ruined or occupied or degraded, the communication with the rest of the island was cut off; we know that when civilisation came back with St. Augustine it had to work through the medium of little courts scattered up and down these shores, and we can presume that writing and record and government thus filtering through the south and east to the rest of the island gradually spread the speech and certain of the customs of that south and east eastward throughout the succeeding centuries. Of more than that we are ignorant. The Lower Thames, therefore, and the part that it played in that first capital piece of fighting lies, unfortunately, outside the field of positive history. We do not begin to get any true record of the Thames as an avenue of invasion until the second raids begin, three centuries after the first: those second raids which are collectively known in this country under the title of “Danish.”