different accompanying art, from the life of the river above bridges.

We have seen that the river when it is regarded as an avenue of access to men for commerce or for travel is, especially in early times, and with boats of light draught, of one piece from Lechlade to London Bridge. There was in this section always sufficient water even in a dry summer to float some sort of a boat. But the river, regarded as a barrier or obstacle for human beings in their movement up and down Britain, did not form one such united section. On the contrary, it divided itself, as all such rivers do, into two very clearly defined parts: there was that upper part which could be crossed at frequent intervals by an army, that lower part in which fords are rare.

In most rivers one has nothing more to do in describing those two sections than to show how gradually they merge into one another. In most rivers the passage of the upper waters is perfectly easy, and as one descends the fords get rarer and rarer, until at last they cease.

With the Thames this is not the case. The two portions of the river are sharply divided in the vicinity of Oxford, and that for reasons which we have already seen when we were speaking of the suitability of its banks for habitation. The upper Thames is indeed shallow and narrow, and there are innumerable places above Oxford where it could be crossed, so far as the volume of its waters was concerned. It was crossed by husbandmen wherever a village or a farm stood upon its banks. Perhaps the highest point at which it had to be crossed at one chosen spot is to be discovered in the word Somer_ford_ Keynes, but the ease with which the water itself could be traversed is apparent rather in the absence than in the presence of names of this sort upon the upper Thames. Shifford, for instance, which used to be spelt Siford, may just as well have been named from the crossing of the Great Brook as from the crossing of the Thames. The only other is Duxford.

While, however, the upper Thames was thus easy to cross where individuals only or small groups of cattle were concerned, the marshes on either side always made it difficult for an army. The records of early fighting are meagre, and often legendary, but such as they are you do not find the upper Thames crossed and recrossed as are the upper Severn or the upper Trent. There are two points of passage: Cricklade and Oxford, nor can the passage from Oxford be made westward over the marshes. It is confined to the ford going north and south.

Below Oxford, after the entry of the Cherwell, and from thence down to a point not very easily determined, but which is perhaps best fixed at Wallingford, the Thames is only passable at fixed crossings in ordinary weather, as at Sandford, where the hard gravels approach the bank upon either side, and at other places, each distant from the next by long stretches of river.

It is not easy, now that the river has been locked, to determine precisely where all these original crossings are to be found.

The records of Abingdon and its bridge make it certain that a difficult ford existed here; the name "Burford" attached to the bridge points to the ancient ford at this spot. It is a name to be discovered in several other parts of England where there has been some ancient crossing of a river, as, for instance, the crossing of the Mole in Surrey by the Roman military road.

The next place below Abingdon may have been at Appleford, but was more likely between the high cliff at Clifton-Hampden and the high and dry spit of Long Wittenham. Below this again for miles there was no easy crossing of the river.

The Thames was certainly impassable at Dorchester. The whole importance of Dorchester indeed in history lies in its being a strong fortified position, and it depends for its defence upon the depth of the river, which swirls round the peninsula occupied by the camp.

It has been conjectured that there was a Roman ford or ferry at the east end of Little Wittenham Wood, where it touches the river. The conjecture is ill supported. No track leads to this spot from the south, and close by is an undoubted ford where now stands Shillingford Bridge.

Below this again there was no crossing until one got to Wallingford; and here we reach a point of the greatest importance in the history of the Thames and of England.

Wallingford was not the lowest point at which the Thames could ever be crossed. So far was this from being the case that the tidal Thames could be crossed in several places on the ebb, notably at the passage between Ealing and Kew, where Kew Bridge now stands; and, as we shall see, the Thames was passable at many other places. But the special character of the passage at Wallingford lay in the fact that it was a ford upon which one could always depend. Below Wallingford the crossings were either only to be effected in very dry seasons or, though normally usable, might be interrupted by rain.

It is at Wallingford, therefore, that the main lowest passage of the Thames was effected, and it was through Wallingford that Berkshire communicated with the Chilterns. Wallingford is, then, the second point of division upon the Thames when one is regarding that river as a defence or a boundary. Below Wallingford there was perhaps a regular crossing at Pangbourne; there was certainly a ford of great importance between Streatley and Goring; and all the way down the river at intervals were difficult but practicable passages—notably at Cowey Stakes between the Surrey and the Middlesex shore, a place which is the traditional crossing of Cæsar. The water here in normal weather was, however, as much as five feet deep, and this ford well illustrates the difficulties of all the lower crossings of the Thames.

The effect of the river as a barrier must, of course, have largely depended upon the level to which the waters rose in early times. It is exceedingly difficult to get any evidence upon this—first, because however far you go back in English history some sort of control seems always to have been imposed upon the river; and secondly, because the early overflows have left little permanent effect.

As an example of the antiquity of the regulation of the Thames we have the embankment round the Isle of Dogs, which is Roman or pre-Roman in its origin, like the sea-wall of the Wash, which defends the Fenland; and at Ealing, Staines, Abingdon, and twenty other places we have sites probably pre-historic, and certainly at the beginnings of history, which could never have been inhabited if the neighbouring fields had not been drained or protected. The regularity of the stream has therefore been somewhat artificial throughout all the centuries of recorded history, and the banks have had ample time to acquire consistency.

It is certain, of course, that works of planting, of draining, or of embankment, which required continuous energy, skill, and capital, decayed after the coming of the Saxon pirates, and were not undertaken again with full vigour until after the Norman Conquest. Even to-day the work is not quite complete, though every year sees its improvement: we are still unable to prevent regularly recurrent floods in the flats round Oxford and below the gorge of the Chilterns; but for the purpose of this argument the chief fact to be noted is that no serious interruption to the approach of the river seems to have existed in historic times.

In pre-historic times many stretches of the river must have afforded great difficulties of approach. The mouths of the Ock, the Coln, the Kennet, the Mole, and the Wandle must each have been surrounded by a marsh; all the plain between Oxford and the Hinkseys must have been partially flooded, as must the upper reaches between Lechlade and Witham (on one side or the other of the stream as it winds from the