That the blind should be able to discourse with ac curacy on the general laws of optics, need not so greatly excite our surprise, when it is considered, that, except it be the mere perception of light and colours, these are all resolvable into the effects of im. pulse and attraction, in causing various deviations from the rectilineal course which luminous rays natu rally pursue. Analogy, therefore, will in most cases supply the blind with means of satisfying themselves of the truth of an optical theorem. Diderot, in his Lettres sur les aveugles, a l'usage de ceux qui voyent, mentions an extraordinary blind man whom he had seen at Puisaux en Gatissois, who was accustomed to express his ideas of visible objects, and of optical re lations, in this analogical manner. He defined a mir ror to be " a machine by which objects are placed in relief, out of themselves ;" and he called the eye, " an organ upon which the air produces the same effect, as a stick does upon the hand." This ana logical mode of expression, however, will be of little or no service where the simple notion of light or of colour is alone concerned, for the communication of which there is no avenue whatever but the eye ; so that, when a man who has been totally blind from his infancy, discourses concerning light and colours, thus simply considered, his language must be like that of a parrot, without appropriate ideas annexed.
Dr Blacklock, however, in his poetical produc tions, alludes to the various beauties of the visible world, and to the charms and delicacies of colour, with all the propriety, and with all the rapture and enthusiasm, that ever fired the breast of a poet who had the fullest enjoyment of his eye-sight. Nor was this done mechanically, or merely by rote ; for having himself put it as a question, " How shall we ac count for the same energy, the same transport of description, exhibited by those on whose minds visi ble objects were either never impressed, or have been entirely obliterated ?" he assures us that, " how ever unaccountable this fact may appear, it is no less certain than extraordinary." This paradox seems to be explained with great ingenuity, and in a very satisfactory manner, by Mr Alison in his Essays on Taste.
" That the blind," says he, " may receive the same delight from the ideas which they associate with colours that they do not see, is a fact which I think every one will be convinced of, who reads the poems of Dr Blacklock. No man who is not acquainted with the history of their ingenious author, could per ceive that he had the misfortune to lose, his sight in early infancy. That from conversation, and from the perusal of books of poetry, it was possible for him to learn the distinguishing colours of certain ob jects, and to apply them with sufficient propriety in his own verses, I do not deny ; but the circumstance of importance, at present, is this, that his poetry is full of the same sentiments, and expresses the same admiration with regard to the different visible quali ties of matter, with that of poets who had no such defect ; and that the same power is ascribed to them in producing the emotions of beauty, and with as great accuracy with regard to particular instances, as in the compositions of those who have had the sense of sight in its fullest perfection. If our perception
of the beauty of coldurs arose from some original fit ness in such qualities to produce this emotion, it is obvious, that the blind must be as incapable of per ceiving this beauty, as of perceiving the colours themselves ; but if the beauty of colours arises from the associations we connect with them, this fact, in the case of Dr Blacklock, admits of a very simple solution. From reading, and from conversation, he has acquired the same associations with the words that express such colours, as we have with the co lours themselves ; that the word zuhite, for instance, signifies a quality in objects, expressive of chearful ness and innocence,—the word purple, the quality of majesty,—the.word black, the qualities of gloom and melancholy, &c. In this case, it is obvious, that he may feel the same emotions from the use of these words, that we do from the colours which they ex press ; and that, from the permanence of these asso• ciations in a great variety of cases, he may apply the terms with sufficient propriety, either in sublime or beautiful descriptions. As this is in reality the case, it seems to be a very strong confirmation of the opi nion, that the beauty of such qualities arises from the associations we connect with them, and not from any original or independent beauty in the colours themselves." Essay ii. chap. 3. sect. 2.
From the instances we hwie now produced, it ap. pears sufficiently evident, that the blind are suscepti ble of a very high •degree of intellectual improve ment ; and are capable of attaining skill and dex terity in many mechanical employments. That a due degree of care and diligence should be bestowed upon their education and improvement, is strongly prompted by. every feeling of humanity and gene rosity ; and is, indeed, no more than they have a right to demand, from the justice and benevolence of their more fortunate fellow creatures. It is with pleasure we add, that their claims have not been slighted nor treated with neglect ; and that the pre sent age is highly distinguished by the attention that has been bestowed, upon the most eligible means of rendering these unfortunate persons useful to then selves and to society. In' London, in Edinburgh, in Paris, and in many other great cities and flourishing towns, asylums have been erected for the indigent blind ; where they are not only fed and clothed by charitable contribution ; but instructed in a variety of trades, such as weaving, spinning, rope-twisting, &c., which it is found they can exercise in great per fection ; and where also the cultivation of their mo ral and intellectual faculties is properly attended to.