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tary muscles of the eyeball, the body seen will appear to change its place, and it will, to our feeling, assume different positions, according to the muscle which is exercised. If we' " raise the pupil we shall see the body elevated, or if we depress the pupil, we shall see the body placed below us ; and all "this takes place when the eyelids are shut, and when no new "impression is conveyed to the retina. The state of the retina " is here associated with a consciousness of muscular exertion; " and it shows that vision, in its extended sense, is a compound "operation, the idea of position of an object having relation to "the activity of the muscles.

"We may also show, by varying this experiment, that an agitated state of the muscles, or a state of action where the "muscles are at variance or confused, affects the idea of the "image. If we look on the luminous body so as to make this impression on the retina, and then cover the face so as to ex"clude the light, keeping the eyelids open, and if we now "squint, or distort the eyes, the image which was vividly im"pressed upon the retina instantly disappears, as if it were wiped "out."-" If we move the eye by the voluntary muscles, while "the impression continues on the retina, we shall have the no"tion of place or relation raised in the mind; but if the motion "of the eyeball be produced by any other cause, by the invo"luntary muscles, or by pressure from without, we shall have "no corresponding change of sensation."

There is much truth in these very remarkable observations, as is shown, not only by Mr Bell's experiments, but by facts of daily occurrence; and it is scarcely possible to place in a stronger view the passive nature of the eye itself in leading the mind to ideas of visible qualities. The eye, in fact, is to the mind just what the telescope is to the eye itself. It receives, modifies, and transmits the luminous rays, but without being in any degree conscious of their properties, and of these the mind itself alone judges; and according to the steadiness with which the telescope is held, and the direction in which it is pointed, do our conceptions become more or less accurate, and more or less different; and the same law holds obviously in regard to the eye.

Indeed, the unsteadiness consequent upon want of exercise and simultaneous co-operation among the voluntary muscles is one of the greatest, if not actually the greatest obstacle that exists to accurate vision, immediately after sudden restoration

to sight; and it is one which, as we shall have occasion to notice, has been altogether neglected, in the many attempts to reconcile the phenomena with preconceived theories of vision. Another difference between the organs of sense and their functions and those of the brain, and which may enable us to distinguish between them, is the much greater amount of im provement of which the cerebral functions are susceptible from exercise and education; whereas, from the organs of sense acting chiefly in obedience to physical laws, they execute their functions (when their development is complete) with almost as much ease and accuracy from the very first, as saf ter the greatest possible amount of experience. If it be said that touch or that taste improves by exercise, it is granted ; but then it must be observed, that the change here is not solely in the amount of impression made by the external object, but almost entirely in the increased attention which the mind bestows in listening to it; and, consequently, even here, it is the cerebral organ, and not the external sense, that is chiefly modified. When a clock strikes in a room in which we sit, intent on another object, no sound is heard. The vi brations strike the ear as before, but the brain does not attend to the impression communicated, in consequence, by the auditory nerve. But suppose that we sit in expectation of hearing a very gentle tap at a particular hour, we hear it dis tinctly when nobody else in the room has heard it. This sensibility on our part cannot be said to arise from a greater and suddenly-acquired perfection of the organ of hearing in us, and is at once admitted to arise from the mind being active in a certain direction; and this is known to depend on the state of the brain. The sensibility of a nerve may, no doubt, be augmented by education; but the degree in which it may be increased, within the limits of health, is very trifling, when compared to the extent to which the action of the internal faculties, which take cognizance of its operations, is modified by exercise. The promptitude of action which the reflecting faculties acquire from exercise is well known; and

