This inhabited part, the mediaeval town of Cambridge, was comprised, (at least from the tenth century to the eighteenth,) in the space bounded by the river on the west, and on the east by a ditch, known finally as the "King's Ditch," from having been widened by Henry the Third in the Barons' War. This ditch left the Cam at the "King's Mill," (the modern representative of which still stands just above Silver Street Bridge,) and proceeded along the line of Mill Lane, Pembroke Street, Tibbs Row, Hobson Street, and Park Street, to fall into the river again opposite Magdalene College. Beyond the "Great Bridge," from which the place derived its name, a small cluster of houses climbed the steep bank, on the summit of which stood the Castle. Our earliest records show this area as by no means thickly covered with houses. Not only the inhabitants, but all their cattle lived in it; so there must have been many little farmyards and gardens interspersed amongst the dwellings. Domesday Book gives the number of these as only 400, and a couple of centuries later, in 1279, when the University was already in full existence, there were scarcely more. By the middle of the eighteenth century this number had trebled. But even in 1801, as may be seen in Lyson's plan of the town, the King's Ditch, which was then still an open watercourse, remained substantially the boundary of inhabited Cambridge. And the vast suburban extensions in the areas of Barnwell, Newnham, Chesterton, and Cherry Hinton are mostly very recent indeed; the bulk in fact belonging to the last half century. Their rise, and the continuous intrusion of ever fresh University and College buildings, has had the effect of once more depleting the area of mediaeval Cambridge, which to-day contains barely 800 houses. The whole of the University buildings, whether ancient or modern, are contained within this area, with the exception of the Colleges of Peterhouse, Pembroke, Christ's and Jesus (which together with a few of the Museums, stand just beyond the Ditch), and the New Court of St. John's College, which is on the other side of the river, in the old Common Field. The ecclesiastical and feminine foundations similarly situated, Selwyn College, Westminster College, Ridley Hall, Newnham College, and Girton College, are not recognised by the University as being strictly "Colleges" at all. [Illustration: _Peterhouse Wall, Coe Fen._]