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structive amusement of young people in the country whose time hangs heavily on their hands in the winter evenings. It consists of a collection of simple experiments in magnetism and electricity, requiring only such apparatus as the experimenters can construct for themselves. The first class of experiments described are with permanent magnets. These are followed with a number of experiments with electro-magnets. A chapter is devoted to experiments with induction coils, in which various forms of Geissler tubes are shown and described. Most of the simpler experiments with static electricity commonly described in the text-books are given in the chapter devoted to this form of electricity, and the electrolysis of water and other liquids and the method of electro-plating in that on electrolytic experiments. Some miscellaneous experiments in thermo-electricity and with the electric light complete the book. The experiments are, on the whole, well selected to illustrate the characteristic phenomena, and are clearly described in simple terms suitable to the audience to whom the book is addressed.

How to make Inventions, or Inventing as a Science and an Art. By Edward P. Thompson, M. E. Second edition, revised and enlarged. New York: D. Van Nostrand Co. Pp. 181. Price, $1.

In his preface Mr. Thompson says that his object is "to establish inventing as a science." In the first chapter he advances excellent reasons for his claim that this may be done, but he does not carry out his reasoning logically. For instance, in the fourteenth chapter the author says that although "Coster was the first to conceive the idea of replacing handwriting by printing," his discovery was "knowledge, not an invention." Science is knowledge, and the application of it to a hitherto unknown art surely might be construed an invention. Nevertheless, Mr. Thompson has given to the world in this book a fund of useful and interesting information which can not fail to be of benefit. It contains some very excellent advice to those who "have ideas," and if only his suggestions were adopted many a tyro inventor would be saved a good deal of both worry and useless expense.

The chapter entitled Suggestive Ideas is full of valuable promptings and advice. So is Chapter VII. In the latter the author lays down four rules which should be observed by inventors. The first rule says, "Do not begin with intricate problems." The others warn inventors against confining themselves to single devices, and exhorts them to "practice medium problems," and study the analysis of the methods by which they desire to accomplish new results.

In the chapters on Principles in Chemistry and Electricity "for making scientific inventions" Mr. Thompson has treated the probabilities of invention with the assistance of these great factors, besides giving a large fund of useful information regarding these elements in the field of invention. The major part of the volume treats of the possibilities of invention in the field of electricity, and consists for the most part of selections from the author's writings upon this subject in the Electrical Engineer and other scientific journals.

Mechanics and Hydrostatics. By S. L. Loney. Cambridge: University Press. 1893. Pp. 304. Price, $1.25.

Prof. Loney has prepared this little manual for the use of beginners, and presumes on only a limited mathematical knowledge by the pupil. The subject-matter comprises statics, dynamics, and hydrostatics, which are treated briefly and concisely, the propositions being illustrated by appropriate examples. A number of selected problems are appended to each chapter for the student to work out, the answers to which are given at the end of the book. In an appendix a sufficient exposition of elementary trigonometry is given to enable the student to follow the text when the mathematical treatment calls for more mathematical knowledge than elementary geometry and algebra.

The Mineral Industry: its Statistics, Technology, and Trade, in the United States and other Countries, from the Earliest Times to the End of 1892. Vol. I. Edited by Richard P. Rothwell. Pp. 628. New York: Scientific Publishing Co., 1893.

This volume is a compilation of statistics, essays, and general information concerning the mineral industries of the United States and of the world, which will be gladly wel-