The castrum at Pevensey retains so much of its enclosing walls and bastions that it is particularly worthy of study if one would learn, by direct observation, what splendid specimens of architecture the Romans erected in this country. Although a mediaeval castle has been built within the boundary of the Roman castrum, the walls of the latter may be traced for almost the whole of the circuit, and on the north, east, and west sides they stand to a considerable height. At the south-western extremity is the main gateway, its two flanking towers forming perhaps the most prominent features. Proceeding to the north of this gate we find three good specimens of bastions of somewhat horse-shoe form on plan. A series of six similarly planned bastions remain at the opposite side of the fortress, the general plan of which may be said to be elliptical. [Illustration: FIG. 14. BASTION ON SOUTH-WESTERN WALL, PEVENSEY] The character of the facing masonry, especially on the south-west side, is quite remarkable. The facing consists of carefully squared blocks of limestone laid with the regularity and precision of brickwork. Two characteristics stand out prominently in comparing this with other Roman castra on the coast of Britain. One is the irregularity of plan, the other is the presence of numerous projecting bastions. Both point to the lateness of the work, and some valuable evidence, confirming this view, has been brought to light in recent years. In 1907 Mr. Charles Dawson, F.S.A., communicated to the Society of Antiquaries[10] some notes on tiles found here bearing the stamp HON AUG ANDRIA The first line apparently refers to the Emperor Honorius (395-423), whilst the second may be regarded as indicating with somewhat less certainty the name Anderida. 9. PORTUS MAGNUS (PORCHESTER) This remarkably fine castrum, which stands on the edge of the most northern creek forming a part of Portsmouth Harbour, consists of a square enclosure containing a space of about 9 acres. Its walls, 10 feet in thickness, are constructed of flint rubble with courses of bonding-tiles. Originally each angle was furnished with a hollow bastion, or tower, and similar bastions, hollow within, were placed along the walls at intervals of from 100 feet to 200 feet. Some of these bastions have been destroyed, but fourteen examples, in a more or less perfect condition, remain. The water-gate, on the eastern side, still survives in a peculiarly perfect state. It is remarkable from the fact that the blocks of stone forming its semicircular arch are of light and dark colour, and are arranged alternately, so as to impart a picturesque and decorative effect. [Illustration: FIG. 15. PLAN OF PORCHESTER ROMAN CASTRUM]