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ANOTHER HETERODOX QUESTION. 293

change his size? Does he ever shrink in his majestic proportions? Is the magnitude of his broad golden disc ever lessened?

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Assuredly this new question, which was not less audacious than its predecessor, did not come-there is sacrilege in the thought from the conservative areopagus of all ancient doctrines; the learned areopagus, or supreme tribunal, which had erected into a dogma the circular orbit and uniform movement of the sun around the earth, the centre of the universe! It could only have been suggested by some unworthy heterodoxical disturber of men's minds,-his name, alas! has not been handed down to us,-who had dared to look upon the heavens, and learn from their bright and beautiful face, without a master, the A B C of science. This "

"pestilent heretic' had, probably, remarked one of the commonest phenomena connected with the celestial bodies, which astronomers hitherto had not deigned to notice.

Undoubtedly, dear reader, you will have been more than once impressed by the appearance of the solar orb, when obscured in one of those mists so frequent towards the end of autumn:

"Cold grew the foggy morn, the day was brief ;

Loose on the cherry hung the crimson leaf;

The dew dwelt ever on the herb; the woods

Roared with strong blasts, with mighty showers the floods."

Such a day, in this sad season of the year, when the glory of the woods is rapidly departing, and from the swollen streams and dewy pastures the vapours ascend in a dense whirl of

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EXPERIENTIA DOCET.

clouds, is of frequent occurrence; and on such a day, the solar sphere, as it struggles through the screening mists, seems like the face of the moon at its full, when slightly veiled. Your eye

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FIG. 66.-"When the glory of the woods is rapidly departing."

rests upon it without pain. And as observation sharpens your mind, you put to yourself the natural question, Is not the sun farther from the earth at this epoch when it affords us the

WHEN IS THE SUN NEAREST EARTH? 295

least heat, than at that period of the year when its vivifying power is greatest? I think it is obvious that, to the unexperienced, such a method of explaining the cold of winter and the heat of summer by the variation in the distance of our great solar luminary would naturally occur.

But the demon of certainty-an excellent demon, whatever the orthodox may say is present, to stimulate us all. You may have just formed your theories, you may cite your tradi tional authorities, but these will not satisfy our awakened curiosity. We ask for demonstrations, for irrefragable proofs drawn from the Bible of Nature. We will listen to no oracles but those which are confirmed by the voices of God's second revelation.

Therefore, men required to be assured that the sun was really nearer to us in summer than in winter. For this purpose, it was requisite to make, at the beginning of summer, an observation analogous to that which had been made at the beginning of winter, and afterwards to compare the apparent magnitudes of the solar disc at these two opposite periods of the year.

Behold us, then, at work. You are perfectly tranquil as to the result; for you are persuaded beforehand that the sun must be farther from us in the cold season than in the hot. You regard this as a self-evident truth, like an axiom of Euclid's.

But Nature is a great magician; she contrives the most dramatic surprises for the mind which takes the trouble to interrogate her in all simplicity and without dogmatic pretensions.

What a coup-de-théâtre it was for the observer who first established experimentally that the apparent diameter of the

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THE SUN'S VISUAL ANGLE.

sun is greater in winter than in summer-that we are nearer the sun in the cold season, than in the hot!

On more closely examining a result apparently so paradoxical, man discovered that the angle which subtracts the sun, as seen from the earth,—the visual angle which gives the sun's apparent diameter,-varies necessarily throughout the year. Thus, the semi-diameter, or radius, which on the 24th of June equals 15′ 45′′, will, a month later, have increased one second (15′ 46′′); on the 2d of August will equal 15′ 47′′; on the 2d September, 15′ 53′′, and so on. We put the exact measurements before the reader in a tabulated form :

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We do not trouble the reader with the fractions of a second, which indicate the quantity of the apparent increase of the radius from the end of June to the end of December, and its apparent decrease from the beginning of January to the end of June.

A glance at the above figures shows that the mean of the apparent diameters, all measured at the moment of the sun's passing the meridian, is about half a degree, or 30'; and

MAXIMUM AND MINIMUM.

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that which is sufficiently curious-720 of these mean suns, set one against another, would be required to fill up the contour of a great circle of the celestial sphere. Is it this fact which suggested the idea of dividing the circle into 720=360°?

Simultaneously with the discovery of the variations of the solar charioteer, it was ascertained that the moments of the sun's passage of the meridian-moments which measure the 365 different positions occupied by the sun in the 365 days of the year-are not separated by equal intervals, or that equal intervals of time do not correspond to the equal angular displacements,-in fine, that the maximum and minimum of the sun's angular velocity coincide with the maximum and minimum of its apparent diameter. Now, remember that the extreme points where the sun experiences its maximum and minimum angular displacement are named, according to Ptolemæus, the former the perigee, the latter the apogee; or, if we follow Copernicus, the former the perihelion, and the latter the aphelion.

The aggregate of these facts was known to the ancients; but the manner in which it was sought to explain them merits notice as a specimen of blind attachment to a preconceived system.

Ptolemæus, the organ of the dictatorial astronomy of antiquity, declares, ex cathedrâ, that "the inequalities of the sun's movements are only apparent; that they are simply the effects of the position and of the arrangements

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