What were the approaches on the west? There were none. Beyond Earith, where now run the great washes of the Bedford Level, was a howling wilderness of meres, seas, reed-ronds, and floating alder-beds, through which only the fen-men wandered, with leaping-pole and log canoe. What in the east? The dry land neared the island on that side. And it may be that William rowed round by Burwell to Fordham and Soham, and thought of attempting the island by way of Barraway, and saw beneath him a labyrinth of islands, meres, fens, with the Ouse, now increased by the volume of the Cam, lying deep and broad between Barraway and Thetford-in-the-Isle; and saw, too, that a disaster in that labyrinth might be a destruction. So he determined on the near and straight path, through Long Stratton and Willingham, down the old bridle-way from Willingham ploughed field,--every village there, and in the isle likewise, had and has still its “field,” or ancient clearing of ploughed land,--and then to try that terrible half-mile, with the courage and wit of a general to whom human lives were as those of the gnats under the hedge. So all his host camped themselves in Willingham field, by the old earthwork which men now call Belsar’s Hills; and down the bridle-way poured countless men, bearing timber and fagots cut from all the hills, that they might bridge the black half-mile. They made a narrow, firm path through the reeds, and down to the brink of the Ouse, if brink it could be called, where the water, rising and falling a foot or two each tide, covered the floating peat for many yards before it sunk into a brown depth of bottomless slime. They would make a bottom for themselves by driving piles. The piles would not hold; and they began to make a floating bridge with long beams, says Leofric, and blown-up cattle-hides to float them. Soon they made a floating sow, and thrust it on before them as they worked across the stream; for they were getting under shot from the island. Meanwhile the besieged had not been idle. They had thrown up, says Leofric, a turf rampart on the island shore, and _antemuralia et propugnacula,_--doubtless overhanging “hoardings,” or scaffolds, through the floor of which they could shower down missiles. And so they awaited the attack, contenting themselves with gliding in and out of the reeds in their canoes, and annoying the builders with arrows and cross-bow bolts. At last the bridge was finished, and the sow safe across the West water, and thrust in, as far as it would float, among the reeds on the high tide. They in the fort could touch it with a pole. The English would have destroyed it if they could. But Hereward bade them leave it alone. He had watched all their work, and made up his mind to the event. “The rats have set a trap for themselves,” he said to his men, “and we shall be fools to break it up till the rats are safe inside.”