PHYSIOLOGICAL PARADOXES. 



made by a very similar picture in exactly the 

 same position. So we get the effect of changes 

 in one and the same continuous picture or 

 we should do so, if the instrument did not jump, 

 and if cracks in the films did not produce fre- 

 quent representations of lightning in weather 

 and scenes in which it is inopportune. 



So with sound and hearing. Each impres- 

 sion lasts for an appreciable time ; and if, 

 while it is still in force, another impression of 

 exactly the same kind is made if, that is to 

 say, the sound is a musical one, not too deep 

 in the bass 1 each impression keeps up the 

 effect produced by those which preceded it. 

 Thus an intermittent succession of separate 

 sounds affects our perceptions as one continu- 

 ous sound without a break. 



Here we have another instance of the un- 

 trustworthiness of the senses as instruments of 

 scientific research. They tell us, usually with 

 great efficiency, until they have become dulled 

 by what we call civilised life, the facts which 

 it is important for us as animals to know 

 correctly ; but they are unreliable informants 

 as to the causes, means, and processes to which 

 the facts owe their existence. 



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