IN ELECTRICITY AND MAGNETISM. BY ANDREW GRAY, M.A., F.R.S.E., CHIEF ASSISTANT TO THE PROFESSOR OF NATURAL PHILOSOPHY IN THE London: MACMILLAN AND CO. 1884. S.Mette f. b PREFACE. THIS little book was originally intended to be mainly a reprint of some papers on the Measurement of Electric Currents and Potentials in Absolute Measure contributed to Nature during the winter of 1882-3; but as these were being reprinted, many alterations and additions suggested themselves, which it was thought would render the book more generally useful. Most of the additional matter is mentioned in the introductory chapter, but I may here refer to a sketch of the theory of alternating machines, and of methods of measurement available in such cases, contained in Chapter X., and to Chapter XII. on the Dimensions of Units, which I have thought it desirable to introduce. The work has of course no pretensions to being a complete treatise on Electrical and Magnetic |