In a total eclipse of the sun, 12 May, 1706, a streak of light was observed 6" or 7" before the sun's disc; hence Flamstead infers a lunar atmosphere th of the moon's diameter in height; but this might have been from oblique reflection.-Phil. Trans. 1706..

During a total eclipse of the moon, Ulloa observed that there was a great appearance of light round the moon, which seemed to be agitated, and emitted rays to the distance of a diameter; it was reddish next the moon, then yellowish. Stars of the first and se cond magnitude were seen, those of the first for about 4 minutes. A minute and a quarter before the emersion, a small point was visible near the disc of the moon. From the ruddy colour of the light, the ring is referred to the moon's atmosphere; the spot to a fissure in the moon's substance. Such a fissure must have been above 40 miles in depth.-Phil. Trans. 1779.

The Egyptians reckoned by years of 365 days; Hipparchus and Ptolemy employ the same method. In A.D. 940, the first day of the Egyptian year, was the first of January; another Egyptian year began 31 December. In the new stile, 10 days were omitted in 1582; before this time, each century contained 36,525 days.Robinson.

To find the prime number, sometimes called the solar cycle, add 9 and divide by 28; the indiction, add 3 and divide by 15. Add 4 to the year and divide by 19, the remainder is the golden number, take 1 from the golden number, multiply by 11, and divide by 30, the remainder is the epact, or the moon's age, on the first of Janu ary.-Lalande.

In astronomical language, 1 Jan. 1805, 6 o'clock A.M. is 1804, Dec. 31d. 18h.-Lichtenberg.

CHAP. XXIII;

STARS VISIBLE IN LONDON, INCLUDING ALL OF THE FIRST AND SECOND MAGNITUDE,

WHEN a spherical surface has been projected on a plane, it has been usual to consider it as viewed from a particular point, either

infinitely remote, as in the orthographical projection, or situated in the opposite surface of the sphere, as in the stereographical. The Jatter method produces the least distortion, and is the most commonly used, but even here, at the extremities of the hemisphere, the scale is twice as great as in the middle. Sometimes another principle is employed, and the hemisphere is divided into segments, by omitting portions in the directions of their radii, as if the paper were intended to be fixed on a globe; and in the same form as if a spherical surface were cut in the direction of its meridians, and spread on a plane. If the number of these divisions be increased without limit, the result will be the projection, which is employed in the circular part of this diagram, and in the same manner the zone on each side the equinoctial, being cut open by innumerable divisions, so as to be spread on a plane, will coincide with the two remaining portions. By these means the distortion becomes inconsiderable. In the common stereographical projection indeed, the distortion would be of no consequence, if it represented always those stars only, which are at once above the horizon of a given place, for we actually imagine the stars in the zenith to be much nearer together, than when they are nearer the horizon, and the picture would appear to agree very well with the original; but their positions being continually changing, the inconvenience remains.

It is not however, necessary, in projections of the stars, to refer them in any instance to a spherical surface. Among Dopplemayer's charts, published at Nuremberg, there are six which represent the sides of a cube, on which the various parts of the constellations are represented; the eye being probably supposed to be situated in the centre. Funck and others have represented the stars as projected on the inside of two flat cones. But the most convenient representation of this kind, and which would approach very near to the projection here employed, would be to consider the eye as placed in the centre of a hollow cylinder, so proportioned that all the cir cumpolar stars should be represented on one of its flat ends, and all those which rise and set on its concave surface; or if it were desired to have a division without referring to any particular latitude, the circular part might extend to the limits of the zodiac, and the parallelogram, into which the cylinder unfolds, might comprehend all

the stars to which the planets approach. The horizon, and other great circles, would form lines of various and contrary curvatures.

CHAP. XXIV.

ON THE FUTURE PROGRESS OF ASTRONOMY.

FROM the preceding observations, it has sufficiently appeared that the immense globe of the sun, the focus of all the motions of the heavenly bodies, revolves upon its axis in twenty-five days and a half. Its surface is covered with an ocean of luminous matter, whose active effervescence forms variable. spots, often very numerous, and sometimes larger than the earth. Above this ocean exists an immense atmosphere, in which the planets, with their satellites, move, in orbits nearly circular, and in planes little inclined to the ecliptic. Innumerable comets, after having approached the sun, remove to distances, which evince that his empire extends beyond the known limits of the planetary system. This luminary not only acts by its attraction upon all these globes, and compels them to move around him, but imparts to them both light and heat; his benign influence gives birth to the animals and plants which cover the surface of the earth, and analogy induces us to believe, that it produces similar effects on the planets; for, it is not natural to suppose that matter, of which we see the fecundity develop itself in such various ways, should be sterile upon a planet so large as Jupiter, which, like the earth, has its days, its nights, and his years, and on which observation discovers changes that indicate very active forces. Man, formed for the temperature which he enjoys upon the earth, could not, according to all appearance, live upon the other planets; but ought there not to be a diversity of organization suited to the various temperatures of the globes of this universe? If the difference of elements and climates alone, causes such variety in the productions of the earth, how infinitely diversified must be the productions of the planets and their satellites? The most active imagination cannot form any just idea of them, but still their existence is extremely probable.

However arbitrary the system of the planets may be, there exists between them some very remarkable relatious, which may throw

light on their origin; considering them with attention, we are astonished to see all the planets move round the Sun from west to east, and nearly in the same plane all the satellites moving round their respective planets in the same direction, and nearly in the same plane with the planets. Lastly, the sun, the planets, and those satellites in which a motion of rotation has been observed, turn on their own axis, in the same direction, and nearly in the same plane as their motion of projection.

A phenomenon so extraordinary, is not the effect of chance; it indicates an universal cause, which has determined all these motions. To approximate somewhat to the probable explanation of this cause, we should observe that the planetary system, such as we now consider it, is composed of seven planets, and fourteen satellites. We have observed the rotation of the sun, of five planets, of the moon, of Saturn's ring, and of his farthest satellite; these motions with those of revolution, form together thirty direct movements, in the same direction. If we conceive the plane of any direct motion whatever, coinciding at first with that of the ecliptic, afterwards inclining itself towards this last plane, and passing over all the degrees of inclination, from zero to half the circumference; it is clear that the motion will be direct in all its inferior inclinations to a hun`dred degrees, and that it will be retrograde in its inclination beyond that; so that, by the change of inclination alone, the direct and retrograde motions of the solar system, can be represented. Beheld in this point of view, we may reckon twenty-nine motions, of which the planes are inclined to that of the earth, at most 4th of the circumference; but, supposing their inclinations had been the effect of chance, they would have extended to half the circumference, and the probability that one of them would have exceeded the quarter, would be 1-, or $16170114. It is then extremely probable, that the direction of the planetary motion is not the effect of chance, and this becomes still more probable, if we consider that the inclination of the greatest number of these motions to the ecliptic, is very small, and much less than a quarter of the circumference.

Another phenomenon of the solar system equally remarkable, is the small eccentricity of the orbits of the planets and their satellites, while those of comets are much extended. The orbits of the system offer no intermediate shades between a great and small excentricity. We are here again compelled to acknowledge the effect