G. S. Moler — Transverse Vibrations of Cords and Wires. 339 . 



cords. By carrying a cord as far as I conveniently could, a 

 distance of thirty-fonr feet, and adjusting the tension, I ob- 

 tained twenty-five well formed segments 



The regulating device is an electrical governor, shown at I 

 figure 1, but more in detail in figure 3. The lever J is pivoted 

 at K and whenever the speed exceeds a certain amount it is 

 pulled outward with sufficient force to bend the spring L and 

 make contact with the insulated wire M. The speed at which 

 this occurs is regulated by altering the tension of the spring 

 by means of the screw 1ST. The contact points are of plati- 

 num. The insulated wire runs out through the hollow shaft 

 to the binding post O, thence to the electro-magnet P and 

 the battery. The other pole of the battery is connected with 

 the frame of the machine. The armature of the electro-mag- 

 net is attached to a lever Q (fig. 4), and upon the other end of 

 the lever is a leather pad, which is brought into contact with 

 the wheel whenever the circuit is closed. The friction thus 

 produced reduces the speed until the contact breaks when the 

 speed again increases and closes the circuit. The delicacy of 

 this device is such that these variations of speed are imper- 

 ceptible. 



By driving two cords from the same crank a very accurate 

 secondary speed regulation was obtained. For this purpose a 

 cord of considerable mass was made use of, with tension such 

 as to cause it to vibrate in a single segment. The shaft was 

 driven by means of a small turbine motor, capable of any 

 speed up to seven thousand revolutions per minute. When the 

 vibrating segment of the heavy cord was once well formed it 

 was found that small variations in the motive power made 

 themselves felt in swelling or diminishing the amplitude of the 

 segment without producing changes in speed, and that it was 

 possible to make all necessary adjustments of length or tension 

 in the second cord without in any way interfering with the 

 uniform motion of the instrument. If, however, the govern- 

 ing segment were destroyed in any way the electrical governor 

 already described would soon restore the speed to its normal 

 amount. The amplitude of the governing segment served 

 likewise as a delicate indicator of the condition of the motive 

 power, excess of power causing a swelling out of the segment 

 to large diameter, and diminution of power showing itself by 

 decrease in the amplitude of vibration. 



By means of this apparatus all the laws demonstrated in 

 Melde's experiment may be verified. The following is the 

 record of a single set of observations made to test the working 

 of the instrument. 



The cords used were of braided silk, measuring -55 mm in di- 

 ameter. Four strands of this size were taken for the control- 



