of an internal buttress or centre-piece for this lighthouse, the ground-story of which was, perhaps, masked attractively by a marble-encased colonnade carrying a tile roof.³⁰  The absence of any trace of the main walls of such a structure provides an initial obstacle to this view in detail; and in any case the fact, recently ascertained, that the ’cross‘ is much later than the platform, necessitates a readjustment of the conjecture. The prevailing theory at the present time is that the original superstructure included a great triumphal column or pile, commemorating the pacification of Britain and serving at the same time as a seamark, situated appropriately on a spot which may well have been the principal starting-point of the armies of invasion. But this view is conjecture and nothing more; and, unless and until some lucky discovery shall throw light upon the problem, both the platform and the ‘cross’ of Richborough will retain the allurement of mystery, which speculation has hitherto served only to enhance.
   If we still know little about its purpose, however, we at last know something of the history of the structure. To the north and east of the platform a large area is covered with an irregular layer of whitish mortar or cement identical with that of the platform itself. The excavator remarks that this mortar-layer ‘can only represent the residue left on the mixing-floor’ when the platform was built; and the association of mason’s chippings, piles of flints, and occasional fragments of marble with the layer is confirmatory evidence. This mortar-layer is therefore contemporary with the platform. Under it were found coins of Vespasian (A.D. 69—79) and Samian pottery of about A.D. 60—90, whilst in the sand laid down immediately over it were another coin of Vespasian and pottery of A.D. 75—120. The inference that the layer (and therefore the platform) dates from the latter part of the first century A.D. is confirmed by the occurrence elsewhere of fragments of the marble casing—’ many of them evidently mason’s chippings‘—in deposits of about A.D. 85 or 90.
   How long the building stood, it is more difficult to say. But we now know that by the end of the third century, when the Saxon-Shore fortress was erected, it was already in ruins. Fragments of the moulded marble casing were, as has been remarked, built into the walls of that fortress, and many other pieces were found (as we shall see) in the material used to level the site for its erection. Then at the latest the structure which stood originally on the great platform must have been laid low. We cannot therefore yield to the temptation of identifying the tall building which the platform carried with that ‘ Lapis Tituli’ which is reputed to have formed a notable landmark ‘on the shore of the Gallic sea’ as late as the fifth century ³¹—unless, indeed, the added ‘cross’ bore some such monument in the latter days of Richborough.
   The next structural episode in the history of Richborough as at present known relates to two buildings lying respectively north-east and north-west of the platform. Mention has already been made of a dwelling-house built in what is now the north-eastern corner of the Saxon-Shore fortress at about the end of the first century A.D. and destroyed, apparently, not many years later. It has been suggested that this house may have been erected in connexion
   ³⁰  The excavators of 1900 found roof-tiles scattered over the platform.
   ³¹   Of Guorthemic’s fourth battle against the Saxons, the Historia Brittonum (§ 44) records: Quartum bellum in campo juxta Lapidem Tituli, qui esi super riparn Gallici maris, commisit. There is no other hint as to the locale of this stone.