54 PROCEEDINGS OF THE AMERICAN ACADEMY 



fork, and of the tuning-fork to exciting and sustaining the 

 vibration of threads or cords. 



The elements which comprise the essential features of the machine, 

 now exhibited, are not original. The application of electricity as the 

 maintaining power for such rapid vibrations as belong to tuning-forks 

 is not new, though it is of recent discovery ; and the application of 

 tuning-forks to exciting sympathetic vibrations in cords is not new, 

 though it is also of recent discovery. I am not aware, however, that 

 these two discoveries have been united into one, by Employing a tun- 

 ing-fork, so impelled, for this particular purpose. Such tuning-fork3 

 have already been made and used by Koenig for producing the Lisse* 

 jous' curves, and for exhibiting the phenomena of interference of sounds ; 

 and this new application, therefore, is sufficiently obvious, and may 

 have been already anticipated by other physicists. The tuning-forks 

 in ut, etc., manufactured by Koenig for repeating Melde's experiments 

 on the vibrations of cords, are only adapted to short threads of 

 saddler's silk. My object has been to provide a tuning-fork which 

 would not be overloaded with a stout cord of thirty or forty feet in 

 length. 



The prongs of my tuning-fork are thirty inches in length, two inches 

 in width, and three eighths of an inch in thickness ; and, in spite of the 

 encumbrance of the cord, they will vibrate for many minutes without 

 the aid of electricity, making excursions oPone half of an inch on each 

 side of the position of equilibrium. The outer face of each prong, 

 when at rest, is exposed to one pole of an electro-magnet, at the dis- 

 tance of three fourths of an inch from it. The iron core of this elec- 

 tro-magnet has a circular section of an inch and one fourth in diameter, 

 and is wound with copper wire to the depth of two inches. 



The extremities of this iron core carry nearly cubical blocks of soft 

 iron, of about one inch and a half in linear dimension, through which 

 are screwed pieces of iron of one half of an inch in thickness. The 

 ends of these pieces are the acting poles, and are screwed through the 

 blocks, in order to adjust the distance between the poles of the magnet 

 and the prongs of the tuning-fork. With four cups of Bunsen's bat- 

 tery, the zincs of which are cylinders, four inches in diameter and 

 seven inches in height, and connected for intensity, the magnet has 

 strength sufficient to initiate the motion of the prongs, at the distance 

 even of three fourths of an inch, and to bring them soon into energetic 

 vibration. The current of electricity runs through the stem of the 



