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 ROMANO-BRITISH LONDON Street may have been erected. In this way could be explained the great difference of its structure from that of the wall surrounding London on its east, north, and west sides. Plan and Buildings of Roman London The circuit that has now been traversed measures 3 miles 251 yds., inclosing an area of 323I acres, or including the ground between the southern wall and the river, 380I acres, which considerably exceeds the area of any other Roman town in Britain."'' This leads to the question of the date of so important a work; but before venturing upon any conclusions regarding this much-disputed point, it is necessary to consider some of the discoveries that have been made within the City, and particularly the soil and the natural conditions formerly prevailing. The original surface is that represented by the top of the gravel and brick-earth which overlies the London clay. Owing to continual occupation a vast mass of soil has gradually been accumulated, and where this deposit has been left undisturbed, its successive layers, with the objects of human handiwork preserved in them, can be read like the leaves of a vast book. Modern requirements have for many years necessitated excavations passing through the whole of the accumulated soil and going below the original surface, by means of which many discoveries have been made. The original surface lies at an average depth of about i o f t. to 15 ft. below the present level of the ground, but where natural hollows formerly existed in the surface owing to streams and other causes, the process of levelling-up has been proportionately greater, and the accumulation has been found to exceed 20 and even 30 ft. The rise in the surface has been estimated to have taken place at the rate of a foot a century,^' but for the general average perhaps 9 in. in a century would suffice. It must not be assumed, however, that the rate of increase has at all times and in all places been the same, as this would depend largely on local conditions. Special reasons no doubt occurred in remote periods for artificially raising certain areas, as we know to have been done in later years. Over the whole space contained within the walls, Roman remains have been plentifully found in the lower part of the accumulated soil, of which a large proportion was the result of the Roman occupation. This portion of the deposit is known as the ' Roman level ' ; it varies considerably in thickness, in some places being not more than a foot or two, while in others as much as 6, 8, or even 10 ft. of soil has been found to contain no relics of a later period than the Roman. It has reasonably been argued that in its earlier stages the extent of Londinium must have been much more restricted than the boundary we have already traced, and attempts have been made to define the limits of the earlier City; but such conclusions as have been arrived at are purely con- jectural, and are no less diverse than they are numerous. Examination of the soil has shown that in the time of the early Roman City the surface was far more undulating than at present, and that the higher '"' Figures kindly supplied by Mr. Sydney Perks, F.S.A., City Surveyor. ^* Roach Smith, lllus. Rom. Loud. 58 I 73 10