Oxford: At the Clarendon Press 1873. First Edition. Two volumes, 8vo. Volume One: xxix, [1-blank], , [1-blank], -425, [3-blank], [1-"PLATES"], [1-blank] pages + thirteen lithographed plates (Figs I to XIII). Additional lithographed plate ("Plate 6") in this copy inserted after page 148. Errata slip tipped in at B1. Volume Two: xxiii, [1-blank],-444, [1-"PLATES"], [1-blank] pages + seven lithographed plates (Figs XIV to XX) + 15, [1-blank] pages of ads. A total of 21 plates. Publisher's original blind stamped plum cloth. Both volumes with worn/bumped corners and re-backed with majority of original spines laid down and endpapers preserved. A few pencilled previous owner/dealer notations on flyleaves. Generally bright and clean internally. Very Good. Cloth. 
The first issue of the first edition, with no errata slip in volume two and publisher ads for this title noting "Just published." (Norman) Horblit notes that some copies of this work contain (as here) 8 leaves of advertisements bound at the end of volume two. Nearly all copies (and references) note 20 plates in the first issue. Most contain 21 plates, as does this copy.
"Maxwell once remarked that the aim of his Treatise was not to expound the final view of his electromagnetic theory, which he had developed in a series of five major papers between 1855 and 1868; rather, it was to educate himself by presenting a view of the stage he had reached in his thinking. Accordingly, the work is loosely organized on historical and experimental, rather than systematically deductive lines. It extended Maxwell's ideas beyond the scope of his earlier work in many directions, producing a highly fecund (if somewhat confusing) demonstration of the special importance of electricity to physics as a whole. He began the investigation of moving frames of reference, which in Einstein's hands were to revolutionize physics ; gave proofs of the existence of electromagnetic waves that paved the way for Hertz's discovery of radio waves; worked out connections between the electrical and optical qualities of bodies that would lead to modern solid-state physics; and applied Tait's quaternion formulae to the field equations, out of which Heaviside and Gibbs would develop vector analysis." (Norman, 1466)
Grolier/Horblit #72. Wheeler Gift #1872 ("The first edition of Clerk Maxwell's epoch-making work."). Ekelof, #1163. Norman, #1466 (referring to 1st ed, second issue).