The eastern branch of Ermine Street can be traced for about four miles north of Sleaford, but its subsequent course is unknown. At or near Sleaford it threw off a branch-way, which passes through Ewerby and North Kyme (where it crosses the Cardyke), and points towards Tattershall and Horncastle. At North Kyme, where two bronze leaf-shaped swords have been found, is a small camp with a double vallum, and two more are on record in Tattershall Park. These entrenchments are in a position to protect the draining operations in the upper fen. Nine miles to the north is Horncastle (in mediæval documents always written Horncastre), which was a _castellum_, or walled fort, built in the angle (Saxon “Hyrn”) formed by two streams, the Bane and the Waring. The Celtic name of the chief stream is responsible for its identification with the “Banovallum” of the anonymous Ravennas. A few detached portions of the wall can still be seen, showing its area to have been about four and a half acres, with its longer sides (about 200 yards in length) on the north and south. The masonry is rude, but probably only the core remains, the facing-stones having been removed for building purposes in later ages. The only remains known to have been found are coins, pottery, and some leaden coffins outside the walls. This fort may have been built in the first century if coins are any indication of date, for among a large number, covering the whole Roman period, about ten belong to that century. If so, it may have been purely military in origin—built in order to overawe the natives of the Southern Wolds, and so serving the same object as Caistor among those of the north.