VI TRANSLATOR'S PREFACE. 



from the first page to the last, the practical point of view is 

 never for an instant abandoned. 



No special knowledge of electrical science is needed for 

 the intelligent perusal of this work ; nevertheless,! a reader 

 altogether ne\v to the subject would do well to acquire 

 clear ideas of a few elementary facts. Almost any of the 

 cheap manuals which now abound would suffice to convey 

 all the information required; but it could not, perhaps, -be 

 attained more pleasantly and profitably than by a reference 

 to Professor TyndalFs " Notes of a Course of Seven Lectures 

 on Electrical Phenomena and Theories," which may be had 

 for a few pence. 



The present translation contains all the author's notes, 

 references, and appendices. To these, two other appendices 

 are now added by the translator. The first gives the English 

 equivalents of the French weights, measures, etc., which, on 

 account of their now almost universal employment for 

 scientific purposes, it has been deemed expedient to retain in 

 the text. The second is a brief notice of some forms of 

 incandescent lamps, and of another recent invention, which 

 have come into prominence since the publication of the origi- 

 nal work. Several lamps of this kind may now be said to 

 have proved completely successful in practice, and the forms 

 described in the appendix are those which have attracted the 

 largest share of public attention, as offering the simplest and 

 most effective solution of nearly all the difficulties that have 

 hitherto attended the application of electric lighting to 

 domestic and certain other purposes. 



The translator, having been unable to refer to some of 

 the English and American newspapers, journals, and reports 

 quoted by the author, has usually contented himself with 

 a faithful rendering of the French version; but it is not, 

 of course, to be expected that the ipsissima verba of the 



