February 7 - Pope Pius IX dies, after a 31½ year pontificate (the longest definitely confirmed).
February 8 - The British fleet enters Turkish waters, and anchors off Istanbul; Russia threatens to occupy Istanbul, but does not carry out the threat.
March 27 - In anticipation of war with Russia, Disraeli mobilizes the reserves, and calls up Indian troops to Malta.
April - June
April 16 - The Senate of the Grand Duchy of Finland issues a declaration establishing a city of Kotka on the southern part of the islands from the old Kymi parish.[4]
June 15 - Eadweard Muybridge produces the sequence of stop-motion still photographs Sallie Gardner at a Gallop in California (a predecessor of silent film), demonstrating that all four feet of a galloping horse are off the ground at the same time.
August 9 - The Wallingford Tornado of 1878, the deadliest tornado in Connecticut history, destroys the town of Wallingford, killing 34 people and injuring more than 70.
November 17 - The first assassination attempt is made against Umberto I of Italy by anarchist Giovanni Passannante, armed with a dagger. The King survives with a slight wound in one arm. Prime minister Benedetto Cairoli blocks the aggressor, receiving a leg injury.
November 26 - American-born artist James McNeill Whistler's libel case against English critic John Ruskin, over a review of the painting Nocturne in Black and Gold – The Falling Rocket, (in which Whistler is described as "flinging a pot of paint in the public's face"),[7] is decided in the High Court of Justice in London. Whistler wins a farthing in nominal damages and only half of the costs, leading to his bankruptcy, and alienates patrons.[8]
December 18 - French passenger steamer Byzantin founders in the Dardanelles during a gale after collision with British SS Rinaldo, killing around 210 people, with only 14 crew of the Byzantin saved.[10]
Web site: NRHP. Site of the First Telephone Exchange. nps.gov. National Park Service. 2023-02-14. 2021-10-28. https://web.archive.org/web/20211028094111/https://www.nps.gov/subjects/nationalhistoriclandmarks/site-of-the-first-telephone-exchange.htm. live.
Web site: Kansanedustajat: Jaakko Mäki . . 4 January 2024 . https://web.archive.org/web/20190501004312/https://www.eduskunta.fi/FI/kansanedustajat/Sivut/911109.aspx . 1 May 2019 . Helsinki, Finland . fi.