Page:Popular Science Monthly Volume 43.djvu/575

Rh action include both feeling and motion) is so entirely under the control of definite law that the sequence of every thought is fully determined by its correlatives of all kinds, in the sense that it must obey the associated laws of thought and of things. The mind must perceive objects, must know them, and must reason about them legitimately in true accord with its own mental attitude working in correspondence with the organism and the extra-organic world." We have found nothing in it clearer than this.

manual is intended especially for students beginning the subject, and forms a companion to the author's other elementary manuals on Steam and the Steam Engine and Magnetism and Electricity. The subject is treated under four general divisions, the first being devoted to statics or forces in equilibrium, the second to hydraulics and hydraulic machines, the third to the laws of motion, and the fourth to the properties and strength of materials.

The book consists of twenty-four lectures delivered by Prof. Jamieson, to his students and the method of treatment and the order of arrangement of the subject matter are based upon the author's experience in teaching. In conformity with this, he has placed the consideration of the laws of motion after that of hydraulics and hydraulic machines, as he finds that it is much better for the student to have some knowledge of simple mechanism before trying to understand the abstract laws of motion. Illustrative examples are given in each lecture, and a list of suitable questions at the end.

handbook should prove of interest and value not only to the practical electric light fitter, to whom it is primarily addressed, but to the householder using the electric light who desires to take an intelligent interest in the subject as well. The author begins his exposition with a brief but clear statement of the meaning and relation of current, electromotive force, and resistance, which is quite free from technicalities and understandable by any one without previous knowledge of the subject, and then passes to a consideration of the various appliances and details of construction essential to a complete electric-light outfit. Among the subjects considered are systems of central station supply, switches, cutouts, incandescent and arc lamps and their accessories, electroliers, running of wires, arrangement of circuits in a house, sizes of wires for a given number of lamps, and meters. All these subjects are treated briefly but clearly, so that the ordinary householder can readily understand them. A full statement is given of the rules of the London underwriters, and the work closes with a chapter upon private installations.

very excellent manual is designed for advanced students, and the subject is treated so as to give the student an experimental knowledge, the text being intended to be an aid to the experimental study and not a substitute for it, as is so often the case.

The main experimental facts of the science of magnetism and electricity are set forth by the author, and simple experiments suggested which the student can perform without the use of elaborate apparatus. A chapter is devoted at the close of the book to some of the applications of the principles of the science, in which the telephone, microphone, electric lamps, and the dynamo are briefly described, and a short but instructive account is given of the recent researches of Hertz in proof of the electro-magnetic theory of light of Clerk Maxwell, and those of Tesla with currents of great frequency.

republishing this inquiry into the question whether natural ability is hereditary, Dr Galton has chosen to leave it in much the same form in which it first appeared more than twenty years ago, as to recast it and incorporate data now accessible would have ininvolvedinvolved [sic] greater labor than he could well