It is not very long ago since the prejudice against the capacity of the blind was so great, that a de scendant of the celebrated Lord Verulam, Mr Nicho las Bacon, who had the misfortune to lose his eye sight at nine years of age, and afterwards assiduously addicted himself to study, found great difficulty in procuring admission into the learned seminaries of Brabant, where he resided. This prejudice, how ever, he so completely overcame, that he was after wards created doctor of laws in the city of Brussels, with high approbation ; and having commenced plead ing counsellor, or advocate in the council of Brabant, lie had the pleasure of terminating almost every suit in which he was engaged, to the satisfaction of his clients. It may, nevertheless, be doubted, whether the profession of a barrister affords a sufficiently pro mising opening for the abilities of a blind man, to induce him to devote himself to such a pursuit.
We read also of a celebrated blind sculptor in the Lours de Feint of De Piles, who took the likeness of the Duke de Bracciano in a dark cellar, by means of moulding his face in wax ; and who made a mar ble statue of King Charles I., with great, elegance and justness: yet we would not from all this infer, that the blind arc well qualified to excel in sculpture. A sufficient variety of liberal pursuits, however, will still remain within their reach, in the various depart ments of natural philosophy, mathematics, chemistry, theology, and the belles lettres ; in all of which we have seen that they are well qualified to excel : and in the fine art of music, their eminence has been un rivalled.
A variety of expedients have been devised for fa cilitating the studies of the blind, and rendering that readily intelligible to the touch, which, in those who see, is addressed only to the eye-sight. It is well known, that the celebrated Saunderson had contrived for himself a machine, by which he greatly facili tated his arithmetical calculations, as well as his geo metrical studies. Of this kind of palpable arith metic, lie has himself given an account ; and it is much more minutely described in Diderot's Letters on the Blind, already mentioned. It consisted of a square board of a convenient size, divided by paral lel lines into a considerable number of smaller squares. Each of these.smaller squares, or separate depart ments, was pierced with nine holes, standing in three parallel rows ; and by. fixing a pin in one or other of these nine holes, the nine digits were denoted; ac cording to the position of the pin. In order to faci litate his. calculation, Saunderson made use of two sizes of pins, a larger and a smaller. The pins with large heads were always placed in the centre boles of the squares ; and when they stood alone, without any small pins, they denoted the cypher. The num ber 1 was denoted by a pin with a small head, placed in the centre of a square ; the number 2, by a large pin in the centre, and a small one at the side, in the hole which was first in order ; the number 3, by a pin in the centre, and a small one in the hole at. the side ; and so on in order, to the number
9. By this means, it is evident that any sum could ` be expressed, in a number of squares corresponding to the number of its figures ; and thus, all the arith metical operations performed. Saunderson, it is said, possessed wonderful facility in the use of this ma chine ; and was accustomed also, by means of it, to form diagrams for his geometrical demonstrations ; the pins serving the purpose of making the angles of the figures, either alone, or with silk threads stretched between them.
An arithmetical machine was also contrived by Mr Grenville, who had lost his eye-sight, consisting of a square board full of holes, and ten sets of pegs of different forms, corresponding to the nine digits and cypher. But by far the most simple and com modious of these machines, seems to be that invented by Dr Henry Moyes for his own use ; of which he has himself inserted an account in the Encycl. Brit. 3d. edit. He informs us, that when he began to study the principles of arithmetic, he soon found that a person deprived of sight could scarcely pro. ceed in that useful science, without the aid of pal pable symbols representing the ten numerical charac ters ; and being then unacquainted with Saunderson's method, he embraced the obvious, though, as he afterwards found, imperfect expedient, of cutting into the form of the numerical characters, thin pieces of wood or metal ; which being arranged on the surface of a board by means of a lamina of wax, readily represented. any given number. It soon, however, occurred to him, that his notation, consist ing of ten species of symbols or characters, was much more complicated than was absolutely necessai y ; and that any given number might be distinctly expressed by three species of pegs alone, viz. two with heads. of the form of a right-angled triangle, and distin guished from each other by having a notch cut in the oblique side or hypothenuse of one of them, their other two sides being, one of them a continuation of the peg, and the other at right angles to it ; and. the third peg having a head of the form of a square. These pegs were to be stuck into a board of about a foot square, and divided into 576 little squares, by lines which were cut a little into the wood, so as to form a superficial groove. At each angle or inter section of the grooves, a hole was made for the in sertion of the pegs. Sixty or seventy of each kind of pegs were necessary, which were placed in a case consisting of three boxes or cells,' one for each set.