SENSATION IS GENERAL. 57 



glowing heavens and the green earth ; and as there are 

 few things more calculated to afford us pleasure than 

 our sight, so there are few things that we suffer more 

 by neglecting or using improperly. But from the 

 proverbial happiness of the blind, and their fondness 

 for music, it is extremely probable that all nature be- 

 comes to them as if it were one vast musical instru- 

 ment. Nor is there any 'doubt that sounds convey 

 to them the notions of form and distance, in a man- 

 ner as intelligible to the mind as that which those 

 who have the advantage of sight receive through 

 that medium. Strange as it may seem, too, the 

 touch of blind people may be so educated as not 

 only to distinguish one colour from another, but to 

 distinguish different depths of shade in the same 

 colour. Human perception is a very curious matter ; 

 and the different senses so co-operate with each other, 

 and they are all so linked with nature, that it is dif- 

 ficult to say within what limits we could confine that 

 which any one of them might reveal to us, though 

 we were deprived of all the others. It is probable, 

 indeed, that sensation itself is a much more general 

 principle than any of those modifications of it which 

 reside in the particular organs ; and that it is really 

 those powers of the body by which we move matter 

 from place to place, and change its appearance, that 

 are the original sources of all our knowledge of the 

 mechanical properties of matter. 



In common language, indeed, we are accustomed 

 to say that we measure visible distance by the eye, 

 and the distance of sound by the ear ; but it is ex- 

 ceedingly probable, nay, almost certain, that the 

 origin of our knowledge in those cases is in our 

 muscles, our organs of motion ; and that, even in the 

 case of the eye itself, which is the organ that we 

 can best understand, and most nearly imitated by 

 artificial contrivances, it is the muscular action by 

 which it is adapted to different distances, and not the 

 degree of light, or the magnitude, or intensity of the 



