Oxford: Clarendon Press, 1876. Octavo, original brown cloth. pp viii, 51. Moderate wear and rubbing at ends of lightly darkened spine; light foxing to verso of front free endpaper and title page; light sunning to inner margin of frontcover; else a VG clean and tight copy, no owner names nor text marks. In the Preface, Watson acknowledges his debt to James Clerk Maxwell, Clausius and to Ludwig Boltzmann. "My great object in the following short treatise is to make the existing state of the theory more widely known by presenting some of the scattered memoirs of the writers I have mentioned in a systematic and continuous form, in the hope that mathematicians may be induced to turn their attention to the theory, and thus assist in removing, if possible, the obstacles which yet remain in the way of its complete establishment. For the most part, I have followed the method of treatment adopted by Dr. Ludwig Boltzmann in some very interesting memoirs conducted by him to the Transactions of the Imperial Academy of Vienna, but in some cases I have varied this treatment for the sake of greater conciseness or greater generality ...To Professor Clerk Maxwell I am indebted for much kind assistance, and especially for access to some of his manuscript notes on the subject, from which I have taken many valuable suggestions." "During his last two years Maxwell returned to molecular physics in earnest and produced two full-length papers, strikingly different in scope, each among the most powerful he ever wrote. The first, 'On Boltzmann's Theorem on the Average Distribution of Energy in a System of Material Points,' following a line of thought started by Boltzmann, who in 1868 had offered a new conjectural derivation of the distribution law based on combinatorial theory. A strange feature of the analysis was that it seemed to be free from restrictions on the time spent in encounters between molecules. Maxwell now gave his own investigation of the problem, based partlyon Boltzmann's ideas and partly on an extension of them contained in H. W. Watson's Treatise on the Kinetic Theory of Gases. Following Watson, Maxwell used Hamilton's form of the dynamical equations, and adopted the device of representing the state of motion of a large number n of particles by the location of a single point in a 'phase-space' of 2n dimensions, the coordinates of which are thepositions and momenta of the particles. Together with Boltzmann's articles this paper of Maxwell's marks the emergence of statistical mechanics as an independent science." - DSB (in the article onMaxwell).