you, whose education has been so general-who have gone from east to west, and from north to south, in quest of information-are yet ignorant of many visible wonders, not on your own estate, indeed, but within the compass of your own frame? You know much of the manners and customs of other countries, but of the economy of your own nature you have learned little. You are delighted with the paintings of a Wilkie, or the sculpture of a Flaxman; but the organ of sight, through which you become conscious of this pleasure, attracts but little of your attention. You are charmed with the productions of a Weber or a Rossini, and are a tolerable musician yourself you observe, with a curious eye, the structure of the instrument on which you play, but the organ of hearing, the receptacle of all sound, is not thought worthy of your curiosity. And yet the others are but the bungling efforts of a savage mechanist in the comparison. I shall not speak now of the interior portion of the human machinery, extraordinary as it is. I speak only of its most interesting part-the five external senses the gates by which all earthly knowledge-all good and all evil are transmitted to the mind.

It is my purpose, as I have already declared, in the course of a series of essays, which you can peruse at your leisure, to explain the mechanism and uses of those essential organs, stripping the description of all that technicality of phrase, which might deter you from pursuing the study in a more elaborate physiological work.

My account of each shall, as far as it lies in my power, combine conciseness with accuracy; while the importance of all shall be illustrated by a number of original tales, intended as some compensation for that didactic tone which, however unwillingly, I may sometimes be induced to assume.

As it is my wish to convey only such information as is founded on actual observation, I shall omit all mention of the numberless theories of sensation itself which have been broached at various times, and none of which have yet thrown much light upon the mystery. The mechanical parts of the organ are those only which I shall describe, adding a few words upon their known mode of operating, and on the peculiar advantages of each.

CHAPTER II.

The Mechanism of Sight.

A FEW words, my dear friend, in the first place, upon the senses in general, before we proceed to a particular examination of each.

The first object which the mind of man has to accomplish on coming into the world is the acquisition of knowledge, without which it is incapable of executing a rational action, or, as far as we know, forming a thought. For this purpose it is ordained that the organs used in obtaining it shall rapidly advance to a state of perfection, while the rest of the frame requires a much longer time to become ripe for use. A few days will render all the external senses capable of receiving impressions and conveying them to the mind, while the latter is only developed in all its excellence by a course of many years. The wisdom of this arrangement is self-evident.

Let us now see by what means this purpose of conveying knowledge to the mind has been accomplished.

A mass of inanimate material, composed of solids and fluids, constitutes that body in which your soul is imprisoned during your earthly existence, and to which

it communicates the appearance of that life which is, in reality, its own exclusive possession. The mode in which it exerts this influence on the body has always been, and most probably will always continue to be, a profound secret to the worldly inquirer.

Thus pent up, and closely united with a quantity of lifeless material, it became necessary, in order to prevent the soul from remaining in a state of temporary ignorance and inaction, to furnish it with certain windows in its prison, certain modes of communication with the world outside, which might enable it to know and to act. To accomplish this, the Creator has provided us with peculiar organs or adaptations of that matter which composes our frame, and which organs we have agreed to denominate the senses.

These senses, which constitute the noblest part of the frame, are five in number, and consist of sight, hearing, feeling, smell, and taste. These are the only external channels of information allotted to the mind of man during its time of probation, and by these only it is enabled to collect that external knowledge which furnishes the ground of its actions and conduct.

Concerning the relative importance of these five organs, philosophers have expressed different opinions; but we shall follow the order in which they are above enumerated.

Commencing, therefore, with the eye, the organ of sight, let us first consider its mechanical construction.

It was necessary the mind should be informed of the external appearance, the size, shape, distance, colour, &c., of the objects by which she is surrounded. Observe the manner in which this has been accomplished.

Possessing in herself the faculty of sight, it was needful, however, from her state of confinement in a mass of inactive matter, that some external organ or instrument should be afforded, for the purpose of exercising that faculty. I will now describe the instrument by which she sees.

You have first a nerve, or white fibre, of so peculiarly delicate a structure, that it is capable of conveying to the brain (supposed by many to be the centre of perception) all those impressions concerning the appearances of bodies which can be made on it from without. This nerve (called the optic) passes from the brain to the back part of the eye-ball, over the interior of which it is spread in a thin, fine coat, which is termed the retina of the eye. It is spread out in this manner for the purpose of being enabled to receive a more extensive picture upon its surface. Still, this picture would be very limited if the retina received the images of bodies directly upon itself, for in that case it could, at any distance, embrace no more than its own size of the surface of an object. This would in no respect fulfil all the purposes of the sense, nor fully satisfy the faculty of sight possessed by the mind itself.

In order, therefore, to make this small surface com