WORKS BY THE SAME AUTHOR. All fully Illustrated. A Treatise on THE ALTERNATE CURRENT TRANSFORMER, in Theory and Practice. Two Vols. Vol. I. THE INDUCTION OF ELECTRIC CURRENTS. 12s. 6d. Vol. II. THE UTILISATION OF INDUCED CURRENTS. 600 PP. ELECTRIC LAMPS AND ELECTRIC LIGHTING. A Course of Lectures delivered at the Royal Institution of Great Britain. 93 Original Illustrations. 7s. 6d. ELECTRICAL LABORATORY NOTES and FORMS. A Series of Forty Elementary and Advanced Laboratory Sheets for the use of Demonstrators and Students in Electrical Laboratories. Each sheet contains full practical instructions (illustrated when necessary) for carrying out some one particular measurement in electrical testing, and a ruledup form for entering observations. The Laboratory Notes are useful to all engaged in any description of electrical testing. Price 4d. each; 3s. 6d. per dozen. Complete Set, 10s. 6.; in portfolio, 12s.; bound in cloth, 12s. 6d. A CHEAPER SET, half above prices, is issued for the use of Students in Polytechnics and Science Classes. MAGNETS ELECTRIC AND CURRENTS AN ELEMENTARY TREATISE FOR THE USE OF ELECTRICAL ARTISANS BY J. A. FLEMING, M.A. D.Sc. F.R.S. PROFESSOR OF ELECTRICAL ENGINEERING IN UNIVERSity collegE, LONDON; MEMBER OF THE SECOND EDITION. London: E. & F. N. SPON, LIMITED, 125 STRAND New York: SPON & CHAMBERLAIN, 123 LIBERTY STREET 1902 PREFACE. TWELVE years ago the Author published a reprint of a course of lectures given to the pupils and workmen at an electrical engineering factory under the title 'Short Lectures to Electrical Artisans.' After the issue of several editions of this little book it became necessary to re-write it entirely, and the present volume may be considered therefore as taking the place of the former one. In recasting the information in such a manner as to conform more nearly to the present state of knowledge, the Author still desired to fulfil the original aim of supplying electrical artisans and engineering students with a brief and elementary account of the scientific principles underlying modern applications of electricity in engineering. With this object in view, the use of mathematical symbols has as far as possible been avoided, but at the same time an endeavour has been made to give the reader clear notions on the nature of the quantitative measurements which lie at the root of all applications of electrical facts in the arts. In spite of the attention which has been paid to the subject of electrical and magnetic terminology and units, it can hardly be considered that these are yet reduced to their final and most satisfactory form. The difficulties which students generally experience in grasping the real physical significance of magnetic and electric definitions and state |