1、The London fogLondon used to be famous for its heavy fog. This was because people in London burned coal which gave out heavy smoke, a polluted form that actually is called smog. In 1873, a coal-smoke smog, thicker and more persistent than natural fog, covered the city for days and caused 268 deaths.
2、 Another fog in 1879 lasted from November to March and caused four long months of sunshineless darkness. In 1952, a four-day fog killed about 4,000 Londoners. It was not until then that some measures were taken to stop the heavy fog. In 1956, Parliament enacted the Clean Air Act, Which effectively reduced the burning of coal. It was the beginning of a series of air-pollution reforms in England. Now the air in London is quite cleanthough the city still sometimes is covered in a clean, ordinary fog.
