NA TURE 



169 



THURSDAY, DECEMBER 21, 1905. 



THE JAR AND THE GE.XIE. 



Tin* Theory of Experimental Electricity. By \V. C. D. 

 Whetham. Pp. xi + 334. (Cambridge: The Uni- 

 versity Press, 1905.) Price 8s. net. 



Electric Railways: Theoretically and Practically 

 Treated. By S. YV. Ashe and J. D. Keiley. Pp. 

 285. (New York : D. Van Nostrand Co. ; London : 

 Archibald Constable and Co., Ltd., 1905.) Price 

 10s. 6d. net. 



Modern Electric Practice. Vol. vi. Edited by M. 

 Maclean. Pp. vi + 318. (London : The Gresham 

 Publishing- Co., 1905.) Price gs. net. 



T'HERE is a tale in the " Arabian Nights " of a 

 fisherman who, after a day's ill luck, cast his 

 net for the fourth and last time with a prayer to Allah 

 that he might have a good haul. He drew to shore 

 a copper jar of curious construction and mysteriously 

 sealed, which on being opened was found to have 

 confined a genie possessed of remarkable powers. \^ 

 the genie proposed to reward his liberator by taking 

 his life, the fisherman induced him to return into the 

 jar, in which he again confined him. About two cen- 

 turies ago the bodv of fishermen who called themselves 

 then natural philosophers drew to shore from the sea 

 of natural phenomena a similarly remarkable jar cap- 

 able also of confining' a very powerful genie. The dis- 

 covery of the Leyden jar, we are told, " caused the 

 greatest excitement in Europe and America," two 

 continents which three years ago exchanged congratu- 

 latory messages across 2000 miles of ocean by means 

 of Leyden-jar sparks. This, the most recent sensa- 

 tional demonstration of the powers of the genie, is 

 by no means the most important ; he has truly pro- 

 duced as great a revolution in the doings of mankind 

 as any of his imaginary predecessors. 



Ever since the genie has been released the fishermen 

 have been divided into two camps ; those who were 

 most interested in studying the jar with the view of 

 discovering the wonderful properties by which it could 

 confine so powerful an agent, and those who have 

 preferred to take such things for granted and have 

 devoted themselves to putting these powers to the 

 service of mankind. As time has advanced the work 

 of each camp has become more and more differen- 

 tiated, the " theorists " pressing always deeper and 

 deeper into the region of first causes, but ever and 

 again bringing to the surface some fresh discovery 

 on which the " practical men " are quick to seize and 

 which they soon adapt to useful purposes. Thus 

 each continues to supplement the work of the other 

 until it is hard to tell to which is owed the greater 

 debt of gratitude — to those but for whom the powi rs 

 of the genie would have remained concealed, or to 

 those but for whom they would have remained dis- 

 covered but unused. 



Mr. Whetham's book is an admirable exposition oi 



all that the theorists have discovered so far. " To 



some extent," he writes in the preface, "even a 



scientific text-book must be a piece of literature and a 



NO. 1886, VOL. J$] 



work of art." "Experimental Electricity" can cer- 

 tainly claim to be both. The present writer does not 

 profess to be very old, but the development of elec- 

 trical theory has been so rapid since he first studied 

 its elements that the text-books from which he learnt 

 are more out of date than is Euclid as a text-book of 

 modern geometry. An elementary text-book should 

 give a comprehensive survey of the whole of its sub- 

 ject in such a way as to stimulate the curiosity and 

 imagination of the student and this the book before 

 us does. It is written in a clear and simple style, and 

 the mathematics necessary are such as any student 

 beginning his university career should have at hand. 

 A very prominent and valuable feature of the book is 

 the frequent reference to and quotation from the works 

 of the founders of modern electrical theory, notably 

 Faraday and Maxwell. The story which it tells of the 

 development of this theory from the first suggestions 

 of Faraday to the most recent conceptions of J. J. 

 Thomson, Larmor, and others is one of extraordinary 

 fascination and interest, and we cannot conceive any 

 earnest student laying down the book without a desire 

 to help to the best of his ability in solving the riddle 

 with which it closes. 



Books such as Mr. Whetham's should be read not 

 only by the student who wishes to enrol himself in the 

 scientific camp, but also by those who intend to 

 become engineers. The engineer can never be the 

 worse for a sound knowledge of what the men of 

 science are doing. Incidentally he may be prevented 

 from making some of the mistakes which Messrs. 

 Ashe and Keiley make in the first chapter of their 

 otherwise excellent ( book on electric railways. For 

 example, these writers in the course of a few lines 

 speak of the watt, first as power, then as work, and 

 finally as energy. But after a few pages of this 

 " miscallin' technicalities " they proceed to the more 

 serious business of their book, and here there is little 

 to which objection can be raised. The book is a good 

 example of some of the feats that the genie has 

 accomplished. It is a good example, too, of the 

 extreme specialisation so characteristic now of all 

 branches of electrical engineering. The title is some- 

 what broad, as the subject-matter is practically con- 

 fined to rolling stock and rolling-stock equipment. 

 The illustrations are plentiful and very clear. 



If those who would learn what the jar is made of 

 should study Mr. Whetham's book, those who would 

 know in a general way the genie's powers should read 

 " Modern Electric Practice," of which the present 

 volume is the sixth and last. We have already re- 

 viewed the previous volumes and have pointed out 

 what we consider to be somewhat serious defects in 

 the plan and general arrangement of the work. Still, 

 as a general summary of all the modern applications 

 of electricity these volumes are not to be despised, 

 especially when their very numerous illustrations are 

 remembered. We would like to suggest that in 

 future editions these are published without the text. 

 The present volume contains very good articles on 

 telegraphy and telephony; the article on electromedical 

 appliances is disappointing in the extreme. There is 

 in addition a good index to the whole six volumes. 



