No road of any importance seems to have left Lincoln by the west gate; and the reason for this is to be found in the physical features of the neighbourhood at the time of the Roman occupation. The part of Lincolnshire north of the Witham is still called “Lindsey”—a name which indicates by its final syllable that, when it was given, the district was practically surrounded by water. On all sides but the south it is so to this day—viz. by the sea on the east, by the Humber on the north, and by the Trent on the west. In the Roman period—and indeed for many centuries after—the Witham was tidal as far as the narrow “Gap” between Lincoln and the opposite high land of Kesteven. Geologists tell us that this “Gap,” now intersected by the Witham, was in pre-glacial ages scooped out by the Trent, the course of which from Newark was then north-east instead of north; and that after that river had been “captured” by the Humber (_i.e._ diverted into its present bed by the opening of a longitudinal valley from the north) it would always tend to revert to its original course in time of flood. The result of this constant flooding was the formation of a large mere, extending from the western end of the Gap as far north as Brampton, beyond which the east bank of the Trent was too high for the water to escape. The first syllable of Lindum no doubt represents the Celtic word, which was applied to this large sheet of water. Faint remains of it can still be seen in the small pool of Brayford—just below the south gate of the lower city. The flood-water came through five openings in a low range of sandhills between Spaldford and Brampton; and the first work of the Roman engineers was to build banks across these openings, and so shut out the water of the Trent. The southernmost opening at Spaldford—the most dangerous because the highest up the valley—was closed by a bank from 12 to 15 feet high and a mile and a half in length.