# Theory of Heat (Maxwell, 4th edition)

THEORY OF HEAT
BY
J. CLERK MAXWELL, M.A.
LL.D. Edin., F.R.SS. L. & E.
Honorary Fellow of Trinity College and Professor of Experimental Physics in the University of Cambridge.
FOURTH EDITION.
LONDON: LONGMANS, GREEN, AND CO. 1875
PREFACE.
The aim of this book is to exhibit the scientific connexion of the various steps by which our knowledge of the phenomena of heat has been extended. The first of these steps is the invention of the thermometer, by which the registration and comparison of temperatures is rendered possible. The second step is the measurement of quantities of heat, or Calorimetry. The whole science of heat is founded on Thermometry and Calorimetry, and when these operations are understood we‘may proceed to the third step, which is the investigation of those relations between the thermal and the mechanical properties of substances which form the subject of Thermodynamics The whole of this part of the subject depends on the consideration of the Intrinsic Energy of a system of bodies, as depending on the temperature and physical state, as well as the form, motion, and relative position of these bodies. Of this energy, however, only a part is available for the purpose of producing mechanical work, and though the energy itself is indestructible, the available part is liable to diminution by the action of certain natural processes, such as conduction and radiation of heat, friction, and viscosity. These processes, by which energy is rendered unavailable as a source of work, are classed together under the name of the Dissipation of Energy, and form the ​subjects of the next division of the book. The last chapter is devoted to the explanation of various phenomena by means of the hypothesis that bodies consist of molecules, the motion of which constitutes the heat of those bodies.
In order to bring the treatment of these subjects within the limits of this text-book, it has been found necessary to omit everything which is not an essential part of the intellectual process by which the doctrines of heat have been developed, or which does not materially assist the student in forming his own judgment on these doctrines.
For this reason, no account is given of several very important experiments, and many illustrations of the theory of heat by means of natural phenomena are omitted. The student, however, will find this part of the subject treated at greater length in several excellent works on the same subject which have lately appeared.
A full account of the most important experiments on the effects of heat will be found in Dixon's 'Treatise on Heat' (Hodges & Smith, 1849).
Professor Balfour Stewart’s treatise contains all that is necessary to be known in order to make experiments on heat. The student may be also referred to Deschanel’s 'Natural Philosophy,' Part II., translated by Professor Everett, who has added a chapter on Thermodynamics; to Professor Rankine’s work on the Steam Engine, in which he will find the first systematic treatise on thermodynamics; to Professor Tait’s 'Thermodynamics' which contains an historical sketch of the subject, as well as the mathematical investigations; and to Professor Tyndall’s work on 'Heat as a Mode of Motion' in which the doctrines of the science are forcibly impressed on the mind by well-chosen illustrative experiments. The original memoirs of Professor Clausius, one of the founders of the modern science of Thermodynamics, have been edited in English by Professor Hirst.
CONTENTS.
This work was published before January 1, 1929, and is in the public domain worldwide because the author died at least 100 years ago.
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