THE ARGUMENT APPLIED 2/ 



distance from the tablet upon which the picture is delineated 

 should be shortened or lengthened — this, I say, being the 

 case, ajid the difficulty to which the eye was to be adapted, 

 we £.nd its several parts capable of being occasionally chang- 

 ed, and a most artificial apparatus provided to produce that 

 chaijge. This is far beyond the common regulator of a 

 watch, which requires the touch of a foreign hand to set it ; 

 but it is not altogether unlike Harrison's contrivance for 

 making a watch regulate itself, by inserting within it a ma- 

 chinery which, by the artful use of the different expansion of 

 metals, preserves the equability of the motion under all the 

 various temperatures of heat and cold in which the instru- 

 ment may happen to be placed. The ingenuity of this last 

 contrivance has been justly praised. Shall, therefore, a struc- 

 ture which differs from it chiefly by surpassing it, be account- 

 ed no contrivance at all ; or, if it be a contrivance, that it is 

 without a contriver ? 



But this, though much, is not the whole : by different 

 species of animals, the faculty we are describing is possessed 

 in degrees suited to the diflerent range of vision which their 

 mode of life and of procuring their food requires. Birds, for 

 instance, in general, procure their food by means of their 

 beak ; and the distance between the eye and the point o\ 

 the beak being small, it becomes necessary that they should 

 have the power of seeing very near objects distinctly. On 

 the other hand, from being often elevated much above the 

 ground, living in the air, and moving through it with great 

 velocity, they require for their safety, as well as for assisting 

 them in descrying their prey, a power of seeing at a great 

 distance — a power of which, in birds of rapine, surprising 

 examples are given. The fact accordingly is, that two pe- 

 culiarities are found in the eyes of birds, both tending to fa- 

 nlitate the change upon which the adjustment of the eye to 

 different distances depends. The one is a bony, yet, in most 

 species, a flexible rim or hoop, surrounding the broadest part 

 of the eye, which confining the action of the muscles to that 



