Hellmann was born in Löwen (Lewin Brzeski), Prussian Silesia. Since 1907 to 1922, he was the principal of the Preußischen Meteorologischen Institut (Prussian Meteorological Institute) in Berlin. He died in Berlin.
- An editor of the "Meteorologische Zeitschrift" 1892-1907 (with Julius von Hann)
- Repertorium der Deutschen Meteorologie, 1883
Work with snowflakes
In 1892 Hellmann piqued an interest in pictures of snowflakes, after seeing some of Wilson Bentley's photography, he commissioned a microphotographer to take shots of snowflakes to study. Upon review of these microphotographs, Hellmann noted a large difference in the snowflake pictures he took, and the ones Wilson Bentley had taken. Hellmann's snowflakes were irregular, there were various types, sizes, shapes, and forms. Bentley's snowflakes however, were perfect, symmetrical, six-sided and reminiscent of stars. Hellmann was perplexed by this, and openly questioned the accuracy of Bentley's work. He accused Bentley of manipulating the snowflake to get these perfect results. Bentley eventually admitted to somewhat doctoring the photographs, by scraping emulsion of the negatives, but he claimed that this did not change the integrity or accuracy of the photograph. This argument persisted for years, Hellmann insisted that altering the snowflake was unethical, as it misrepresented the snowflake in its truest form, Bentley argued the opposite. Although the argument never formally ended with one side winning, it is still Bentley's snowflake the world thinks of when they see snow fall.
- "The science of snowflakes". The Globe and Mail. Retrieved 2015-11-18.
- "Under the microscope: snowflakes are not as symmetrical as pictured". The Statesman. Retrieved 2015-11-18.
- "Monthly Weather Review" (PDF). Monthly Weather. December 1900.
- Pilcher, Helen (21–28 December 2013). "No Great Flakes" (PDF). New Scientist. Retrieved 2015-11-18.
- MeteoKust / KiteMeteo - De ultieme kustwebsite met webcams aan zee at www.infometeo.be (about his meter; Flemish)
- NEWI Meteo Fijnaart: Weerkundig woordenboek -H- at home.planet.nl (about his meter; Flemish)
- Jubilaeen 2003 at fa-gem.dmg-ev.de (German)
- Chronik: Berlin am 3. Juli, Fakten Jahr für Jahr at www.luise-berlin.de (German)
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