gree of the meridian, in every latitude, would have been found of the same length; and had the figure been that which was given to it by Cassini, a degree at the polar circle would have been found less than a degree at the equator. But as a degree at the equator appears to be about five hundred and seventy-five feet five-eighths less than a degree in France, and about one thousand two hundred and fifty-four feet three-eighths less than a degree at the arctic circle, it is easy to show, that the figure of the earth must be nearly the same as it was assigned by Newton. Besides this, it may be observed, that several very exact measurements, of the same kind, have since been made in England, France, and other parts of the world, all of which, when taken together, fully confirm the theory here laid down. LETTER XVII. OF THE DISTANCES AND MAGNITUDES OF THE SUN, MOON, AND PLANETS. It was a question, put by Mr. Molineaux to Mr. Locke, whether a blind man, who had been taught to distinguish a globe from a cube by the touch, would be able, if he could be made to see, to tell which was the globe and which the cube, by the use of his sight only. This question he answered in the negative; and, in his celebrated Essay on the Human Understanding, has shown that a person, so circumstanced, could have no dependence whatever upon his newly acquired sense, but would find himself totally unqualified to judge either of the situation and distance of objects, or of their magnitude and figure. A young man, who had been born blind, had the use of his eyes given to him by Mr. Cheselden, an eminent surgeon of that time, and all the ideas of the youth, on whom this singular operation was performed, were in favour of Mr. Locke's opinions. At the age of about fourteen years, he saw the light for the first time in his life; and was so perplexed and embarrassed with every thing about him, that he scarcely knew what to make of his new situation. For a long time, he could form no judgment of things by the use of that sense alone. An object of an inch in diameter, placed before his eyes, which concealed a house from his sight, appeared to him as large as the house. Whatever he saw, seemed to be upon his eyes, and to touch them, as the objects of the sense of feeling touch the skin. It was also observed, that what he had judged to be round, by the help of his hands, he could not distinguish from what he had judged to be square; nor could he discern by his eyes, whether what his hands had perceived to be above or below, was really above or below. It was not till after two months experience, that he could tell pictures from solid bodies; he thought bodies, and not surfaces, were in the painted canvas; and when he applied his hand to them, was amazed to find that they vanished from his touch. He was continually asking which of the senses it was that deceived him, that of feeling, or that of seeing. Nor could he understand how it was possible for the house he was in to be larger than his chamber; and even after he had acquired the proper use of his eyes, he was at a loss to conceive how sight had given him that idea. This was an indisputable decision, that the manner in which we see objects is no immediate consequence of the angles formed in our eyes; for the same angles were formed in the eyes of this young man, but they were of no use to him without the aid of experience, and the other senses. In what manner then do we represent magnitudes and distances to ourselves? and how do we judge of the figure and situation of objects? Certainly by the joint use of the senses of seeing and feeling to gether, and not by means of either of them separately employed. Neither the touch, nor the sight, can any more convey an idea of the figure or magnitude of a body to the mind, than the taste can convey an idea of colour. After having acquired these ideas by experience, the mind has received impressions which remain with her for ever afterwards. Being now enlightened and instructed, she forms a judgment without entering into all the circumstances and deductions that were necessary for her first information; and, like a skilful artist, employs the fewest means to attain the end proposed. Having thoroughly acquainted ourselves with the objects around us, we find connections and relations that enable us to form a judgment of those that are more remote; and by creating to ourselves artificial organs, which supply the defects of the natural ones, we extend our faculties beyond the apparent limits prescribed to them by nature, and subject the sense of feeling to the sense of sight. Astronomy has enlarged the sphere of our conceptions, and opened to us an universe without bounds, where the human imagination is lost. Surrounded by infinite space, and swallowed up in an immensity of being, man seems but as a drop of water in the ocean, mixed and confounded with the general mass. But from this situation, perplexing as it is, he endeavours to extricate himself, and by looking abroad into nature, employs the powers she has bestowed upon him in investigating her works. He proportions his own dura tion to that of the world; and representing to himself the insensible flux of time by similar analogies, he forms an idea of things which have no immediate existence, and places before his mind a picture of the past, present, and future state of the world. These are the fruits of genius and curiosity. To an active and persevering mind apparent impossibilities become probable: where the will and de-. sire are not wanting, we are always able to extend the circle of human activity beyond its ordinary limits. The progress of reason, and the powers of the imagination, are almost without bounds; and if we add to these, the invention of instruments, which are so many new organs of power and perception, man becomes a being worthy of admiration. He increases his strength by the assistance of the elements, augments and multiplies the powers of his senses, assures himself of their truth, and corrects their errors; and by this means creates to himself a new being, and adds to his faculties an extension and exactitude which nature seemed to have denied him. It should appear, that Astronomy depends altogether upon the sight. This is the most extensive of all our senses: it transports us every where, and enables us to enjoy the entire spectacle of the universe. "Takes in, at once, the landscape of the world, YOUNG. |