150 SOUNDING-BOARDS RESONANCE. SECT. XVII. 



hammers strike the strings so as to make them vibrate at right 

 angles to it. In the guitar, on the contrary, they are struck 

 obliquely, which renders the tone feeble, unless when the sides, 

 which also act as a sounding-board, are deep. It is evident that 

 the sounding-board and the whole instrument are agitated at once 

 by all the superposed vibrations excited by the simultaneous or 

 consecutive notes that are sounded, each having its perfect effect 

 independently of the rest. A sounding-board not only recipro- 

 cates the different degrees of pitch, but all the nameless qualities 

 of tone. This has been beautifully illustrated by Professor 

 Wheatstone in a series of experiments on the transmission 

 through solid conductors of musical performances, from the 

 harp, piano, violin, clarinet, &c. He found that all the varieties 

 of pitch, quality, and intensity are perfectly transmitted with 

 their relative gradations, and may be communicated, through 

 conducting wires or rods of very considerable length, to a pro- 

 perly disposed sounding-board in a distant apartment. The 

 sounds of an entire orchestra may be transmitted and reciprocated 

 by connecting one end of a metallic rod with a sounding-board 

 near the orchestra, so placed as to resound to all the instruments, 

 and the other end with the sounding-board of a harp, piano, or 

 guitar, in a remote apartment. Professor Wheatstone observes, 

 " The effect of this experiment is very pleasing ; the sounds, 

 indeed, have so little intensity as scarcely to be heard at a dis- 

 tance from the reciprocating instrument ; but, on placing the ear 

 close to it, a diminutive band is heard in which all the instru- 

 ments preserve their distinctive qualities, and the pianos and 

 fortes, the crescendos and diminuendos, their relative contrasts. 

 Compared with an ordinary band heard at a distance through 

 the air, the effect is as a landscape seen in miniature beauty 

 through a concave lens, compared with the same scene viewed 

 by ordinary vision through a murky atmosphere." 



Every one is aware of the reinforcement of sound by the 

 resonance of cavities. When singing or speaking near the aper- 

 ture of a wide-mouthed vessel, the intensity of some one note in 

 unison with the air in the cavity is often augmented to a great 

 degree. Any vessel will resound if a body vibrating the natural 

 note of the cavity be placed opposite to its orifice, and be large 

 enough to cover it, or at least to set a large portion of the 

 adjacent air in motion. For the sound will be alternately re- 



