266 PLEASANT WAYS IN SCIENCE. 



similar sound alphabet Suppose, now, four tuning-forks at 



the transmitting station, whose notes are Do I r7\~ I Mt, 



" 



I 



t __ I 



- I 



Sol, and Do I j ^ , or say C, E, G, and C", then by each 



t 



of these forks a separate message may be transmitted, all the 

 messages being carried simultaneously by the same line to 

 separate sounding reeds (or forks, if preferred), and received 

 by different clerks. With a suitable key-board, a single 

 clerk could send the four messages simultaneously, striking 

 chords instead of single notes, though considerable practice 

 would be necessary to transform four verbal messages at 

 once into the proper telephonic music, and some skill in 

 fingering to give the proper duration to each note. 



Lastly, we come to the greatest achievement of all, Pro- 

 fessor Graham Bell's vocal telephone. In the autumn of 

 1875 I na d the pleasure of hearing from Professor Bell in the 

 course of a ride all too short from Boston to Salem, Mass., 

 an account of his instrument as then devised, and of his 

 hopes as to future developments. These hopes have since 

 been in great part fulfilled, but I venture to predict that we 

 do not yet know all, or nearly all, that the vocal telephone, 

 in Bell's hands, is to achieve. 



It ought to be mentioned at the outset that Bell claims 

 to have demonstrated in 1873 (a year before La Cour) the 

 possibility of transmitting several messages simultaneously 

 by means of the Morse alphabet 



Bell's original arrangement for vocal telephony was as 

 follows : At one station a drumhead of goldbeaters' skin, 

 about af inches in diameter, was placed in front of an 

 electro-magnet To the middle of the drumhead, on the 

 side towards the magnet, was glued a circular piece of clock- 

 spring. A similar electro-magnet, drumhead, etc, were 

 placed at the other station. When notes were sung or 

 words spoken before one drumhead, the vibrations of the 

 goldbeaters' skin carried the small piece of clockspring 



