June 21 - In the battle at Bomarsund in Åland, Royal Navy mate Charles D. Lucas throws a live Russian artillery shell overboard by hand before it explodes - the incident is the first that will be retroactively awarded the Victoria Cross in 1857
An epidemic of cholera in London kills 10,000. Dr John Snow traces the source of one outbreak (that killed 500) to a single water pump, validating his theory that cholera is water-borne, and forming the starting point for epidemiology.