This is the story of two brothers born into the working class in a small town in Germany in the late eighteenth century. Both of them were recognised as mathematically gifted whilst still teenagers and went on to study mathematics at university. The younger brother was diligent and studious and completed his doctorate in mathematics with a good grade. There followed a series of good teaching jobs before he obtained a lectureship at the then leading university of Berlin, ten years after graduating. In due course, there followed positions as associate and the full professor. As professor he contributed some small but important proofs to the maths cannon, graduated an impressive list of doctoral students and developed an interesting approach to maths textbooks. He became a respected and acknowledged member of the German mathematical community.

The elder brother’s life ran somewhat differently. He started at the local university but unlike his younger brother he was anything but studious preferring a life of dancing, ice -skating and playing billiards to learning mathematics. His father a hard working craftsman was disgusted by this behaviour and forced him to leave the university and take up a teaching post in Switzerland. On the advice of his mathematics professor he taught himself mathematics by reading the greats. He returned to his home university and obtained his doctorate in the same year as his brother. There then followed a series of dead end jobs first as a badly paid university lecturer with little prospect of promotion and then a series of deadbeat jobs as a schoolteacher. In the last of these he had access to a good physics laboratory and began a series of investigations in a relatively new area of physics. At the age of thirty-eight, something of a failure, he published the results of his investigations in a book, which initially failed to make any impact. At the age of forty-four he obtained an appointment as professor at a polytechnic near to his home town and things began to finally improve in his life. At the age of fifty-two his work received acknowledgement at the highest international levels and finally at the age of sixty-three he was appointed professor for physics at a leading university.

The younger brother whose career path had been so smooth, fairly rapidly disappeared from the history of mathematics after his death in 1872, remembered by only a handful of specialists, whereas the much plagued elder brother went on to lend the family name to one of the most frequently used unit of measure in the physical sciences; a name that can be found on multiple appliances in probably every household in the western world.

The two bothers of my story are Georg Simon Ohm (1789–1854), the discover of Ohm’s Law, and his younger brother, the mathematician, Martin Ohm, who was born on 6 May 1792 and the small German town where they were born is Erlangen where I (almost) live.

Georg Simon and Martin were the sons of the locksmith Johann Wolfgang Ohm and his wife Maria Elizabeth Beck, who died when Georg Simon was only ten. Not only did the father bring up his three surviving, of seven, children alone after the death of their mother but he also educated his two sons himself. The son of a locksmith he had enjoyed little formal education but had taught himself philosophy and mathematics, which he now imparted to his sons with great success. As Georg Simon was fifteen he and Martin were examined by the local professor of mathematics, Karl Christian von Langsdorf, who, as already described above, found both boys to be highly gifted and spoke of an Erlanger Bernoulli family.

The plaque reads: The locksmith Johann Wolfgang Ohm (1753–1823) brought up and taught in this house as a true master his later famous sons

Georg Simon Ohm (1789–1854) the great physicist and Martin Ohm (1792–1872) the mathematician

I’ve already outlined the lives of the two Ohm brothers so I’m not going to repeat myself but I will fill in some detail.

As above I’ll start with Martin, the mathematician. He made no great discoveries as such and in the world of mathematics his main claim to fame is probably his list of doctoral students several of whom became much more famous than their professor. It was as a teacher that Martin Ohm made his mark, writing a nine volume work that attempted a systematic introduction to the whole of elementary mathematics his, Versuch eines vollkommenen, consequenten Systems der Mathematik (1822–1852) (Attempt at a complete consequent system of mathematics); a book that predates the very similar, but far better known, attempt by Bourbaki by one hundred years and which deserves far more attention than it gets. Martin Ohm also wrote several other elementary textbooks for his students. In his time in Berlin Martin Ohm also taught mathematics for many years at both the School for Architecture and the Artillery Academy.

I first stumbled across Martin Ohm whilst researching nineteenth-century algebraic logics. When it was first published George Boole’s *Laws of Thought* (1864) received very little attention from the mathematical community. With the exception of a small handful of relatively unknown mathematicians who wrote brief papers on it, it went largely unnoticed. One of that handful was Martin Ohm who wrote two papers in German (the first works in German on Boole’s logic). Thus introducing Boole’s ground-breaking work to the German mathematical public. Boole had written and published other mathematical work in German so he was already known in Germany. Later Ernst Schröder would go on to become the biggest proponent of Boolean logic with his three volume *Vorlesungen über die Algebra der Logik* (1890-1905). It is perhaps worth noting that Boole like the Ohm brothers was the son of a self-educated tradesman who gave his son his first education.

Martin Ohm has one further claim to notoriety; he is thought to have been the first to use the term “golden section” (goldener Schnitt in German) thus opening the door for hundreds of aesthetic loonies who claim to find evidence of this wonderful ration all over the place.

We now move on to the man in whose shadow Martin Ohm will always stand, his elder brother Georg Simon.

The Plaque reads: In this house the physicist Georg Simon Ohm (1789–1854) taught physics in the years 1811 to 1812 and the mathematician Martin Ohm (1792–1872) in the years 1812 to 1817

The school where Georg Simon began the research work into the physics of electricity was the Jesuit Gymnasium in Cologne, which even granted him a sabbatical in 1826 to intensify his researches. He published those researches as *Die galvanische Kette, mathematisch bearbeitet* (The Galvanic Circuit Investigated Mathematically) in 1827. It was the Royal Society who started his climb out of obscurity awarding him the Copley Medal, its highest award, in 1842 and appointing him a foreign member in the same year. Membership of other international scientific societies, such as Turin followed. Georg Simon’s first professorial post was at the Königlich Polytechnische Schule (Royal Polytechnic) in Nürnberg in 1833. He became the director of the Polytechnic in 1839 and today the school is a technical university, which bears the name Georg Simon Ohm. Georg Simon ended his career as professor of physics at the University of Munich.

The town of Erlangen is proud of Georg Simon and we have an Ohm Place, with an unfortunately rather derelict fountain, the subject of a long political debate concerning the cost of renovation and one of the town’s high schools is named the Ohm Gymnasium. The city of Munich also has a collection of plaques and statues honouring him. Ohm Straße in Berlin, however, is named after his brother Martin.

Any fans of the history of science with a sweet tooth should note that if they come to Erlangen one half of the Ohm House is now a sweet shop specialising in Gummibärs.