Sight and touch : an attempt to disprove the received (or Berkeleian) theory of vision / by Thomas K. Abbott.
- Thomas Kingsmill Abbott
- Date:
- 1864
Licence: Public Domain Mark
Credit: Sight and touch : an attempt to disprove the received (or Berkeleian) theory of vision / by Thomas K. Abbott. Source: Wellcome Collection.
Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.
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![[ ™6 ] CHAPTER VIIL OF BINOCULAR VISION. Although we have some perception of distance with one eye it is comparatively imperfect; and we must now proceed to consider the special phenomena of binocular vision. That it should be possible at least to see singly with both eyes, is a necessary consequence of the laws of sight, as they have now been stated. For since each retina presents to us an extended field, every part being at some distance, the two fields must admit of superposition, and from their position and angular magnitude (about 150° each) they must of ne- cessity overlie one another. It only remains then to ascer- tain what are the conditions of their superposition. These will be found to result from the laws of arrangement of each field separately. It is very commonly stated (after Reid, Brewster, and others) that an impression on any point of the retina determines vision in a direction perpendicular to the retina at that point, or, as it ought to be stated, in a line through the optical centre. It is generally added that single vision is the necessary consequence of seeing an object in two intersecting directions. But every object is seen in two intersecting directions; therefore double vision ought to be impossible. We must suppose then, in addition, that each eye gives an accurate perception of the distance as well as the direction. But in that case the slightest error would occasion double vision, whereas we are liable to considerable errors, which however never interfere with single vision. Indeed, it seems absurd to suppose that we construct the place of an](https://iiif.wellcomecollection.org/image/b21037930_0118.jp2/full/800%2C/0/default.jpg)
