ANIMALS. 29 



which we see most strongly marked with light 

 and shade, we readily know to be nearer than 

 those on which the colours are more faintly 

 spread, and that in some measure take a part of 

 their hue from the air between us and them. 

 Bright objects also are seen at a greater distance 

 than such as are obscure ; and most probably for 

 this reason, that being less similar in colour to 

 the air which interposes, their impressions are 

 less effaced by it, and they continue more dis- 

 tinctly visible. Thus a black and distant object 

 is not seen so far off as a bright and glittering 

 one ; and a fire by night is seen much farther off 

 than by day." 



The power of seeing objects at a distance is 

 very rarely equal in both eyes. When this in- 

 equality is in any degree, the person so circum- 

 stanced then makes use only of one eye, shutting 

 that which sees the least, and employing the 

 other with all its power. And hence proceeds 

 that awkward look which is known by the name 

 of strabism. 



There are many reasons to induce us to think 

 that such as are near-sighted see objects larger 

 than other persons ; and yet the contrary is most 

 certainly true, for they see them less. M. Buffon 

 informs us that he himself is short-sighted, and 

 that his left eye is stronger than his right. He 

 has very frequently experienced, upon looking at 

 any object, such as the letters of a book, that 

 they appear less to the weakest eye ; and that 

 when he places the book so as that the letters 

 .appear double, the images of the left eye, which 



