The identification of Porchester with the Portus Magnus of the Romans has been questioned by Professor Haverfield, and there can be no doubt that it rests upon insufficient evidence. Conceivably it may be the Portus Adurni of the Romans: but this is not certain. A Norman castle, with remarkably fine keep, still practically intact, was built in the north-west corner, and the parish church, also of Norman architecture, was constructed near the south-east angle, within the walls of the castrum. _Clausentum_, an important Roman station, now known as Bitterne, is situated a little to the north of Southampton, on the banks of the tidal estuary of the River Itchen. Practically nothing in the shape of architectural traces now remain, but from accounts written before their complete destruction we know that it was enclosed with walls 9 feet thick, and constructed of flint bonded with large flat tiles and roughly faced with small square stones. It has been supposed that the outer defences when perfect measured 500 yards in length. The station was three-sided, the walls each having an outward curve. The outer defences are believed to have enclosed an area of 20 acres: the inner defences, 10 acres. [Illustration: FIG. 16. THE WATER-GATE, PORCHESTER] _Cardiff._--Although not situated near the Continent, it is probable that Cardiff took its part in the defence of our coast during the Roman period. Whether the Roman fortress at this point formed part of the defences which were placed under the control of the Count of the Saxon Shore may be doubted, but in size and general plan it certainly resembled the coast fortresses of the south-eastern shores. [Illustration: FIG. 17. PORCHESTER. EXTERIOR OF WEST WALL] In the course of recent excavations in and near Cardiff Castle the nearly complete ground-plan of this castrum was found. Its form was nearly quadrangular, the only irregularity being in the western wall, which was inclined eastward at its southern end. Gates were situated about the middle of the northern and southern walls, whilst semicircular bastions were placed along the walls at intervals, roughly, of about 120 feet. At the angles were built towers of irregular form and of somewhat unusual interest, from the fact that they were obviously additions to the original work. The area enclosed by the walls was roughly a square of 600 feet. The question of angle-towers or bastions is one of considerable importance. Their presence in a Roman castrum may generally be taken as evidence of late date; but it is necessary to bear in mind that in some cases they have certainly been added to give strength to fortresses of early type, which, as we have seen in the cases of Reculver and Brancaster, were furnished with rounded angles, without any such projecting features as angle-towers or bastions. At Cardiff[11] it is perfectly clear that the original building had rounded angles against which towers of irregularly circular plan were subsequently built.