Bell's Telephonic Researches 



pendently discovered that permanent magnets 

 might be employed instead of voltaic batteries. 

 Indeed, one gentleman, Professor Dolbear, of 

 Tufts College, not only claims to have discovered 

 the magneto-electric telephone, but, I under- 

 stand, charges me with having obtained the idea 

 from him through the medium of a mutual friend. 



A still more powerful form of apparatus was 

 constructed by using a powerful compound horse- 

 shoe magnet in place of the straight rod which 

 had been previously used (see Fig. n). Indeed, 

 the sounds produced by means of this instru- 

 ment were of sufficient loudness to be faintly 

 audible to a large audience, and in this condition 

 the instrument was exhibited in the Essex In- 

 stitute, in Salem, Massachusetts, on the. 1 2th 

 of February, 1877, on which occasion a short 

 speech shouted into a similar telephone in Boston 

 sixteen miles away, was heard by the audience in 

 Salem. The tones of the speaker's voice were 

 distinctly audible to an audience of six hundred 

 people, but the articulation was only distinct at 

 a distance of about six feet. On the same oc- 

 casion, also, a report of the lecture was trans- 

 mitted by word of mouth from Salem to Boston, 

 and published in the papers the next morning. 



From the form of telephone shown in Fig. 10 

 to the present form of the instrument (Fig. i 2) 

 is but a step. It is, in fact, the arrangement of 

 Fig. 10 in a portable form, the magnet F. H. be- 

 ing placed inside the handle and a more con- 

 venient form of mouthpiece provided .... 

 77 



