96 SCIENTIFIC APPARATUS. 



Among the class of springs or rods -the nail-fiddle seems the 

 simplest. A circle of metal vibrators, each of which speaks to a 

 certain note, is here touched by a bow, or even plucked by the 

 finger. In the musical-box these vibrators are arranged in a long 

 comb, being weighted on their underside and plucked by steel 

 pins inserted into a rotating barrel kept in motion by clockwork and 

 regulated by a fly. In the Jew's-harp the controlling power over 

 the note is the volume of air in the cavity of the mouth, the lax 

 " reed " or spring of the instrument being capable of responding 

 to very different rapidities of vibration. 



In tuning-forks, the necessity for firmly fixing the base of the 

 rod or spring is obviated by attaching it to a second similar rod 

 or spring, which vibrates in opposition, and keeps the whole mass 

 in equilibrium. An instrument with single springs struck by 

 hammers, and furnished with a key-board, is made by Messrs. 

 Cramer and Co. 



The wire gongs of American and other clocks are coiled into a 

 flat spiral, attached to a heavy mass of metal at the outer end, and 

 firmly screwed to the wood of the case ; being struck by a hammer 

 close to the fixed end, they produce very profound complex 

 notes, much resembling those of a large church-bell. 



Plates are illustrated by various instruments commonly called 

 harmonicons, which may be made of wood, glass, steel, or even of 

 compact storie. Many Oriental instruments are formed out of 

 the first material, usually the outer silicious layer of the bamboo, 

 and are remarkable for the presence of resonators reinforcing the 

 note, which will be adverted to farther on. The amount of tone 

 is astonishingly large and pure. Such an instrument, under the 

 name of the " Xylophone," has recently been produced at many 

 London concerts. Another, made of crystalline slate' in bars, 

 termed the " rock harmonicon," was exhibited a few years back. 

 Mozart writes for a like instrument, probably made of steel, in his 

 Flauto Magico, where it is supposed to imitate the sounds of the 



