III. 



VISION. 1 



FEW truths can be more surprising when first we 

 become aware of them than the indirectness of the 

 communication of the mind with the external world 

 through the senses. Our sensations, like our move- 

 ments, are the results of action of most complex 

 machinery working without our having knowledge 

 of its structure, or even, it may be, of its existence. 

 We have no consciousness of the myriad changes 

 taking place within it before a momentary sensa- 

 tion of sight, or sound, or touch can occur. 



Not only so, but it is impossible to give any 

 reason why the peculiar actions of the various sen- 

 sory mechanisms are followed by the particular 

 sensation which they each induce. Thus, although 

 science discovers to us the existence of vibrations of 

 light and sound, we cannot say why the irritation of 



1 In greater part re-arranged from portions of two popular lectures. 



