Fitzstephen is the earliest writer who mentions the wall. He lived in the reign of Henry II., towards the end of the twelfth century, and describes the wall as high and thick, with seven double gates and many towers and turrets placed at proper distances. Originally there were only four exits from the City—by way of Aldgate on the east, Cripplegate on the north, Newgate on the west, and Dowgate on the south; the latter was the entrance to the "Trajectus," or ferry across the Thames, and derived its name from Dwr or Dour—water; or perhaps from Dwyr Dover, as leading to the Dover-road. Near to this gate was placed the _Miliarium_, a portion of which may still be seen in the wall of St. Swithin's Church, whence distances were measured along the roads, and from which radiated four roads—one by Dowgate and across into Kent, and three others which passed respectively through Aldgate, Cripplegate, and Ludgate. The wall commenced at the eastern fort, and had a postern gate at its commencement which occupied the position of the row of posts in Postern-row, north of the Tower, whence it ran northward to Aldgate, the eastern exit (some portions of the old wall are still remaining at the back of the houses in America Crescent); from Aldgate it went in a north-western direction between Hounds-ditch and Camomile Street to Bishopgate, whence it proceeded directly west to Cripplegate. In the street called London-wall a fragment may be seen, and the remains of a bastion may be found between St. Giles's Church and the Barber Surgeons' Hall. From this point it turned southward for a short distance down Noble Street, and again deflected to the west, arriving at Aldersgate, after which it passed St. Botolph's Church and Christ's Hospital, then turned southward at a sharp angle, coming to Ludgate (which stood immediately to the west of St. Martin's Church), and hence to the Thames. In 1276 that portion south of Ludgate was taken down, and a new wall built from Ludgate to the Fleet river, and hence south to the Thames, so as to enclose the new Blackfriars' Monastery. It has been doubted whether the wall was continued along the river bank, but Fitzstephen says:—"London once had its walls and towers on the south, but that vast river, the Thames, which abounds with fish, and enjoys the benefit of tides, and washes the City on this side, hath in a long track of time totally subverted and carried them away;" and adds, that in his day some relics might be seen. Salmon, in his _Survey of England_, vol. i., disputes this, chiefly on the ground that we have no historical account of any great inundation such as would be necessary to effect such a result; and Maitland combats his arguments at great length, contending that a period of 777 years was quite sufficient to account for their decay and disappearance; and Lord Lyttelton remarks that long previously it had not been necessary to repair the south wall, the Tower and the bridge being amply sufficient