May 30. St. Maguil. St. Felix. St. Ferdinand. St. Walstan. Orises at III. 56'. and sets at VIII. 4'. CHRONOLOGY.-The renowned Voltaire died in 1778, aged 85. Notwithstanding the many false accounts of the miserable and penitent death of Voltaire, it is well known that he died, as he lived, a determined unbeliever; and though we may lament that he was not in the bosom of the catholic church, yet he had the merit of consistency throughout his whole life-a thing possessed by but few philosophers. Pope died also on this day in 1744, at Twickenham. FLORA. Cat's Ear Hypochaeris radicata is now in flower every where; its first appearance is about the 18th inst. This Plant as well as the Rough Dandelion continues to flower till after Midsummer. The Lilac, the Barberry tree, the Maple, and other trees and shrubs, now flower. The meadow grasses are fullgrown and flowering in the fields laid in for hay. The flowers of the Garden Rose in early and warm years begin to open. We gave, April 17th, some lines in the original, from Göthe, on a Violet: we subjoin some, as a translation from the same author, on a young Rose Bud in May. The Rose Bud, from the German of Goëthe. A Rose, that bloomed the roadside by, My little Rose, my Rosebud dear! The child exclaimed, "My hands shall dare, My little Rose, my Rosebud dear! My Rose that blooms the roadside near! Regardless of its thorny spray, The child would tear the Rose away; To quell the urchin's pow'r. My little Rose, my Rosebud dear! My Rose that bloomed the roadside near! The Reader will judge of the boasted poetic powers and grand style of the Author of Werther's Leiden by the above Romanzen!!! The following simile drawn from a Tulip may amuse the Reader at this season while the gaudy look of a bed of these flowers is still fresh in his memory: Lines by Dryden, on a Tulip. As some fair Tulip by a storm opprest, The Hawthorn. On Summer's breast the Hawthorn shines Mid slopes where the' evening flock reclines, When yellow Autumn decks the plain, Amid the ripening fields of grain May 31. Ste. Petronilla Virgin. SS. Cantius, Cantianilla, &c. MM. CHRONOLOGY.-Coronation of Anne Boleyne in 1533. Repertory, iii. 202. See Antiq. FLORA. The Midsummer Daisy Chrysanthemum Leucanthemum now begins to flower, and continues to increase in numbers till Midsummer, during which time the flowers of this plant cover certain meadows and mix with or succeed the Crowsfoot. FAUNA.- In early and warm seasons a few Glowworms are already seen of an evening: the green May Bug, a coleopterous insect burnished with gold, and the brown Cockchafer Melolontha vulgaris, are now common. CHRONOS.-On Time and its Application.- From La Lande.-From a simple exposition of the subject given in any book of Astronomy, it may readily be conceived, that in virtue of the obliquity of the ecliptic, combined with the inequality in the motion of the Sun, the equation of time becomes nothing four times in the course of the year; viz. once between the Winter solstice and the perigee of the Sun, twice between the vernal equinox and the Summer solstice, and again between the apogee and the autumnal equinox. These epochs, however, are not fixed, but vary with the position of the major axis of the solar orbit, the 16th of June, and the 1st of September. The progressive change in the position of the major axis of the apparent solar orbit ought also to produce a gradual and small corresponding variation in the absolute value of the equation of time. The causes, however, which make the equation of time vanish at certain intervals, ought still to produce their effect, notwithstanding the trifling variations which the effects of nutation may occasion; for, as 'these variations never exceed a few seconds, they can only produce a small change in the four epochs in each year when the equation of time becomes nothing, but they can neither destroy it altogether, nor cause it to deviate from the limits above assigned to it. If the inclination of the ecliptic to the plane of the equator were to become nothing, or the planes of the two circles to coincide with each other, that part of the equation of time which depends upon this inclination would also become nothing. Then the mean and real motions would only differ from each other by the effects produced by the inequalities of the latter motion, and which the French astronomers express by the equation of the centre. The real and the mean Sun would then meet only at the perigee and apogee, and apparent time would coincide with mean time only twice a year, when the Sun was in the line of his apsides. From this explanation, it is easy to conceive that the instant of apparent noon, as marked by the shadow on the dial, will generally differ from that of mean noon. As, however, the equation of time is known for each day at this time, the direction and limit of the shadow may be marked on the dial at the instant of mean noon; and there will thus be obtained a series of points on both sides of the apparent meridian, which will mark the positions of the mean meridians at these successive instants. The curve described through all these points ought evidently to meet the meridian in four points, answering to the four times in the year in which the equation of time becomes nothing. This curve ought also to return to itself, since the equation of time takes the same values after each revolution. It will not, however, be symmetrical, since the epochs at which the equation of time vanishes are not equal to each other. There is a meridian of this kind drawn by M. Bouvard upon the Palace of Luxembourg at Paris. The time which elapses between two consecutive passages of the Sun through the same equinoctial point, is very nearly equal to 365d. 5. 48. 51., and as this time answers to one complete revolution of the sphere, or 360°, we have which is the arc daily described by the Sun in his orbit, supposing his motion to be uniform. His passage would therefore be daily retarded, with regard to sidereal time, by (59′ 8′′33) 3' 36" 33" 32 of sidereal time; and which is therefore the excess of the mean above the sidereal day. The duration of the mean hour is to the duration of the sidereal hour as 360° 59′ 8′′-33 is to 360°, or as 24h. 3. 