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CHAPTER III.

APPLICATION OF THE ARGUMENT.

THIS is atheism: for every indication of contrivance, every manifestation of defign, which exifted in the watch, exifts in the works of nature; with the difference, on the fide of nature, of being greater and more, and that in a degree which exceeds all computation. I mean that the contrivances of nature surpass the contrivances of art, in the complexity, fubtlety, and curiofity of the mechanifin; and still more, if poffible, do they go beyond them in number and variety: yet, in a multitude of cafes, are not less evidently mechanical, not lefs evidently contrivances, not lefs evidently accommodated to their end, or fuited to their office, than are the most perfect productions of human ingenuity.

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I know no better method of introducing fo large a fubject, than that of comparing a single thing with a single thing; an eye, for example, with a telescope. As far as the examination of the inftrument goes, there is precisely

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the fame proof that the eye was made for vifion, as there is that the telescope was made for affifting it. They are made upon the fame principles; both being adjusted to the laws by which the tranfmiffion and refraction of rays of light are regulated. I fpeak not of the origin of the laws themselves; but, fuch laws being fixed, the conftruction, in both cafes, is adapted to them. For inftance; these laws require, in order to produce the fame effect, that the rays of light, in paffing from water into the eye, should be refracted by a more convex surface, than when it paffes out of air into the eye. Accordingly we find, that the eye of a fish, in that part of it called the cryftalline lenfe, is much rounder than the eye of terreftrial animals. What plainer manifestation of defign can there be than this difference? What could a mathematical inftrument-maker have done more, to fhew his knowledge of his principle, his application of that knowledge, his fuiting of his means to his end; I will not fay to difplay the compass or excellency of his fkill and art, for in thefe all comparison is indecorous, but to testify counfel, choice, confideration, purpose? -To fome it may appear a difference fufficient to destroy all fimilitude between the eye and

the telescope, that the one is a perceiving organ, the other an unperceiving inftrument

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The fact is, that they are both instruments. And, as to the mechanism, at least as to mechanism being employed, and even as to the kind of it, this circumftance varies not the analogy at all. For obferve, what the conftitution of the eye is. It is neceffary, in order to produce diftin&t vision, that an image or picture of the object be formed at the bottom of the eye. Whence this neceffity arifes, or how the picture is connected with the fenfation, or contributes to it, it may be difficult, nay we will confefs, if you please, impoffible for us to fearch out. But the prefent question is not concerned in the enquiry. It may be true, that, in this, and in other instances, we trace mechanical contrivance a certain way; and that then we come to fomething which is not mechanical, or which is infcrutable. But this affects not the certainty of our investigation, as far as we have gone. The difference between an animal and an automatic ftatue, confifts in this, that, in the animal, we trace the mechanism to a certain point, and then we are stopped; either the mechanism becoming too fubtile for our difcernment, or fomething

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elfe befide the known laws of mechanifm taking place; whereas, in the automaton, for the comparatively few motions of which it is capable, we trace the mechanifm throughout. But, up to the limit, the reasoning is as clear and certain in the one cafe as the other. In the example before us, it is a matter of certainty, because it is a matter which experience and obfervation demonftrate, that the formation of an image at the bottom of the eye is neceffary to perfect vifion. The image itself can be fhewn. Whatever affects the distinctnefs of the image, affects the diftinctness of the vifion. The formation then of fuch an image being neceffary (no matter how), to the fenfe of fight, and to the exercife of that sense, the apparatus by which it is formed is constructed and put together, not only with infinitely more art, but upon the felf-fame principles of art, as in the telescope or the camera obfcura, The perception arifing from the image may be laid out of the queftion: for the production of the image, thefe are inftruments of the fame kind. The end is the fame; the means are the fame. The purpose in both is alike; the contrivance for accomplishing that purpose is in both alike. The lenfes of the telescope,

and the humours of the eye bear a complete refemblance to one another, in their figure, their pofition, and in their power over the rays of light, viz. in bringing each pencil to a point at the right distance from the lenfe; namely, in the eye, at the exact place where the membrane is spread to receive it. How is it poffible, under circumftances of fuch clofe affinity," and under the operation of equal evidence, to exclude contrivance from the one; yet to acknowledge the proof of contrivance having been employed, as the plaineft and clearest of all propofitions, in the other?

The refemblance between the two cafes is ftill more accurate, and obtains in more points than we have yet reprefented, or than we are, on the first view of the fubject, aware of. In dioptric telescopes there is an imperfection of this nature. Pencils of light, in paffing through glass lenses, are separated into different colours, thereby tingeing the object, especially the edges of it, as if it were viewed through a prism. To correct this inconvenience had been long a defideratum in the art. At last it came into the mind of a fagacious optician, to enquire how this matter was managed in the eye; in which there was exactly the fame difficulty to contend

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