REVIEWS 329 



of literature which sets out to present a difficult and often mathematical 

 subject in a manner easily comprehended by the student. The general 

 outline of the work follows the same plan as that adopted for the earlier edi- 

 tions, the first of which appeared in 191 1 , but a number of additions have been 

 made which enhance the value of the volume. These additions include 

 recent progress in the development of the theory of the subject, with some 

 references to practical work in the same direction. Amongst them may be 

 mentioned in particular a useful table of circular and hyperbolic functions, 

 and an extended chart of such functions, which did not appear in the original 

 layout. These tables and chart are given in terms not of the usual degree, 

 but of the more useful radian. 



Extensive additions have been made to the chapter on the theory of wave 

 propagation along wires ; and also to Chapter IV, on Telephony and Tele- 

 phonic Cables, where the instructive mechanical analogy of the vibrations 

 of loaded strings has been added. The arrangement described is the one 

 developed by Dr. Fleming in his laboratories, using a small motor to apply 

 a sustained series of simple harmonic or circular impulses to the end of a 

 stretched cord along which various loads may be arranged. The method 

 forms an extremely pretty demonstration of wave propagation, and in par- 

 ticular the special properties of non-uniformly loaded lines may be rendered 

 visible. Photographic examples of some of the results obtainable have been 

 included in the book. 



Chapter VII, on the Measurement and Determination of Cable Constants, 

 has also been revised, but there would appear to be room for still further 

 additions here, with the inclusion of more recent practical work. No measure- 

 ments made on or with triode vacuum tubes, used either as telephone repeaters 

 or for laboratory work, are here mentioned, while their use for repeating is, in 

 fact, merely referred to in a later chapter. Possibly, however, there is in- 

 sufficient data of this nature available in this country to render a useful 

 summary practicable. 



It is to Chapter IX that the most extensive additions have been made, 

 and interesting particulars have been incorporated relative to the New York- 

 San Francisco and other long loaded telephones lines, while a considerable 

 amount of new theoretical matter on the predetermination of the constants 

 of loaded cables has also been included. 



The revision of the book for this edition has enabled the author to correct 

 most of the misprints that occurred in the earlier copies, but a few numerical 

 errors in the table on p. 114 have apparently escaped attention. 



The book is written more for the student than for the telephone engineer, 

 who is often by necessity forced to employ some empirical solution other than 

 the theoretically best one, but as such it forms an excellent introduction 

 to the theoretical side of the subject. 



P. R. C. 



Physical Laboratory Experiments for Engineering Students. By Samuel 

 Sheldon, Ph.D., D.Sc, and Erich Hausmann, E.E., Sc.D. [Pp. 

 vi + 134, with 40 figures and 16 tables.] (London: Constable & 

 Co., 1919. Price 6s. net.) 



" The material in this volume was prepared for the use of sophomore stu- 

 dents in the Pol5rtechnic Institute of Brooklyn. All of these students are 

 candidates for engineering degrees." 



This extract from the Preface fully explains the title, otherwise it would 

 be hard to understand why these experiments could not be used by all and 

 sundry studying mechanics, sound, heat, and light. As the engineer has 

 to deal with problems involving space, time, matter entropy, and elec- 

 tricity, it is a little hard at first to follow the order in which the experiments 



