A "Brief History Of Magnetism" James Clark Maxwell
James Clerk Maxwell (1831 - 1879) was a 19th century Scottish physicist who demonstrated that electric and magnetic forces are two aspects of electromagnetism. He further showed that electric and magnetic fields traveled through space, in the form of waves, at a speed of 3.0E5 k/s. He thus argued that light was a form of electromagnetic radiation.
Maxwell codified earlier work on electricity and magnetism by Michael Faraday, Andre Marie Ampere, and others into a linked set of twenty differential equations in quaternions, the same mathematical system used later by Einstein for the relativity theory. Both theories have many similarities and we can say that Maxwell's theory of electromagnetism was a precursor of the relativity. Heaviside simplified the theory down to four differential equations, known collectively as Maxwell's Laws or Maxwell's equations. Maxwell's Laws describe the nature of static and moving electric and magnetic charges, and the relationship between the two, namely electromagnetic induction. The equations allow for the existence of a self-propagating electromagnetic wave which has the same velocity as that of light, suggesting that light is in fact that electromagnetic wave. The validity of that suggestion was later demonstrated in experiments by Heinrich Rudolf Hertz, and was fundamental to the invention of radio, usually attributed to Guglielmo Marconi.
Maxwell also did basic work on Thermodynamics which led him to the well known thought experiment, Maxwell's demon.
The Special Theory of Relativity owes its origins to Maxwell's equations of the electromagnetic field -- Albert Einstein. There is a mountain range on Venus, Maxwell Montes, named after James Clerk Maxwell.
Upon arriving at Cambridge University, he was told there would be a compulsory 6am church service (now discontinued, fortunately!) He stroked his beard thoughtfully, and slowly pronounced, in a thick Scots Brogue, "Aye, I suppose I could stay up that late"