MUSICAL SOUNDS FROM VIBRATION OF SOLID BODIES. 251 



same manner as we have already explained with regard to 

 vibrating strings. By opening other holes we may sub- 

 divide a vibrating column into any number of smaller 

 vibrating columns. The holes in flutes, clarionets, &c., 

 are made for this purpose. When they are all closed up 

 the air vibrates in one column, and by opening and 

 shutting the different holes in succession, the number of 

 vibrating columns is increased or diminished at pleasure, 

 and consequently the harmonic sounds will vary in a 

 similar manner. 



Curious as these phenomena are, they are still surpassed 

 by those which are exhibited during the vibration of solid 

 bodies. A rod or bar of metal or glass may be made to 

 vibrate either longitudinally or laterally. 



An iron rod will vibrate longitudinally like a column 

 of air if we strike it at one end in the direction of its 

 length, or rub it in the same direction with a wetted 

 finger, and it will emit the same fundamental note as a 

 column of air ten or eleven times as long, because sound 

 moves as much faster in iron than in air. When the iron 

 rod is thus vibrating along its length, the very same 

 changes which we have shown in Fig. 41, as produced in 

 a spiral spring or in a column of air, take place in the 

 solid metal. All its particles move alternately towards A 

 and towards B, the metal being in the one case condensed 

 at the end to which the particles move, and expanded at 

 the end from which they move, and retaining its natural 

 density in the middle of the rod. If we now hold this 

 rod in the middle, by the finger and thumb lightly 

 applied, and rub it in the middle either of A B or B C 

 with a piece of cloth sprinkled with powdered rosin, or 

 with a well-rosined fiddle-bow drawn across the rod, it 

 will divide itself into two vibrating portions A B, B C, 

 each of which will vibrate, as shown in Pig. 42, like the 

 two adjacent columns of air, the section of the rod, or the 



