The family moved to Prague in 1864. Three years later Wilhelm Fiedler was appointed to fill the chair of descriptive geometry at the Polytechnic in Zürich, which had been vacant since Wolfgang von Deschwanden's death. The family stayed in Zürich then, and they became Swiss citizens in 1875.
Ernst attended the Gymnasium in Zürich and, from 1879 onwards, the Polytechnic, where he studied mathematics at the Department for Mathematics and Physics Teachers. Among his lecturers were his own father, Frobenius and Geiser. In 1882 he moved to Berlin, where he attended lectures by Kummer, Kirchhoff, Helmholtz and Weierstrass in particular. Two years later he moved to Leipzig in order to study under Klein and the philosophy professor Wilhelm Wundt. They both supervised his doctoral thesis, Über eine besondere Klasse der Modulargleichungen der elliptischen Funktionen , which he completed in 1885. He then became Privatdozent for mathematics at the Polytechnic and assistant teacher at the Kantonsschule in Zürich. In 1889 he became professor for mathematics at the Industrieschule in Zürich. Fiedler was influential in the school's development, especially after having become Director of the school in 1904, when it was re-organised and renamed as Oberrealschule. He held this post until his retirement in 1926. Under his guidance, the school became 'an acknowledged institution preparing for studies at the Polytechnic' . Fiedler seems to have been very good at choosing his teaching staff; he also supported extra-curricular activities, founding both the school's orchestra and rowing club .
Fiedler did not produce any mathematical research papers; he was very much a schoolteacher and not a research mathematician. His publications include a couple of secondary school textbooks on descriptive geometry, a graduation speech entitled Lebenserfahrung und Bescheidenheit (Zürich, 1908) that he gave at his school in 1908, and several papers on ballistics and military education.
Early on Fiedler made a name for himself in the Swiss army, which he joined in 1881. After a swift career he became the then youngest colonel at the age of forty-three. From 1889 onwards he lectured on ballistics and shooting theory at the Polytechnic, instead of mathematics. He retired from this post in 1923.
In 1899, the Polytechnic's Board decided that the school's assistants would no longer be asked to work during the entry examinations. Instead, Bleuler asked Fiedler to assist with the exams in descriptive geometry, conducted by his father, who remarked that 'due to the amount of candidates it is absolutely necessary to have two experts in the hall' . Since similar requests were sent to Fiedler in the two following years, we can assume that he was responsive to Bleuler's pleas .
Fiedler was a member of the Schweizerische Gesellschaft für Schulgesundheitspflege, a society taking charge of all aspects of health and hygiene in Swiss schools. He was also a consultant of the Schweizerische Rektorenkonferenz (Swiss Universities Association) and served on the supervisory board of the Teachers' College in Küsnacht. It is due to Fiedler that shorthand was introduced as an optional subject in secondary schools. Furthermore, he was the creator and first curator of the Archive of Secondary Schools. Following a nervous breakdown, Fiedler became heavily involved in the temperance movement of the late 19th and early 20th centuries, educating the public on the dangers of alcohol abuse.
Fiedler is only mentioned once in the minutes of the committee of the first International Congress of Mathematicians: he attended the meeting on 08 December 1896. Having said that, there does not exist an attendance record for every meeting so he may have attended more meetings. He attended the congress but did not give a talk. Fiedler attended two further congresses, the 1908 ICM in Rome and the 1912 ICM in Cambridge, but did not give a talk at either.
He married Lina Knoch in 1886; the marriage lasted until Lina's death in 1949. The couple had four sons and one daughter. Two of his sons also studied at the Polytechnic: Karl (1892-1965), the oldest son, became a civil engineer; the third son Max (1893-1944) was a mechanical engineer.
The obituary in  gives 6 October 1954 as his day of death, whereas  claims that he died on 16 July 1954.
Article by: Stefanie Eminger, University of St Andrews