APPLICATION OF THE ARGUMENT. 10 



justment required. The cornea, or outermost coat of the 

 eye, is rendered more round and prominent ; the crystalline 

 Jens underneath is pushed forwards ; and the axis of 

 vision, as the depth of the eye is called, is elongated. 

 These changes in the eye vary its power over the rays of 

 light in such a manner and degree as to produce exactly 

 the effect which is wanted, viz. the formation of an image 

 upon the retina, whether the rays come to the eye in a 

 state of divergency, which is the case when the object is 

 near to the eye, or come parallel to one another, which is 

 the case when the object is placed at a distance. Can any 

 thing be more decisive of contrivance than this is ? The 

 most secret laws of optics must have been known to the 

 author of a structure endowed with such a capacity of 

 change. It is, as though an optician, when he had a 

 nearer object to view, should recti/}/ his instruaient by 

 putting in another glass, at the same time drawing out 

 also his tube to a different leiiojth. 



Observe a new born child first lifting up its eyelids. 

 What does the opening of the curtain discover] Tlie an- 

 terior part of two pellucid globes, which, when they come 

 to be examined, are found to be constructed upon strict op- 

 tical principles ; the selfsame principles upon which we 

 ourselves construct optical instruments. We find them 

 perfect for the purpose of forming an image by refraction : 

 composed of parts executing different offices : one part 

 having fuliilled its office upon the pencil of light, deliver- 

 ing it over to the action of another part ; that to a third, 

 and so onward ; the progressive action depending for its 

 success upon the nicest and minutest adjustment of the 

 parts concerned ; yet, these parts, so in fact adjusted as to 

 produce, not by a simple action or effect, but by a combi- 

 nation of actions and effects, the result which is ultimate- 

 ly wanted. And forasmuch as this organ would have to 

 operate under different circumstances, with strong degrees 

 of light, and with weak degrees, upon near objects, and 

 upon remote ones, and these differences demanded, accord- 

 ing to the laws by which the transmission of light is regu- 

 lated, a corresponding diversity of structure ; that the 

 aperture, for example, through which the light passes, 

 should be larger or less ; the lenses rounder or flatter, or 

 that their distance from the tablet, upon which the picture 

 is delineated, should be shortened or lengthened : this, I say, 

 being the case and the difficulty, to which the eye was to 

 he adapted, we find its several parts capable of being oc- 



