NATURAL THEOLOGY. 27 



ted (and these laws are fixed,) could not be done 

 without the organ itself undergoing an alteration, 

 and receiving an adjustment, that might correspond 

 with the exigency of the case, that is to say, with 

 the different inclination to one another under 

 which the rays of light reached it. Rays issuing 

 from points placed at a small distance from tlie 

 eye, and which consequently must enter the eye 

 in a spreading or diverging order, cannot, by the 

 same optical instrument in the same state, be 

 brought to a point, i. e. be made to form an image, 

 in the same place with rays proceeding from ob- 

 jects situated at a much greater distance, and 

 which rays arrive at the eye in directions nearly 

 (and physically speaking,) parallel. It requires a 

 rounder Jens to do it. The point of concourse be- 

 hind the lens must fall critically upon the retina, 

 or the vision is confused ; yet, other things re- 

 maining the same, this point, by the immutable 

 properties of light, is carried further back when 

 the rays proceed from a near object than when 

 they are sent from one that is remote. A person 

 who was using an optical instrument would man- 

 age this matter by changing, as the occasion re- 

 quired, his lens or his telescope, or by adjusting 

 the distance of his glasses with his hand or his 

 screw : but how is this to be managed in the eye ? 

 What the alteration w^as, or in what part of the 

 eye it took place, or by what means it w as effect- 

 ed, (for if the known laws which govern the re- 

 fraction of light be maintained, some alteration in 



