Two essays: one upon single vision with two eyes; the other on dew / A letter to the Right Hon. Lloyd, Lord Kenyon [on the case of Dr. Stanger], and an account of a female of the white race of mankind, part of whose skin resembles that of a negro; with some observations on the causes of the differences in colour and form between the white and negro races of men. By the late William Charles Wells ... With a memoir of his life, written by himself.

  • Wells, William Charles, 1757-1817.
Date:
1818
Catalogue details

Licence: Public Domain Mark

Credit: Two essays: one upon single vision with two eyes; the other on dew / A letter to the Right Hon. Lloyd, Lord Kenyon [on the case of Dr. Stanger], and an account of a female of the white race of mankind, part of whose skin resembles that of a negro; with some observations on the causes of the differences in colour and form between the white and negro races of men. By the late William Charles Wells ... With a memoir of his life, written by himself. Source: Wellcome Collection.

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    both these axes to them, it must be evident, to such as are acquainted with the common rules of optics, that the pictures of those objects do not fall upon the centres of the retinas, but more internally ; and, therefore, that the centres and all the other points of those membranes, which by the present system are supposed to represent objects single, do in fact exhibit them double. Tt will be said here, perhaps, that the line* passing from each eye, which we turn to objects when we see them single, is not a production of the common axis of the cornea and globe, but some other, disposed in such a manner, that the pictures of those objects are received by the centres of the retinas. I answer; I readily grant the possibility of the thing, but I assert, at the same time, that we have no proof of it, * J am of opinion, that this line, or at least the line which we turn to objects when we see them most distinctly with one eye, is not the common axis of the globe and cornea, For I find, that, when I place the flame of a candle between either of my eyes, and a plane mirror, in such a manner that it may conceal its own image in the mirror from the sight of that eye, or rather that it may be a little below this image, but in the same vertical plane with it, the image of the flame, seen by reflection from the cornea, does not appear upon the middle point of this coat, but upon that point of it which is opposite to the centre of the pupil. Cg