1666, who, it is said, foresaw the lustre which the culture of the sciences would diffuse over his reign. This monarch, worthily seconded by the excellent Colbert, invited many learned strangers to fix themselves in his capital. Huygens accepted the proposal, and published, as it were, in the midst of the academy, of which he was a distinguished member, his adinirable work "De Horologio Oscillatorio." He would gladly have finished his days in France, had it not been for the tyrannical edict which towards the close of the 17th century deprived France of so many valuable citizens. Huygens was among that number, who, departing from a country in which the religion of his ancestors was proscribed, retired to the Hague, where he had been born in 1629, and he died there in June 1695.

Cassini, another celebrated astronomer, was likewise induced to go to Paris by the benefits held out to the learned by Louis XIV, and for forty years he enriched the growing science of astronomy with a great number of useful discoveries, of which some are as follow; the theory of the satellites of Jupiter, the motions of which he determined from observations of their eclipses; the discovery of four of the satellites of Saturn; those of the rotation of Jupiter, of the belts parallel to his equator; of the rotation of Mars; of the zodiacal light; of a very exact knowledge of the Sun's parallax; a table of refractions and above all the complete theory of the libration of the Moon. About this period the application of the telescope to the quadrant, the invention of the micrometer and heliometer, the successive propagation of light, which was formerly supposed to be instantaneous, the magnitude and form of the Earth, and the diminution of gravity at the equator, were discovered, and according to La Place were all the fruits of the labours of the French Academicians. Still he is not at all unwilling to render justice to our own countrymen, as the following passage, taken from the

;

translation of Mr. Pond, the present Astronomer Royal, will show.

Astronomy does not owe less to the Royal Society of London, the origin of which is a few years anterior to that of the Academy of Sciences. Among the astronomers which it has produced, I shall cite Flamstead, one of the greatest observers that have ever appeared. Halley, rendered illustrious by his travels, undertaken for the advantage of science, by his beautiful investigation concerning comets, which enabled him to discover the return of the comet in 1759; and by the ingenious idea of employing the transit of Venus over the Sun, in the determination of its parallax. I shall mention, lastly, Bradley, the model for observers, and who will be for ever celebrated for two of the most beautiful discoveries ever made in astronomy, the abberration of the fixed stars, and the nutation of the axis of the Earth.

When the application of the pendulum to clocks, and of telescopes to quadrants, had rendered the slightest changes in the position of the celestial bodies perceptible to observers, they endeavoured to determine the annual parallax of the fixed stars; for it was natural to suppose, that so great an extent as the diameter of the terrestrial orbit would be sensible even at the distance of these stars. Observing them carefully, at every season of the year, there appeared slight variations; sometimes favourable, but more frequently contrary to the effects of parallax. To determine the law of these variations, an instrument of great radius, and divided with extreme precision, was requisite. The artist who executed it, deserves to partake of the glory of the astronomer who owed his discovery to him. Graham, a famous English watch-maker, constructed a great sector, with which Bradley discovered the abberration of the fixed stars, in the year 1727. To explain it, this great astronomer conceived the fortunate idea of combining the

motion of the Earth with that of light, which Roemer had discovered at the end of the last century, by means of the eclipses of Jupiter's satellites. We should be surprised that none of the distinguished philosophers who then existed, and who knew the motion of light, should have paid any attention to the very simple effects which result from it, in the apparent position of the fixed stars. But, the human mind, so active in the formation of systems, has almost always waited till observation and experience have acquainted it with important truths, which its powers of reasoning alone might have discovered.

It is thus that the invention of telescopes has followed by more than three centuries that of lenses, and even then was only due to accident.

In 1745, Bradley discovered by observation the nutation of the terrestrial axis. In all the apparent variations of the fixed stars, observed with extraordinary care, he perceived nothing which indicated a perceptible parallax. The measures of the degrees of the terrestrial meridian, and of the pendulum, multiplied in different parts of the globe, of which France gave the example, by measuring the whole arc of the meridian which crosses it, and by sending the academician to the north and to the equator, to observe the magnitude of these degrees, and the intensity of the force of gravity. The arc of the meridian, comprised between Dunkirk and Barcelona, determined by very precise observations, and forming the base of the most natural and simple system of measures; the voyages undertaken to observe the two transits of Venus over the Sun's disk in 1761 and 1769, and the exact knowledge of the dimensions of the solar system, which has been derived from these voyages; the invention of achromatic telescopes, of chronometers, of the sextant and repeating circle; the discovery of the planet Uranus, by Herschel, in

1781; that of its satellites, and of two new satellites of Saturn, due to the same observer; all the astronomical theories being brought to perfection, and all the celestial phenomena, without exception, being referred to the principle of universal gravitation: these, with the discoveries of Bradley, are the principal obligations which astronomy owes to the last century, which, with the preceding, will always be considered as the most glorious epoch of the science.'

[To be continued]

Astronomical Occurrences.

THE Sun enters Cancer on the 21st of June, at past 2 o'clock at noon. Saturn is stationary on the 1st day on the 5th day Mercury is at his greatest elongation, and on the 19th he is stationary: on the 26th Jupiter is stationary.

TABLE

Of the Sun's Rising and Setting every 5th Day.

Equation of Time. [See Occurrences for Jan.]

m. sec.

June 1, from the time on the dial subtract 2 34

true Time by the Clock.

30,

The Moon enters her first quarter at 18 m. past five in the morning on the 3d: she is at full on the 10th, at 19 m. past I in the morning: enters her last quarter on the 17th, at 48 m. past 7 in the even

ing; and is at change, or new Moon, on the 25th, at 7 m. past 2 in the afternoon.

On the 9th of June, the Moon will be eclipsed, visible, in these parts; it will continue about three hours and a half from the commencement to the end, as will be seen below. Previously to putting down the particulars, we may observe, for the sake of those who are not conversant with these subjects, when our view of a celestial body is obstructed by the interposition of another celestial body, or of its shadow, the phenomenon is called an eclipse, an occultation, or a transit: the word eclipse is applied particularly (1) to the obscuration of the Sun by the interposition of the Moon between it and the Earth; (2) and to the obscuration of the Moon by its coming within the shadow of the Earth; and (3) to the obscuration of the satellites of other planets by their coming within the shadows of their respective primaries. The word occultation is usually applied to the disappearance of the fixed stars or planets, occasioned by the interposition of the Moon. The word transit is more commonly used to denote the passage of the inferior planets, Venus and Mercury, over the disk of the Sun. Of all these phenomena, the eclipses of the Sun and of the Moon are by far the most striking, and have frequently excited the fears of the vulgar, and the diligent attention of the most enlightened part of the human species.

An eclipse of the Moon can only happen at the time of full Moon, when the Sun, the Earth, and the Moon, are in the same right line. As the orbit of the Moon does not coincide with that of the Earth, but is inclined to it in a certain angle, an eclipse does not take place every full Moon. It can only happen when the full Moon is in or near the nodes, that is, in or near those points in which the orbits of the Earth and Moon cross one another. The quantity of the Moon's disk which is eclipsed is expressed by twelfth parts, called digits of that