184 



SCIENCE 



[N. S. Vol. XXXVII. No. 944' 



these omissions are not as serious as they are 

 in England, for here one can probably find 

 them discussed in the Sunday editions of the 

 daily papers ! 



There are some omissions, however. In the 

 chapter on radiation no mention is made of 

 the sensitive instruments for detecting and 

 measuring radiant energy — the thermoele- 

 ment, the radiometer, the bolometer. In fact, 

 the discussion of radiation is rather inade- 

 quate. In the chapter on the interference of 

 light several pages are given to the discussion 

 of Fresnel's mirrors and biprism, but no men- 

 tion is made of the interferometer, although 

 the latter is as important theoretically as the 

 former and vastly more important in its nu- 

 merous applications to exact measurement. 



In the chapters devoted to heat, however, 

 admirable illustrations of the application of 

 the principles to modern heat engines are 

 given. In electricity, too, the points of con- 

 tact of the subject with the world of to-day 

 are shown. 



In a book where so much material is pre- 

 sented in so few pages the method of approach 

 is abrupt and the style at times uninteresting. 

 The text will not find favor with those teach- 

 ers who place emphasis on the inductive as- 

 pect of the science nor will it be pleasing to 

 those students who look for entertainment in 

 their reading, but it is a very dependable, 

 clear and fairly complete statement of the 

 principles of physics. 



G. F. Hull 



Dartmouth College 



Essentials of Physics for College Students. 

 A Text-book for Undergraduates and a 

 Lecture Course and Reference Work for 

 Teachers and Other Students of Physics. 

 By Daniel W. Heeing. The D. Van Nos- 

 trand Co. 353 pages, with 166 illustrations. 

 The author tells us in the preface that the 

 work is the outgrowth of a course of lectures 

 which he has delivered for several years past 

 to undergraduate students, and that it is in- 

 tended for that class of students preparing to 

 fill the position of educated men and women 

 who are not specialists in science. As the 



contents of the book are intended to be pre- 

 sented in " sixty lectures of fifty minutes 

 each " some rather important, perhaps essen- 

 tial, parts of the subject have received a very 

 brief description. On the other hand, libera! 

 space is given to some pseudo-philosophic 

 topics. One notes that the author gives only 

 two pages to the presentation and discussion 

 of the mechanical equivalent of heat and the 

 laws of thermodynamics. The connection be- 

 tween the absorbing and reflecting power of 

 surfaces is given in two lines. But notwith- 

 standing this brevity the author devotes the 

 larger part of the first twelve pages to these 

 captions or questions : Physics, is it or is it 

 not a study of matter, ether and motion? 

 Why study physics? Space, time, matter;; 

 Energy " a capability of matter." The best 

 feature in this discussion is found in the defi- 

 nitions and statements quoted from Max- 

 well's ■' Matter and Motion." 



A couple of pages are given to the discus- 

 sion of inertia in which the author decides 

 that one can no more measure the quantity 

 of matter by its inertia than one can measure 

 the size of a dead elephant by its deadness. 

 This adherence to the notion that inertia is a, 

 property of matter which can not be repre- 

 sented quantitatively is not in accord with the 

 custom of physicists. The terms inertia and 

 moment of inertia are used quantitatively in 

 physics. Such authors as Crew and Ames set 

 forth in a very clear manner the mode of 

 measuring the quantity of a bit of matter by 

 its inertia or reluctance to change of linear 

 motion. The author does not deal with the- 

 large topic of rotational motion, consequently 

 he makes no reference to moment of inertia. 



In dealing with the units involved in force 

 and work the author brings in the engineer's 

 system (footnote, p. 32) : " If force be meas- 

 ured in pounds then the mass will be in 

 pounds -f- 32 and work will be in foot-pounds."" 

 Had the equation of force been written F^ 

 l-ma instead of F ^. ma there would have been 

 no necessity for this statement and the confu- 

 sion it brings to students would have been 

 avoided. 



Apart from these criticisms the text is to- 



