ACOUSTICAL INSTRUMENTS. 95 



Air. Speaking-tubes, speaking trumpets, bells of wind 

 instruments, velocity experiments, reinforcement-con- 

 sonance in resonators, consonant vessels, as in Indian 

 instruments and in Greek theatres. 

 Metal. Wires, destruction of echo by interference 

 Wood. Telephone. 



3. The determination and measurement of sound may be 

 accomplished by Savart's wheel, Sirens, Optical and Graphical 

 methods, by Beats and Interferences. 



4. Its history and ethnology from ancient instruments and 

 their reproduction, EgyptiaiTpipes, hydraulic organs, Oriental and 

 national instruments. 



5. Temperaments, &c. Perronet Thompson's inventions, 

 Ellis's duodenes, Bosanquet's harmonium. Effects of Heat and 

 Electricity. 



6. Special applications to music. Discoveries as to timbre 

 or quality. 



PHYSIOLOGICAL ASPECT OF ACOUSTICS. 



The audibility of acute sounds has been noticed above. Very 

 elaborate apparatus is exhibited for determining the lower limit of 

 musical character. Professor Helmholtz's experiments being made 

 with a thin string, loaded with a copper coin, offered slight power 

 of consonance or reinforcement, and the tone consequently soon 

 faded out. In Messrs. Elliot's instrument, and in the four-string 

 double-bass shown, better conditions of sympathetic vibration 

 being afforded, and a larger mass of air being set in vibration, 

 notes considerably lower in the scale were produced with musical 

 character. 



The perception of distinction, harmony, discord, and of melo- 

 dious succession, appear to be in great measure due to acquire- 

 ment, aided by natural sensitiveness of ear in the learner. 



i. Modes of production are almost innumerable, if every variety 

 be included. 



