54 



SCIENCE 



[N. S. Vol. XXXVIII. No. 967 



geometrical construction, as has been done 

 by numerous teachers, it would appear more 

 reasonable. 



The two-thousand-year-old physics of Archi- 

 medes is a part of every text. That many 

 developments in the domain of physics have 

 been made in recent years is also generally 

 recorded. But what physicist of ten years 

 ago would have prophesied that the path of a 

 helium atom could and would be photo- 

 graphed? And what must be the astonish- 

 ment of even Mr. Wilson — whose patience and 

 skill achieved this brilliant result — ^when he 

 sees in the frontispiece of this elementary text 

 published a few months after he did his work 

 a reproduction of the photographs he obtained. 



It is an extraordinary thing that some of 

 the great facts of science, so difficult to obtain 

 in the first case, are so easily understood after 

 they have been obtained. The authors have 

 eclipsed all others, as far as the reviewer 

 knows, in their inclusion of new and striking 

 developments in physics. 



There is one general criticism which applies 

 to this text and to several others. They 

 introduce the student to the subject of physics 

 by a study of liquids. The argument is that 

 this study is fascinating. If that argument 

 were to apply throughout the subject we would 

 begin electricity with the discharge of elec- 

 tricity through gases, we would come to light 

 through spectrum analyses and soap-bubble 

 colors. The fascination which these phenom- 

 ena have for students would be none the less if 

 they were introduced in their logical place. 

 The custom of placing the study of liquids 

 first implies that a boy knows more about row- 

 ing or sailing a boat than he does about pull- 

 ing an express- wagon or coasting on a sled; 

 in general, that he is more at home in water 

 or on water than on land. It may be that 

 high-school laboratories are better equipped to 

 show experiments setting forth the properties 

 of liquids than experiments demonstrating 

 motions and forces. But that does not alter 

 the fact that force is a more elemental thing 

 than pressure. Nor does it alter the fact that 

 boys have a great fund of knowledge — un- 

 classified, of course — in regard to motion and 



force, which knowledge can at once be made 

 use of by a capable teacher. 



It is interesting to compare the text written 

 by Mr. Hawkins for technical high schools 

 with the other texts arranged for general stu- 

 dents of physics. In this text the student 

 meets in the first chapter the difiicult topics: 

 machines, horse-power, and the Prony-brake. 

 Later he begins the subject of electricity by 

 the study of the dynamo. He continues this 

 study to the performance of transformers, 

 multiple generators, induction motors, etc. 

 Evidently the technical high-school student 

 must be prepared to assimilate strong food. 

 Evidently, too, where facts of value to the 

 commercial world are given large prominence, 

 there is not much room for the discussion of 

 scientific principles. Eor example, the ex- 

 periment on the mechanical equivalent of heat 

 is not described. Ohm's law is based on the 

 definition of a volt ! These but illustrate the 

 criticisms which a physicist would make on 

 the text. It does not give enough space to 

 the presentation of the scientific method. But 

 it does present in brief compass the main 

 points at which physics touches conamerce. 



A Texthook of Physics. By Hurst and Lat- 

 TEY. Van Nostrand Co. In three volumes. 

 Vol. I., Dynamics and Heat ; Vol. II., Sound 

 and Light; Vol. III., Heat, Magnetism and 

 Electricity; a total of 640 pages. 

 This text is characteristic in places by its 

 very elaborate and detailed explanations — the 

 discussion of the passage of a beam of light 

 through a prism takes up five pages — carried 

 out into all the geometrical and arithmetical 

 details. The problems are very numerous and 

 are always identified as having been set in a 

 certain examination. An American student 

 may wonder why it is necessary to identify 

 so highly original a question as this : " De- 

 scribe shortly how a mercury thermometer is 

 made. (Camb. Loe. June, '07.) " One sees 

 that it is not the question, but the examina- 

 tion that is the principal thing. This text 

 would be a very complete guide to a student 

 going up for the army or university exam- 

 inations. 



