Against raids and incursions Oxford was naturally protected on three sides. For the Thames on the west and south and the Cherwell on the east cut her off from the attack of land forces, whilst even against Danes coming up the Thames from Reading, marsh lands and minor streams within the belt of these outer waters protected her. For in those early days, when Nature had things almost entirely her own way, there were many more branches of the river, many minor tributary streams flowing where now you see nothing but houses and streets. The Trill Mill stream, for instance, which left the main stream on the west of what is now Paradise Square, is now covered over for the greater part of its course; whilst the main stream, after passing beneath the road some seventy yards outside South Gate, gave off another stream running due south, parallel with the road to Folly Bridge, but itself evidently continued its own course across Merton Fields by the side of what is now Broad Walk, and finally found its way into the Cherwell. And besides this stream, which ran under S. Frideswide's enclosure, there were, on the east, the minor streams which now enclose the Magdalen Walks. But what Oxford needed to strengthen her was some wall or fosse along the line occupied afterwards by the northern wall of the city, along the line, that is, of George Street, Broad Street and Holywell, and also some _place d'armes_, some mound, according to the fashion of the times, with accompanying ditches. With these defences it seems probable that she was now provided. Thus fortified Oxford becomes the chief town of Oxfordshire, the district attached to it. And during the last terrible struggle of England with the Danes its position on the borders of the Mercian and West-Saxon realms seems for the moment to have given it a political importance under Æthelred and Cnut strikingly analogous to that which it acquired in the Great Rebellion. After Sweyn's death Oxford was chosen as the meeting-place of the great gemot of the kingdom. The gemots, which were now and afterwards held at Oxford, were probably held about the Mound, where houses were erected for the royal residence. In one of these Æthelweard, the King's son, breathed his last; one was the scene of another dastardly murder of Danes, when Eadric (1015) ensnared Sigeferth and Morkere into his chamber, and there slew them. And here it was, according to Henry of Huntingdon, that King Edmund, who had been making so gallant a struggle against the conquering Cnut, was murdered by Eadric's son. Eadric, we know, was a traitor, and well-skilled in murders at Oxford. He, when his son had stabbed Edmund by his directions, came to Cnut and [Illustration: Cornmarket Street]