£6,000—three times his annual salary—with an additional £4,000 to be shared among his three assistants. Although the idea was subsequently dropped following criticism, Halliday observes that the large amounts discussed "at a time when parsimony was the dominant characteristic of public expenditure is a firm indication of the depth of public interest and approval that appears to have characterised the work." Northern drainage system The northern side of the Thames was the more populous, housing two-thirds of London's population, and the works had to proceed through congested streets and overcome such urban hurdles as canals, bridges and railway lines. Work began on the system on 31 January 1859, but the builders encountered numerous problems in construction, including a labourers' strike in 1859–60, hard frosts in winter, and heavier than normal rainfall. The rain was so heavy in June 1862 that an accident occurred at the works re-building the Fleet sewer. The deep excavations were running parallel to the excavation of a cutting at Clerkenwell for the Metropolitan Railway (now the Metropolitan line), and the wall dividing the two trenches collapsed, spilling the waters of the Fleet onto Victoria Street, damaging the gas and water mains. The high-level sewer—the most northern of the works—ran from Hampstead Heath to Stoke Newington and across Victoria Park, where it joined with the eastern end of the mid-level sewer. The mid-level sewer began in the west at Bayswater and ran along Oxford Street, through Clerkenwell and Bethnal Green, before the connection. This combined main sewer ran to the Abbey Mills Pumping Station in Stratford, where it was joined by the eastern end of the low-level sewer. The pumps at Abbey Mills lifted the effluent from the low-level sewer into the main sewer. This main sewer ran —along what is now known as the Greenway—to the outfall at Beckton. Like the Crossness Pumping Station, Abbey Mills was a joint design by Bazalgette and Driver. Above the centre of the engine-house was an ornate dome that, Dobraszczyk considers, gives the building a "superficial resemblance ... to a Byzantine church". The architectural historian Nikolaus Pevsner, in his Buildings of England, thought the building showed "exciting architecture applied to the most foul purposes"; he went on to describe it as "an unorthodox mix, vaguely Italian Gothic in style but with tiers of Byzantine windows and a central octagonal lantern that adds a gracious Russian flavour". To provide the drainage