Page:Popular Science Monthly Volume 48.djvu/464

424 Prof. A. Milnes Marshall's monograph on The Frog, intended as an introduction to anatomy, histology, and embryology, was written to guide and direct the student through the practical part of this work, and met a want the whole ground of which was not covered by any manual existing at the time of the original publication. It gives, in the introduction, practical instruction in the methods employed in biological investigation; followed by the application of these methods to the anatomical and histological examination of the animal; the frog being selected because it is easy to get and convenient to dissect, and is a fairly typical example of the group of vertebrates. The preparation of the present, the fifth, edition was Prof. Marshall's last professional act, and was completed only a week before his death. (Manchester and London: Smith, Elder & Co. New York: Putnams, $1.40.)

An Elementary Textbook of Mechanics, by R. T. Glazebrook, is the latest of the Cambridge Natural Science Manuals to reach us. The most satisfactory method of teaching the natural sciences is by means of experiments which can be performed by the learners themselves. This book consists of a series of such experiments which have been used by the author in teaching his classes; the experiments are followed by an explanation and an account of the deductions to be drawn from them. (Macmillan, $1.25.)

Imagination in Dreams, by Frederick Greenwood (Macmillan & Co., $1.75), treats of a subject with which most of us are familiar through personal experience. Two essays, previously published in English periodicals, form the foundation for the work, which as a whole is a rather unscientific discussion of curious psychic phenomena, which are in many cases closely allied, and dependent on morbid and diseased conditions of body and mind, and very probably have little value in determining the normal working of the brain. A number of queer dreams are detailed, many of them the author's own products. He thinks that the limits generally set for the imagination are at times over-leaped in sleep and that "some dream visions are creations of the mind."

Volume XXXII, Part I, of the Annals of the Astronomical Observatory of Harvard College contains an interesting statement of the methods in astronomical photography followed at the Harvard Observatory. There are also two chapters giving the results of researches by Prof. William H. Pickering on the Great Nebula in Orion and on the lunar surface. The former was conducted exclusively by photography while the latter embraced both visual and photographic observations.

Part I of Volume III of the final report on the Geology of Minnesota is devoted to paleontology, and is made up of contributions by Leo Lesquereux, Anthony Woodward, Benjamin W. Thomas, Charles Schuchert, Edward O. Ulrich, and Newton H. Winchell. Prefixed to the special monographs which it contains is a historical sketch of investigation of the Lower Silurian in the upper Mississippi Valley. The report is printed in large quarto form, and the present part is illustrated with about forty plates, besides figures in the text.

Prof. N. Story-Maskelyne describes his Crystallography as a treatise on the morphology of crystals (London: Frowde, 12s. 6d.; New York: Macmillan, $3.50). In addition to giving full descriptions of the several systems of crystallization, he discusses the properties of zones and the varieties of symmetry possible in a crystalloid system of planes. He also describes modes of representing crystals and of measuring and calculating angles. While the author has deemed it necessary to treat some parts of his subject in the simplest form compatible with strict geometrical methods, he hopes that his book will not be found lacking in demonstrations that will satisfy students with high mathematical training.

In an easily readable little book Uriel H. Crocker essays to point out The Cause of Hard Times (Little, Brown & Co., 50 cents). He ascribes the recent business depression and that of 1873-'76 to overproduction, and in supporting this view he comes into conflict with Mill and other authorities of the past and present. One reason that he gives why production outruns demand is that owners of factories frequently prefer to sustain a loss that may not continue so long as to be serious rather than the certainly large loss involved in shutting down their works.

The Brush Arc Light Dynamo, by H. C. Reagan, Jr., is a handbook for electrical