Page:Popular Science Monthly Volume 49.djvu/730

708 The Nature of Variation, The Causes of Variation (including Natural Selection), and The Inheritance of Variation, with chapters on The Energy of Evolution, The Function of Consciousness, and The Opinions of Neo-Lamarckians.

In view of the recent successful trial of Prof. Langley's flying machine and the encouraging results obtained by Lilienthal in Germany, the Aëronautical Annual for 1896 is of especial interest. It consists of a number of disconnected papers, from men prominent in aëronautical matters, on the various aspects of the subject. The first article is one by Otto Lilienthal, entitled Practical Experiments for the Development of Human Flight, in which he describes his recent experiments and pictures the apparatus. The editor has an article on Wheeling and Flying, in which he calls attention to the analogy between the slow development of the two methods of locomotion. A long paper by Hiram S. Maxim on Natural and Artificial Flight, which is said to be made up of abstracts from an unpublished work, and to contain the results of Mr. Maxim's latest thought, comes next. An article by Octave Chanute, on Sailing Flight, is prefaced by a short biographical sketch and portrait of the author. This is followed by a three-page contribution on How a Bird Soars, by Prof. W. H. Pickering, in which a mechanical explanation of this apparent paradox is offered. There are a number of other interesting papers, several of which are on Kites and Kite-flying, and a short bibliography of aëronautics. Good illustrations are quite numerous.

The last of the Technological Handbooks to reach us is No. 10, Gas Manufacture, by J. Hornby. It is intended as a student's manual, and was especially arranged with reference to the examinations of the city and guilds of London (England) Institute. The author opens the book with a brief consideration of the various kinds of coal and their value for gas-making purposes. The following chapters and the main portion of the book treat of the technical processes and the special apparatus used in manufacturing, purifying, and testing the gas. The final chapters are devoted to special topics, such as the laying of mains and surface pipes, the construction of gas meters, gas burners, and the composition of coal gas (London: George Bell & Sons, 5.s.; New York: Macmillan & Co., $1.50).

Concrete Geometry for beginners, by A. R. Hornbrook, is an introduction to the study of geometry by means of object lessons. The author very truly says that the "universal demand of the learning mind is for the concrete and the particular as stepping stones to the abstract and the general." He has found in the course of his teaching that a student might be able to recite glibly demonstration after demonstration of geometric principles and still be totally at a loss when asked to make simple applications of them, this condition being evidently due to the inability of the student to picture the physical quantities on which he was working. The text consists of an apparently carefully selected and graded series of simple problems for fixing in the beginner's mind the elementary facts of geometry from lines and angles to squares and cubes. After each two or three chapters there is a "cumulative review" for testing the student's grasp of the new principles and combinations (American Book Company, 75 cents).

The Home Study Review, published by the Home Study Association at Ann Arbor, Mich. (15 cents; $1.25 per annum), is designed to offer to those who can not attend a school or college an opportunity of pursuing studies at home under direction. The first course is to include the following subjects: History, German, biology, rhetoric, English literature, and a commercial course. While it is to be hoped that the publication may prove useful, the scheme does not seem promising.

The Transactions of the American Microscopical Society for 1895, Volume XVII, contains the usual number of valuable papers, which are, however, most of them so technical as to have little interest except for the biologist or microscopist. Among the few papers of general interest is one by Simon Henry Gage, the president, on The Processes of Life revealed by the Microscope: A Plea for Physiological Histology,