uated, than when they are in the meridian. In misty weather they appear unusually enlarged, when they are horizontal. And this is sometimes noticed to be the case, when the atmosphere is clear immediately around us; and may be owing to an accumulation of vapours and exhalations in some other place, through which the rays pass.

§. 53. Of the knowledge of the figure of bodies by the sight.

A solid body presents to the eye nothing but a certain disposition of colours and light. We may imagine ourselves to see the prominencies or cavities in such bodies, when in truth we see only the light or the shade, occasioned by them. This light and shade, however, we learn by experience to consider as the sign of a certain, solid figure.

A proof of the truth of this statement is, that a painter by carefully imitating the distribution of light and shade, which he sees in objects, will make his work very naturally and exactly represent, not only the general outline of a body, but its prominencies, depressions, and other irregularities. And yet his delineation, which by the distribution of light and shade gives such various representations, is on a smooth and plain surface.

It was a problem submitted by Mr. Molyneux to Mr. Locke, whether a blind man, who has learnt the difference between a cube and a sphere by the touch, can, on being suddenly restored to sight, distinguish between them, and tell, which is the sphere and which is the cube, by the aid of what may be called his new sense merely? And the answer of Mr. Locke was, that he cannot. The blind man knows what impressions the cube and sphere make on the organ of touch and by that sense is able to distinguish between them, but, as he is ignorant what impression they will make on the organ of sight, he is not able by the latter sense alone to tell, which is the round body, and which is the cubic.

It was remarked, that solid bodies present to the eye nothing but a certain disposition of light and colours.

It seems to follow from this, that the first idea, which will be conveyed to the mind on seeing a globe, will be that of a circle, variously shadowed with different degrees of light. This imperfect idea is corrected in this way. Combining the suggestions of the sense of touch with those of sight, we learn by greater experience what kind of appearance solid, convex bodies will make to us. That appearance becomes to the mind the sign of the presence of a globe; so that we have an idea of a round body by a very rapid mental correction, whereas the idea first conveyed to the mind is truly that of a plane, circular surface, on which there is a variety in the dispositions of light and shade. It is an evidence of the correctness of this statement, that in paintings plane surfaces, variously shaded, represent convex bodies, and with great truth and exact

ness.

It appears then, that distance, extension, magnitude and figure, are originally perceived, not by sight, but by touch. We do not judge of them by sight, until we have learnt by our experience, that certain visible appearances always accompany and signify certain distances, extensions, magnitudes, and figures. This knowledge we acquire at a very early period in life, so much so, that we lose in a great measure the memory both of its commencement and progress.

And yet many people can recollect the time, when they considered the sky to be a transparent and solid concave. resting on the tops of distant mountains. How different is this idea, which we receive from the sight, from what we find in our subsequent experience to be the fact!

§. 54. The senses reciprocally assist each other.

The errours and deficiences of one sense are made up and corrected by the friendly presence and suggestions of another. And when any of the senses entirely fail, the others are proportionably quickened and improved.

A multitude of instances go to show to what extent this correction and this aid take place.

We will suppose, as an illustration, that, at an early

period of life, a person loses his sight. An effect on the sense of hearing and of touch is immediately perceived; they are greatly improved.

The blind man cannot see his friend, but he knows, when he enters the room by the sound of his tread; or if his hearing should lead him into errour, he corrects his mistake by a grasp of the hand. He cannot see the large and heavy bodies, which happen in his way when he walks about, but he suspects their too great nearness to him in consequence of the increased resistance of the atmosphere.* And a blind person, owing to the increased accuracy of the remaining senses, would be better trusted to go through the various apartments of a house, in the darkness of midnight, than one, possessed of the sense of seeing, but without any artificial light to assist him. It is stated on the authority of a Roman historian, that there was a blind man, who made it his employment to conduct merchants and other travellers through the sands and deserts of Arabia. This statement seems not to be improbable, when we recollect what is related in the transactions of the Manchester Society in England of John Metcalf, otherwise called Blind Jack. He became blind at an early

It is a singular circumstance, that something similar to what is here stated of the ability of blind men to discover the nearness or distance of objects by changes in the resistance of the atmosphere, has been noticed by the naturalist, Spallanzani, in respect to bats. He discovered, that bats when perfectly blinded and afterwards set at liberty, had the extraordinary faculty of guiding themselves through the most complicated windings of subterraneous passages, without striking against the walls, and that they avoided with great skill cords, branches of trees, and other obstacles, placed by design in their way.

