**Siméon-Denis Poisson** (1781-1849) was forced into the study
of medicine by his family but he abandoned it for mathematics. In
Paris at the École Polytechnique, Laplace and Lagrange were his
instructors, and later his lifelong friends. Poisson's most
important work concerned the application of mathematics to
electricity and magnetism, and other areas of physics. In 1812
he published a paper which contained many of the most useful laws
of electrostatics and his theory that electricity is made up of
two fluids, in which like and unlike repel and attract each other.

**Joseph Fourier **(1768-1830) was a French mathematician who
was also a prominent figure in the politics of the Napoleonic
era. He exerted a strong influence on mathematical physics through
his analysis of the conduction of heat in solid bodies. He also
served as cultural ambassador to Egypt during the French occupation
and achieved a reputation as an Egyptologist who was responsible
for amassing the collection of Egyptian antiquities for the Louvre.

**Hans Christian Ørsted** (1777-1851), a son of the village
apothecary on a small Baltic island without a school, was educated by
the villagers and went on to become a professor at the University of
Copenhagen. In 1820 he was performing a classroom demonstration of the
heating effect of electric currents when he observed the deflection of
a nearby compass. Within a short while he announced this astounding
discovery in a four-page Latin pamphlet he distributed to scientists
throughout Europe. He had discovered a connection between electricity
and magnetism.
Photo: Ørsted's compass.

**Georg Simon Ohm** (1789-1854) was the German physicist who in
1827 discovered the law that the current flow through a conductor
is proportional to the voltage and inversely proportional to the
resistance. Ohm was then a professor of mathematics in Cologne.
His work was coldly received. The Prussian minister of education
announced that "a professor who preached such heresies was unworthy
to teach science." Ohm resigned his post, went into academic exile
for several years, and then left Prussia and became a professor in Bavaria.
Photo: Ohm's Apparatus.

**George Green** (1793-1841) was a self-taught mathematician who
worked in his family's windmill until the age of forty. In 1828 he
privately published* "An Essay on the Application of Mathematical
Analysis to the Theories of Electricity and Magnetism"* in which he
extended the work of Poisson to obtain a general method of solution for
the potential. It gained him admittance to Cambridge as an undergraduate
in 1833. He graduated in 1837 and was elected to a fellowship in 1839,
two years before his death.