**August Adler** was a mathematician who was born in what was then Austria and who worked on geometric constructions using compasses only.

- The city was the capital of Austrian Silesia for almost all of Adler's life, only becoming part of Czechoslovakia in 1919 after the defeat of Germany and Austria-Hungary in World War I.
- All Adler's publications were in German but he did publish a few in Czech journals.
- In 1879 Adler graduated from the secondary school in Opava (known as Troppau at that time) and began his university studies at the University of Vienna and the University of Technology in Vienna where he was taught and greatly influenced by Emil Weyr.
- After taking undergraduate courses at the two universities, Adler undertook research in descriptive geometry graduating with a doctorate in 1884.
- Emil Weyr sent further papers by Adler to the Academy while he was his student.
- Adler was appointed as an assistant in astronomy and geodesy at the Technische Hochschule in Vienna in 1885 holding this position for two years.
- Adler taught at Döll's Realschule in Vienna beginning in 1888.
- When Adler taught in Prague there were both German and Czech speakers and education was provided for pupils in both languages.
- In 1901 Adler submitted his habilitation thesis on descriptive geometry to the German Technical University in Prague and became a docent there.
- Adler went to Göttingen for the summer semester of 1902, applying to the University to he a guest auditor.
- These notes, written in Adler's own hand, are now in the Reading Room of the Göttingen Mathematical Institute.
- In 1906 Adler left Prague and took up an appointment as a teacher at a high school in the 6th district of Vienna and, in addition, he was a Privatdozent at the Technische Hochschule there.
- Let us now look in a little more detail at Adler's mathematical contributions.
- In 1906 Adler applied the theory of inversion to solve Mascheroni construction problems in his book Theorie der geometrischen Konstruktionen Ⓣ(Theory of geometric constructions) published in Leipzig.
- Since he was using inversion Adler now had a symmetry between lines and circles which in some sense showed why the constructions needed only compasses.
- However Adler did not simplify Mascheroni's proof.
- This 1906 publication was not the first by Adler studying this problem.
- Since we know from Steiner's work that using the ruler alone can only solve any second degree problem if a fixed circle can be used in the plane, the use of the ruler in the sense of Mr Adler is of course different understand as with Steiner, namely in such a way that it also allows a parallel to a straight line to be drawn at a fixed distance (width of the ruler).
- Hilbert refers to this paper by Adler in the 1902 course which was attended and recorded by Adler.
- As well as his interest in descriptive geometry, Adler was also interested in mathematical education, particularly in teaching mathematics in secondary schools.
- David Eugene Smith wrote the Report of Sub-Commission A of the International Commission on the Teaching of Mathematics: Intuition and Experiment in Mathematical Teaching in the Secondary Schools which he delivered to the International Congress of Mathematicians held in Cambridge, England, on 27 August 1912.
- One final work by Adler should be mentioned, namely the five figure logarithm tables Fünfstellige Logarithmen Ⓣ(Five-figure logarithms) which he published in 1909.

Born 24 January 1863, Opava, Austrian Silesia (now Czech Republic). Died 17 October 1923, Vienna, Austria.

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Astronomy, Origin Czech Republic

**O’Connor, John J; Robertson, Edmund F**: MacTutor History of Mathematics Archive