Editing 1880 (section)

=== July–September ===
* July – [[John Venn]] popularises [[Venn diagram]]s.<ref>{{cite journal|last=Venn|first=J.|title=I. On the Diagrammatic and Mechanical Representation of Propositions and Reasonings|journal=[[The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science]]|volume=10|issue=59|date=July 1880|series=5|doi=10.1080/14786448008626877|pages=1–18|url=https://www.cis.upenn.edu/~bhusnur4/cit592_fall2014/venn%20diagrams.pdf|url-status=live|archive-url=https://web.archive.org/web/20170516204620/https://www.cis.upenn.edu/~bhusnur4/cit592_fall2014/venn%20diagrams.pdf|archive-date=2017-05-16}} [http://www.tandfonline.com/doi/abs/10.1080/14786448008626877] [https://books.google.com/books?id=k68vAQAAIAAJ&pg=PA1]</ref>
* [[July 14]] – [[Dorchester Penitentiary]] opens in Canada.
* [[July 22]] – [[Abdur Rahman Khan]] becomes [[Emir of Afghanistan]].
* [[July 27]] – [[Second Anglo-Afghan War]] – [[Battle of Maiwand]]: Afghan troops under Ayub Khan defeat British and Indian forces, under [[George Burrows (Indian Army officer)|Brigadier General George Burrows]]. 
* [[August 14]] – [[Cologne Cathedral]] is completed, after construction began in [[1248]], 632 years earlier.
* [[August 24]] – The [[SS Columbia (1880)|SS ''Columbia'']] completes her maiden voyage, arriving without incident in [[Portland, Oregon]], after a stopover in [[San Francisco]].
* [[August 26]] – Competing circus owners [[P. T. Barnum]] and [[James Anthony Bailey|James A. Bailey]] sign a contract in [[Bridgeport, Connecticut]], to create the [[Barnum & Bailey Circus]].  In 1907, the circus will merge forces with another competitor, the [[Ringling Brothers Circus]].<ref>{{cite book|first=Neil|last=Harris|title=Humbug: The Art of P. T. Barnum|publisher=University of Chicago Press|year=1981|page=250}}</ref> 
* [[September 1]] – [[Second Anglo-Afghan War]] – [[Battle of Kandahar (1880)|Battle of Kandahar]]: [[Frederick Roberts, 1st Earl Roberts|General Frederick Roberts]], commanding British forces, defeats the Afghan troops of [[Mohammad Ayub Khan (Emir of Afghanistan)|Mohammad Ayub Khan]], bringing an end to the war.<ref>{{cite book|first=Howard|last=Hensman|title=The Afghan War of 1879–80|publisher=Lancer Publishers|year=2008|page=532}}</ref>