BLINDNESS

, a privation of the sense of sight. The ordinary causes of blindness are, some external violence, vicious conformation, growth of a cataract, gutta serena, small-pox, &c; or a decay of the optic nerve; an instance of which we have in the Academy of Sciences, where, upon opening the eye of a person long blind, it was found that the optic nerve was extremely shrunk and decayed, and without any medulla in it. The more extraordinary causes of blindness are malignant stenches, poisonous juices dropped into the eye, baneful vermin, long confinement in the dark, or the like.

We find various recompenses for blindness, or substitutes for the use of eyes, in the wonderful sagacity of many blind persons, related by Zahnius in his Oculus Artificialis, and others. In some, the defect has been supplied by a most excellent gift of remembering what they had seen before; others by a delicate nose or the sense of smelling; others by a very nice ear; and others again by an exquisite touch, or sense of feeling, which they have had in such perfection, that as it has been said of some, they learned to hear with their eyes, it may be said of these that they taught themselves to see with their hands.

Some have been able to perform all sorts of curious works in the nicest and most dexterous manner. Aldrovandus speaks of a sculptor, who had become blind at 20 years of age, and yet 10 years afterwards he made a perfect marble statue of Cosmo II de Medicis, and another of clay like pope Urban VIII. Bartholin speaks of a blind sculptor in Denmark, who, by mere touch, distinguished perfectly well all sorts of wood, and even colours; and father Grimaldi relates an instance of the same kind; besides the blind organist, lately living in Paris, who it was said did the same thing. What seems more extraordinary still, we are told, by authors of good report, of a blind guide, who used to conduct the merchants through the sands and desarts of Arabia: and a not less marvellous instance is now existing in this country, in one John Metcalf near Manchester, who became quite blind at a very early age; and yet passed many years of his life as a waggoner, and occasionally, as a guide in different roads during the night, or when the paths were covered with snow; and, what is stranger still, his present occupation is that of surveyor and projector of highways in difsicult and mountainous parts, particularly about Buxton, and the Peak in Derbyshire.

There are also many instances of blind men who have been highly distinguished for their mental and literary talents, not to speak of the poets Homer, Milton, Ossian, &c; of which we have a remarkable instance in the late Dr. Sanderson, professor of mathematics in the university of Cambridge, and in the present Dr. Henry Moyes, public lecturer in philosophy, who both of them lost their sight by the small pox at an age before they had any recollection; these men were well skilled in all branches of the mathematics, philosophy, and optics, &c, which they taught with the greatest reputation; besides the monument of fame which the former has left behind him in his mathematical and philosophical works.

The effects of a sudden recovery of sight in such as have been born blind, are also very remarkable: devoid of the experience of distance and figure arising from sight, they are liable to the greatest mistakes in this respect, in so much it has been said that they could not distinguish by the mere sight which was a cube and which a globe, without first touching them. Mr. Boyle mentions a gentleman of this sort, who having been restored to sight at eighteen years of age, was near going distracted with the joy: see Boyle's works abridg. vol. 1. pa. 4. See also a remarkable case of this kind in the Tatler, N° 55, vol. 1. And the gentleman couched by Mr. Cheselden had no ideas of colour, shape, or distance: though he knew the colours asunder in a good light during his blind state; yet when he saw them after he had been couched, the faint ideas he had of them before, were not sufficient for him to know them by afterwards: as to distance, his ideas were so deficient, that he thought all the objects he saw touched his eyes, as what he felt did his skin; and it was a considerable time before he could remember which was the dog and which the cat, though often informed, without feeling them.