520 THE SENSORIAL FUNCTIONS. 



to it. This association is, in man at least, not 

 original, but acquired. The objects of sight and 

 touch, as Bishop Berkeley has justly observed, 

 constitute two worlds, which although they have 

 a very important correspondence and connexion, 

 yet bear no sort of resemblance to one another. 

 The tangible world has three dimensions,^ 

 namely, length, breadth, and thickness ; the 

 visible world only two, namely, length and 

 breadth. The objects of sight constitute a kind 

 of language, which Nature addresses to our eyes, 

 and by which she conveys information most im- 

 portant to our welfare. As, in any language, the 

 words or sounds bear no resemblance to the 

 things they denote, so in this particular language 

 tlie visible objects bear no sort of resemblance to 

 the tangible objects they represent. 



The theory of Berkeley received complete 

 confirmation by the circumstances attending the 

 well-known case, described by Cheselden, of a 

 boy, who, from being blind from birth, suddenly 

 acquired, at the age of twelve, the power of see- 

 ing, by the removal of a cataract. He at first 

 imagined that all the objects he saw touched his 

 eyes, as what he felt did his skin ; and he was 

 unable either to estimate distances by the sight 

 alone, or even to distinguish one object from 

 another, until he had compared the visual with 

 what has been called the tactual impression. 

 This theory also affords a satisfactory solution 



