James Clerk Maxwell was possibly the greatest physicist of the 19th century and this splendidly produced book does him full justice. The editor, P. M. Harman, intends "the reproduction of an accurate text of all Maxwell's scientific letters and substantive manuscript papers" and, since access to extant materials spins the historian's wheel of fortune, who could ask for more?

This volume covers the years 1862-73 when Maxwell "joined the elite of science" and when his election, in 1871, to the professorship of experimental physics initiated nearly a century of renown for Cambridge physics.

Maxwell is now mainly remembered for his formulation of the theory of electromagnetism and the identification of light as an electromagnetic wave, for the kinetic theory of gases and for Maxwell's relations in thermodynamics. These are all enshrined as equations and so we tend to think of him as merely a theoretical physicist. Yet, as this volume shows, he was at heart at least as much an experimenter, preoccupied with precise measurements and the practical details of apparatus. As he wrote to J. W. Strutt (Lord Rayleigh) shortly after his election, "It will need a good deal of effort to make Exp. Physics bite into our university system which is so complete without it."

A little later he is advising Strutt on setting up his laboratory, so cogently that one is tempted to quote the whole thing. Then again his report on the natural sciences tripos of 1873: "AnswersI of a very unsatisfactory kind arising partly from a familiarity with the appearance of instruments without any knowledge of the principles on which their action dependsI The questions should therefore be so arranged to give full occupation to the real student of physicsI while they afford no chance of making marks to the man of hearsay information." In fact from the beginning of the volume, when Maxwell was at King's College and complaining about the poor accuracy of lithographic printing of examination papers, examinations and examination questions keep recurring; thus to Thomson (Lord Kelvin) he writes in 1868, "Can you give me a good elementary thermodynamics problem"?

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Maxwell was not only part of the scientific elite but he corresponded with such distinguished figures as Stokes, Airy, Thomson, Helmholtz, Tyndall, Tait, Sylvester, Pattison, Cayley, Rankine, Strutt, Siemens, Rowland, the duke of Devonshire, and even Clifton at Oxford who had built a laboratory and filled it with apparatus.

Perhaps the single most exciting thing is Maxwell's lecture to the Greenock Philosophical Society in 1873 on Faraday's lines of force; here we can see exhibited the strands that he finally drew together, and which we now know as Maxwell's equations. Here too the reviewer comes up against the fundamental problem with a book like this, which contains the writings of a profound, numerate, literate and witty thinker. Every time, attracted by something in the list of contents, you turn to one of its 999 pages, you are brought to a halt by its neighbours; thus the examiner's report is flanked on one side by a letter to Herbert Spencer about the use of words in science and on the other by a brief discussion of continuity ending with the statement, "electric and magnetic potentials, being mere artificial concepts, cannot affect the state of a body"!

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Harman provides a "full historical commentary" in footnotes to elucidate Maxwell's allusions and argument. There are well-designed cross references between this and the earlier volume, as well as to documents in the present volume and publications by Maxwell's correspondents. Maxwell's hand writing and his drawings required "editorial interpretation" and Harman has favoured clarity rather than precise reproduction.

Certainly the reproduction of archival material can only mirror the classification of extant papers, and so reflect earlier decisions about what should be conserved and what thrown away. Collection of any kind effects a loss, and scholars interested in Maxwell have become aware of just how few of his papers survive.

The scholarly market place has its own ideas about historical "accuracy", and discussions of "experimental physics" have illuminated the many premises of Maxwell's "natural philosophy". Harman's edition provides a standard of reference for these negotiations, and it allows less peripatetic scholars, or scholars unfamiliar with the geography of Maxwelliana, to participate in these exchanges. It is an important resource for science students interested in the origins of modern physics and technology, and how they were influenced by Maxwell and his friends (it is not a text for the politically correct).

But however scientific a reference this volume is, it also affords anyone interested in Victorian society an entertaining account of some very witty social exchanges.

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Unhappily it is, as Queen Victoria remarked of one of Gladstone's works, "a very heavy book" (it weighs nearly seven ? avoirdupois and costs ?190). It is therefore neither good bedtime reading nor likely to reach a popular audience, nor to appear on a bestseller list, but no university making any claim to study physics, or to care about the intellectual history of the 19th century can possibly afford to omit it from its library.

Joanie Kennedy of Trinity College, Oxford, is preparing a thesis on astrophysics and the contributions of the third and fourth Lords Rayleigh. F. N. H. Robinson is an emeritus fellow, St Catherine's College, Oxford.