166 THE APPLICATIONS OF PHYSICAL FORCES. [BOOK n. 



each note, and which are struck together when the finger is placed on 

 a key, would continue to sound after the blow, if they were not 

 furnished with a small piece of wcroct covered with felt, called 

 damper. As soon as the finger rests on a key, the damper E' is 

 raised, and the string vibrates ; it remains up if the finger con- 

 tinues to press down the note ; on the other hand it falls and cuts off 

 the vibration, so soon as the finger leaves it. 



We must next point out by what mechanism the pedals produce 

 the increase and decrease of the intensity of the sound. One of them 

 communicates by a lever with the whole system of dampers. When 

 pressed down by the foot, a vertical rod is made to act on this system, 

 and all the dampers are raised up at the same time; each note is 

 therefore prolonged and gives a more intense sound ; moreover, it 

 communicates its own vibrations to other strings bearing harmonic 

 relations of pitch to its own tone, so that the sonorousness of the 

 instrument is considerably increased. If, on the contrary, the per- 

 former uses the other pedal, a slight movement from left to right is 

 communicated to the key-board ; each hammer then only strikes 

 one or two of the three strings designed to produce the tone or sound, 

 the intensity is thus diminished one or two-thirds. 



The piano does not date further back than the second half of the 

 eighteenth century. It is nothing more than an improved clavecin, 

 an instrument first made in Italy, whence it has been imported to 

 European countries. The clavecin often had several key -boards ; but 

 that which distinguished it from the modern piano, was the way in 

 which the metallic strings were put into vibration. We have just 

 seen that in the piano the percussion of a hammer causes them to 

 sound; in the clavecin, or harpsichord, the keys move small pieces 

 of wood called jacks, furnished with a crow-quill point. It is 

 this point which plucks the strings. The notes of the harpsichord 

 have not the same character or tone as those of the piano, they are 

 thinner, and sharper, the tone is not so soft, and less sweet and 

 intense. 



The spinet was a kind of small harpsichord, with only one string 

 to each note, and therefore only one row of jacks. This was in fact 

 the primitive form of the harpsichord itself. 



