7o8 



POPULAR SCIENCE MONTHLY. 



The Nature of Variation, The Causes of Va- 

 riation (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 en- 

 couraging results obtained by Lilienthal in 

 Germany, the Aeronautical Annual *^ for 

 1896 is of especial interest. It consists of 

 a number of disconnected papers, from men 

 prominent in aeronautical matters, on the 

 various aspects of the subject. The first arti- 

 cle is one by Otto Lilienthal, entitled Prac- 

 tical Experiments for the Development of 

 Human Flight, in which he describes his re- 

 cent 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 pa- 

 per 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 of abstracts from an unpublished work, and 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 ex- 

 planation of this apparent paradox is offered. 

 There are a number of other interesting pa- 

 pers, several of which are on Kites and Kite- 

 flying, and a short bibliography of aeronau- 

 tics. Good illustrations are quite numerous. 



The last of the Technological Handbooks 

 to reach us is No. 10, Oas Manufacture^ by 

 J. Hornby. It is intended as a student's 

 manual, and was especially arranged with ref- 

 erence to the examinations of the city and 

 guilds of London (England) Institute. The 

 author opens the book with a brief consid- 

 eration 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, 



* The Aeronautical Annual, 1806, No. 3. Ed- 

 ited by James Means. Pp. 158, 800. Boston: W. 

 B. Clarke & Co. ; London: William Wesley & 

 Son. Price, $1. 



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 : Mac- 

 millan & 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 con- 

 crete 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 dem- 

 onstration 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 in- 

 ability of the student to picture the physical 

 quantities on which he was working. The 

 text consists of an apparently carefully se- 

 lected and graded series of simple problems 

 for fixing in the beginnei-'s mind the elemen- 

 tary facts of geometry from lines and angles 

 to squares and cubes. After each two or 

 three chapters there is a " cumulative re- 

 view " 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 de- 

 signed to offer to those who can not attend 

 a school or college an opportunity of pursu- 

 ing studies at home under direction. The 

 first course is to include the following sub- 

 jects : 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 Mi- 

 croscopical Society for 1895, Volume XVII, 

 contains the usual number of valuable pa- 

 pers, 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 Micro- 

 scope : A Plea for Physiological Histology, 



