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THE POPULAR SCIENCE MONTHLY.

once so minute and complex that its action is inconceivable." Appendix II is devoted to a discussion of telegony, much of which has appeared in this magazine. Dr. Romanes believes in centripetal heredity, and therefore cannot agree with Mr. Spencer, whose theory is of the centrifugal order.

Electric Waves: Being Researches on the Propagation of Electric Action with Finite Velocity through Space. By Dr. Heinrich Hertz. London and New York: Macmillan & Co. Pp. xv ${\displaystyle +}$ 278. Price, \$2.50.

The impossibility of reviewing in brief a work of such transcendent importance to electrical science as this volume undoubtedly is, will become apparent to the reader when we declare that the progress—exclusive of the author's own discoveries—so concisely recounted, not only embraces the names and experiments of and from Newton and Bernoulli and their day, down through a line of seventy-five prominent men of genius, but also includes with Faraday and Ampère—of late years—Helmholtz, Lodge, Maxwell, Siemens, and Sir W. Thomson in our own day. The volume before us is the aijthorized English translation from the German work, by Prof. D. E. Jones, B. Sc, and includes an able preface by Lord Kelvin, President of the Royal Society.

Dr. Hertz was primarily induced to carry out the experiments elucidated in this volume through the proffered prize in 1879 of the Berlin Academy of Science, for a solution of the problem to establish by experiments "any relation between electromagnetic forces and the dielectric polarization of insulators," which simply meant that a force electromagnetic in itself might be exerted in non-conductors by polarizations, or that electromagnetic induction is the cause of the polarization of a non-conductor. The attention of the professor was first drawn to the problem by Herr von Helmholtz, who promised the assistance of the Physical Institute in Berlin if Dr. Hertz determined upon making the research and necessary experimentation. After many failures, and his first abandonment of the solution, he finally gives to the world the impressive deductions of the original papers—now in the form of fourteen chapters—contributed to Wiedemann's Annalen. These are, in the present volume, supplemented by an ample introduction and various explanatory notes of vast import. Proceeding from the introduction, which emphasizes the experimental and theoretical phases of the subject, we gather from chapter to chapter the crowning results embodied in such phenomena as rapid electric oscillations, the effect of ultraviolet light upon the electric discharge, the action of rectilinear electric oscillations upon a neighboring circuit, the finite velocity of propagation of electromagnetic actions, electric radiation, the fundamental equations of electromagnetics for bodies at rest, and other all-important subdivisions. The work in the aggregate represents the fervid expression of a scientific explorer, whose heart was indubitably in his work, and who now presents us at minimum cost a wealth of labor and a store of new knowledge.

Romance of the Insect World. By L. N. Badenoch. New York: Macmillan & Co. Pp. 341. Price, \$1.25.

This volume contains one of the best efforts that have been made recently to put scientific facts into an attractive form. If one can be interested at all in the wonderful ways of insects, this book will spur to better acquaintance. Valuable data have been culled from every quarter, not neglecting the investigations of our American naturalists. Dr. McCook, Mrs. Treat, and the Peckhams. These are grouped under the four topics of metamorphoses of insects, their food, home-building, and defenses.

The transformations of insects, although seemingly abrupt transitions, are but progressive stages toward maturity, mainly due to the nature of an insect's skin, which does not permit enlargement of form.

The bill of fare relished by insects exceeds in variety that demanded by the larger members of the animal kingdom. Anything from a nettle to a fungus may be acceptable, horn, cork, or grease being the favored diet of some species. There is also a long list of insects that are parasitic, and others who breed their own cattle.

Among those who build hermit homes are described the mining, carpenter, and mason bees; the wasps, making nests of clay; the gall-makers; the lictor moths that carry their curious dwellings about with them, and the