A HISTORY OF LONDON record of how it was finished or what was its original height. If we may judge, however from examples elsewhere and from Roman representations of walls, it was probably at least 20 ft. to 25 ft. high and was battlemented. The line of the plinth may be taken in a general way to represent the surface of the ground when the wall was built, but from the varying height of the substructure it would appear that the builders endeavoured, as far as possible, to keep the plinth on a level, the inequalities of the surface being made up by increasing the amount of ragstone beneath (Fig. 22). Their object might have been attained by stepping the plinth, but no evidence has been found to show that this device was resorted to ; possibly, however, at such points as the gates, where the ground was uneven, a new line of plinth was started at a different level. The mortar used is almost entirely white lime mortar without the admixture of pounded tile. Pink mortar occurs in certain exceptional parts or rather subsidiary structures, such as the culverts and drains carried under the base of the wall, the bastions, and the one gate of which definite Roman remains have been found. In the wall proper it has been found only where a bastion has been removed, or is the result of later patching in Roman times. Bastions. Additional strength was given to the wall by the erection of a number of projecting buttress towers or bastions, such as are commonly found in late Roman mural defences. These occur at varying distances, the interval being frequently 150 ft. to 200 ft., but sometimes more than twice as much ; possibly a few have been destroyed without record or still remain undiscovered. It is noteworthy that none have been recorded on the line of the supposed south wall. They were mostly of horse-shoe shape in plan, being 20 ft. wide and projecting from the wall about 15 ft. The base, which was solid, was carried a few feet below the wall foundation. One at least appears to have been rectangular, but the only record of this is a sketch made by Gough in the 18th century, an engraving from a copy of which appears in Roach Smith's Illustrations of Rofnan London.^' No remains of it seem to have been met with in more recent times.^" Judging by the sketch it differed from the others in structure as well as in shape ; but this will be dealt with more fully later, when the wall is described in detail. Maitland states that fifteen bastions were standing in his time, and the positions of several are indicated on the plan of Braun and Hogenberg (1572) and on that ascribed to Agas (1591), while the more precise map of Ogilby and Morgan (1677) shows twelve, the positions of which have mostly been identified, while others have been brought to light by the excavations of recent years. In the method of construction and in the material employed the bastions differ greatly from the City wall, against which they are built without being bonded or tied into it in any way. Several of them have been examined with some thoroughness during recent excavations, and it is quite clear that they were built at a subsequent period to that of the wall. They are con- structed of a variety of stones, oolites predominating, and a large proportion of the material has evidently been taken from former buildings or monu- ments — sculptural figures, capitals, columns, portions of entablatures, cornices,
- " Op. cit. 16.
'" These forms of bastions are found together elsewhere, for instance at Richborough, where round towers are placed on the corners, and those on the side walls are square. 48
