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 A HISTORY OF LONDON thrown in or had got washed there.*' On the north of the City the water continued to flow unchecked until it reached the wall, where the stream first tilled up its bed with fine sandy silt, choking the channels between the pile structures, which were quickly buried, and then spread in a vast sheet over the hollow ground, converting it into a quagmire,'^ in which a growth of peat was set up, forming a deep deposit of dark mud over what before was dry land and had been used extensively by the Romans for burial. The inhabitants seem to have been powerless to remedy this altered state of things, and the effect within the City must have been disastrous. The water gradually soaked beneath the wall,*' swamping the greater part of the City on the north, and the refuse from the pile structures in the stream and the houses on its banks was no longer carried away, but helped to fill up the bed of the stream and to increase the area of the swamp, which eventually spread from about Cripple- , gate on the west to Broad Street on the east, and to the south as far as Cheapside and Throgmorton Street, until beyond the Bank of England it passed into the more restricted space of the original stream valley, continuing under the Poultry and the Mansion House to Dowgate. The pile dwellings continued to be occupied for a time, as is proved by the heaps of shells and refuse which have been found in the successive growth of peat;'* but at last the whole district covered by the morass seems to have been abandoned as unsuitable for occupation, and only gradually was its extent reduced and the admission of water from the north regulated by sluices. The streams continued to flow, but in an attenuated condition and at a higher level, until in later times they were covered as sewers, and partly in this manner and partly by finding their own course through the gravel, they still work their way to the Thames. Wherever excavations are made in their course the water is met with. For instance, during the building of the Council Chamber at the Guildhall (Plan C, 165), Mr. J. Terry says that a strong stream of water was found which made it necessary to lay down a large table of concrete as a foundation, while at Barge Yard the water was noticed to rise and fall with the tide, showing a difference of 2 ft. between high and low water. Throughout the line of the main stream the accumu- lation of soil has been greater than in any other part of London, this being 20 ft. in depth at the north near the wall and exceeding 30 ft. near the Bank, while throughout this line Roman objects have been most abundant. Further striking evidence of the great rise in the soil after the building of the City wall, but in Roman times, is afforded by the gate at Newgate (Fig. 21 and Fig. 22, No. 9). The base of the wall adjoining the gate rests at a depth of 12 ft. or 13 ft., but that of the gate itself was found to be only 6 ft." It is clear that the surface must have risen at this point to this extent or a bed of clay and stone several feet deep would not have been used as a foundation. Such a footing, if beneath the surface and carried to the gravel, would be sufficiently good, but above ground it could never have served any purpose, more especially to support such a massive structure as a gate. The clay and flint puddling under the wall, it should be " Cat. Antiq. Roy. Exch. xxxi. *' Arch. Journ. Ix, 137, &c. ^ Lond. and Midd. Arch. Soc. Trans, iii, 492, 527 ; Arch. Ix, 169-250. " Anthropological Rev. v (1867), p. Ixxi. " See above, p. 66. 78