565554 is to 24"; and hence we have the equation, Thus the duration of the mean hour is equal to 1.00273791 of the sidereal hour; and the duration of the sidereal hour is equal to the duration of the mean hour 99726967 of the mean hour. 1.00273791 If s be any duration whatever, expressed in sidereal time, and m the same duration in mean time, we have it will therefore be expressed by a less number in mean time than in sidereal time. From the equation, s=100273791, we readily deduces — m = 1-00273791 m — m = 0·00273791 m; so that when we know m, we have only to add 0.00273791 m, in order to obtain s. Thus, if we suppose m=1., we shall find 9.8568 to be added to it, in order to have s = 1. 0m. 9-8568. Again, if we suppose m = 7. 30., the quantity to be added to obtain s, will be 9*8568 × 7·5 = 1". 13926; and, consequently, s = 7. 30m. +1. 18926 7. 31m. 13"-926. The same result may be obtained from the previous equation, in which s=1-0027S791m; for, multiplying m by this number, we shall have the value of s. Taking the last example, 100273791 × 7.5 = 7h 520534325 7. 31. 13.924. When is given and m required, it is evident from the above equation, that, if the value of s be multiplied by the reciprocal of the preceding number, or '99727, we shall have the value of m. It is also obvious, that if we subtract ⚫00273* from the given time, we shall also obtain the value of m. Thus, taking the above value of s, namely 7h. 31. 13924, as an example, we have 7-521 x 99727 = 7. 30m. Or, by the second method, we have 7521 × 00273 =·021 nearly; and 7·521 — ·021 = 7. 30, as before. One sidereal hour answers to 15° of motion of the celestial sphere. One mean hour answers to 15° + 2′ 27′′-8526 15° 2′ 27′′-8526: and it is upon this principle that astronomers have calculated tables for converting mean time into degrees; according to which, 1". of mean time answers to 15' 2"4642, and 18. of mean time corresponds to 15" 04107 of a degree. The table thus formed is necessary to those astronomers who regulate their clocks by mean solar time, in order to find the borary angles of the stars, or the differences of mean right ascensions, ms(100278791) + (0·002738) - &c.s-0027344. Let s 1 sidereal hour, m = 1a. — 9′′·8292. From this formula the table for reducing sidereal time to mean time is calculated at the rate of 98292 per hour, or 3. 55.901 for 24 hours.-This table is necessary for astronomers who regulate their clocks by sidereal time, for when they have observed the time of any phenomena, it is only in this species of time that it is known. And in order to have it expressed in mean time, they calculate the mean place of the Sun referred to the apparent equinox. This mean longitude, converted into time at the rate of 1h. to 15o, is the Sun's mean right ascension, or the sidereal time of the passage of the Sun's mean place over the meridian, or, in other words, the sidereal time at mean noon. This time subtracted from the time of the observation, gives an interval of sidereal time, which is then to be converted into mean time. The following example will illustrate this process. Suppose, then, any observation to be made at 17h. 9m. 23.5 of sidereal time, and that the mean longitude of the Sun at mean noon was This is the mean time elapsed since the passage of the mean Sun over the meridian, and is what is called the mean time of the observation. This time supposes the motion of the Sun on the equator to be uniform; and it is the passage of the point of the equator which corresponds to this uniform motion, which determines what is called mean noon, and the interval from this noon constitutes mean time, as the interval from apparent noon constitutes apparent time. Apparent time is too unequal a measure for astronomers, though it may answer for civil purposes. Clocks can mark only mean or sidereal time, as these alone are uniform; they can never indicate apparent time, except by a particular construction, and then not with accuracy. Hence all astronomers regulate their clocks by sidereal time, when they have a fixed observatory, and by mean solar time in other cases. Apparent time, therefore, serves only to find mean or sidereal time. If the transit of the Sun over the meridian be observed by means of a clock regulated to sidereal time, and the rate of which is known, we shall have the Sun's right ascension; but if the rate be not known, the time of the observation is to be compared with the Sun's right ascension, either as calculated or taken from an Ephemeris, and the difference is the correction of the clock. By calculating at the same time the equation of time, or the mean right ascension of the Sun, we have the difference between the clock and mean time for the instant of apparent noon. If the observation of the Sun's passage over the meridian be ascertained by means of a clock regulated to mean time, the time is to be compared with the Sun's mean right ascension in time, and the difference is the error of the clock at the instant of apparent noon; and if this observation be repeated for several successive days, the rate of the clock will be found, and we shall be able to assign the time of any observation whatever. If the Sun's zenith distance were observed, with this distance, the height of the pole, and his declination, the apparent horary angle is calculated, and this, corrected by the equation of time, gives the mean time of the observation, and consequently the actual error of the clock. Comparisons of this kind give the progress of this error, and consequently the rate of the clock. Mean time multiplied by 15 gives the mean horary angle, which, added to the Sun's right ascension calculated for the same time, gives the right ascension of midheaven, or sidereal time. Hence it is obvious, that apparent time, or that which is shown by the apparent motion of the Sun in the heavens, serves astronomers only for calculating mean and sidereal time.— See Delambre's Abrégé d'Astronomie, Leçon xii. Concerning the Epact and Style, see p. 179 of this work. Table of the Equation of Time for every Fifth Day. M. S. May 1st, from the time by the Dial subtract 3 1 |