Vol 55

40 David Lewislater the Great Conduit. The system used onlythe forces of gravity to move water through thepipes that ascended Ludgate Hill — apparentlycontradicting the forces of nature — to reachan elaborate conduit fountain at the easternend of Cheapside. Although the developmentof the system was tentative at first, it wasgradually extended, so that by the 15th centuryit represented a significant distribution networkthat stretched from Fleet Street to GracechurchStreet (Schofield & Vince 1994, 52). Regrettably,this early public utility, incorporating a complexof water filtering devices, pipes and cisterns,was largely destroyed in the Great Fire or in thesubsequent reordering of the City infrastructure.In addition, and probably at the same time, itseems that the primary records of the system, mostlikely consisting of wardens' accounts, journals,and plans, were comprehensively destroyed.Although the London conduit was probablythe first purely urban water system in England,the paucity of either direct documentary orarchaeological evidence has consigned it to aminor footnote in the history of the City. It isnot known, for example, who designed andbuilt the system, although undoubtedly theapplication of complex hydraulic technologywithin an established city environment wouldhave required considerable expertise.Evidence of the London conduit however isnot entirely lost. Most significantly, the recentarchaeological discoveries of the undercroft ofGreat Conduit house or fountain (1994) anda section of the conduit pipe (2001) allow theLondon conduit to be reassessed and comparedto other conduit water systems that are betterpreserved and even, in some cases, documented(Birch et al forthcoming; Rowsome 2000, 61).The relatively few documentary references to theconduit that have survived, such as the City letterbooks, property deeds, and wills, add furtherdetail, together providing sufficient informationto piece together the likely history of the system.From a review of the available source materialand considering the likely existing knowledgeof conduit technology, the construction ofthe London conduit was an extremely boldproject. There could have been little certaintyat the outset that the system would work,although its construction consumed largequantities of raw materials (particularly leadand timber) and required a substantial labourforce, of both skilled and unskilled workers. Itrepresented a considerable financial risk. Thefact that it subsequently operated for threehundred years until the Great Fire representsa major achievement that should be rankedin importance beside the building of LondonBridge or the Guildhall. Clearly it deserves to bebetter understood.THE DEVELOPMENT OF THE LONDONCONDUITThe availability of drinking water from springsand streams was one of the principal reasonswhy the Romans decided to site London on theterraces above the marshy north bank of theThames. Geologically, London sits on a basin ofchalk approximately 200m thick, with a northernrim coming to the surface at the Chilterns anda southern rim at the North Downs. Overlayingthis deposit of chalk are relatively thin beds oftertiary sands and pebbles, which themselves areoverlaid first with a thick layer of London clayand then with a clay and sand mixture knownas Bagshot sand. The water-bearing strata forLondon are found in the tertiary deposits andwhere these levels are exposed or cut, fresh watersprings form. The dissection of these levels in theLondon basin by the Thames accounts for thenumber of fresh water springs found close to itsbanks, such as the St Clements well spring nearFleet Street. The cutting action of the Thamesis not consistent however, and particularly inthe area occupied by the western part of theCity, the number of natural springs is limited.With the growth in the population of Londonfrom the 11 th century and the parallel increasein demand for fresh water, there was an evermounting pressure to access new convenientsources of water.At first this demand was met through diggingwells, but for these to be certain of reachingthe tertiary levels that held pure, filtered waterthey would need to be, in most cases, greaterthan 16m deep. These wells were thus known as'deep wells'. To be sure of only containing purewater, these wells would additionally require aninterior lining of stone to prevent the ingress ofsurface and ground water that could be pollutedwith soakage from stables and cess pits, decayingmatter from burial grounds, and the residuefrom water intensive industries such as tanningand metal working (Foord 1910, 250). Inevitablysuch wells were expensive to construct and wereconsequently infrequently built. A more commontype of City well was the insubstantial 'shallow