Simeon Poisson. Portrait of Simeon Denis Poisson (1781-1840), French mathematical physicist. Poisson put forward an early theory of electricity, proposing that charge was carried by two 'fluids'. This theory has since been superceded. He developed equations for use in electrostatics, particularly with regard to the force exerted by the charge on the surface of a conductor and the distribution of charge on a sphere. He also worked on theories of heat and elasticity. Studying probability theory, Poisson developed binomial distribution. He was the first person to integrate complex functions by contour integration.