experience shows, that those of Form, Colour, Size, and Locality, which are most employed in the sense of vision, are no exceptions to the general rule, the facility and accuracy of all of them being susceptible of great increase from education; but always in exact relation to the original endowment. No education whatever could ever make Mr Mylne, for example, a judicious colourist. When, therefore, a blind person is restored to sight, even supposing that the eye itself instantly returns to a healthy state, it is quite to be expected that he will be a less perfect judge of colour, form, and distance at first than after six months' practice. But as the organs, when present and in health, always execute their functions in a greater or less degree, so, from the first moment that a distinct image is formed upon the retina, will such a person be able, to a certain extent, to distinguish a bright from a dark colour, or a large from a small object, or a square from a round one, although he may not be able to apply the, proper name to designate what he sees for the first time. For the same reasons, the facility and accuracy of his perceptions will be gradually increased as he proceeds to compare and to contrast a greater variety of objects of different qualities, and to collect materials for forming that mental standard of comparison which is absolutely necessary for correct judgment, and which every one acquires only by varied and extensive experience. But when, by way of explaining this increased accuracy of perception and of judgment, we are seriously told, that it arises solely from the illusions of vision being corrected by the sense of touch, and that without such aid we could have no idea of form, magnitude, or distance, we cannot but demur to the proposition. Touch, we have already seen, cannot alter the impression made by the luminous rays on the retina, and conveyed to the mind by the optic nerve; and, therefore, if touch, repeated till the end of time, cannot alter in any degree the light or the shade, the form or the size of the objects, as seen by the eye, it is self-evident, that no re

petition of touch could ever suffice to enable us to see distances different from what they at first appeared.

In looking at distant hills in very clear weather, objects actually remote seem then to be near at hand; and, if allow ance is not made by the reasoning faculties for modifying circumstances, our decision as to the fact will inevitably be wrong. But in this case it is the internal faculties that decide on the data supplied by the sense, and not the sense itself that is corrected.

Precisely the same principle holds good with Colour, Form, and Size, as in regard to distance. The newly-acquired sense is but an inlet and an outlet to the operations of internal mental faculties, which judge of these qualities. And as the organs of Colour, Form, and Size are, like those of Tune or Causality, susceptible of education, it follows, that exercise improves their powers. But, as these are also innate, and not artificial, it necessarily happens that, being possessed in a greater or less degree by all mankind, the moment clear and distinct vision is acquired, the qualities corresponding to them must be perceived more or less perfectly from the very first: And such, accordingly, is found invariably to be the case.»!

Having explained the functions of all the parts connected with vision, and with the appreciation of visible objects, we might now usefully proceed to consider the history of a very interesting case of restoration to sight in a lady aged forty six, who was blind from infancy, and an account of which, by Mr Wardrop of London, has been published in the Phi losophical Transactions for 1826, and which, moreover, has been the subject of much hypothetical speculation; but, our limits being exhausted, this must be deferred to another op portunity.

ARTICLE XVI. .

SUBSTANCE OF A LETTER TO DR A. COMBE, FROM THE SURGEON OF H. M. S. BLOSSOM.

OUR readers are aware that, about two years and a half ago, H.M. S. Blossom, Captain Beechey, left England for the Pacific, on her way to Behring's Straits, on a voyage of discovery, and to endeavour to fall in with Captain Franklin's party, proceeding in the opposite direction overland. That Captain Beechey was not successful in the latter object is now also generally known and regretted, particularly as it appears that at one time the distance between these enterprising travellers was very small; and that, had they been aware of each other's proximity, they could easily have met. Interesting as all information connected with the progress of such an expedition must be, we are happy to be able to lay before our readers the substance of a letter just received by Dr A. Combe, from his friend, the very intelligent and able surgeon of the Blossom, whose phrenological remarks so greatly add, in our eyes, to the value of the information communicated. The late arrival of this letter (our present Number being then almost printed off) precludes us from making any comments. The beginning is dated H. M. S. Blossom, 55 miles east of Chain Island, Pacific Ocean, 10th March, 1826, and the end 28th February, 1827.

"At Rio de Janeiro the negroes are so numerous as to be about six to every white, and from forty to fifty thousand are imported annually. They are of different tribes, and come as well from the Mozambique Channel as the western coast of Af rica. Their general resemblance consists in the dark colour of their skin, their black hair, flattened noses, small rounded heads, the considerable projection of the frontal eminences over the VOL. IV.-No XVI. 2 R