VOL. XLVI.J PHILOSOPHICAL TRANSACTIONS. 683 



Other the sea must have covered this whole country : but then we may be assured 

 by the present condition of this camp, that the sea has not exceeded the level of 

 it since it has been in being, which if we credit several of our ancient historians, 

 it was upwards of 1 700 years ago. It may therefore serve to prove, that the sea 

 since that time has not exceeded these bounds, and that the fossils dug up above 

 this level are more ancient than it, though we have no proper data to discover 

 how long before the sea had passed this height. 



The figure of the camp is not a square, but a parallelogram, whose 2 longest 

 sides are each 440 yards, and its ends or 2 shorter sides 36o yards each. These 

 are its dimensions withoutside the rampart and ditch ; but within the length is 

 392 yards, and the breadth 264. The breadth of the fosse and rampart, in 

 some places where it remains most perfect, was 48 yards, though in others not 

 above 30. And the whole ground taken up, including the ditch and rampart, 

 is 32 acres, 2 roods, and 36 poles ; or the area within the ditch and rampart 21 

 acres, 1 rood, 21 poles. 



Three sides only of this camp have been fortified with a rampart, whose upper 

 part was faced with a thick and strong wall, made of lime and flints ; of which 

 wall there are still remains in several places of the rampart, besides a very deep 

 ditch, that seems to have been most considerable on the east and south sides. 

 The wall on the north side appears to have been built at 2 different times ; that 

 is, it seems to have been raised higher than it was built at first, at some distance 

 of time afterwards ; for a parting may be observed at a certain height running 

 from end to end. 



The ruins of 2 old towers still remain, one of which stood on the north side, 

 and the other at the west end; the Jast of which is at present the most consi- 

 derable of the two. They were both built in a manner perhaps peculiar to the 

 Romans at that time, and which it may not be improper to describe. They be- 

 gan first with a layer of bricks laid flat as in pavements ; on that they placed a 

 layer of clay and marl mixed together, and of the same thickness as the bricks; 

 then a layer of bricks, afterwards of clay and marl, then of bricks again, making 

 in the whole 3 layers of bricks and 2 of clay : over this were placed bricks and 

 lime 29 inches, the outside being faced with bricks cut in squares, like the mo- 

 dern way of building in some parts of Norfolk, then bricks and clay, again stra- 

 tum super stratum, as high as the old ruins now remain standing. 



The mortar is found extremely hard at this day : it is a composition of lime, 

 sand, and ashes, and so compact, that he could by no means break a piece of it, 

 of an inch diameter, from the base of one of the towers at the east gate, but on 

 striking it with a sharp flint it flew off in dust. 



The Roman bricks which he examined, were made of 2 different sorts of clay 



4s2 



