November 17, 1911] 



SCIENCE 



685 



TRANSFERENCE OK THE TERM " GENOTYPE 



To THE Editor of Science : Science for Oc- 

 tober 13 just to hand contains announcement 

 of Professor Johannsen's Columbia Lectures. 

 Permit us to protest again in the strongest 

 possible manner against this unwarranted 

 transference of the term " genotype " and 

 change of its meaning. Professor DeVries 

 set a bad example by using " mutation " in a 

 new sense. Is there to be no limit to this 

 rough riding over workers in other branches 

 of biology? 



F. A. Bather, 

 W. T. Calman 

 British Museum (Natural History), 

 London, S. W., 

 October 23, 1911 



SCIENTIFIC BOOKS 

 steinmetz's engineering mathematics 

 This book is based upon a lecture course 

 given for some years by the author to stu- 

 dents of electrical engineering at Union Col- 

 lege. The title might well lead one to expect 

 that here at last is a book by a competent au- 

 thority presenting the mathematical founda- 

 tion which in his opinion should constitute a 

 part of the training of every engineer. But 

 upon reading the preface expectations and 

 hopes of this nature are abruptly terminated 

 when the reader learns from the summary 



" Thus the following work is not intended 

 as a complete course in mathematics, but as 

 supplementary to the general college course of 

 mathematics, or to the general knowledge of 

 mathematics which every engineer and really 

 every educated man should possess." 



The book is even further limited in its scope 

 than is indicated by the quoted paragraph. 

 For it is largely devoted to the particular sort 

 of mathematics which is of great service to 

 the electrical engineer only. In spite of this 

 the mastery of its contents would unquestion- 

 ably not be a useless accomplishment to the 

 student in any branch of engineering. 



The first chapter is devoted to an elementary 

 exposition of the properties of the general 

 number or complex quantity and the chapter 



is replete with graphical illustrations. A par- 

 ticular feature of this chapter showing the 

 usefulness of the theory developed is the dis- 

 cussion of the steam path in a turbine. 



In the second chapter is given a discussion 

 of series of the types 1 -\- x -\- x' -{- x' . . . 

 and 1 — X -{-x" — x' -{- . . ., designated as po- 

 tential series. Examples from electrical engi- 

 neering problems are given to illustrate the 

 applicability of such series to the develop- 

 ment of certain functions. The properties of 

 the exponential function are adequately 

 treated and the subject of differential equa- 

 tions is briefly touched upon. 



The third chapter treats quite extensively 

 of trigonometric functions and series. Inter- 

 esting illustrative problems are discussed. 



Chapter IV. deals in an elementary but 

 sufficiently comprehensive manner for the pur- 

 poses of the engineer with the subject of max- 

 ima and minima of functions. Numerous 

 practical examples in electrical engineering 

 are worked out numerically. There is also 

 given a short discussion of the method of 

 least squares with an illustrative example 

 from the theory of the induction motor. 



Methods of approximation are treated in 

 Chapter V. This subject, an art in itself, is 

 one which is rarely discussed explicitly in 

 books on mathematics or engineering. 



Chapter VI. contains an extensive discus- 

 sion of the subject of empirical curves and the 

 methods of obtaining analytical equations to 

 fit them. 



The eighth chapter and the final one is de- 

 voted to methods of numerical calculation. A 

 thorough knowledge of the subject matter of 

 this chapter and that of the two preceding 

 chapters obviously should be a part of the 

 equipment of every computing engineer, elec- 

 trical or otherwise. A striking feature of the 

 book is the author's continual insistence 

 throughout upon the importance to every 

 engineer of a thorough mastery of the sadly 

 neglected art of numerical computation. 



There are two appendices, one containing 

 notes on the theory of functions, the other 

 tables of exponential and hyperbolic func- 

 tions. 



