58 



NATURE 



{Nov. 2 1, 1878 



phone, it is stated in Prescott's work on the telephone 

 that Mr, Bentley, President of the local telegraph com- 

 pany at Philadelphia, has succeeded in working with it 

 over a wire of 720 miles in length, and has foundjt a 



Fig. I. — Section of Carbon Telephone — Early form. 



practicable instrument upon wires of 100 to 200 miles in 

 length, notwithstanding the fact that the latter were 

 placed upon poles with numerous other wires, which 

 occasioned sufficiently powerful induced currents in them 



apparatus ; and that several way stations could exchange 

 business telephonically upon a wire which was being 

 worked, quadruplex, without disturbing the latter, and not- 

 withstanding, also, the action of the powerful reversed 

 currents of the quadruplex on the diaphragms of the 

 receiver. It would thus seem as though the volume of 

 sound produced by the voice with this apparatus more 

 than compensated for the noise caused by such actions." 

 Mr, Edison's assistant, Mr. Adams, now in England, 

 states that conversation has been carried on during the 

 night between New York and Chicago, places nearly 

 1,000 miles apart ; and that under less favourable cir- 

 cumstances during the day the carbon telephone has been 

 successfully used over a line of about half this length. 

 Mr, Adams also informs the writer that at the Paris 

 Exhibition he was able to transmit the music of a piano 

 from Paris to Versailles, a distance of more than 20 

 miles ; the piano standing 50 feet from the carbon tele- 

 phone and yet not a note was lost at Versailles. 



The present writer has had an opportunity of testing 



Line 



Fig. 2.— Section of Carbon Telephone — Latest form. 



to entirely destroy the articulation of the magneto-tele- 

 phone. Further, he has found the instrument practicable 

 " when included in a Morse drcutt, with a battery and 

 eight or ten stations, provided with the ordinary Morse 



YiQ. 3.— Electric arrangement of the Carb;n Telephone. 



Earth. 



this instrument in a recent lecture at the Midland) 

 Institute, Birmingham, and the surprising loudness of 

 the tones received has been noticed in Nature. Words 

 spoken some thirty feet from the transmitter were clearly 

 heard in the distant receiver, whilst loud speakmg close 

 to the transmitter enabled more than a hundred persons 

 to hear simultaneously the words spoken when a paper ] 

 cone was added to the receiver. And furthermore, smgle 

 exclamations, such as Bravo ! could be heard by the 

 whole of a crowded audience of upwards of a thousand 

 people. Even when the line wire was broken, the frac-^ 

 tured ends being near to, but not touchmg each otherJ 

 conversation could still be carried on through the circuit 

 with the carbon telephone, though communication by the 

 magneto-telephone and the ordinary telegraphic instru-'' 

 ments was entirely interrupted. The writer has also just 

 made further and more severe trials with this instrument 

 on, he believes, the longest private wire m constant use 

 in England, namely, that belonging to Messrs. Colman, 



