PULSATIONS MEASURED BY MUSICAL SOUNDS. 



second, it will produce by its motion some definite musical sound, 

 and if the note formed upon a pianoforte, which is in unison with 

 it, be found, the rate of vibration of the string producing that note, 

 will be the same as that of the lever. 



When it is stated that the vibrations imparted by the pulsations 

 of the current to levers, mounted in the manner here described, have 

 produced musical notes nearly two octaves higher than the highest 

 note on a seven octave piano, tuned to concert pitch, it may be 

 conceived in how rapid a manner the transmission and suspension 

 of the electric current, the acquisition and loss of magnetism in 

 the soft iron rods, and the consequent oscillation of the lever, upon 

 which these rods act, take place. The string which produces the 

 highest note, on such a piano, vibrates 3520 times per second. A 

 string which would produce a note an octave higher would vibrate 

 7040 times per second, and one which would produce a note two 

 octaves higher would vibrate 14080 times per second. 



It may, therefore, be stated, that by the marvellously subtle 

 action of the electric current, the motion of a pendulum is produced, 

 by which a single second of time is divided into from twelve to 

 fourteen thousand equal parts ! 



150. It has been already shown how the motion of clock- 

 work may be applied to control and regulate the pulsations of the 

 electric current. We shall now show how, on the other hand, the 

 pulsations of the current may be made to govern the motion of 

 wheel-work. This expedient must be regarded with the more 

 interest inasmuch as it has been applied with the greatest effect 

 in several of the varieties of electric telegraph, which have been 

 proposed or brought into operation. 



151. If we suppose the lever g A, fig. 58, to be put into connection 

 with the anchor of the escapement wheel of a system of clock-work, 

 it will be easy to see how that clock-work can be regulated by the 

 pulsations of the electric current. 



In fig. 59 (p. 202), w w 7 is the escapement wheel which is con- 

 stantly impelled by the force of a descending weight or mainspring 

 in the direction of the arrows. The anchor A B c, of the escapement, 

 is connected with an axis D, by the straight rod B D. This rod B B 

 may be either the vibrating arm of a lever, such as g h, fig. 58, 

 kept in oscillation by the current acting on an electro-magnet, or 

 it may be connected with such a lever in any convenient manner, 

 so as to oscillate simultaneously with it, and to have the extent of 

 play necessary for the action of the pallets A and c of the anchor 

 on the teeth of the escapement wheel. 



When the anchor is not in a state of oscillation, a tooth of the 

 wheel will rest upon one of its pallets, and the wheel and clock- 

 work connected with it will be stopped. When the anchor moves 



201 



