These are defects in vision which, however distressing, and in themselves, that is, as far as the eye itself is concerned, incurable, may be borne with resignation or remedied by scientific agency. But human beings are often called to still greater trials--to total loss of sight--in other words, to perfect blindness. This calamity results from many causes; for example, the cornea may become so opaque as to be incapable of transmitting rays of light into the interior chamber of the eye; or the crystalline lens, also, may become opaque (_cataract_;) disease of the iris, attended by closure of the pupil, will produce blindness, as will also paralysis, or loss of energy, in the retina or optic nerve, (_Amaurosis_ or _Gutta serena_.) Accidents may destroy the powers of the eye, and a flash of lightning may produce _Amaurosis_; there are, besides, other causes of loss of vision, into which it is not requisite that we should here enter. In certain cases, blindness is congenital, that is, the individual was born blind, but in most instances blindness comes on at various periods of life, subsequent to the age of infancy. Great as is the calamity of blindness, it is not, we think, so heavy an affliction as total deafness. Privation of sight does, indeed, close one avenue leading from matter to mind, but, perhaps, not the most important avenue; we may assume this fact--had Euclid been blind he could still have written on mathematics. Homer and Milton were both blind, and had Shakspere been blind, the extraordinary creations of his genius would have been what they are--the visions of mighty intellect. An admirably written passage in one of our periodical publications may be here introduced; it proves that blindness closes but a small inlet to the immortal soul: "We are all familiar with many well-authenticated instances of blind persons having attained to a distinguished position both in literature and science. The celebrated Saunderson, who filled the chair of Newton in the University of Cambridge, lost his very eye-balls by the small-pox, when only twelve years old; yet before he was thirty, we find him giving public lectures on _optics_, explaining clearly the theory of vision, and discoursing admirably on the phenomena of light and colours--thus furnishing by his own extensive acquirements a convincing proof of the extraordinary powers of language, and of the full efficiency of the ear, as an avenue to the mind. The darkness of the blind, such as instances like this sufficiently show, is but a physical darkness; they still possess a ready channel, through which the brightest beams of intellectual light may be freely poured: but the darkness of the deaf mute is a mental and moral darkness; and though he can gaze abroad upon creation, yet it is little more than mere animal gratification that he feels; he looks not through nature up to nature's God, nor does he participate in that high communion which, through