Deaths on December 12

Jacques Viger, Canadian archeologist and politician, 1st Mayor of Montreal (b. 1787)

Jacques Viger (May 7, 1787 – December 12, 1858) was an antiquarian, archaeologist, and the first mayor of Montreal, Quebec, Canada.

25 Jan

Felix Mendelssohn
The Wedding March by Felix Mendelssohn is played at the marriage of Queen Victoria's daughter, Victoria, and Friedrich of Prussia, and becomes a popular wedding processional.
11 Feb

Lourdes apparitions
Bernadette Soubirous's first vision of the Blessed Virgin Mary in Lourdes, France.
5 Aug

Transatlantic telegraph cable
Cyrus West Field and others complete the first transatlantic telegraph cable after several unsuccessful attempts. It will operate for less than a month.
16 Aug

Transatlantic telegraph cable
U.S. President James Buchanan inaugurates the new transatlantic telegraph cable by exchanging greetings with Queen Victoria of the United Kingdom. However, a weak signal forces a shutdown of the service in a few weeks.
20 Aug

Evolution
Charles Darwin first publishes his theory of evolution through natural selection in The Journal of the Proceedings of the Linnean Society of London, alongside Alfred Russel Wallace's same theory.