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276 Variation gives the results of further evidence and further thought in that line, qualifying and developing certain views enunciated in the first edition. Various modern ideas are considered under the title Recent Criticisms and Hypotheses. The chapter on The Arguments from Embryology has been largely rewritten. Smaller additions appear in the form of new sections incorporated in pre-existing chapters. The assistance needed in the work of revision has been given by Prof. W. H. Perkin in Organic Chemistry and its derived subjects; Prof. A. G. Tansley in Plant Morphology and Physiology; Prof. E. W. MacBride and Mr. J. T. Cunningham in Animal Morphology; and Mr. W. B. Hardy in Animal Physiology. In all sections not marked as new the author desires it to be understood that the essential ideas set forth are the same as they were in the original edition of 1864.

Prof. Silas W. Holman attempts the presentation, in Matter, Energy, Force, and Work, of some of the fundamental ideas and definitions of physics in a plain and logical manner. His purpose is not to set forth the experimental side of the subject or to describe phenomena or laws. He rather assumes a slight knowledge of these, and proceeds to develop the concept and definitions. The author regards a clearer thinking on these subjects as of special importance to engineers and members of the other technical professions, because correct views upon them have become essential in those professions through the progress of the applications of science to the industrial arts. These applications are likewise of considerable interest to the untechnical members of the community. Professor Holman has composed his book with the principle of presenting the subject of physics in logical sequence, and has divided it into two parts, the first of which contains the matter immediately proper to the subject, with discussions of substance or matter, motion; energy and its forms; force; kinetic energy, force-measurements, work, potential energy, and matter again, as distinguished from substance. The second part comprises summaries of the chief theories of the nature of matter, force, and energy, including the kinetic theory of gases, Le Sage's theory of gravitation, the vortex-atom theory, and a discussion of the nature of energy and matter, with observations on chemical energy and the ether.

The Short Course in Music, prepared for use in schools where a complete course is not thought necessary, by F. H. Ripley and Thomas Tappen, is embraced in two books, of which we notice the second (American Book Company). Familiar songs are made the basis of instruction, some of those which appear as melodies in Book One being repeated here in full score. All other material has been prepared especially for this book. The music and directions are adapted equally for unchanged and changed voices. Voice training and the elements of phrasing and expression are furnished in a group of solfeggios at the close of the book. Theory is given in condensed form, but one that, it is claimed, embraces all the essential elements of vocal music.

Mr. J. E. Marr has prepared his exposition of The Principles of Stratigraphical Geology (Cambridge University Press; The Macmillan Company, New York, $1.60), under the belief that an idea of the subject can be obtained most satisfactorily if a large number of the details connected with the study of the stratified rocks are omitted. He has accordingly given very brief accounts of the strata of the different systems, paying more attention to the bearings of the facts than to their enumeration. The history of the earth is presented as a connected one, in which one period is linked on to the next, every event that occurs introducing a new complication into the conditions, which are consequently never quite the same—the changes showing an advance from the simple to the more complex. The study proves that an enormous period elapsed subsequent to the formation of the earth and previous to the deposition of the stratified rocks, of which we have only the slightest, if any, knowledge. The stratigraphical geologist has to establish the order of succession of the