MAXWELL, James Clerk (1831-1879). "On Physical Lines of Force," in The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science, Fourth Series, March-May 1861 and January-February 1862, nos 139-141 and 151-152.

The first publication of Maxwell's electromagnetic equations, untrimmed and almost entirely unopened in parts. Maxwell, "who may well be judged the greatest theoretical physicist of the nineteenth century," built upon the conceptual work of Faraday to develop his elegant mathematical theory of electromagnetism (PMM). Richard Feynman deemed Maxwell’s discovery of the mathematical laws of electromagnetism “the most significant event of the 19th century,” and the present article is in a league with Newton’s Principia and Einstein’s 1905 paper on Special Relativity.

After wrestling unsuccessfully with electromagnetic theory for almost a decade, Maxwell realized that Ampere’s Law was incomplete and required an additional term for a “displacement current.” Maxwell came to this critical discovery midway in the course of composing this article, forcing a reorganization of his thought and a 10-month hiatus in the article’s publication. The 1862 portions of Maxwell’s paper explicitly deal with this new displacement current and further include the highly significant discovery that the electromagnetic medium was capable of supporting oscillating waves. Maxwell here delineates the mathematical formulas for electromagnetism as “a linked set of differential equations with 20 equations in 20 variables” and further postulates that light is an electromagnetic phenomenon.

Although Maxwell would go on to refine the mathematical form of his electromagnetic equations in his later work, this paper includes all four of Maxwell’s primary equations. Maxwell’s postulation that light is an electromagnetic phenomenon would be empirically confirmed in 1888 by Heinrich Hertz. This article, published as it was in 5 parts over the course of a year, is rare in commerce. See PMM 355 (Maxwell's "Dynamical Theory of the Electromagnetic Field").

Five parts, octavo (225 x 143mm). 2 plates? Nos 139 and 140 in unbound signatures; nos 141 and 151 in original blue printed wrappers (minor soiling), no. 152 stab sewn without wrapper, all parts unopened except for gathering M in no. 139. All housed together in modern cloth box.