258 



SCIENCE. 



[N. S. Vol. XIV. No. 346. 



important as for additions. On page 207 a para- 

 graph about the audiphone sta^tes that ' ' not 

 merely deaf people, but even those who are 

 deaf and dumb, can hear musical sounds and 

 even speech.'''' The amiable admission implied 

 in what the present writer italicizes is evidently 

 due to the acceptance of a Chicago advertise- 

 ment. On page 370, in discussing the mechan- 

 ical equivalent of heat, the name of Eowland has 

 been forgotten by the reviser. A few wood 

 cuts might have been omitted, such as that (page 

 27) in which the source of the wind that pro- 

 pels a sail-boat is a cherub face nestled among 

 the clouds, its cheeks distended to the bursting 

 point. 



The ' Twentieth Century Text-book,' by Hen- 

 derson and Woodhull, is decidedly more mod- 

 ern, and is comparable with Ganot in the 

 abundance and attractiveness of the illustra- 

 tions. An appeal is made to the student's 

 human sympathies by the introduction of por- 

 traits, with short life sketches, of men whose 

 researches have enlarged the domain of phys- 

 ics, such as Newton, Franklin, Tyndall, Fara- 

 day and Lord Kelvin. To this list is added 

 Mozart, naturally in the chapter on music. A 

 comparison of this chapter with those on heat 

 and electricity indicates plainly, without refer- 

 ence to the title page, that the book has been 

 prepared by two men of quite different tastes 

 and aptitudes. The introductory chapters and 

 those on sound and music indicate a writer 

 whose fondness for metaphysics and sesthetics 

 is quite equal to his appreciation of physics. 

 A prosaic student, after studying through the 

 first chapter, is stimulated by such problems as 

 these : 



1. " Select five events and analyze them into 

 their matter and motion content." 



2. " If a monkey sit on the top of a pole, and 

 always face a man who walks around the pole, 

 with his face always turned toward the monkey, 

 can the man be said to walk around the mon- 

 key?" 



The mathematical solution of the second 

 problem is easy. Teachers may differ about 

 the metaphysical solution. In the chapter on 

 music are introduced themes from Beethoven, 

 Schumann and Palestrina, in musical notation, 

 as illustrations of melody, harmony, and coun- 



terpoint, respectively. The authors in their 

 preface give the opinion that " laboratory exer- 

 cises, questions and problems given in a text- 

 book are manifestly inadequate and unsatisfac- 

 tory." This expresses quite a reaction from 

 the popular tendency manifested some years 

 ago, especially in the text-books by Gage and 

 Avery. Many will sympathize with them in 

 thinking that the laboratory guide book and 

 the class text-book should be kept separate. 

 Printed questions are often less valuable than 

 those formulated for the occasion by an experi- 

 enced teacher. It is not so obvious, however, 

 that problems should be excluded ; indeed there 

 are probably few teachers of physics who would 

 agree, with the present authors on this point. 

 In fact the first part of the book includes sev- 

 eral dozen problems and experiments, a few of 

 which are not very well selected. The general 

 style, selection of material and mode of treat- 

 ment are, however, good, and the book will 

 probably be popular, particularly on account of 

 the emphasis given to the relations of physics 

 on all sides to human life and the interests of 

 educated people. 



The leading idea inHoadley's text-book is to 

 insure the coordination of reliability in the 

 text, class demonstrations of stated laws, prac- 

 tical questions and problems on the application 

 of these laws, and personal experimentation in 

 the laboratory. The volume is a combination of 

 text-book and laboratory manual intended to 

 cover the work of a scholastic year in the high 

 school. If it be admitted that two small sepa- 

 rate volumes should be so combined — and every 

 teacher has a perfect right to judge for himself 

 about this — the work done by the author is ex- 

 ceedingly good. Considerable labor, it is true, 

 will be required of the teacher who uses this 

 book for the first time, and therefore has to se- 

 cure the construction of the special apparatus 

 for which the laboratory exercises are adjusted. 

 But these exercises are well selected and well 

 described. The practical questions and prob- 

 lems are numerous, and every page indicates 

 that the author is methodical, careful and well 

 informed regarding the needs and limitations 

 of the class of students for whom he writes. 

 He does not shun algebraic formulas or ' dodge ' 

 any real difficulties. Some formulas are given, 



