SURELY, and not slowly, the views of Thomson, Maxwell, and the modern electricians generally are finding acceptance throughout the Continent. The absolutely unanimous acceptance of the British Association's system of electrical units since the indorsement of that system by the Paris Congress of 1881 has proved the immense gain to the electrical world of having a uniform means of expressing electrical quantities, and has compelled electricians not only to read but to comprehend the writings of the pioneers of this most important reform. The work now before us for review, though professing to be but a text-book for use in the lyceums and schools of Italy, gives ample evidence that its author, Prof. Ròiti, of the Royal Institute of Higher Studies in Florence, is not only abreast of all the latest developments of electricity, but that he has mastered the theory also. Few text-books of its size have we seen that will compare favourably with Prof. Ròiti's little volume of 356 duodecimo pages. The faults which have been hitherto so conspicuous in most of the Continental text-books on electricity are in this work conspicuously absent. As an example we may refer to the author's treatment of the relation between the capacities, potentials, and charges of similar conductors. The elementary theory of the magnetic shell and that of the mutual potential of two magnetic shells are neatly expounded in pages 131 to 133. The absolute electrometer and the quadrant electrometer of Sir W. Thomson are both described, and illustrative figures given. The system of absolute and derived (C.G.S.) units, and that of the practical units of electric quantities based upon them, are explained at length on pages 204-5. There is a short chapter on the electric light, and another on electric motors, in which the anello elettro-magnetico di Pacinotti is described, the author remarking with emphasis that it contained the germ of almost all the machines by which the marvellous strides recently made in the applications of electricity have been achieved. The experiments of Deprez at Paris on the electric transmission of power, and the economic questions involved are also touched upon. Crookes's researches on “radiant matter” are mentioned and illustrated. Amongst points of novelty may be mentioned Pellat's -method of measuring the electromotive force due to polarisation, which has not yet, we believe, found its way into any English text-book. Two points of criticism we have to offer in conclusion. The first is that the author defines electric tension as identical with the electric force, equal to 4 π times the surface density of the charge, instead of defining it, in the sense of Faraday and Maxwell, as the stress on the dielectric, which is proportional to the square of the surface density, and therefore proportional also to the square of the electric force or electromotive intensity at the point of the surface considered. The only other complaint we have to make of the work—and this does not detract greatly from its value—is that the author does not acknowledge the sources from which some of his descriptions and cuts are taken. Elementi di Fisica. Vol. IV., Elettricità e Magnetismo. By Prof. Antonio Ròiti. (Florence, 1883.)