Excavations have been made below the northern portion of this western wall in hopes of finding some of the original flooring of the church, but could not be further prosecuted because vaults, and even detached skeletons, were met with at a distance of only one foot below the existing pews.
The style of the north and south walls of the nave is much the same as that of the western wall; and behind the wood-work are considerable pieces of pink plaster, remarkable both for its hardness and texture. About this plaster we must say a few words, as it is, in our opinion, an important piece of evidence. It is composed of carbonate of lime imperfectly burned, of silicious sand, and pounded Roman brick, in almost equal proportions. It is true that some examples of this plaster have been occasionally found in Saxon, Norman, and even Early English buildings, but they are feeble imitations, distinguishable by the greater preponderance of sand, neither so bright nor crisp in section, more soft and pliable, and of a dullish colour. Two pieces of plaster were put side by side, one from St. Martin's and another from a Roman villa at Wingham, and to an experienced eye the texture was identical, except that the latter was rather thinner. And on our sending to such an undoubted expert as Mr J. T. Irvine (who had previously expressed much scepticism as to the Roman claims of St. Martin's, though he candidly confessed that he had not seen our recent explorations) a specimen of this plaster, he wrote in reply that, "both as regards texture of tile and lime mixture, and the colour produced thereby in section, it certainly seem to accord with that of _good Roman date_."
About the middle of the north wall of the nave is a doorway, 4 ft. 2 in. wide, with jambs of Caen stones of irregular size, some of them showing marks of axe-tooling. The date of this doorway is uncertain. The head is destroyed and the rubble filling-up irregular, but the general appearance seems to favour the theory that it is Norman. On the east side of the doorway is a =stoup= for Holy Water, certainly of great antiquity. The shape is not regular, but it may be described roughly as measuring 20 by 17 inches.
At the south-east corner is the celebrated Norman =piscina=, said to be one of the earliest and most beautiful in England. The size of the actual opening is 13 by 7-½ inches with additional 4 inches to the top of the tympanum. Its jambs are of Caen stone, with the usual tool-marks. In it are three curious holes, two above and one below, penetrating about 2 inches into the stone. What these holes were intended for has been a great puzzle, but perhaps short poles were inserted in them which supported an ornamental canopy. It is not impossible that the piscina was originally placed somewhere nearer the east wall of the nave.