In the following section Dr. Draper shows how, by means of Lord Kelvin's "harmonic analysis," which separates the tide-generating forces of each kind into a number of ideal components, results of practical value are obtained. In Chapter XIII a very ingenious instrument for tide prediction which has been in use for some time by the Indian Government is described. The recording part of the machine is simply a paper-wound drum, on which a pencil point makes a graphic record. When the tides of a given port are desired, it is only necessary to set the instrument according to the tidal components, obtained by harmonic analysis and the time chosen for the beginning of the tide table, and then start it at the proper moment. It takes about four hours to run off the tidal curve for a year. This curve is then measured, and the year's tide table readily made out. Dr. Darwin informs us that a very similar instrument is now in course of construction for the United States Government. The remainder of the work consists of a more detailed discussion of the various disturbing influences which interfere with the simplicity of tidal movements--displacement of the earth's axis, earthquakes, etc, a long discussion of tidal friction, a study of the laws of rotating liquid masses, the nebular hypothesis, and finally a chapter on Saturn's rings. The text in many places will be found difficult to understand by the general reader, despite the author's efforts to fully and simply explain every point, and it seems questionable whether a thorough discussion of tidal phenomena can be made simple enough for the layman's comprehension. The volume can not be read by any one, however, without instruction, and is much the best general discussion of tidal phenomena which we have seen. FOOTNOTES: [43] Sketch of the Evolution of our Native Fruits. By L. H. Bailey, New York: The Macmillan Company. Pp. 472. Price, $2. [44] The Tides; and Kindred Phenomena in the Solar System. The Lowell Institute Lectures for 1898. By George Howard Darwin. New York: Houghton, Mifflin & Co. Pp. 378. $2. GENERAL NOTICES.