Elements of natural philosophy (Volume 2-3) . Norhas it been necessary to discuss these particulars, sincethe velocity, pitch and intensity are wholly independentof these considerations. But while the amplitude andtime of vibration of the particles of the auditory nerves,induced by different sonorous waves, may be the same, Determined bythus inducing a constant intensity and pitch, yet the Cor-peculiarityofresponding sensations may derive a peculiarity of hue, soto speak, from the variations in the mode of molecularmotions above referred to, sufficient to account for thedistinction of quality.
Elements of natural philosophy (Volume 2-3) . Norhas it been necessary to discuss these particulars, sincethe velocity, pitch and intensity are wholly independentof these considerations. But while the amplitude andtime of vibration of the particles of the auditory nerves,induced by different sonorous waves, may be the same, Determined bythus inducing a constant intensity and pitch, yet the Cor-peculiarityofresponding sensations may derive a peculiarity of hue, soto speak, from the variations in the mode of molecularmotions above referred to, sufficient to account for thedistinction of quality. § 48. To ascertain what length of wave corresponds to i^nsth of waye .. j? .. ! .,t . i ,, corresponding to our sensation ot a particular pitch, we must have the a certain pitchmeans of measuring the lengths of different waves. These determined byare furnished in an elegant little instrument called theSiren ; a device of Baron Cogniard de la Tour. Inthis instrument the wind of a bellows is emitted through -i 50 NATURAL PHILOSOPHY. Fig. siren; a small hollow tube A, before the end of whicha circular disc J5, pierc-ed with a number ofequal and equidistantholes arranged in thecircumference of a cir-cle concentric with theaxis ,of motion C, ismade to revolve. The tube through which the air passes is so situated that theholes in the disc shall pass in rapid succession over itsopen end and permit the air to escape, being at the sametime so near to the plane of the disc that intervals be-tween the holes serve as a cover to intercept the air. If construction and the holes be pierced obliquely, the action of the currentof air alone will be sufficient to put the disc in motion;if perpendicular to the surface it must be moved bywheel work, so contrived as to accelerate or retard therotation at pleasure. The bellows being inflated andthe disc put in motion, a series of rapid impulses arecommunicated to the air in front of the holes; and,when the rotation is sufficiently rapid, a mus
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