The four equations that are presented in modern textbooks under the title of 'Maxwell's Equations' did indeed appear throughout Maxwell's 1861 paper "On Physical Lines of Force". They did not however appear as a distinct grouping. A distinct grouping of eight equations did however appear in Maxwell's 1865 paper "A Dynamical theory of the Electromagnetic Field" and this group contained more information about electromagnetism than the group of four that appears in modern textbooks. One of these eight equations ironically appears today in modern textbooks as a supplement to Maxwell's equations, as if it had never been one of Maxwell's equations in the first place. This original Maxwell equation appeared as equation (77) in his 1861 paper, and as equation (D) in the original list of eight equations in the 1865 paper, but it is nowadays introduced in modern textbooks under the misnomer of 'The Lorentz Force'.
See "Maxwell's Original equations" at http://www.wbabin.net/Science-Journals/Essays-Mechanics%20/%20Electrodynamics/Download/3889
Another important feature of the original list of eight Maxwell's equations is that it includes the equation curl A
, whereas the modern list uses the lesser informative divergence of this equation, div B
= 0, hence missing out on the full physical significance of the electromagnetic momentum vector A
which corresponds to Faraday's electrotonic state. The equation curl A
when understood in the context within which it was derived by Maxwell, reveals the underlying fine-grained fly-wheel nature of the medium for the propagation of light.