ACOUSTICAL INSTRUMENTS. 97 



sistrum, with which Papageno is entrusted. A remarkable 

 instance of a large vibrating plate of metal is the so-called 

 Chinese " bell" which is exhibited. 



Bells proper are usually in the form of 'vessels either of hemi- 

 spherical shape, as in clock-bells, or of a very complex outline, as 

 in church and house-bells. 



The musical-glasses, formerly in great repute, and recently 

 revived, were a collection of glass vessels selected so as to form an 

 approximate scale, and further tuned by pouring in water. Their 

 note was excited by rubbing the free edge, either with the 

 moistened finger, or with a wetted cloth. An ingenious modifi- 

 cation of this arrangement is shown, wherein the bells are fixed to 

 a rotating spindle, and touched while in rotation with a wetted 

 excitor. The sounds thus obtained are continuous, and of pecu- 

 liarly luscious, though cloying quality. 



Strings embrace too many varieties for full discussion. The 

 chief novelties exhibited are the flattened spiral strings described 

 farther on, and the heavily covered string attached to a double 

 bass, from which the sixteen-foot C can be produced without 

 unwieldly increase of length. 



The use of strings formed of an open coil has been before 

 attempted, but without success, the coil being unable to withstand 

 the necessary strain. This difficulty has been overcome by Mr. 

 Baillie Hamilton, who has invented a process of rolling and tem- 

 pering steel wire into a form such that the coil has enormous 

 power of resistance to any strain that can be applied to a piano- 

 forte string. Moreover, as the strain on every coil is chiefly 

 lateral, the tension is that of a spring, and is not greatly affected 

 by the causes which derange the pitch of ordinary strings. It is 

 needless to point out the advantage of gaining more than the 

 length of a grand pianoforte string in the space occupied by that 

 of a small upright instrument. 



