LECT. XVIII. REED INSTRUMENTS. 339 



but more especially to Miiller, for observations best fitted 

 for demonstrating the correctness of this manner of view- 

 ing the organ of voice in man. I shall endeavour to give 

 you, as briefly as possible, an analysis of these investiga- 

 tions. 



Reed Instruments. Allow me first, however, to show you 

 some general facts on sounds produced by reeds. When 

 a rectangular metallic plate is fixed by one extremity, on 

 the edges of an opening almost equal in extent to that of 

 the plate, we have then 1 a reed instrument, provided that 

 the piece which contains the opening has a cylindrical or 

 other form, and closes the orifice of a pipe into which a 

 current of air is propelled. The mouth- harmonicon is the 

 simplest instrument of this kind. A sound is also produced 

 when a current of air is propelled by means of a tube, against 

 a small metallic tongue fixed in some way, but not mounted 

 on the chink. Some experiments seem to show that the 

 pitch of sounds thus produced by these tongues, is inde- 

 pendent both of the intensity of the current, and of the 

 chemical nature of the air or gas: these circumstances 

 merely vary the intensity of the sound. Some experiments, 

 again, seem to have proved that, in order to vary the acuity 

 and the gravity of a sound, the thickness of the tongues re- 

 quires to be altered. We may explain in two different 

 ways the sounds produced by a metallic tongue : it may be 

 said, that the latter vibrates like an elastic rod, and that 

 these vibrations are the cause of the sound ; or rather that the 

 tongue, forced from the opening, in which it is fixed, by the 

 current of air, returns to its former position in consequence 

 of its elasticity ; and thus, by its position of equilibrium 

 being disturbed, undergoes oscillations which give rise to 

 impulses of the air, as in the sirene, or in Savart's machine. 

 It must, however, be observed, that the sounds furnished 

 when the tongue is made to vibrate by striking it, are never 



