818 



SCIENCE 



[N. S. Vol. XL. No. 1040 



It would seem desirable that, for comparison, 

 reference should have been made to the ex- 

 tended series of similar maps recently pub- 

 lished by Schuchert, and also to the series by 

 Willis; especially as the three sets of maps 

 show very difierent conceptions of the ancient 

 epicontinental seas. 



This book is probably the most comprehen- 

 sive, original and suggestive of any single 

 volume in geology now printed. 



H. L. Fairohild 



The University of Eochestek 



Technical Mechanics. By Edward E. Maurer, 

 Professor of Mechanics in the University of 

 Wisconsin. Third edition, rewritten. New 

 York, John Wiley and Sons, 1914. 

 Maurer's " Technical Mechanics," of which 

 the first edition was published in 1903, has a 

 recognized position among useful text-books 

 for students of engineering. The reprints 

 previous to the present or third edition con- 

 tained few changes; but practically the whole 

 book has now been rewritten. The aim of the 

 author, however, remains unchanged, the words 

 of the original preface describing the book as 

 " a theoretical mechanics for students of engi- 

 neering " being again used as applying to the 

 present rewritten edition. It has been the 

 author's object to " furnish an adequate course 

 of instruction for students of engineering in 

 one semester, five times per week." The re- 

 casting for the present work has involved not 

 only changes in arrangement and form of 

 presentation, but some changes in subject- 

 matter, such as the omission of the chapter on 

 attraction and stress and some amplification of 

 rigid-body dynamics. The scope and order of 

 the work are indicated by the chapter headings : 

 Composition and resolution of forces ; forces in 

 equilibrium; simple structures; friction; cen- 

 ter of gravity; suspended cables; rectilinear 

 motion; curvilinear motion; translation and 

 rotation; work, energy, power; momentum and 

 impulse ; two-dimensional motion ; three-dimen- 

 sional motion ; appendices on theory of dimen- 

 sions of units and moment of inertia of plane 

 areas. Especially worthy of note are the twelve 

 pages in the chapter on momentum and im- 



pulse devoted to a lucid explanation of gyro- 

 scopic action and its applications to the gyro- 

 compass, the mono-rail car, the gsrro-stabilizer 

 for ships, and the self-steering torpedo. A 

 wholly new collection of problems is given, 

 most of which are collected at the end of the 

 book, thus avoiding interruption of continuity 

 of exposition in the text. The illustrations, 

 more than 500 in number, are executed with 

 notable care. 



Those who know the original edition need 

 not be told that the author's presentation is, 

 with few if any exceptions, sound, and that a 

 notable quality of his exposition is concise- 

 ness without sacrifice of logical accuracy or 

 completeness. Some teachers may perhaps 

 think the virtue of conciseness is at times car- 

 ried so far as to make the book unduly diffi- 

 cult reading for the beginner. The many 

 teachers who have successfully used previous 

 editions will, however, undoubtedly find the re- 

 written work even more satisfactory. 



In reviewing the first edition'^ of this book, 

 the writer took occasion to discuss certain 

 questions regarding the presentation of funda- 

 mental principles of dynamics. At the present 

 time special interest attaches to Professor 

 Maurer's presentation of principles because of 

 his position as chairman of the committee on 

 the teaching of mechanics appointed in 1913 

 by the S. P. E. E. The appointment of this 

 committee seems to have been due largely to 

 certain rather vigorous criticisms of current 

 methods of presenting fundamental principles, 

 especially the " fundamental equation of 

 dynamics " and the definitions of units of force. 



Professor Maurer uses the equation F = ma, 

 but his explanation of it makes it seem 

 subsidiary to the equation F/W^a/g, or 

 F = (J/?/g)a; the latter equation being ex- 

 plained as a special case of F/F' = a/a', where 

 a, a' are the accelerations due to forces F, F' 

 acting on the same body at different times. In 

 order to pass from the equation F=(W/g')a 

 to the equation F = ma (or F = Kma if units 

 are unrestricted) use is made of the fact that 

 different bodies in the same locality are equally 

 accelerated by gravity. In the view of the 



1 Science, Vol. XXI., p. 302. 



