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Note: This text has been automatically extracted via Optical Character Recognition (OCR) software. The text has not been manually corrected and should not be relied on to be an accurate representation of the item.
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action depending for its success upon the nicest and minutest adjustment of the parts concerned yet these parts so adjusted as to produce , not by a
simple action or effect , but by a combination of actions and effects * the result of which is ultimately wanted . And since this organ has to operate under different circumstances with
different decrees of light , and upon objects differently situated with regard to distance , these differences demanded , according to the laws by which the transmission of light is regulated , a corresponding diversity of structure : thus the aperture through
which the light passes , should be larger or less ; the lens should be more or less convex , or , which is the same thing , its distance from the tablet upon which the picture is delineated , should be shortened or lengthened ; this being the case , and the difficulty to Avhich the eye -was to
fee adapted , we find its several parts capable of being occasionally changed , and a most artificial apparatus provided to produce the change . " This , " says our author , " is far beyond the common regulator of a watch , which requires the touch of a foreign haud to set it , but it is not altogether unlike Harrison's contrivance for
making a chronometer regulate itself , by inserting within it a machinery 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 instrument nray happen to be -placed . The ingenuity of this
contrivance has been highly and justly praised . Shall a structure , therefore , which differs from it chiefly by surpassing it , be accounted no contrivance at all ? Or , if it be a contrivance ^ that it is without a contriver !" Moreover , the faculty of vision is possessed by different species of
animals , in degrees exactly suited to their mode of life . Birds procure their food by means of their beak , and the distance between the eye aind the point of 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 wej& as for towsisthng them in descrying their prey ,
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a power of seeing at a distance , power of which , in many birds , butprising examples are given . A ccordm gty » peculiarities are found in the eyes of birds , tending to facilitate
the change upon which the adjustment of the eye to different distances depends , and by which the eyes of birds can pass from one extreme to another of the scale of adjustment with more ease and readiness than the eves of other animals .
the eyes of fishes are also adapted to their state and element : the figure of the crystalline compensating , as we have seen , by its roundness , the density of the medium through which it passes . The iris in the eyes of fishes does not admit of contraction , the
reason of which probably is , that the diminished light in water is never too strong for the retina . In the eel , which has to work its head through sand and gravel , there is placed
before the eye , and at some distance from it , a transparent , horny , convex case , which without obstructing the sight , defends the organ . What could be more useful to such an animal ?
Hence in comparing together the eyes of different kinds of animals , we are struck with their resemblance and distinctions ; one general plan is laid down , and that plan varied with the varying exigences to which it is to be applied .
We may refer to other subjects connected with the eye : to keep that organ moist and clean , qualities which are necessary to its brightness and
even its use , a wash is constantly supplied by a secretion for the purpose ; and the superfluous brine is conveyed to the nose through a perforation in the bone as large as a goose-quill . As soon as the fluid has entered the nose , it spreads itself upon the inside of the nostril , and is evaporated by a current of warm air , it
which is continually passing over . " Can a pipe or outlet , for carrying off the waste liquor from a dyehouse or a distillery be more mechanical than this is ? It is easily imag ined that the eye must want moisture , but could the wants of the eye generate the gland which produces the tear ; or bore the hole through a bone by which it is discharged ?" Another contrivance is the ««**" fating membrane , found in t j * e L of birds and many quadruped * , w
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236 Natural Theology . No . IV . —The Eve .
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Citation
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Monthly Repository (1806-1838) and Unitarian Chronicle (1832-1833), April 2, 1815, page 236, in the Nineteenth-Century Serials Edition (2008; 2018) ncse.ac.uk/periodicals/mruc/issues/vm2-ncseproduct1759/page/36/
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