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Rh consigns them to darkness, and often to solitude, would seem favourable to contemplative habits, and to the pursuits of abstract science and pure speculation. Undisturbed by external objects, the mind necessarily turns within, and concentrates its ideas on any point of investigation with greater intensity and perseverance. It is no uncommon thing, therefore, to find persons setting apart the silent hours of the evening for the purpose of composition or other purely intellectual exercise. Malebranche, when he wished to think intensely, used to close his shutters in the daytime, excluding every ray of light; and hence Democritus is said to have put out his eyes in order that he might philosophize the better — a story, the veracity of which Cicero, who relates it, is prudent enough not to vouch for.

Blindness must also be exceedingly favourable to the discipline of the memory. Whoever has had the misfortune, from any derangement of the organ, to be compelled to derive his knowledge of books less from the eye than the ear, will feel the truth of this. The difficulty of recalling what has once escaped, of reverting to, or dwelling on the passages read aloud by another, compels the hearer to give undivided attention to the subject, and to impress it more forcibly on his own mind by subsequent and methodical reflection. Instances of the cultivation of this faculty to an extraordinary extent have been witnessed among the blind, and it has been most advantageously applied to the pursuit of abstract science, especially mathematics.