Many contrivances have also been de vised by the ingenious for supplying the want of sight, and for facilitating those analytical or mechanical operations, which would otherwise perplex the most vigorous mind and the most retentive memory. By means of these they have become eminent proficients in various departments of science. Indeed there are few sciences, in which, with 01' with out mechanical helps, the blind have not distinguished themselves. .
The case of Professor Saunderson at Cambridge is well known. His attainments and performances in the languages, and also as a learner and teacher in the ab stract mathematics, in philosophy, and in music, have been truly astonishing ; and the account of them appears to he almost incredible, if it were not amply attested and confirmed by many other instances of a similar kind, both in ancient and mo dern times.
Cicero mentions it as a fact scarcely credible, with respect to his master in philosophy, Diodotus, that " he exercised himself in it with greater assiduity after he became blind, and which he thought next to impossible to be performed with out sight ; that he professed geometry, and described his diagrams so accurate ly to his scholars, as to enable them to draw every line in its proper direction." Jerome relates a more remarkable in stance of Didymus in Alexandria, who, " though blind from bis infancy, and therefore ignorant of the letters, appear ed so great a miracle to the world, as not only to learn logic, but geometry also, to perfection, which seems (he adds) the most of any thing to require the help of sight." Professor Saunderson, who was de prived of his sight by the small pox, when he was only twelve months old, seems to have acquired most of his ideas by the sense of feeling ; and though he could not distinguish colours by that sense, which, after repeated trials, he said was pretending to impossibilities, yet be was able, with the greatest exact ness, to discriminate the minutest differ ence of rough and smooth in a surface, or the least defect of polish. In a set of Ro man medals, he could distinguish the genuine from the false, though they bad been counterfeited in such a manner as to deceive a connoisseur, who judged of them by the eye His sense of feeling was so acute, that he could perceive the least variation in the state of the air; and, it is said, that in a garden where observa tions were made on the sun, he took no tice of every cloud that interrupted the observation almost as justly as those who could see it. He could tell when any
thing was held near his face, or when he passed by a tree at no great distance, provided the air was calm, and there was little or no wind : this he did by the dif ferent pulse of air upon his face. He possessed a sensibility of hearing to such a degree, that he could distinguish even the fifth part of a note ; and, by the quick ness of this sense, he not only discri minated persons with whom he hail once conversed so long as to fix in his memo ry the sound of their voice, but he could judge of the size of a room into which he was introduced, and of his distance from the wall ; and if he had ever walk ed over a pavement in courts, piazzas, &c. which reflected a sound, and was afterwards conducted thither again, he could exactly tell in what part of the walk he was placed, merely by the note which it sounded.
Sculpture and painting are arts, which, one would imagine, are of very difficult and almost impracticable attainment to blind persons, and yet instances occur, which chew, that they are not excluded from the pleasing, creative, and exten sive regions of fancy.
De Piles mentions a blind sculptor, who thus took the likeness of the Duke de Bracciano in a dark cellar, and made a marble statue of King Charles I. with great justness and elegance.
However unaccountable it may appear to the abstract philosophers, yet nothing is more certain in fact, than that a blind man may, by the inspiration of the Muses, or rather by the efforts of a cultivated genius, exhibit in poetry the most natural images and animated descriptions even of visible objects, without deservedly in curring the charge of plagiarism. We need not recur to Homer and Milton for attestations to this fact: they had pro bably been long acquainted with the visi ble world before they had lost their sight, and their descriptions might be animated with all the rapture and enthu siasm which originally fired their bosoms, when the grand and delightful objects delineated by them were immediately beheld. We are furnished with instances, in which a similar energy and transport of description, at least in a very consider able degree, have been exhibited by those, on whose minds visible objects were never impressed, or have been en tirely obliterated.