586 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



committee as the third in efficiency, showing in the arc a 

 useful result equivalent to 2 7 per cent, of the power em- 

 ployed, or of 31 per cent, after deducting friction. The com- 

 mittee state further concerning this apparatus, that although 

 somewhat inferior to the Gramme, it is nevertheless admi- 

 rably adapted for the production of intense currents, and has 

 the advantage of being capable of furnishing currents of 

 widely varying electro-motive force. It possesses the advan- 

 tage of division of the conductor into two circuits, simplicity 

 and ease of repair of the commutator, and comparative free- 

 dom from heating. 



The Wallace-Farmer machine, according to the commit- 

 tee's report, does not return to the effective circuit as large a 

 proportion of power as the other machines (14 per cent., or 

 15^ per cent., deducting friction), although it uses in electri- 

 cal work a large amount of power in small space. The cause 

 of this low economy the committee attribute to the expendi- 

 ture of a large proportion of the power in producing local ac- 

 tion. They express the opinion, however, that by remedying 

 this defect an admirable machine would be produced. 



TELEGRAPHY. 



In this department the progress made during the past year 

 is specially noteworthy. The most prominent advances to 

 be noticed are the invention of the microphone, by which 

 minute sounds are rendered audible ; the improvement of the 

 phonograph, or talking-machine, the announcement of which 

 invention was made in our last volume, but which was not 

 practically brought out until the early part of 1878; and the 

 considerable progress of the problem of electric lighting, 

 which we have esteemed of sufficient importance to be given 

 a separate consideration. The Telegraphic Journal, referring 

 to the telephone, the phonograph, and the microphone, tersely 

 defines their functions and utility as follows : " We have now 

 a command over sound similar in kind to that which we pos- 

 sess over light. For the telephone is for the ear what the 

 telescope is for the eye; the phonograph is for sound what 

 the photograph is for light ; and the microphone finds its an- 

 alogue in the microscope." The last-named instrument has 

 already received some highly useful applications, and as it is 

 improved, and its capabilities .are better understood, its utility 



