that of nutation, as far as these are produced by the disturbing force of the sun.
A similar deviation, the author observes, is produced by the action of the moon; but a minute investigation of the deviation from that cause is foreign to the design of the present communication.
The design of the present communication is to explain a disagreement between the results of former experiments on this subject; since a very intelligent boy, thirteen years of age, couched by Mr. Cheselden in 1728, was unable, upon receiving his sight, to distinguish the outline of any object placed before him, and thought that everything before him touched his eye ; but the cases communicated to this Society by Mr. Ware in 1801 lead to a different conclusion.
The subjects of Mr. Home's experiments were not equally sensible of light previous to the operation of couching, and consequently were not similarly affected by objects presented to them after receiving their sight.
The first was a lad twelve years of age, with cataracts in both eyes, that appeared to have existed from the time of his birth, as it had been noticed from his earliest infancy that his eyes rolled about in an unusual manner, and were not directed to objects before him, nor were his hands ever stretched out to catch at anything; but it was not till the child was six months old that his mother examined his eyes with attention, and observed cataracts as distinct as when he was brought to Mr. Home.
Previous to the operation, this boy could distinguish light from darkness, and the light of the sun from that of a candle, saying, it was redder and more pleasant to look at; but lightning made a still stronger impression. He was accustomed to call all light red. He had some conception of size, and said the sun was the size of his hat, and that the flame of the candle was larger than his finger, but less than his am. He directed both his eyes at once to these objects; and when a candle was nearer than twelve inches he said it touche him, but at twenty-two inches it was invisible.
The operation of extracting the crystalline lens was first performed on the left eye ; but as the cataract was in this instance found to be fluid, and the inflammation which followed was considerable, the operation of couching was preferred to it for the right eye, and was performed after an interval of eight weeks.
After the first operation, the eye was so imperfect in its powers, the pupil so contracted, and the surface of the cornea so irregular, that he could not discern any object distinctly. but imagined that
