September 6, 1895.] 



SCIENCE. 



307 



ence upon the doctrine to which he gave such 

 emphatic expression in its predecessor. He 

 states that it is simply a text-book, not a labor- 

 atory manual, but that its teachings should be 

 supplemented by laboratory work and that ' ' ex- 

 periments are introduced chiefly for the purpose 

 of illustrating principles aud laws. ' ' With this 

 clear statement of the object in view, he writes, 

 not a revision of the older volume, but an inde- 

 pendent expression of his riper experience in 

 adapting the expression of truth to the capacity 

 of those for whom the book is intended. These 

 are in the main high school pupils, but a con- 

 siderable amount of interesting material is intro- 

 duced that is confessedly beyond the range of 

 most of these pupils. The book is intended to 

 include two courses, one for the high school and 

 the other an advanced course suited for 'the re- 

 quirements of the so-called classical courses in 

 many colleges. ' In such courses it is customary 

 to avoid mathematical difficulties as far as pos- 

 sible ; but it is safe to say that in many of them, 

 certainly in our leading colleges, the course in 

 general physics is so given as to include many 

 applications of not only algebra and geom- 

 etry, but also plane trigonometry and elemen- 

 tary analytical geometry. Indeed, the careful 

 avoidance of equations, and the almost entire 

 exclusion of trigonometry from the present 

 volume, necessitates such fullness of verbal ex- 

 planation as to amount to redundancy in some 

 parts. 



But, despite the objection just expressed, the 

 explanations contained in this text-book are al- 

 ways clear, and the work has been admirably 

 done. On every page are the marks of the 

 skillful teacher, methodical, careful and accu- 

 rate. To say.that there are no mistakes would 

 be, of course, inadmissible, but they are unusu- 

 ally few. The author has been alert in keeping 

 up with the results of recent physical investiga- 

 tion, and many old definitions and technical 

 terms have been so modified as to adapt them to 

 modern demands. The book will undoubtedly 

 be very useful, not only in the high school, but 

 as a book for parallel reading by the college 

 student, whose course in the class room is more 

 mathematical, but who wants the ' plain Eng- 

 lish of it ' where difficulties are encountered. 

 To such it can be heartily commended, although 



he will perhaps find less than he wants on some 

 special topics, such as elasticity, moment of in- 

 ertia, and the physical pendulum. The presen- 

 tation of the elementary principles underlying 

 the dynamo, the motor, the transformer, and 

 other familiar applications of electricity will be 

 found particularly good. 



A few words of adverse criticism may per- 

 haps be applied to some points that are capable 

 of easy modification and relatively of inferior 

 importance. 



The term ' centroid ' is employed in many 

 places where ' center of mass ' is implied. The 

 latter is explicit ; the former is unnecessary. 

 The two expressions are used about equally fre- 

 quently. Centroid has not come into general 

 use, whatever may be the objection to such gen- 

 erally used expressions as ' center of mass, ' 

 ' center of inertia,' or 'center of gravity.' 



In saying (p. 223) that ' if t\^o tones form a 

 narrower interval than a minor third, the com- 

 bined sound is harsh and grating on the ear,' 

 the author forgets that this is not true for the 

 higher parts of the musical scale. These facts 

 were fully investigated by Mayer about twenty 

 years ago. 



The specific heat of water (p. 263) is repre- 

 sented to increase continually from 0° to 80° C. 

 The figures given are those of Eegnault (1850). 

 More recent careful investigation by Rowland 

 and others has shown that the specific heat of 

 water decreases slightly from 0° to about 30° 

 and then increases gradually to 100° C. 



Absolute zero (p. 273) is said to be ' a point 

 of absolute cold or absence of heat, beyond 

 which no cooling is conceivable.' This state- 

 ment is admissible only on the assumption that 

 the laws of Boyle and Gay Lussao are applica- 

 ble rigidly at even the lowest temperatures, an 

 assumption which is now known to be not ad- 

 missible. 



It is stated (p. 417) that ' carbon bisulphide is 

 exceptionally transparent to all forms of radia- 

 . tion.' This may be qualified by adding ' except 

 the violet and ultra-violet.' 



There are a few other points, the noting of 

 which would unduly extend this criticism. 

 There are few text-books in which the first edi- 

 tion is so free from serious errors. 



W. Lb Conte Stevens. 



