202 SENSE OF HEARING. 



one favourite pursuit, but not perhaps to be wholly explained by this 

 circumstance; and, whilst we find them often unmarked by any of the 

 kindlier sympathies, we see those, that are " not moved with concord 

 of sweet sounds," alike distinguished as philosophers and philanthro- 

 pists. 



The defect, in these cases, differs probably, in an essential manner, 

 from one to which attention has been drawn by the late Dr. Wollas- 

 ton, 1 who has detailed many curious facts, regarding what he terms a 

 peculiarity in certain ears, which seem to have no defect in their gene- 

 ral capacity for being impressed by sound, or in the perception of mu- 

 sical tones ; but are insensible to very acute sounds. This insensibility 

 commences when the vibrations have attained a certain degree of rapi- 

 dity ; beyond which all sounds are inaudible to ears thus constituted. 

 Thus, according to Dr. Wollaston, certain persons cannot hear the chirp 

 of the grasshopper ; others, the cry of the bat ; and he refers to one 

 case, in which the note of the sparrow was inaudible. He himself was 

 incapable of hearing any sound higher than six octaves above the mid- 

 dle E of the piano forte. The defect would, at first sight, appear to 

 be referable to the physical part of the ear, rather than to the auditory 

 nerve, or to the part of the brain concerned in the appreciation of 

 sounds; the vibrations that are performed with J great rapidity not 

 being responded to by the parts of the organ destined for that purpose; 

 and, consequently, never reaching the auditory nerve. Researches, 

 however, by M. Savart, 2 a most dexterous and ingenious experimenter, 

 seem to show that the defect in the appreciation of acute sounds, in 

 such cases, is not owing to their acuteness but to their feebleness; that 

 if the sound can be made sufficiently intense, the ear is capable of 

 hearing a note of upwards of forty thousand simple oscillations in a 

 second; and that the cases referred to by Dr. Wollaston are, conse- 

 quently, owing to defective hearing, rather than to insensibility to very 

 acute sounds. 



Another acquired perception of the ear is that of forming a judg- 

 ment of the distance of bodies. This we do by attending to the loud- 

 ness of the sound ; for we instinctively believe, that a loud sound pro- 

 ceeds from a body near us, and a feeble sound from one more remote. 

 This is the cause of numerous acoustic errors, in spite of all reason and 

 experience. In the theatres, the deception is often admirably managed, 

 when the object is to give the idea of bodies approaching. The sound 

 that of martial music, for example is rendered faint and subdued ; 

 and, under such circumstances, appears to proceed from remote dis- 

 tance ; and, by adding gradually and skilfully to its intensity, we are 

 irresistibly led to the belief that the army is approaching; and the 

 illusion is completed by the appearance of the military band on the 

 stage, allowing its soul-inspiring strains to vibrate freely in the air. In 

 like manner, we are deceived by the ventriloquist. He is aware of the 

 law that guides us in our estimation of distance ; and, by skilfully 

 modifying the intensity of his voice, according as he wishes to make 



1 Philosophical Transactions for 1820, p. 306. 



2 Journal de Physiologic de Magendie, v. 367. 



