The temperature on December 15, 1911 was between 3.0 °C and 8.9 °C and averaged 5.7 °C. There was 1.8 mm of rain. The average windspeed was 4 Bft (moderate breeze) and was prevailing from the south-southeast. Source: KNMI
January 26 » Glenn Curtiss flies the first successful American seaplane.
February 18 » The first official flight with airmail takes place from Allahabad, United Provinces, British India (now India), when Henri Pequet, a 23-year-old pilot, delivers 6,500 letters to Naini, about 10 kilometres (6.2mi) away.
May 21 » President of Mexico Porfirio Díaz and the revolutionary Francisco Madero sign the Treaty of Ciudad Juárez to put an end to the fighting between the forces of both men, concluding the initial phase of the Mexican Revolution.
May 31 » The President of Mexico Porfirio Díaz flees the country during the Mexican Revolution.
September 18 » Russian Premier Pyotr Stolypin is shot at the Kiev Opera House.
December 29 » Mongolia gains independence from the Qing dynasty, enthroning 8th Jebtsundamba Khutughtu as Khagan of Mongolia.
When copying data from this family tree, please include a reference to the origin: J. Harpman, "Family tree Harpman", database, Genealogy Online (https://www.genealogieonline.nl/stamboom-harpman/I121.php : accessed February 24, 2026), "Henriette Spier (1911-)".
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