were often open and prone to overflowing. An 1847 ordinance of the Metropolitan Commission of Sewers requiring all waste to be discharged into sewers meant that the Thames, where all the discharge went, became much more polluted. The combination of cesspools and the raw sewage pumped into the city's main source of drinking water led to repeated outbreaks of cholera in 1832, 1849, 1854, and 1866 and culminated in The Great Stink of 1858. The 1866 cholera epidemic was the fourth in the city's history, but also the last and the least deadly. Further epidemics were forestalled by Bazalgette's improved sanitation system. Following the Great Stink of 1858 Parliament finally gave consent for the MBW to construct a massive system of sewers. The engineer put in charge of building the new system was Joseph Bazalgette. In one of the largest civil engineering projects of the 19th century, he oversaw construction of over 1300 miles or 2100 km of tunnels and pipes under London to take away sewage and provide clean drinking water. When the London sewerage system was completed, the death toll in London dropped dramatically, and epidemics were curtailed. Bazalgette's system is still in use today. While the problems of disposal of sewage and human waste were much improved by the late 19th century, there also remained problems of sanitation on the streets of London. With some 300,000 horses in use in the city by the 1890s, 1,000 tons of dung were being dropped on London's streets each day. Boys between 12 and 14 were employed to collect horse waste from the streets, which remained the main method until cars gradually replaced horse-drawn vehicles in the 20th century. The social reformer Edwin Chadwick condemned the methods of waste removal in British cities, including London, in his 1842 Report on The Sanitary Condition of the Labouring Population of Great Britain. In the poorer areas of London, rotting food, excrement and mud accumulated on the streets, where drains were few and far between and there were no supplies of water to flush them clean. Chadwick attributed the spread of disease to this filth, advocating improved water supplies and drains, and criticising the inefficient system of labourers and street sweepers then employed to maintain cleanliness. The result was the passing of the Public Health Act 1848, which placed the responsibility for street cleansing, paving, sewers, and water supply on the municipal boroughs