348 SCIENCE PROGRESS 



deals also with the current density that can be used in the conductors, and with the 

 limits of heating that can safely be employed without injuring the materials which 

 are used for insulation. This discussion necessarily involves the consideration of 

 ventilation and cooling (a subject on which Prof. Walker himself has done a great 

 deal of original work), and the chapters dealing with it are of great interest and 

 value. 



In the second half of the book the author deals with sixteen specifications of 

 electrical machines, including alternators, both high and low speed, induction 

 motors, rotary converters, direct current generators, boosters, and phase advancers. 

 The method used is first to draw up a model specification for some prescribed 

 running conditions, and then to work out from the manufacturers' standpoint the 

 complete design. A detailed design is given, together with calculation sheets from 

 which all dimensions can be obtained, with the least possible delay. 



In the preface he has written to the book the author states he has had in 

 mind as a model the Conveyancing Precedents of Prideaux, which are used so 

 much by lawyers. He has endeavoured to produce a book which will take an 

 analogous position in electrical engineering. Whatever the average engineer may 

 think of Prof. Walker's precedent, and of his attempt to copy in a productive 

 science the methods used in a profession essentially parasitic, one cannot but be 

 impressed by the value of what he has done. The labour of collecting the material 

 for this volume, and of drawing up and working out the various designs, is no light 

 task for a designer engaged on practical work ; that it has been done by such a 

 man will add enormously to its value. 



The latter part of the book is not confined, however, to design ; it includes a 

 complete and careful abstract of the work that has been published on such sub- 

 jects as tooth ripples, besides covering a good deal of the theory of the parallel 

 running of alternators, commutation in direct current machinery, and the starting 

 of rotary converters and induction motors. The book is not a mere designer's 

 handbook, it approaches more nearly a treatise on electrical machinery, and as 

 such it will take its place on the shelves of all electrical engineers who wish to 

 possess in a convenient form a comprehensive survey of electrical machine 

 design. 



The Telephone and Telephone Exchanges. Their Invention and Development. 

 By J. E. Kingsbury, M.I.E.E. [Pp. x + 558, with 170 figures.] 

 (London : Longmans, Green & Co., 191 5. Price lis. 6d. net.) 



The early chapters of this book, in which there is presented in a most complete 

 and interesting form the history of the telephone, provide a story which is with- 

 out parallel in any other branch of applied science. The name of Alexander 

 Graham Bell will always be associated with the telephone, and it is interesting to 

 find that heredity once more has shown its influence, for both Graham Bell's father 

 and grandfather were professors of elocution, and studied the science of word pro- 

 duction at first hand. It is to Graham Bell's father that the invention of " visible 

 speech" is due, and a most interesting account of the testing of this theory is given 

 in the chapter on " The Spoken Word." Melville Bell taught his two sons Edward 

 and Alexander Graham his sound alphabet, and " wrote down the queer and 

 purposely exaggerated pronunciations and mis-pronunciations " of his friend Mr. 

 Alexander Ellis, F.R.S., who describes the experiment "in such a manner that 

 his sons, not having heard them, so uttered them as to surprise me by the extremely 

 correct echo of my own voice." 



