SIR WILLIAM THOMSON, LL.D., D.C.L., F.R.S., PROFESSOR OF NATURAL PHILOSOPHY IN THE UNIVERSITY OF GLASGOW, AND PETER GUTHRIE TAIT, M.A., PROFESSOR OF NATURAL PHILOSOPHY IN THE UNIVERSITY OF EDINBURGH, 531 PREFACE. Les causes primordiales ne nous sont point connues; mais elles sont assujetties à des lois simples et constantes, que l'on peut découvrir par l'observation, et dont l'étude est l'objet de la philosophie naturelle.-FOURIER. THE term Natural Philosophy was used by NEWTON, and is still used in British Universities, to denote the investigation of laws in the material world, and the deduction of results not directly observed. Observation, classification, and description of phenomena necessarily precede Natural Philosophy in every department of natural science. The earlier stage is, in some branches, commonly called Natural History; and it might with equal propriety be so called in all others. Our object is twofold: to give a tolerably complete account of what is now known of Natural Philosophy, in language adapted to the non-mathematical reader; and to furnish, to those who have the privilege which high mathematical acquirements confer, a connected outline of the analytical processes by which the greater part of that knowledge has been extended into regions as yet unexplored by experiment. In the present volume, the mathematical development (printed in smaller type) necessarily occupies considerably more space than the experimental and descriptive portion. We commence with a chapter on Motion, a subject totally independent of the existence of Matter and Force. In this we are naturally led to the consideration of the curvature and tortuosity of curves, the curvature of surfaces, and various other purely geometrical subjects. The Laws of Motion, the Law of Gravitation and of Electric and Magnetic Attractions, Hooke's Law, and other fundamental 933 |