Described by Einstein as "the most important event in physics since Newton's time," the discovery by James Clerk Maxwell that a vast array of phenomena could be united by four elegant formulas remains one of the greatest successes of modern physics. This book, based on the third originally published in 1891, presents the original work which underpins the electronic revolution in the 20th century and which inspired both Lorentz's theories on the electron and Einstein's theory of relativity. Volume II covers magnetism and electromagnetism.