A probationary essay on the anatomy and physiology of the eye : submitted, ... to the examination of the Royal College of Surgeons of Edinburgh, ... / by John Argyll Robertson ... February, 1822.

  • Robertson, John Argyll, 1798 or 1799?-1855.
Date:
1822
Catalogue details

Licence: Public Domain Mark

Credit: A probationary essay on the anatomy and physiology of the eye : submitted, ... to the examination of the Royal College of Surgeons of Edinburgh, ... / by John Argyll Robertson ... February, 1822. Source: Wellcome Collection.

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    objects touched his eye; he could not conceive the house larger than the room r thus proving that the minima vi- sibilia are in all cases the same in number. Distances are known, 1. By varying the convexity of the cornea. 2. By the sensation of the motion necessary to direct both eyes to the same object. 3. The visible magnitude of known objects suggest to us their distance. But this is not the case with unknown objects, as the Stars. Nor do objects seen through power¬ ful microscopes appear nearer. 4. The faintness of colours transmitted through the atmosphere gives us an idea of distance, remote objects being more indistinct than near. 5. Intervening objects, whose distances are already known, suggest to us the idea of the distance of those more remote. But we are still liable to mistakes, for a distant plane appears to us to rise at an angle of 4®. We judge much more correctly of distance when objects are on the same level with us. Thus the distance of the upper part of a house appears to us less than that of the under which is seen by intervening objects. The dis¬ tance joined to the visible magnitude is the rule by which we judge of the real size of bodies. Faintness of colour seems to give us an idea of magnitude, by previously suggesting that of great di¬ stance. Thus a gentleman on a journey being attacked with incipient amaurosis, the stones, as he turned blind¬ er, appeared to him to increase in size; which could de¬ pend on the faintness of colour only.