FOR ELECTRO-MAGNETS. BY COUNT TH. DU MONCEL, MEMBRE DE L'INSTITUT DE FRANCE. TRANSLATED FROM THE FRENCH BY C. J. WHARTON. LONDON: E. & F. N. SPON, 16, CHARING CROSS. NEW YORK: 44, MURRAY STREET. 1883. 196.7.30. PREFACE. IN presenting the accompanying translation of the 'Détermination des Eléments de Construction des Electro-Aimants' by Count Th. du Moncel I need offer no apology, as the researches of this eminent French scientist are well known both in England and America, but to facilitate the studies of those not understanding French I have undertaken the translation which I now put forward as a faithful copy of the original, but in an English dress. The electrical units are almost throughout based on the French system of measurements of a Daniell as the unit of E.M.F. and the metre of telegraph wire as the unit of resistance, but to calculate these values according to the mode now usually obtaining here, viz. the volt and the ohm, the results must be divided by 1.079 and 100 respectively. With respect to the tables of values, I should mention I have omitted some given by the author containing information as to the weight, price, &c., of copper wires supplied by a Paris maker. |