This ability is probably owing to an extreme delicacy in the wing, which is of a very large size in proportion to that of the animal, and is covered with an exceedingly fine net-work of nerves. The bat, as it strikes the air with its wing, receives sensations of heat, cold, and resistance, and, in consequence, is enabled to avoid objects, which would otherwise obstruct its flight, apparently in the same way that blind persons perceive a door or a wall by a change in the temperature or in the resistance of the air.

period; but, notwithstanding, followed the profession of a waggoner and occasionally of a guide in intricate roads, during the night, or when the tracks were covered with snow. At length he became a projector and surveyor of highways in difficult and mountainous districts; an employment, for which one would naturally suppose a blind man to be but indifferently qualified. But he was found to answer all the expectations of his employers, and most of the roads over the peak in Derbyshire in England were altered by his directions. Says the person, who gives this account of Blind Jack, "I have several times met this man with the assistance only of a long staff traversing the roads, ascending precipices, exploring vallies, and investigating their several extents, forms, and situations, so as to answer his designs in the best manner." (Ed. Ency. Art. Blindness.)

This improvement of the remaining senses, when one of them is lost, is probably owing to the increased attention, which people then bestow upon the various and nicely distinguished suggestions, which they furnish. Nothing escapes them, and those dim perceptions, which were formerly almost unnoticed, now convey to them important information.

§. 55. Supposed feelings of a being called into existence in the full possession of his powers.

In the Natural History of the celebrated Buffon we have an account of the process, by which the use of the sight and of the other external senses is acquired. He invents a delightful recital, and puts it in the mouth of our first parent; and thus instructs us in the most abstruse subjects by an appeal to the imagination.

"Let us suppose (says he) a man newly brought into existence, whose body and organs are already perfectly formed, but who, awaking amidst the productions of Nature, is an utter stranger to every thing he perceives both from without, and from within. Of a man thus circumstanced what would be the first emotions, the first sensations, the first opinions? Were he himself to give us a detail of his

conceptions at this period, how would he express them? Might it not be in some measure as follows?

"Well do I recollect that joyful, anxious moment, when I first became conscious of my own existence. I knew not what I was, where I was, or whence I came. On opening my eyelids, what an addition to my surprise! The light of day, the azure vault of heaven, the verdure of the earth, the chrystal of the waters, all employed, all animated, and filled me with inexpressible delight."

"At first, I imagined that all those objects were within me, and formed a part of myself. Impressed with this idea, I turned my eyes towards the sun, whose splendour instantly dazzled and over-powered me. Involuntarily I closed my eyelids, though not without a slight sensation of pain; and, during this short interval of darkness, I imagined that I was about to sink into nothing."

"Full of affliction and astonishment, I had begun to ponder on this great change, when, listening, I heard a variety of sounds. The whistling of the wind, and the melody of the grove, formed a concert, of which the soft impression pervaded the inmost recesses of my soul. I continued to listen; nor could I banish the persuasion, that all this music was actually within me."

"So much was I engrossed with this new kind of existence, that I entirely forgot the light, that other part of my being, which I had known the first, till again I had opened my eyes. What joy to find myself once more in possession of so many brilliant objects! The present pleasure surpassed the former, and for a time suspended the charming effect of sounds."

"I turned my eyes upon a thousand different objects. These, which I still considered as a part of myself, I soon found that I could lose, and restore, at pleasure; and with a repetition of this new power I continued to amuse myself."

"I had begun to see without emotion, and to hear without confusion, when a light breeze, of which the freshness communicated a new sensation of pleasure, wafted its per