cholera, smallpox, tuberculosis, and typhus were commonplace. After studying previous outbreaks, physician John Snow drew the conclusion that cholera was a water-borne disease. When the 1854 broke out, Snow mapped the locations of the cases in Soho, London, and found that they centered around a well he deemed contaminated. He asked that the pump's handle be removed, after which the epidemic petered out. Snow also discovered that households whose water supplies came from companies that used the Thames downstream, after many sewers had flown into the river, were fourteen times more likely to die from cholera. He thus recommended boiling water before use. Sanitation reforms, prompted by the Public Health Acts 1848 and 1869, were made in the crowded, dirty streets of the existing cities, and soap was the main product shown in the relatively new phenomenon of advertising. A great engineering feat in the Victorian Era was the sewage system in London. It was designed by Joseph Bazalgette in 1858. He proposed to build of sewer system linked with over of street sewers. Many problems were encountered but the sewers were completed. After this, Bazalgette designed the Thames Embankment which housed sewers, water pipes and the London Underground. During the same period, London's water supply network was expanded and improved. John Simon, as chief medical officer of the General Board of Health, secured funds for research into various common infectious diseases at the time, including cholera, diphtheria, smallpox, and typhus. Using his political influence, he garnered support for the Public Health Act of 1875, which focused on preventative measures in housing, the water supply, sewage and drainage, providing Britain with an extensive public health system. By mid-century, the stethoscope became an oft-used device and designs of the microscope had advanced enough for scientists to closely examine pathogens. The pioneering work of French microbiologist Louis Pasteur from the 1850s earned widespread acceptance for the germ theory of disease. It led to the introduction antiseptics by Joseph Lister in 1867 in the form of carbolic acid (phenol). He instructed the hospital staff to wear gloves and wash their hands, instruments, and dressings with a phenol solution and in 1869, he invented a machine that would spray carbolic acid in the operating theatre during surgery. Infection-related deaths fell noticeably as a result. As the British Empire expanded, Britons found themselves facing novel climates and contagions; there was active research into tropical diseases.