Kelvin, William Thomson, 1st baron, ELEMENTS OF NATURAL PHILOSOPHY BY SIR WILLIAM THOMSON, LL.D., D.C.L., F.R.S., AND PETER GUTHRIE TAIT, M.A., PROFESSOR OF NATURAL PHILOSOPHY IN THE UNIVERSITY OF EDINBURGH. PART 1. SECOND EDITION. Cambridge: 1879 [All Rights reserved] gt-wenley let 6-20-39 PREFACE. Ob. To the first Edition of this work, published in 1872, the following statement was prefixed : “The work consists, in great part, of the large-type, or non-mathematical; portion of our Treatise on Natural Philosophy. "As it is designed more especially for use in Schools and in the junior classes in Universities, the mathematical methods employed are, almost without exception, limited to those of the most elementary geometry, algebra, and trigonometry. Where higher methods are required for an investigation, the reader is, in general, simply referred to our larger work. "It is particularly interesting to note how many theorems, even among those not ordinarily attacked without the help of the Differential Calculus, have here been found to yield easily to geometrical methods of the most elementary cha racter. Simplification of modes of proof is not merely an indication of advance in our knowledge of a subject, but is also the surest guarantee of readiness for farther progress. “A large part of Chapter VII is reprinted from a series |