short petticoats, and ornaments of flowers and ribands. (See Plumtre's Residence in France, vol. iii, p. 28.) These curious sports were suspended during the Revolution, but, since the return of the ancien regime, have again contributed to amuse the people. Astronomical Occurrences In APRIL 1818. THE. Sun enters Taurus at 20 m. after 5 in the evening of the 20th of this month; and he rises and sets as stated in the following TABLE Of the Sun's Rising and Setting for every fifth Day. April 1st, Sun rises 34 m. after 5. Sets 26 m. after 6 36 6th, 11th, 6 5 ap If it were required to find the mean time from parent time, as shown on a good sun-dial, the quantities must be added or subtracted as shown in the following table; and if the quantity be required for any intermediate time, it is to be found by proportion. TABLE. m. s. Wednesday, April 1st, to the time by the dial add 4 5 2 35 Monday, 6th, Saturday, - 11th, Thursday, Tuesday, Sunday, 1 18 2 16 There will be a visible eclipse of the Moon on the 20th of this month, the circumstances of which are as follow; viz. Beginning of the eclipse, 11 m. after 11 at night Ecliptic opposition End of the eclipse Digits eclipsed 5° 32', from the north side of the Sun's shadow, or on the Moon's southern limb. Moon's Passage over the Meridian. The Moon will be on the meridian which passes through the Royal Observatory at the following times, which will be convenient moments for observation if the weather be clear. The time of her passage over any other meridian must be computed by means of her horary motion. April 13th, at 15 m. after 6 in the evening. 14th, 6 Eclipses of Jupiter's Satellites. The only eclipses of Jupiter's satellites that will be visible at Greenwich this month are the following; viz. IMMERSIONS. 1st Satellite, 5th day, at 34 m. after 3 in the morning. 28th Other Phenomena. Mercury will be in his superior conjunction at 15 m. after 12 on the 3d of this month; and Jupiter will be in quadrature at 20 m. past 1 in the morning of the 2d. The Moon will be in conjunction with Venus at 38 m. after 4 in the morning of the 6th; and with the star marked a in Libra, at 58 m. after 8 in the evening of the 21st. On the 7th, Mercury and Venus will be in conjunction, the former being 39' south of the latter. On the DISTANCES, MAGNITUDES, MOTIONS, &c., of the HEAVENLY BODIES. [Continued from p. 66.] From having the times of the sidereal revolutions of the several planets, it is easy to derive their mean daily motions, or the arcs they respectively describe in 24 sidereal hours. This is done by dividing 360, the number of degrees in the circumference of a circle, by the number of days occupied by the planet in making one complete revolution. Thus we obtain the mean daily motions as below : Mercury Mars o / " 4 5 33 1 36 8 0 59 8 0 31 27 The mean velocities of the planetary motions may also be found from the same source; for the mean distance being known, a circle is easily found equal to the extent of the planetary orbit; and this being divided by the time of the planet's revolution, in days or hours, will give the space described in that period, and, consequently, the velocity of the planet. In this manner the following spaces hourly described by each planet have been determined, in English miles, taken to the nearest mile : Perhaps scarcely any thing within the whole sphere of creation is more adapted to astonish and overpower the reflecting mind, than the velocity with which the planets pursue the undeviating courses marked out by the Great Author of their existence. Who can reflect upon the inconceivable rapidity of more than thirty miles per second, with which Mercury has moved since the commencement of time, and not be led to exclaim with the enraptured MILTON, while with his mental eye he surveyed the true sublime of creation, These are thy glorious works, Parent of good! Thus wondrous fair; thyself how wondrous then? The apparent diameters of the heavenly bodies are found by observation. For this purpose a micrometer is generally used, the two parallel wires of which are brought into apparent contact with two opposite points of the disc of the planet, and then the apparent diameter of the planet is marked by the index of the instrument. Having thus ascertained the apparent diameters, and knowing their distances from the earth, their real diameters are easily calculated by the rules of trigonometry. The apparent diameters of the old planets have been found, by the most accurate observations, to subtend the following angles at their greatest and least distances from the earth; viz. The apparent diameters of the planets at their mean distances may be found by taking the mean of the above numbers for each. The apparent diameter of the Sun at his mean distance from the earth is 32′ 3"; and that of the Moon 31′ 8′′. The apparent diameters of the four new planets are so small as not to be susceptible of being measured by common micrometers, and consequently considerable difficulty arises in ascertaining them with sufficient accuracy to constitute the basis of calculation. According to the observations of some astronomers, the diameters of these planets would not exceed the fraction of a second; but according to the observations of M. Shroëter, the apparent diameter of Ceres, when nearest the earth, is double that of the first satellite of Jupiter, or about 3". Ceres is encompassed with a nebulous appearance, the diameter of which appeared to that astronomer to be about 2"-5; but the real diameter of the planet was only about 1"-83. These diameters, at the mean distance of the Sun, would subtend angles of 6"-382 and 3"-057. He also found for Pallas, under the same circumstances, that the angles were 6"-514 and 4" 504. Juno is still less, and at the same distance it would have only 3"-057 for its apparent diameter; but it has no sensible nebula. The diameter of Vesta has not been ascertained; but it is supposed not to be greater than these. It must be remarked, however, that these results are |