251 



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. 



An Account of two Children born with Cataracts in their Eyes, to show 

 that their Sight was obscured in very different Degrees ; with Ex- 

 periments to determine the proportional Knowledge of Objects ac- 

 quired by them immediately after the Cataracts were removed. By 

 Everard Home, Esq. F.R.S. Read January 15, 1807. [Phil. 

 Trans. 1807,^.83.] 



The design of the present communication is to explain a disagree- 

 ment between the results of former experiments on this subject; since 

 a very intelligent boy, thirteen years of age, couched by Mr. Che- 

 selden hi 1728, was unable, upon receiving his sight, to distinguish 

 the outline of any object placed before him, and thought that every- 

 thing 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 liis 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 arm. He directed both his eyes at once to these objects ; 

 and when a candle was nearer than twelve inches he said it touched 

 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 



