CONCERNING SCIENTIFIC APPARATUS. 519 



7. Electroscopes and electrometers, Coulomb's torsion balance, voltameters, 



galvanometers and electrodynamometers, magnetometers. 



8. Standards of resistance, capacity, electro-motive force, &c., as the Ohm, 



the microfarad, L. Clark's voltaic constant cell. 



From the physical, as distinguished from the physiological point of view, 

 the science of Acoustics relates to the excitement of vibrations and the propa- 

 gation of waves in solids, liquids, and gases, and that of Optics to the excitement 

 of vibrations, and the propagation of radiation, in the luminiferous medium. 



From the physiological point of view, only those waves in ordinary matter 

 are considered which excite in us the sensation of Sound, though waves which 

 do not excite this sensation can be detected and studied by appropriate methods. 



In the physiological treatment of Optics, only those radiations are considered 

 which excite in us the sensation of Light, though other radiations can be 

 detected and studied by their thermal, chemical, and even mechanical effects. 



VIBRATIONS AND WAVES. 

 PHYSICAL ASPECT OF ACOUSTICS. 



1. Sources. Vibrations of various bodies. 



Air Organ pipes, resonators and other wind instruments. 



Reed instruments. 



The Siren. 



Strings . . . Harp, &c. 



Membranes . . . Drum, &c. 



Plates . . . Gong, &c. 



Bods . . . . Tuning-fork, &c. 



2. Distributors. Air . . Speaking tubes, stethoscopes, &c. 



Wood, . Sounding rods. 

 Metal, . Wires. 



3. Pugging of floors, &c. 



4. Reservoirs. Resonators, Organ Pipes, Sounding-boards. 



5. Dampers of pianofortes. 



6. Regulators. Organ Swell. 



7. Detectors, the ear; Sensitive Flames, Membranes, Phonautographs, &c. 



8. Tuning-forks, pitch-pipes, and musical scales. 



