ANIMAL MECHANISM. 



121 



ral, in land animals, on the absolute magnitude of the 

 semi-diameter of the external surface of the cornea. The 

 larger this is, the greater is the number of rays that reach 

 from distant objects through the cornea to the interior of 

 the eye; and the more easily are such objects rendered 

 visible. But this applies to land animals only. The 

 cornea has no such value in aquatic animals, in arresting 

 the rays of light, as that the limits of vision can be de- 

 termined by it. If we arrange land animals and birds ac- 

 cording to the measure of their power of seeing in the 

 distance, we obtain the following series : 



32 

 28 

 27 

 27 

 25 

 25 

 23 

 22 

 22 

 20 

 19 

 17 

 15 

 11 

 20 

 19 

 19 

 18 

 14 

 12 

 4 

 9 



In this table the larger animals, in general, are those 

 that see farthest. But there are exceptions to this rule. 

 It is worthy of remark, that birds which, in the distinct 

 vision of a point, precede quadrupeds of similar magni- 

 tude, are inferior to them in distant vision, and that man 

 agrees with birds in this respect. Thus the great owl, 

 (Striee, Bubo,) ostrich, and golden eagle, excel in the 



VOL. I. NO. T. 11 



