Thus Wallingford was probably the walled or embattled ford, and Oxford almost certainly the "ford of the droves"—droves going north from Berkshire. One may say roughly that all the "hams" were Teutonic save where one can put one's finger on a probable Celtic derivation such as one has, for instance, in the case of Witham, which should mean the settlement upon the "bend" or curve of the river, a Celtic name with a Teutonic ending.

One may also believe that the termination "or" or "ore" is Teutonic; Cumnor may have meant "the wayfarers' stage," and Windsor probably "the landing place on the winding of the river."

Hythe also is thought to be Teutonic. One can never be quite sure with a purely Anglo-Saxon word, that it had a German origin, but at least Hythe is Anglo-Saxon, a wharf or stage; thus Bablock Hythe on the road through the Roman town of Eynsham across the river to Cumnor and Abingdon, cutting off the great bend of the river at Witham; so also the town we now call "Maidenhead," which was perhaps the "mid-Hythe" between Windsor and Reading. Some few certainly Celtic names do survive: in the Sinodun Hills, for instance, above Dorchester; and the first part of the name Dorchester itself is Celtic. At the very head of the Thames you have Coates, reminding one of the Celtic name for the great wood that lay along the hill; but just below, where the water begins, to flow, Kemble and Ewen, if they are Saxon, are perhaps drawn from the presence of a "spring." Cricklade may be all Celtic, or may be partly Celtic and partly Saxon. London is Celtic, as we have seen. And in the mass of places whose derivation it is impossible to establish the primitive roots of a Celtic place name may very possibly survive.

The purely Roman names have quite disappeared, and, what is odd, they disappeared more thoroughly in the Thames Valley than in any other part of England. Dorchester alone preserves a faint reminiscence of its Romano-Celtic name; but Bicester to the north, and the crossing of the ways at Alchester, are probably Saxon in the first part at least. Streatley has a Roman derivation, as have so many similar names throughout England which stand upon a "strata" or "way" of British or of Roman origin. But though "Spina" is still Speen, Ad Pontes, close by, one of the most important points upon the Roman Thames, has lost its Roman name entirely, and is known as Staines: the stones or stone which marked the head of the jurisdiction of London upon the river.

To return to the river regarded as a boundary, it is subject to this rather interesting historical observation that it has been more of a boundary in highly civilised than in barbaric times.

One would expect the exact contrary to be the case. A civilised man can cross a river more easily than a barbarian; and in civilised times there are permanent bridges, where in barbaric times there would be only fords or ferries.

Nevertheless, it is true of the Thames, as of nearly every other division in Europe, that it was much more of a boundary at the end of the Roman Empire, and is more of a strict boundary to-day, than it was during the Dark Ages, and presumably also before the Claudian invasion. Thus we may conjecture with a fair accuracy that in the last great ordering of boundaries within the Roman Empire, which was the work of Diocletian, and so much of which still survives in our European politics to-day (for instance, the boundary of Normandy), the Thames formed the division between Southern and Midland Britain. It is equally certain that it did not form any exact division between Wessex and Mercia.

The estuary has, of course, always formed a division, and in the barbarian period it separated the higher civilisation of Kent from that of the East Saxons, who were possibly of a different race, and certainly of a different culture. But the Thames above London Bridge was not a true boundary until the civilisation of England began to form, towards the close of the Dark Ages. It is perpetually crossed and recrossed by contending armies, and the first result of a success is to cause the conqueror to annex a belt from the farther bank to his own territories.

It is further remarkable that the one great definite boundary of the Dark Ages in England—that which was established for a few years by Alfred between his kingdom and the territory of the Danish invaders—abandons the Thames above bridges altogether, and uses it as a limitation in its estuarial part only, up to the mouth of the Lea.

With the definition of exact frontiers for the English counties, however, a process whose origin can hardly antedate the Norman Conquest by many years, the Thames at once becomes of the utmost importance as a boundary.

Its higher and hardly navigable streams are not so used. The upper Thames and its little tributaries for some ten miles from its source are not only indifferent to county boundaries, but run through a territory which has been singularly indefinite in the past. For instance, the parish of Kemble, wherein the first waters now appear, has been counted now in Gloucester, now in Wilts. But when these ten miles are run, just after Castle Eaton Bridge, and not quite half way between that bridge and the old royal palace at Kempsford, the Thames becomes the line of division between two counties, and from there to the sea it never loses its character of a boundary.

It is a tribute to the great place of the river in history that there is no other watercourse in England nor any other natural division of which this is so universally true.

The reason that the Thames, like so many other European boundaries, has come late into the process of demarcation, and the reason that its use as a limit is more apparent in civilised than in uncivilised times, is simply the fact that limits and boundaries themselves are never of great exactitude save in times of comparatively high civilisation. It is when a complex system of law and a far-reaching power of execution are present in a country that the necessity for precise delimitation arises. In the barbaric period of England there was no such necessity. Doubtless the men of Berkshire and the men of Oxfordshire felt themselves to be in general divided by the stream; but had we documents to hand (which, of course, we have not) it might be possible to show that exceptional tracts, such as the isolated Hill of Witham (which is much more influenced by Oxford than by Abingdon), was treated as the land of Oxfordshire men in early times, or was perhaps a territory in dispute; and something of the same sort may have existed in the connection of Caversham with Reading.

In this old age of our civilisation the exactitude of the boundary which the Thames establishes is apparent in various survivals. Islands now joined to the one bank and indistinguishable from the rest of the shore are still annexed to the farther shore. Such a patch is to be found at Streatley, geographically in Berkshire, legally in Oxford; there is another opposite Staines, which Middlesex claims from Surrey. In all, half-a-dozen or more such anomalous frontiers mark the course of the old river. One arrested in process of formation may be seen at Pentonhook.

A boundary—that is, an obstacle to travel—has this further feature, that the point at which it is crossed—that is, the point at which the obstacle is surmounted—is certain to become a point of strategic and often of commercial importance. So it is with the passes over mountains and with the narrows of the sea, and so it is with fords and bridges over rivers. So it is with the Thames.

The energies both of travel and of war are driven towards and confined in such spots. Fortresses arise and towns which they may defend. Depots of goods are formed, the coining and the change of money are established, secure meeting places for speculation are