AN ELEMENTARY TREATISE ON HEAT BY BALFOUR STEWART, LL.D., F.R.S. LATE PROFESSOR OF NATURAL PHILOSOPHY, VICTORIA UNIVERSITY FIFTH EDITION, Oxford AT THE CLARENDON PRESS 1888 [All rights reserved] PREFACE TO THE FIRST EDITION. In this work the Author has endeavoured to place before his readers in an elementary form the facts and principles of the Science of 'Heat,' and also to give some of the most prominent practical applications of our knowledge of this subject. His object has been to begin with the study of wellascertained facts and to proceed onwards to general principles. Accordingly, the work has been divided into three parts; the first of which embraces the study of the various effects produced by heat upon bodies. In this part many of the most recent investigations, as well as the apparatus used in conducting them, are described at length, while numerical examples are given, which, it is hoped, may enable the student to attain to the accuracy needful in physical research. The second division contains the laws which regulate the distribution of heat through space, and includes radiation, conduction, convection, and the measurements of specific and latent heat. Theoretical views are here for the first time introduced. The third and last part relates to the nature of Heat, its sources, and connexion with other properties of matter. In this part Heat is viewed as a kind of energy, and the leading principles by which Heat becomes related to other forms of energy are discussed. It may be well to state the basis on which the reasoning of this part has been founded. It has appeared to the Author that the foundation which involves the smallest amount of assumption is that adopted by Professor Sir W. Thomson, namely the denial of the possibility of a perpetual motion of any kind, and it will be shewn in the sequel that the denial of one form of perpetual motion involves the principle of the conservation of energy,' while the denial of another form involves the principle of the dissipation of energy.' In our ignorance of the ultimate constitution of matter it would thus appear that both the 'conservation of energy' and the 'degradation or dissipation of energy' should be viewed as principles having very strong claims to recognition, and as increasing these claims every day by the new facts which their employment as instruments of research is constantly bringing to light. A few words with regard to the mode in which the subject of temperature is viewed. Some eminent philosophers are of opinion that our methods of subdividing a range of temperature are to a great extent arbitrary, so that provided we always adhere to the same method we shall not be led into error. Be this as it may, there can be no question that some methods of doing this are much more convenient than others; nay, even that one method, that by the air thermometer, enjoys such a pre-eminence of convenience that it may with propriety be termed the proper method of subdividing a range of temperature. Starting with the assumption that there is a proper method of measuring temperature, it is shewn near the beginning of this work that even if we are ignorant of this proper method there is yet an advantage in employing an air thermometer. This advantage consists in the fact that we may use any permanent gas we choose for our air thermometer, and yet obtain results as nearly as may be identical with one another if all our instruments are read on the same principle; while, on the other hand, the indications of two thermometers filled with different liquids, and both graduated on the same principle, are not strictly comparable with each other. If we determine to prefer an air thermometer we still have to decide on what principle it ought to be read, and while this principle is indicated at the commencement of the work, the reasons in favour of its adoption are not fully discussed until the end. The Author cannot omit the opportunity of acknowledging his obligations to several scientific friends for the suggestions and advice they have kindly given him; more especially is he indebted to the organizing Secretary of this Series of Works at Oxford for much valuable assistance throughout the book. PREFACE TO THE SECOND EDITION. In this edition the Author has noticed those discoveries connected with 'Heat' which have taken place since his first edition was published. He has also added to the problems at the end of the volume by introducing Sir W. Thomson's applications of the dynamical theory of 'Heat' to the establishment of relations between the physical properties of bodies. He takes the opportunity of acknowledging his obligations to various scientific friends, and more especially to the Rev. Professor Price of Oxford, for many suggestions while the edition was passing through the Press. |