VOL. XXXV.] PHILOSOPHICAL TRANSACTIONS. 235 



pumice-stones interspersed. Towards noon, they found the pumice somewhat 

 thinner: latitude 37° 35' s. and longitude 1° 4' w. 



Thursday the 25th, in the evening, the drifts were near as large as above, 

 but towards next morning they decreased much ; so that about noon they were 

 clear of the pumice-stones, several of which were as large as a man's head. 

 They sailed 317 miles since they first discovered them. They lay just in the 

 track for ships outward bound ; and all the ships that went out the same year, 

 and since, who go so far to the southward, have fallen in with them. In the 

 morning they tried the current, but found none: and no ground at 130 fathoms. 

 At noon, latitude 37° 54' s. longitude 0° 38' e. they judged Tristan d'Acunha 

 bore w. 3° 39' n. Distance 256 leagues, supposing it to lie in latitude 37° 5' s. 

 and longitude 1 5° 38' w. 



Observations made by a young Gentleman, who was born blind, or lost his Sight 

 so early, that he had no Remembrance of ever having seen, and tvas couched 

 between 13 and 14 Years of Age. By Mr. JVilliam Chesselden, F.R.S. 

 N*'402, p. 447. 



Though we say of the gentleman that he was blind, as we do of all people 

 who have ripe cataracts, yet they are never so blind from that cause, but that 

 they can discern day from night ; and for the most part in a strong light, dis- 

 tinguish black, white, and scarlet ; but they cannot perceive the shape of any 

 thing ; for the light by which these perceptions are made, being let in obliquely 

 through the aqueous humour, or the anterior surface of the crystalline, by 

 which the rays cannot be brought into a focus upon the retina, they can discern 

 in no other manner, than a sound eye can through a glass of broken jelly, where 

 a great variety of surfaces so differently refract the light, that the several distinct 

 pencils of rays cannot be collected by the eye into their proper foci ; therefore 

 the shape of an object in such a case, cannot be at all discerned, though the 

 colour may. And thus it was with this young gentleman, who, though he 

 knew these colours asunder in a good light, yet when he saw them after he was 

 couched, the faint ideas he had of them before, were not sufficient for him to 

 know them by afterwards ; and therefore he did not think them the same, 

 which he had before known by those names. Now scarlet he thought the most 

 beautiful of all colours, and of others the most gay were the most pleasing; 

 whereas the first time he saw black, it gave him great uneasiness, yet after a 

 little time he was reconciled to it ; but some months after, seeing by accident 

 a negro woman, he was struck with great horror at the sight. 



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