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Rh which embodies the latest and most wonderful mode of transmitting messages—the photophone. The author has avoided technicalities, and has left out descriptions of complex instruments and operations which he deemed more likely to weary than to interest the reader. In dealing with the conflicting claims of rival inventors, he has endeavored to present the leading attainable facts without partisan bias. For the most part, historical data have been gathered from publications contemporary with the date of first production of the several discoveries and inventions, and, in many cases, from the original writings of the inventors and discoverers themselves. The text is illustrated with 143 figures, and the pages are freshened here and there by anecdotes and scientific poetry.

the exact sciences geodesy is the one most specially devoted to ascertaining what are the exact form and dimensions of the earth. In the book under review no new theories are advanced, none of the questions requiring solution are discussed. The author, who is Professor of Mathematics in the Columbian University, has endeavored to give in a concise and readable manner all that the student ought to be acquainted with. As he himself states in his preface: "The advanced student and practiced observer will find nothing new in this work." And also: "It is hoped that the beginner will be enabled to get a clear insight into the subject, and feel grateful that the discoveries and writings of many have been so condensed or elaborated as to make the study of geodesy pleasant."

The first chapter, which is an historic sketch of geodetic operations, is interesting and full of facts tending to show what progress has been made from the earliest times, and how the desire to know the real dimensions of the earth has kept man busy in devising and perfecting the methods of measurement. The progress made is given step by step, and, as no intricate mathematical questions are mentioned, this chapter can be read with profit by even those who are absolutely profane in mathematical studies.

Other chapters treat of instruments and methods of observation; base-measurements; field-work; the theory of the least squares; the calculations of the triangulation; formulæ for the computation of geodetic latitudes, longitudes, and azimuths; calculation of the figure of the earth. The dimensions obtained by some observers are given, as follows; Equatorial radius: Bessel (1841), 6,337,397.2 metres; Clarke (1866), 6,378,206.4 metres; Coast Survey (1877), 6,378,054.3 metres; Clarke (1880), 6,378,248.5 metres. Length of the quadrant: Bessel (1841), 10,000,856 metres; Clarke (1866), 10,001,888 metres; Clarke (1880), 10,001,869 metres. Over twenty pages of formulas and factors are added at the close which will be useful for easy reference. Although this work is intended for students, practiced observers will find it a useful addition to their shelves.

volume constitutes three numbers of the Johns Hopkins University" Studies in Historical and Political Science." It was undertaken by the author in pursuance of special instructions from the Japanese Government to investigate certain questions of agrarian and economic interest in the United States. In the introduction are considered the general questions relating to the origin and importance of the public domain and to the principles of land-tenure. The story of the formation of the public domain is then told, its acquisition being the result of cessions by the States, the purchases of Louisiana and the Floridas, Texas annexation and Texas cession, the Mexican cessions, and the purchase of Alaska. Under the heading of "The Administration of the Public Domain" are related the histories of the Ordinance of 1787 and of the General Land-Office. Finally, the "History and Present Condition of the Land System of the United States" are surveyed in detail.

two books, or rather the two parts of the same book, here combined into one volume, have been before the public for